Chem2021 Virtual Poster Session - proudly sponsored by Merck
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Filter displayed posters (125 keywords)
Electrochemistry (2)
MOFs (2)
Structural Biology (2)
colorimetric (2)
nanozyme (2)
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2D nanomaterials (1)
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Show Posters:
Tracks
▼ Analytical Chemistry Back to top
Nanozyme array for detection of S. aureus strains
Pabudi Weerathunge, Mahdieh Yazdani, Tarun K. Sharma, Vincent M. Rotello, Anandwardhan Hardikar, Mughdha V. Joglekar, Wilson K.M. Wong, Vipul Bansal, Rajesh Ramanathan
Abstract
Staphylococcus aureus, an important human pathogen, causes more than 500,000 infections and 94,000 deaths in the United States alone each year. Traditional strategies of bacterial culture and identification take several days, leading to downtime for patients who are suffering severe S. aureus infections. Although nucleic acid-based detection has addressed this limitation; costs associated with the assay, infrastructure, and personnel/skillset limits the widespread use of such technologies. Here, we developed an array-based colorimetric aptasensor that generates a unique colorimetric fingerprint for each strain tested. Machine-learning algorithms using a train and test approach identified aptamer signatures that enable accurate identification of several S. aureus strains. Additionally, important information about the virulence factors associated with pathogenicity/susceptibility to common antibiotics and the presence of Panton-Valentine leukocidin (PVL) marker responsible for making some strains virulent, could be derived. The capacity to identify unique signatures enable sensors to be trained to recognize unknown strains of S. aureus not previously encountered. This allows for an unbiased detection system for quick and reliable screening. The ability to accurately predict S. aureus strains in simulated wound fluids further underscores the robustness of this new platform technology.
Presented by
Rajesh Ramanathan
Institution
RMIT University
Keywords
array-based sensing, gold nanoparticles, aptamer, S. aureus, MRSA, colorimetric
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Available June 6-8 (1330-1400)
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Diabetes monitoring made easy using colors
Sanjana Prasad, Vipul Bansal & Rajesh Ramanathan
Abstract
Renal complications are long-term effect of diabetes mellitus where glucose is excreted in urine. Therefore, reliable glucose detection in urine is critical. While commercial urine strips offer a simple way to detect urine sugar, poor sensitivity and low reliability limits their use. A hybrid glucose oxidase (GOx)/ horseradish peroxidase (HRP) assay remains the gold standard for pathological detection of glucose. A key restriction is poor stability of HRP and its suicidal inactivation by hydrogen peroxide, a key intermediate of the GOx-driven reaction. An alternative is to replace HRP with a robust inorganic enzyme-mimic or Nanozyme. While colloidal nanozymes show promise in glucose sensing, they detect low concentrations of glucose, while urine have high (mM) glucose concentration.
In this study, free-standing nanoparticles on the 3D matrix of cotton fabric was used for the colorimetric detection of glucose in human urine. The sensor could operate in a biologically relevant dynamic linear range of 0.5 – 15 mM, while showing minimal sample matrix effect such that glucose could be detected in urine without significant sample processing or dilution. This ability could be attributed to the Cu nanozyme that for the first time showed an ability to promote the oxidation of a TMB substrate to its double oxidized diimine product rather than the charge-transfer complex product commonly observed. Additionally, the sensor could operate at a single pH without the need to use different pH conditions as in a gold standard assay. These outcomes outline the high robustness of the nanozyme sensing system for direct detection of glucose in human urine.
In this study, free-standing nanoparticles on the 3D matrix of cotton fabric was used for the colorimetric detection of glucose in human urine. The sensor could operate in a biologically relevant dynamic linear range of 0.5 – 15 mM, while showing minimal sample matrix effect such that glucose could be detected in urine without significant sample processing or dilution. This ability could be attributed to the Cu nanozyme that for the first time showed an ability to promote the oxidation of a TMB substrate to its double oxidized diimine product rather than the charge-transfer complex product commonly observed. Additionally, the sensor could operate at a single pH without the need to use different pH conditions as in a gold standard assay. These outcomes outline the high robustness of the nanozyme sensing system for direct detection of glucose in human urine.
Presented by
Sanjana Naveen Prasad
<s3702344@student.rmit.edu.au>
Institution
RMIT University
Keywords
nanozyme, copper nanoparticles, functional fabrics, peroxidase, colorimetric, glucose sensing
Chat with Presenter
Available July 6-12th 10AM-12PM
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▼ Applied Chemistry Back to top
NanoZymes as an alternative antibacterial to antibiotics
Pyria Rose Divina, Mandeep Singh, Rajesh Ramanathan, Vipul Bansal
Abstract
Antimicrobial resistance (AMR) is the ability of the microorganism to stop antimicrobial (such as antibiotics, antivirals and antimalarial) from working against them. Each year, antibiotic resistant microbes cause at least 2,049,442 illnesses 700,000 deaths (globally). Therefore, it’s demanding urgency to search for a fresh generation of antimicrobial agents, which are constructive and risk-free. Nanotechnology offers a fantastic solution in the form of nanomaterials, performing as nano-antimicrobial for fighting the multi-drug resistant microbial infections, acting as an alternative to conventional antibiotics.
This research focuses on the synthesis of 2D Iron sulfide (FeS) nanosheets and explores their enzymatic behaviour to cater the need, to be an effective antibacterial agent. The work outlines a facile method to fabricate high surface area FeS nanosheets which were highly magnetic. The rich optical property of the FeS nanosheets allowed us to explore the use of light to trigger the generation of photoinduced reactive oxygen species (ROS). The enhanced production of ROS allowed effective killing of bacteria. The enhanced photoactive antibacterial performance further reduces the amount of nanomaterial required to low µg/ml concentrations and H2O2 to low mM concentrations while increasing the efficiency of bacterial killing.
This research focuses on the synthesis of 2D Iron sulfide (FeS) nanosheets and explores their enzymatic behaviour to cater the need, to be an effective antibacterial agent. The work outlines a facile method to fabricate high surface area FeS nanosheets which were highly magnetic. The rich optical property of the FeS nanosheets allowed us to explore the use of light to trigger the generation of photoinduced reactive oxygen species (ROS). The enhanced production of ROS allowed effective killing of bacteria. The enhanced photoactive antibacterial performance further reduces the amount of nanomaterial required to low µg/ml concentrations and H2O2 to low mM concentrations while increasing the efficiency of bacterial killing.
Presented by
Pyria Rose Divina MariaThomas
Institution
RMIT University
Keywords
Nanozymes, Nanomaterials,antibacterial
L-Cysteine as an irreversible inhibitor to NiO's nanozyme activity
Piyumi Dinusha Liyanage, Pabudi Weerathunge, Mandeep Singh, Vipul Bansal and Rajesh Ramanathan
Abstract
Nanozymes are inorganic nanomaterials that show catalytic activity similar to natural enzymes. A range of nanomaterials based on metals, metal oxides, metal sulphides, and carbon have been reported to mimic the catalytic activity of natural enzymes. An important aspect in natural enzymes is our ability to control the catalytic activity through molecules that bind to the active site inhibiting its catalytic activity. The ability to modulate the catalytic activity of inorganic nanozymes is therefore of high interest. In particular, understanding the interactions of inhibitor molecules with nanozymes can bring them one step closer to the natural enzymes and has thus started to attract intense interest. To date, a few reversible inhibitors of the nanozyme activity have been reported. However, there were no reports of irreversible inhibitor molecules that can permanently inhibit the activity of nanozymes. This study, for the first time, shows the ability of L-cysteine to act as an irreversible inhibitor to permanently block the nanozyme activity of 2-dimensional (2D) NiO nanosheets. Determination of the steady state kinetic parameters allowed us to obtain mechanistic insights into the catalytic inhibition process. Further, based on the irreversible catalytic inhibition capability of L-cysteine, a highly specific sensor for the detection of this biologically important molecule was developed.
Presented by
Piyumi Liyanage
<dinusha.piyumi@gmail.com>
Institution
RMIT University
Keywords
nanozyme, biosensor, inhibitor, 2D-nanomaterials
ZIF-C for targeted RNA interference and CRISPR/Cas9 based gene editing in prostate cancer
Suneela Pyreddy1, Arpita Poddar1 2, Cara M. Doherty 2, Paolo Falcaro3 and Ravi Shukla*1
Abstract
Prostate cancer (PC) is the second leading cause of deaths in male population, the advanced form of which continues to be incurable; and nature of the disease being such that it is highly suitable for gene therapy. However, therapy is hampered by lack of appropriate gene delivery agents available. Recently, metal-organic-framework (MOF) biocomposites have seen increasing applications in biomolecular encapsulation and delivery. In this work, a ZIF-C biocomposites are used as gene delivery agents for knockdown of a Laminin 67 kDa receptor protein overexpressed by the gene ribosomal protein RPSA in PC. Feasibility of ZIF-C mediated knockdown of RPSA is demonstrated using RNAi and CRISPR/Cas9. Further enhanced uptake of ZIF-C in cancer cells is achieved by coating of ZIF-C with epigallocatechin-gallate (EGCG), a natural polyphenol obtained from green tea. Cellular transfection assays reveal the gradual expression of ZIF-C delivered RPSA-targeting nucleic acids for up to 96 hours. Quantitative polymerase chain reactions and genomic cleavage detection demonstrate gradual knockdown, with ~20% reduction in RPSA expression that is almost doubled to ~40% on EGCG-mediated targeted cellular uptake.
Presented by
Suneela Pyreddy
Institution
School of science, RMIT university.
Keywords
RNAi, CRISPR/Cas9, gene delivery, MOFs, ZIF-C, Prostate cancer
Fluorescence Based Aptasensors For The Detection Of Neuro-pathological Protein Conformers
Gayatri Bagree1,2,3, Sanje Mahasivam1, Sandeep K. Sharma2,3, Rajesh Ramanathan1, Vipul Bansal1
Abstract
Gold nanoparticles (AuNPs) have been utilized in the development of molecular beacons based on their remarkable ability to act as quenchers of fluorescence.1 In addition, owing to their ability to form efficient and stable complexes with oligonucleotides2, they have been a popular choice for aptasensor development3,4,5. The current study explores the applicability of AuNPs in sensing neuroscience-related proteins. This approach uses fluorophore labelled DNA aptamers specific for alpha-synuclein (a-syn) protein adsorbed onto the surface of AuNPs. This leads to the quenching of fluorescence. Target recognition is achieved through the recovery of fluorescence by aptamer desorption from AuNPs surface due to extremely high affinity and selectivity of the aptamers for a-syn. We demonstrate the importance of a fine balance of binding forces between AuNP-aptamer versus aptamer-target for the working of the sensor. Further, we show that quenching is sensitive to temperature and ratio of AuNP to aptamer concentration; with almost 80% of fluorescence being quenched at a temperature below the melting point of the aptamers. In the presence of a-syn target protein, these aptamers desorb from the AuNP surface in a concentration dependent manner, detected by a simultaneous regain in fluorescence. Our approach provides a simple model for stable and selective sensing for pathological proteins, that can be expanded into a multiplexing system to include a battery of disease-specific target molecules.
1. D. J. Maxwell, J. R. Taylor, S. Nie. J Am Chem Soc. 2002, 124, 9606. 2. P. Vorobjev, A. Epanchintseva, A. Lomzov, A. Tupikin, M. Kabilov, I. Pyshnaya, et al. Langmuir. 2019, 35, 7916. 3. P. Weerathunge, R. Ramanathan, R. Shukla, T. K. Sharma, V. Bansal. Anal Chem. 2014, 86, 11937. 4. T. K. Sharma, R. Ramanathan, P. Weerathunge, M. Mohammadtaheri, H. K. Daima, R. Shukla, et al. Chem Commun. 2014, 50, 15856. 5. P. Weerathunge, R. Ramanathan, V. A. Torok, K. Hodgson, Y. Xu, R. Goodacre, et al. Anal Chem. 2019, 91, 3270.
1. D. J. Maxwell, J. R. Taylor, S. Nie. J Am Chem Soc. 2002, 124, 9606. 2. P. Vorobjev, A. Epanchintseva, A. Lomzov, A. Tupikin, M. Kabilov, I. Pyshnaya, et al. Langmuir. 2019, 35, 7916. 3. P. Weerathunge, R. Ramanathan, R. Shukla, T. K. Sharma, V. Bansal. Anal Chem. 2014, 86, 11937. 4. T. K. Sharma, R. Ramanathan, P. Weerathunge, M. Mohammadtaheri, H. K. Daima, R. Shukla, et al. Chem Commun. 2014, 50, 15856. 5. P. Weerathunge, R. Ramanathan, V. A. Torok, K. Hodgson, Y. Xu, R. Goodacre, et al. Anal Chem. 2019, 91, 3270.
Presented by
Gayatri Bagree
Institution
1Sir Ian Potter NanoBioSensing Facility, NanoBiotechnology Research Laboratory (NBRL), School of Science, RMIT University, Melbourne, Australia; 2Food, Drug & Chemical Toxicology Group, CSIR-Indian Institute of Toxicology Research, Lucknow, India; 3Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
Keywords
Gold nanoparticles, aptamers, alpha synuclein, fluorescence quenching, transient interactions, sensors
▼ Chemical Biology Back to top
Biochemical characterisation of the Haemophilus influenzae PsaA homolog, HIPsaA
Katherine Ganio, Jonathan J Whittal, Ulrike Kappler and Christopher A McDevitt
Abstract
Haemophilus influenzae is a host-adapted pathogen that colonizes the human nasopharynx that can mediate diseases of the upper and lower respiratory tract. Isolates can be found as encapsulated and non-encapsulated forms which both have similar morphology but produce divergent clinical infection. H. influenzae has an array of molecular mechanisms that permit growth and virulence in diverse host niches. Notably, H. influenzae can respond to exogenous, host-mediated and endogenous, i.e. metabolically produced, reactive oxygen and nitrogen stresses. Transition metal ions serve crucial roles in bacterial growth, survival and stress response, but the majority of these mechanisms in H. influenzae remain to be determined. Bioinformatic analyses of H. influenzae 2019 revealed that it encoded two ATP-binding cassette (ABC) transporter solute binding proteins (SBPs) that belonged to the cluster A-I subgroup. Primary sequence analyses suggested that these were orthologs of a manganese-specific (locus tag: C645_00940) and zinc-specific (locus tag: C645_02340) SBPs. Given the central role of manganese in metabolism and resistance to oxidative stress we investigated the biochemical and biophysical properties of C645_00940. We combined recombinant protein purification with in vitro metal binding assays to show that C645_00940 was a manganese-binding SBP. Building on this finding, the gene was renamed as HIPsaA due to the functional and structural similarity to Streptococcus pneumoniae PsaA. Furthermore, these techniques indicate that this SBP is capable of stably binding other first row transition metal ions including zinc, copper, cobalt and nickel. Collectively, this work provides insight into manganese acquisition in H. influenzae and the contribution of this transition metal ion to bacterial virulence.
Presented by
Katherine Ganio
Institution
The University of Melbourne
Keywords
▼ Chemical Engineering Back to top
Conversion of γ‐Valerolactone to Ethyl Valerate over Metal Promoted Ni/ZSM‐5 Catalysts: Influence of Ni0/Ni2+ Heterojunctions on Activity and Product Selectivity
Deshetti Jampaiah, Vijay Kumar Velisoju, Naresh Gutta, Ursula Bentrup, Angelika Brückner, Suresh K. Bhargava, Venugopal Akula
Abstract
Catalysts containing two active metal components have been widely studied in different reactions e. g. CO2 methanation, catalytic hydrotreating of bio‐liquids and CO oxidation, owing to their improved activity and selectivity toward the desired products.1-3 The combined geometric and electronic effects are the key reasons for cooperative and synergistic catalytic performances between two metals present in the catalysts. In our work, promoter (Cr, Mo and W) modified Ni/ZSM‐5 catalysts were explored in the vapour phase conversion of γ‐valerolactone (GVL) to ethyl valerate (EV; gasoline blender) at atmospheric pressure. Among the three different promoters (Cr, Mo and W) tested the Mo‐modified catalyst was found to be the best candidate. In addition, this catalyst was found to be stable up to 50 h reaction time with an insignificant decrease in activity. The good catalytic performance is related to an optimal ratio of acid and hydrogenation functions provided by Ni2+ and Ni0, respectively. In situ FT-IR spectroscopic studies revealed a strong adsorption of GVL on all catalysts which quickly reacts with dosed ethanol by formation of EV, most pronounced on the Mo‐modified catalyst, while VA was identified as side product. These findings suggest the preferred GVL ring opening by cracking the C−O bond on the methyl side of the GVL molecule on this type of catalysts leading to pentenoic acid as intermediate, which is quickly hydrogenated and esterified.
Presented by
Jampaiah Deshetti
Institution
School of Science, RMIT University
Keywords
Biofuel, Ni-based catalysts, Biomass, γ-Valerolactone, in-situ IR
THE 1974 UK FLIXBOROUGH DISASTER
IAN F THOMAS
Abstract
In 1974 the UK Nypro Ltd caprolactam plant exploded killing 28 people and injuring 36 others. A 250 tonne vapour cloud of cyclohexane ignited when it reached a furnace on the site. This, the largest explosion in the UK since WWII, triggered massive improvements in process safety both in the UK and in Australia. Herein the author briefly describes what happened, the chemistry of the processes and his own theory as to the cause. A full paper is also available on request.
Presented by
Dr Ian F Thomas
<ifta@ifta.com.au>
Institution
FORMERLY WITH RMIT UNIVERSITY
Keywords
Unconfined Vapour Cloud Explosion; UVCE; Cyclohexane; Caprolactam; Nylon 6
▼ Computational Chemistry Back to top
Employing the Ferroelectric Material CuInP2S6 to Tune the Band Alignment and Optics of van der Waals Heterostructures
Patrick D. Taylor, Sherif Abdulkader Tawfik, and Michelle J.S. Spencer
Abstract
Two-dimensional (2D) materials have been rigorously explored as potential candidates for miniaturising our current electronic and photonic devices and their components, such as diodes, photodiodes, light-emitting diodes (LEDs), and solar cells. Furthermore, bi-layer materials consisting of two different 2D nanomaterials have been of great interest as these materials (called vdW heterostructures) offer flexibility in designing p-n heterojunctions.1 One particular class of materials can offer a way for designing tuneable p-n junctions. The electronic structure of ferroelectric materials can be controlled by the application of an electric field, changing the ferroelectric polarization direction. In this work we aim to exploit ferroelectric materials as one of the components in the design of vdW heterostructure. We show that CuInP2S6 (CIPS),2 an exciting candidate for room-temperature ferroelectric devices, opens a pathway for tuning the band alignment of vdW heterostructures. Density functional theory, as implemented in the Vienna ab initio simulation package (VASP), was used for the construction and investigation of the structural and electronic properties of each van der Waal heterostructure. In this work we present 19 new tuneable vdW heterostructures and their structural and electronic properties. We find that the two ferroelectric polarisation states in CIPS lead to a difference in the band alignment and a change of the band gap of the material, indicating that the application of an electric field can be used to influence the materials electronic properties. This work offers a method for designing tuneable and atomically thin p-n junctions.
[1] G. Iannaccone, F. Bonaccorso, L. Colombo and G. Fiori. Nat Nanotechnol. 2018, 13, 183-191.
[2] S.A. Tawfik, J.R. Reimers, C. Stampfl and M.J. Ford. J. Phys. Chem. C 2018, 122, 22675-22687.
Presented by
Patrick Taylor
<s3484746@student.rmit.edu.au>
Institution
RMIT University
Keywords
Ferroelectric Materials, 2D nanomaterials, CuInP2S6, vdW Heterostructures, DFT
Computational studies of a novel whey protein-based nutraceutical and its interaction with the peptidoglycan component of lactic acid bacteria
Kevion Darmawan, Tom Karagiannis, Jeff Hughes, Darryl Small, and Andrew Hung
Abstract
Lactoferrin (LF) is a whey protein, known for conferring health advantages, including antimicrobial properties. In its apo form (apo-LF), the anti-bacterial activity is more effective than the other forms because of the sequestering capacity, limiting iron from iron dependent pathogens, including Listeria monocytogenes. Many probiotics from those of lactic acid bacteria (LAB) are known to be resistant to apo-LF because they can grow without iron. Therefore, we proposed that a combination of apo-LF and LAB can potentially enhance the health benefits for human consumption, with apo-LF, α-lactalbumin (α-La), and β-lactoglobulin (β-Lg), acting as the protectants. Past experimental works have performed studies regarding the encapsulation of LAB; nevertheless, the molecular interaction between these two components is poorly understood. Accordingly, molecular dynamics (MD) simulations were utilised to understand the interaction between these proteins and the peptidoglycan component of LAB at spray drying temperatures (68 and 110 °C). The results show that the peptidoglycan component interacts with the edge of β-Lg and the posterior N-lobe of apo-LF through van der Waals, electrostatic, and non-polar solvation interactions. Free energy calculations also illustrated higher binding affinity at 110 °C than 68 °C, indicating that high temperatures are essential to promote effective binding capacity via hydrophobic forces. Additionally, the anti-bacterial motifs and the secondary structure in apo-LF are conserved after thermal processing. Overall, the results highlight that the peptidoglycan component of LAB can bind with apo-LF, α-La, and β-Lg, whose functionalities are preserved following thermal stress and therefore may be of value to future development of nutraceuticals.
Presented by
Kevion Darmawan
Institution
RMIT University
Keywords
Lactic acid bacteria, lactoferrin, spray drying, molecular dynamics simulations
▼ Electrochemistry Back to top
Evaluation of electrocatalytic activity of phase controlled cobalt hydroxide and porous cobalt oxide on oxygen evolution reaction
Oshadie De Silva, Mandeep Singh, Rajesh Ramanathan, Vipul Bansal
Abstract
Electrochemical water splitting has been identified as one of the sophisticated and efficient approaches to generate hydrogen gas as a fuel. The hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are the cathodic and anodic reactions involved in water splitting, where their sluggish reaction kinetics limits the practical applicability.[1] Among them, OER is the most difficult reaction to undergo as it has a four step reaction mechanism. Developing efficient electrocatalysts for the OER in alkaline media can enhance the overall performance of the water splitting reaction.[2] Cobalt hydroxide and oxide have been explored due to the abundance and promising activity. Herein we report that, having mixture of alpha and beta phase in Cobalt hydroxide can reduce the catalytic activity while the pure beta phase can increase the activity which shows low overpotential (369 mV at 10 mA cm-2) with low Tafel slope (96.5 mV dec-1). As we calcinate the hydroxides at two different temperatures (300 °C and 450 °C) to obtain Co3O4 phase, the surface area and the pore volume reduced at 450 °C. Herein, we found that as the temperature increased the surface area can be reduced by ~58% while the pore volume reduced by ~55% which can significantly influence on the activity. Large surface area and high pore volume may facilitate the electrolyte penetration and expose more catalytic active sites with fast oxygen diffusion which exhibits at 300 °C with 232 mV of overpotential at 10 mA cm-2 with low Tafel value (87.8 mV dec-1).[3]
References [1] X. Li, X. Hao, A. Abudula, G. Guan. Nanostructured catalysts for electrochemical water splitting: current state and prospects. Journal of Materials Chemistry A. 2016, 4, 11973. [2] X. Li, L. Zhao, J. Yu, X. Liu, X. Zhang, H. Liu, et al. Water Splitting: From Electrode to Green Energy System. Nano-Micro Letters. 2020, 12, 131. [3] J. Qi, W. Zhang, R. Cao. Porous Materials as Highly Efficient Electrocatalysts for the Oxygen Evolution Reaction. ChemCatChem. 2018, 10, 1206.
References [1] X. Li, X. Hao, A. Abudula, G. Guan. Nanostructured catalysts for electrochemical water splitting: current state and prospects. Journal of Materials Chemistry A. 2016, 4, 11973. [2] X. Li, L. Zhao, J. Yu, X. Liu, X. Zhang, H. Liu, et al. Water Splitting: From Electrode to Green Energy System. Nano-Micro Letters. 2020, 12, 131. [3] J. Qi, W. Zhang, R. Cao. Porous Materials as Highly Efficient Electrocatalysts for the Oxygen Evolution Reaction. ChemCatChem. 2018, 10, 1206.
Presented by
Oshadie De Silva
Institution
RMIT University, Australia
Keywords
Electrocatalysts, OER,Overpotential, Pore volume, Surface area
A Novel approach for the determination of homogeneous kinetics using 2nd HARMONIC FT-AC Voltammetry.
Samridhi Bajaj, Dr. Georgina Armendáriz-Vidales, Dr. Peter Ó Conghaile and Prof. Conor Hogan
Abstract
Electrochemical techniques are the most effective tool for measuring the rates of reactions associated with charge transfers. Comparing experimental responses with simulated experiments is the most accurate approach to determine heterogeneous or homogeneous kinetics (k^o,k_f), but the process is complex, time consuming and requires specialized software. Looking at the variation in cyclic voltammetric (CV) peak parameters as a function of timescale, which are then compared to a standard working curve is another common method, which was pioneered by Nicholson and Shain in the 1960’s. This way a much faster but often less accurate, due in part to subjectivity in defining the CV baseline, especially for the reverse peak.
Here, we describe a novel methodology to determine the value of the homogeneous rate constant k_f, associated with an EC process, in a single forward scan rather than comparing the forward and reverse scans. This approach uses Fourier transform alternating current voltammetry (FT-ACV), and focuses on the harmonics, which have dramatically diminished capacitive background, thus removing the uncertainty associated with the baseline. Because only a single scan is needed to determine the value of k_f, the approach is faster and there is less chance of the data being compromised by electrode passivation, which often occurs on the reverse scan. The accuracy of the methodology was tested by comparison with simulated responses and real data for the oxidation of dopamine.
Presented by
Samridhi Bajaj
Institution
Department of Chemistry, La Trobe University
Keywords
Electrochemistry, Homogeneous kinetics, Fourier transform-alternating current voltammetry.
▼ Food Chemistry Back to top
A simple RP-HPLC method for the simultaneous determination of citrulline and arginine in Australian cucurbits
Joel B. Johnson, Kerry B. Walsh and Mani Naiker
Abstract
Citrulline is a non-proteinaceous amino acid found in high concentrations in melons and other cucurbits.1 Via its subsequent biotransformation into arginine by the kidneys, citrulline plays important roles in nitric oxide production, vasodilation and ammonia detoxification. Dietary citrulline supplementation provides a range of benefits, including improved endothelial and cardiovascular function,2 and enhanced exercise capacity and post-exercise recovery.3 Hence there is considerable interest in developing citrulline-rich food products from melon cultivars containing high citrulline contents.4 However, most current methods for citrulline and arginine quantification require time-consuming chemical derivatization steps and use higher-end detection methods such as fluorescence detection. We report a simple, rapid reversed-phase high performance liquid chromatography method using ultraviolet detection (RP-HPLC-UV), without requiring analyte derivatization. Following optimisation of the column type, mobile phase composition, flow rate and detection wavelength, the method showed good linearity (R2=0.9995), a low limit of detection (0.6 and 0.3 mg L-1 for citrulline and arginine, respectively) and high repeatability (0.2% relative standard deviation). The optimised method was used to quantify the citrulline and arginine content of 13 Central Queensland fruit and vegetable cultivars, primarily cucurbits. The highest citrulline content and citrulline:arginine ratio were found in mature colocynth (Citrullus colocynthis) fruit (39.2 mg/g DWB), while red watermelon (Citrullus lanatus) flesh also contained high levels of citrulline (22.9 mg/g) and arginine (8.1 mg/g). Lower concentrations of citrulline and arginine were found in other melon cultivars, pumpkins and squash samples. This HPLC method may find use for the rapid screening of citrulline and arginine contents.
References 1. V. Joshi V, A.R. Fernie. Amino Acids. 2017, 49, 1543-1559. 2. C. Papadia, S. Osowska, L. Cynober, A. Forbes. Clin Nutr. 2018, 37, 1823-1828. 3. O.Á. Huerta, H.A. Domínguez, G. Barahona-Fuentes. Nutr Hosp. 2019, 36, 1389-1402. 4. H. Speer, N.M. D’Cunha, M.J. Davies, A.J. McKune, N. Naumovski. Beverages. 2020, 6, 11.
References 1. V. Joshi V, A.R. Fernie. Amino Acids. 2017, 49, 1543-1559. 2. C. Papadia, S. Osowska, L. Cynober, A. Forbes. Clin Nutr. 2018, 37, 1823-1828. 3. O.Á. Huerta, H.A. Domínguez, G. Barahona-Fuentes. Nutr Hosp. 2019, 36, 1389-1402. 4. H. Speer, N.M. D’Cunha, M.J. Davies, A.J. McKune, N. Naumovski. Beverages. 2020, 6, 11.
Presented by
Joel Johnson
<joel.johnson@cqumail.com>
Institution
CQUniversity Australia, School of Health, Medical & Applied Sciences
Keywords
Analytical chemistry, HPLC, amino acids, functional food
▼ Inorganic Chemistry Back to top
Chiral Detection with Fluorescent Coordination Polymers
Shannon Thoonen, Carol Hua
Abstract
Chirality is an intrinsic property of life on Earth. Biological systems have evolved alongside chiral molecules like proteins, DNA, and sugars, which has lasting impacts on the pharmaceutical and food industries. Common drugs like ibuprofen differ in their effectiveness on the human body based on the chiral purity of the dose, and artificial sweeteners like aspartame can taste bitter if unwanted enantiomers are not filtered out prior to consumption. The need to differentiate and separate the enantiomers of chiral compounds has led to the development of chiral sensors: molecular systems that can identify the enantiomeric purity of a sample.
Coordination polymers (CPs) and metal-organic frameworks (MOFs) are ideally suited to chiral sensing. These frameworks consist of extended structures of organic ligands bridging metal centres, and are both easily tuned and potentially porous, enabling the incorporation of small guest compounds into their internal voids. When the parent framework is chiral,1 one enantiomer of a chiral guest molecule will have a stronger interaction with the structure than its opposite. This dichotomy in binding strength can be paired with methods like circular dichroism (CD) spectroscopy and fluorescent techniques to assess a sample’s enantiomeric composition.
This poster presentation describes the synthesis and crystal structure of a chiral CP constructed from a 1,1′-bi-2-naphthol (BINOL) ligand, which acts as a simultaneous fluorescent centre and source of chirality. The ability of this framework to differentiate the enantiomers of chiral guest compounds through fluorescent quenching measurements is also highlighted.
Please contact me via email if you have any questions! I would be happy to arrange a chat.
Coordination polymers (CPs) and metal-organic frameworks (MOFs) are ideally suited to chiral sensing. These frameworks consist of extended structures of organic ligands bridging metal centres, and are both easily tuned and potentially porous, enabling the incorporation of small guest compounds into their internal voids. When the parent framework is chiral,1 one enantiomer of a chiral guest molecule will have a stronger interaction with the structure than its opposite. This dichotomy in binding strength can be paired with methods like circular dichroism (CD) spectroscopy and fluorescent techniques to assess a sample’s enantiomeric composition.
This poster presentation describes the synthesis and crystal structure of a chiral CP constructed from a 1,1′-bi-2-naphthol (BINOL) ligand, which acts as a simultaneous fluorescent centre and source of chirality. The ability of this framework to differentiate the enantiomers of chiral guest compounds through fluorescent quenching measurements is also highlighted.
Please contact me via email if you have any questions! I would be happy to arrange a chat.
Presented by
Shannon Thoonen
<sthoonen@student.unimelb.edu.au>
Institution
The University of Melbourne, School of Chemistry
Keywords
Coordination polymers, metal organic frameworks, chirality, chiral sensing, fluorescence,
Iron regulation by C. elegans ferritins
Sanjeedha S. M. Mubarak, Tess R. Malcolm, Megan J. Maher, Gawain McColl, Guy N. L. Jameson
Abstract
Regulation of iron is required to maintain an optimum cellular concentration range. An excess concentration may catalyse the generation of reactive oxygen species resulting in oxidative cell damage to protein, lipid and DNA while insufficient iron concentrations arrests cell growth and eventually causes cell death [1]. Ferritin is primarily involved in iron storage, iron release and thereby detoxification of cellular iron [2]. This 500 kDa protein consist of 24 subunits and illustrates a spherical architecture, creating an interior cavity that permits iron storage in the form of a ferric oxy-hydroxide mineral [3]. Extensive in-vitro enzymological studies have greatly assisted our understanding but important questions remain. In particular it is not yet fully understood how iron is released from ferritin in-vivo. A clearer understanding could aid iron related disorders, including iron overload (hemochromatosis) or deficiency and anaemia. We propose to answer this fundamental question by using the model organism Caenorhabditis elegans [4] which will allow genetic manipulation to understand the action-response correlation and corresponding mechanisms within the context of a whole organism. Having 60–80 % of C. elegans homologs identified in the human gene pool [4, 5], C. elegans ferritins share a high identity with human heavy chain subunit with conserved ferroxidase site residues [3]. Here we present kinetics and stoichiometry of iron oxidation of recombinant ferritins in comparison with the native protein from C. elegans and recombinant human ferritin homologs to explore mechanisms of iron uptake and release. Structural characterisation of C. elegans ferritins by single crystal X-ray crystallography and cryo-electron microscopy aid understanding of the origin of differences in our biochemical characterisation.
1. Hentze, M.W., M.U. Muckenthaler, and N.C. Andrews. 2004, 117, 3, 285-297. 2. Octave, J.-N., et al. Trends in Biochemical Sciences. 1983, 8, 6, 217-220. 3. Honarmand Ebrahimi, K., P.-L. Hagedoorn, and W.R. Hagen. Chemical reviews. 2015, 115, 1, 295-326. 4. Kaletta, T. and M.O. Hengartner. Nature reviews Drug discovery. 2006, 5, 5, 387-399. 5. Lai, C.-H., et al. Genome research. 2000, 10, 5, 703-713.
1. Hentze, M.W., M.U. Muckenthaler, and N.C. Andrews. 2004, 117, 3, 285-297. 2. Octave, J.-N., et al. Trends in Biochemical Sciences. 1983, 8, 6, 217-220. 3. Honarmand Ebrahimi, K., P.-L. Hagedoorn, and W.R. Hagen. Chemical reviews. 2015, 115, 1, 295-326. 4. Kaletta, T. and M.O. Hengartner. Nature reviews Drug discovery. 2006, 5, 5, 387-399. 5. Lai, C.-H., et al. Genome research. 2000, 10, 5, 703-713.
Presented by
Sanjeedha Mubarak
Institution
university of Melbourne, School of Chemistry
Keywords
A Simple Computational Approach for Predicting Transition Temperatures of Valence Tautomeric Molecular Switches
F. Zahra M. Zahir, Jett T. Janetzki, Robert W. Gable, Lars Goerigk and Colette Boskovic
Abstract
Valence tautomeric (VT) transitions are potentially important for the miniaturization of functional
materials. Octahedral cobalt complexes with dioxolene ligands exhibit such transitions upon application
of an external stimulus. In these complexes an electron transfer occurs from a catecholate (cat2−) ligand
to a low spin (LS) cobalt(III) ion, resulting in a high spin (HS) cobalt(II) ion coordinated to a
semiquinonate (sq•−) ligand,1. The temperature at which an equal proportion of these two forms are
found are known as the transition temperature (T1/2). The ability to computationally predict these
switching temperatures in the candidate molecules prior to synthesis would be a considerable advance
in the development of switchable molecular materials.
In VT complexes with general formula [Co(dbdiox)(dbsq)(N2L)] (dbdiox = 3,5-di-tert-butyl-dioxolene,
in catecholate (dbcat) / semiquinonate (dbsq) form, N2L = ancillary diiminium ligand), the T1/2 between
LS-Co(III)-cat and HS-Co(II)-sq was found to increase with decreasing reduction potential of the
ancillary ligand,2. In this study, we synthesized and characterized the new VT variant
[Co(dbdiox)(dbsq)(MeO-bpy)] and determined the T1/2 to be 336 K. We employed state-of-the-art
density functional theory (DFT) methods to provide (1) accurate electronic description of the tautomers;
(2) a method to obtain accurate relative energies; and (3) a simple model of correlation between the
experimental T1/2 and calculated orbital energies of the ligand. Our results indicate that π-back bonding
effects of the ancillary ligand are the dominant effect governing the T1/2 values. This model will facilitate
the future targeted synthesis of VT compounds with desired T1/2 values.
Presented by
F. Zahra M. Zahir
Institution
University of Melbourne, School of Chemistry
Keywords
Valence Tautomerism, density functional theory, transition temperature
Chat with Presenter
Available July 9th 10 am - 1 pm
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Structure Transformations and Responsive Properties of Porous Iron-based Mixed-Valence Frameworks
Martin P van Koeverden, Deanna M D'Alessandro, Carol Hua, Timothy A Hudson, Guy N L Jameson, Richard Robson, Ashley L Sutton, Brendan F Abrahams
Abstract
Porous materials with switchable magnetic and electrically conductive properties have diverse potential applications in sensing, advanced separations, and energy conversion devices.[1, 2] Constructing porous frameworks from redox-active ligands in multiple valence states, is an important strategy to obtain materials with these properties.[3] Tetraoxolenes have three accessible valence states and tailorable electronic properties. Therefore, they have emerged as promising candidate ligands, in combination with redox-active metals such as Fe, to produce intrinsically conductive and magnetic frameworks.[4-6] We recently demonstrated incorporating a redox-active viologen-like countercation into a mixed-valence Fe–tetraoxolene framework, provides an additional handle to alter the framework properties.[7]
Herein we describe further structural, spectroscopic and transport studies on novel Fe–tetraoxolene frameworks containing methyl viologen (MeV2+) countercations. The compounds undergo structural distortions upon changes in the guest solvent content, as shown by X-ray structural analysis. Although, the structure distortions are subtle, the two solvates exhibit markedly different electronic structures, arising from a transient Fe valence fluctuation in one compound. This disparity in electronic structure between the frameworks produces materials with different magnetic and electrical transport behaviour, affording the tantalising possibility to synthesise porous materials with responsive or reversibly switchable physical properties.
[1] A. E. Thorarinsdottir, T. D. Harris, Chem. Rev. 2020, 120, 8716-8789. [2] L. S. Xie, G. Skorupskii, M. Dincă, Chem. Rev. 2020, 120, 8536-8580. [3] R. Murase, C. F. Leong, D. M. D’Alessandro, Inorg. Chem. 2017, 56, 14373-14382. [4] L. E. Darago, M. L. Aubrey, C. J. Yu, M. I. Gonzalez, J. R. Long, J. Am. Chem. Soc. 2015, 137, 15703-15711. [5] J. A. DeGayner, I.-R. Jeon, L. Sun, M. Dincă, T. D. Harris, J. Am. Chem. Soc. 2017, 139, 4175-4184. [6] R. Murase, C. J. Commons, T. A. Hudson, G. N. L. Jameson, C. D. Ling, K. S. Murray, W. Phonsri, R. Robson, Q. Xia, B. F. Abrahams, D. M. D’Alessandro, Inorg. Chem. 2020, 59, 3619-3630. [7] M. P. van Koeverden, B. F. Abrahams, D. M. D’Alessandro, P. W. Doheny, C. Hua, T. A. Hudson, G. N. L. Jameson, K. S. Murray, W. Phonsri, R. Robson, A. L. Sutton, Chem. Mater. 2020, 32, 7551-7563.
Herein we describe further structural, spectroscopic and transport studies on novel Fe–tetraoxolene frameworks containing methyl viologen (MeV2+) countercations. The compounds undergo structural distortions upon changes in the guest solvent content, as shown by X-ray structural analysis. Although, the structure distortions are subtle, the two solvates exhibit markedly different electronic structures, arising from a transient Fe valence fluctuation in one compound. This disparity in electronic structure between the frameworks produces materials with different magnetic and electrical transport behaviour, affording the tantalising possibility to synthesise porous materials with responsive or reversibly switchable physical properties.
[1] A. E. Thorarinsdottir, T. D. Harris, Chem. Rev. 2020, 120, 8716-8789. [2] L. S. Xie, G. Skorupskii, M. Dincă, Chem. Rev. 2020, 120, 8536-8580. [3] R. Murase, C. F. Leong, D. M. D’Alessandro, Inorg. Chem. 2017, 56, 14373-14382. [4] L. E. Darago, M. L. Aubrey, C. J. Yu, M. I. Gonzalez, J. R. Long, J. Am. Chem. Soc. 2015, 137, 15703-15711. [5] J. A. DeGayner, I.-R. Jeon, L. Sun, M. Dincă, T. D. Harris, J. Am. Chem. Soc. 2017, 139, 4175-4184. [6] R. Murase, C. J. Commons, T. A. Hudson, G. N. L. Jameson, C. D. Ling, K. S. Murray, W. Phonsri, R. Robson, Q. Xia, B. F. Abrahams, D. M. D’Alessandro, Inorg. Chem. 2020, 59, 3619-3630. [7] M. P. van Koeverden, B. F. Abrahams, D. M. D’Alessandro, P. W. Doheny, C. Hua, T. A. Hudson, G. N. L. Jameson, K. S. Murray, W. Phonsri, R. Robson, A. L. Sutton, Chem. Mater. 2020, 32, 7551-7563.
Presented by
Martin van Koeverden
Institution
School of Chemistry, The University of Melbourne
Keywords
conductivity, mixed-valence, coordination polymer, magnetism
Chat with Presenter
Available July 2nd, 2-3 pm; July 9th, 2-3 pm
Hypervalent I(III) Compounds
a = Tania, Dr. Tiffany B. Poynder, Lachlan Sharp-Bucknall, Aishvaryadeep Kaur, Lachlan Barwise, Dr. Mathew T. Flynn, Dr. Sevan D. Houston, Dr. David J. D. Wilson, Prof. Jason L. Dutton,;b =Analia I. Chamorro Orue, Dr. Kasun S. Athukorala Arachchige, Akshay J. Nair, Prof. Jack K. Clegg.
Abstract
Hypervalent I(III) compounds have been used in organic and inorganic reactions since their first reported synthesis.[1] Among these I(III) oxidants, PhI(OTf)2 and PhICl2 have been widely used. The recent findings regarding these two compounds by our research team are represented here.
PhI(OTf)2 has been used as a strong I(III) oxidant for organic and inorganic transformations for decades.[2] The reported syntheses involve in-situ generation of PhI(OTf)2 in the reaction of either PhI(OAc)2 or PhI=O with two equivalents of TMS-OTf. The spectroscopic analysis of these reaction solutions provided data inconsistent with PhI(OTf)2 structure and supporting theoretical calculations rendered other I(III) compounds (figure 1) as more favorable products. Thus, PhI(OTf)2 should not be invoked as the species acting as the oxidant for transformations that have been associated with its use.[3]
PhICl2 has been used widely as a chlorinating agent.[4] However, for best results PhICl2 must be activated by a catalyst. The most cited catalyst for this manipulation is pyridine which has been reported to form [PhI(Pyr)(Cl)]+ cation as a reactive intermediate.[5] However, in our recent findings, we have shown formation of a square planar complex instead of reported cation. This interaction was analysed using NMR, structural, charge density, and theoretical investigations. Also, another potential catalysts that can activate these reactions were studied.[6]
REFERENCES
1. Yoshimura, A.; Zhdankin, V. V., Advances in synthetic applications of hypervalent iodine compounds. Chemical reviews 2016, 116 (5), 3328-3435.
2. Zhdankin, V. V., Hypervalent iodine (III) reagents in organic synthesis. ARKIVOC: Online Journal of Organic Chemistry 2009.
3. Houston, S. D.; Sharp‐Bucknall, L.; Poynder, T. B.; Albayer, M.; Dutton, J. L., PhI (OTf) 2 Does Not Exist (Yet). Chemistry–A European Journal 2020, 26 (68), 15863-15866.
4. Zhao, X.-F.; Zhang, C., Iodobenzene dichloride as a stoichiometric oxidant for the conversion of alcohols into carbonyl compounds; two facile methods for its preparation. Synthesis 2007, 2007 (04), 551-557.
5. Coffey, K. E.; Murphy, G. K., Dichlorination of α-diazo-β-dicarbonyls using (dichloroiodo) benzene. Synlett 2015, 8, 1003-1007.
6. Poynder, T. B.; Orué, A. I. C.; Sharp-Bucknall, L.; Flynn, M. T.; Wilson, D. J.; Arachchige, K. S. A.; Clegg, J. K.; Dutton, J. L., On the activation of PhICl 2 with pyridine. Chemical Communications 2021.
PhI(OTf)2 has been used as a strong I(III) oxidant for organic and inorganic transformations for decades.[2] The reported syntheses involve in-situ generation of PhI(OTf)2 in the reaction of either PhI(OAc)2 or PhI=O with two equivalents of TMS-OTf. The spectroscopic analysis of these reaction solutions provided data inconsistent with PhI(OTf)2 structure and supporting theoretical calculations rendered other I(III) compounds (figure 1) as more favorable products. Thus, PhI(OTf)2 should not be invoked as the species acting as the oxidant for transformations that have been associated with its use.[3]
PhICl2 has been used widely as a chlorinating agent.[4] However, for best results PhICl2 must be activated by a catalyst. The most cited catalyst for this manipulation is pyridine which has been reported to form [PhI(Pyr)(Cl)]+ cation as a reactive intermediate.[5] However, in our recent findings, we have shown formation of a square planar complex instead of reported cation. This interaction was analysed using NMR, structural, charge density, and theoretical investigations. Also, another potential catalysts that can activate these reactions were studied.[6]
REFERENCES
1. Yoshimura, A.; Zhdankin, V. V., Advances in synthetic applications of hypervalent iodine compounds. Chemical reviews 2016, 116 (5), 3328-3435.
2. Zhdankin, V. V., Hypervalent iodine (III) reagents in organic synthesis. ARKIVOC: Online Journal of Organic Chemistry 2009.
3. Houston, S. D.; Sharp‐Bucknall, L.; Poynder, T. B.; Albayer, M.; Dutton, J. L., PhI (OTf) 2 Does Not Exist (Yet). Chemistry–A European Journal 2020, 26 (68), 15863-15866.
4. Zhao, X.-F.; Zhang, C., Iodobenzene dichloride as a stoichiometric oxidant for the conversion of alcohols into carbonyl compounds; two facile methods for its preparation. Synthesis 2007, 2007 (04), 551-557.
5. Coffey, K. E.; Murphy, G. K., Dichlorination of α-diazo-β-dicarbonyls using (dichloroiodo) benzene. Synlett 2015, 8, 1003-1007.
6. Poynder, T. B.; Orué, A. I. C.; Sharp-Bucknall, L.; Flynn, M. T.; Wilson, D. J.; Arachchige, K. S. A.; Clegg, J. K.; Dutton, J. L., On the activation of PhICl 2 with pyridine. Chemical Communications 2021.
Presented by
Tania
<20112563@students.latrobe.edu.au>
Institution
a = La Trobe Institute of Molecular Sciences, La Trobe University, Melbourne; b = School of chemistry and molecular biosciences, University of Queensland, Queensland.
Keywords
Hypervalent, Iodine, Organometallics, Chlorination
Chat with Presenter
Available July 8, 3-4 pm
Mediated Electrosynthesis of AuIII Dichlorides
1=Lachlan Barwise, Lachlan Sharp-Bucknall, Jason Dutton
Abstract
High oxidation state Au complexes have seen a resurgence in interest recently as new methods and synthetic routes are developed and rediscovered. Traditional synthesis of [AuIIIL2Cl2]+ complexes requires the use of chlorinating oxidants that can be costly, or difficult to handle and synthesize.1–3 Recently our group has presented a method for the oxidative chlorination of AuI using IIII species.4 Through electrochemical means achieving the II/III oxidation potential for synthesizing PhICl2 occurs at a similar voltage to the AuI/III transition, but can be effectively bypassed by electrochemical oxidization of Cl-, allowing attack of PhI at lower voltages than required for the II/III transition to generate the PhICl2 oxidant used for the AuI/III oxidation.5,6
In this work we present multiple mediated electrochemical approaches to accessing AuIII dichlorides via electro-oxidation of Cl- ions and in-situ generation of PhICl2. Using an IKA brand Electrasyn 2.0 potentiostat, Cl- radicals were generated holding +2 V in either aqueous or immiscible solvent systems of either saturated KCl or 10 M HCl as both electrolyte and reagent. Dependent on solvent system employed, both in-cell and ex-cell methods were seen to be sufficient to oxidize AuI pyridyl species. While the in-cell route only proceeded within a spilt electrochemical cell, the yield of the ex-cell method could be enhanced by the in-situ synthesis of PhICl2 from addition of PhI to a 9:1 H2O/DCM solution. This preliminary work shows mediated electrosynthesis with a nucleophilic halogen is a valid route for the synthesis of stable AuIIIL2X2 species.
Presented by
Lachlan Barwise
<17371166@students.latrobe.edu.au>
Institution
1=Department of Chemistry and Physics, La Trobe University, Melbourne, VIC, Australia
Keywords
Inorganic Chemistry, Electrochemistry, Gold Chemistry
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Available Friday 9th July 2PM-3PM
▼ Materials Chemistry Back to top
Ultrasonic spray pyrolysis of tin oxide thin films for transparent electrodes
Jaewon Kim, and Enrico Della Gaspera
Abstract
Transparent conductive oxides (TCOs) are metal oxide materials that are usually doped to enhance their electrical conductivity while keeping their optical transmittance. TCOs can be used for optoelectronic devices such as smartphones, laptops, solar panels, LED displays, and smart windows. Tin doped indium oxide (ITO) is commonly used for TCO applications. However, indium is about 10 times more expensive than Zn and Sn, which causes an increased manufacturing cost. Tin oxide (SnO2) with suitable dopants is one of the most attractive alternatives for TCOs because it has both excellent electrical and optical properties. Among all deposition methods for TCO, spray coating is beneficial because it allows for high-quality films to be fabricated inexpensively with large area scalability and precise control of thickness compared to PVD and CVD methods. In this study, I will present the deposition of SnO2 films doped with either antimony (ATO) or fluorine (FTO) using ultrasonic spray pyrolysis. A precursor solution including both tin and dopant precursors is sprayed on a hot substrate resulting in the precursor decomposition and the concurrent formation of the thin film. Characterizations of the SnO2 films including SEM, XRD, UV-Vis-NIR spectroscopy, XPS and electrical conductivity are performed to analyze the effect of many deposition parameters including substrate temperature, doping concentration, and film thickness. With this method, we have achieved typical sheet resistances of ~20 Ohm/sq at >85 % of transmittance in the visible range for optimized coatings which is comparable to commercial FTO products.
Presented by
Jaewon Kim
Institution
RMIT University, School of Science,
Keywords
doping, optoelectronics, SnO2, solution-processing, thin films, transparent electrodes
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Available July 08th-09th, 4 pm-5pm, AEST
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Heterometallic Metal Organic Frameworks for Gas Separation and Sensing Application
Karuppasamy Gopalsamy, Mohammed Waqas Kahn & Ravichandar Babarao
Abstract
Metal-organic frameworks (MOFs) have emerged as a special class of hybrid nanoporous materials. The variation of metal oxides and the vast choice of controllable organic linkers allow the pore size, volume and functionality of MOFs to be tailored for specific applications. Separation of oxygen (O2) from air (78% N2 and 20% O2) and sensing of harmful gases are consider as a challenging issue. In the present study, we use multiscale modelling technique including both density functional theory calculations (DFT) and Monte Carlo (MC) simulation to study the adsorption-based storage and separation properties of heterometallic MOF structures. The electronic structure and the binding energies of O2 and N2 molecules over several MOF structures containing redox-active transition metals (Fe, Mn, Co Ni and Zn) oxide units and the nitrogen-containing linker have been calculated using DFT based on UM06L functional employing with def2-TZVP basis set. Both the O2 storage and separation properties have been calculated with the help of grand canonical Monte Carlo simulation techniques at ambient conditions. Similarly, the sensing properties of various redox-active transition metals show different sensing behavior and the Mn – substituted MOF structure show selective sensing of NO2 gas over gases. The DFT calculated binding energies validates the experimental findings
Presented by
Ravichandar Babarao
Institution
RMIT University
Keywords
MOFs, gas separation, storage, sensing, toxic gases, simulation
▼ Medicinal Chemistry Back to top
Alternate Synthesis & Structural Elaboration of 2 Aminobenzimidazole Antimalarials
Jomo Kigotho (1), Shane Devine (1), Darren Creek (2), Raymond Norton (1), and Peter Scammells (1)
Abstract
Malaria is a parasitic disease caused by species of Plasmodium and infects over 200 million people each year, resulting in over 400,000 deaths. (1) While these numbers have been progressively decreasing annually, the COVID-19 pandemic will likely cause an increase in these numbers due to disruptions in the control and prevention of malaria. Resistance to frontline therapies is currently emerging, requiring the development of new antimalarials operating via novel mechanisms of action. A series of 2 aminobenzimidazoles (ABIs), containing a crucial N1 phenol, were found to be potent inhibitors of both drug sensitive and drug resistant strains of Plasmodium falciparum, suggesting a possible novel mechanism of action. (2) Substitution around the phenol was explored with various substituents leading to improved antimalarial activity, while benzimidazole substitution had yet to be explored due to regioselectivity issues in the synthesis. An alternate synthetic route was developed to explore the positional impact of various substituents and all compounds were assessed for antiparasitic activity against P. falciparum. Several substituents improved antimalarial activity, exemplified by a 5',6' dimethylated ABI which was 10-fold more potent than the unsubstituted parent compound, with an IC50 of 5.4 ± 0.3 nM. A major metabolic pathway of phenolic compounds in the body is glucuronidation so the effect of different substituents on this metabolic rate was evaluated. Preliminary results have shown that the glucuronidation rate can be reduced through benzimidazole substitution.
(1) World Malaria Report 2020; World Health Organisation: Geneva, 2020.
(2) Devine, S. M.; Challis, M. P.; Kigotho, J. K.; Siddiqui, G.; De Paoli, A.; Macraild, C. A.; Avery, V. M.; Creek, D. J.; Norton, R. S.; Scammells, P. J., Discovery and Development of 2-Aminobenzimidazoles as Potent Antimalarials. Eur. J. Med. Chem. 2021, 113518.
Presented by
Jomo Kigotho
Institution
(1) Medicinal Chemistry and (2) Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria, Australia
Keywords
Malaria, Aminobenzimidazoles, Antimalarials, Phenols
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Available July 12th, 2-3 pm
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When Chemistry meets Structural Biology: The first X-ray Structure of the Adenosine A1 Receptor
Manuela Jörg
Abstract
Irreversible ligands, which are compounds that are able to form a covalent bond with a protein of interest, have proven to be valuable drugs and pharmacological tools in drug discovery. Recent advances in the field, which made it possible to obtain ligand-bound X-ray structures by co-crystallizing G protein-coupled receptors (GPCRs) with covalently bound probes, have been one of the major drivers behind the increased interest in the development of novel irreversible probes targeting GPCRs.1 Here, we will present our quest to solve the first active- and inactive-state X-ray structure of the adenosine A1 receptor.2 This includes our efforts to obtain the first X-ray structure of the adenosine A1 receptor, which was stabilized using DU-172, an irreversible antagonist.2 Furthermore, we have successfully designed, synthesized and evaluated novel irreversible agonists of the adenosine A1 receptor,2 which offer an attractive starting point for a range of experiments including our quest to solve the first active-state X-ray structure of the adenosine A1 receptor.
Presented by
Manuela Jorg
Institution
Monash University & Newcastle University (UK)
Keywords
Structural Biology, X-ray Structures, GPCRs, Adenosine Receptors
The Development of Biased Bitopic Ligands Acting at the A1 Adenosine Receptor as Cardioprotective Agents
J. Kyle Awalt, Manuela Jörg, EeVon Moo, Anh Nguyen, Lauren May, Peter Scammells
Abstract
The adenosine A1 receptor (A1R) is a therapeutic target for its ability to provide cardio protection during episodes of myocardial ischemia and reperfusion injury. To date, clinical translation of prototypical A1R agonists has been hindered due to dose-limiting adverse effects, such as bradycardia and hypotension. Previously, we demonstrated that the biased, bitopic agonist VCP746, consisting of an adenosine pharmacophore linked to an allosteric moiety, can stimulate cardioprotective A1R signaling effects in the absence of unwanted bradycardia.1 This study aimed to investigate the structure−activity relationships of VCP746 through a series of modifications focussing on the linker moiety. A series of novel derivatives of 1 differing in the flexibility, length and nature of the linker were synthesized and pharmacologically evaluated. Our findings demonstrate that the linker is tolerant of several modifications including added rigidity, as even the most rigid ligands retained most, if not all, of the activity and bias. This indicates that the bitopic ligands do not require a great amount of flexibility for the two pharmacophores to find their appropriate binding sites, allowing future, more drug-like ligand designs to include fewer freely rotatable bonds.
(1) Aurelio, L.; Baltos, J. A.; Ford, L.; Nguyen, A. T. N.; Jörg, M.; Devine, S. M.; Valant, C.; White, P. J.; Christopoulos, A.; May, L. T.; et al. A Structure-Activity Relationship Study of Bitopic N6-Substituted Adenosine Derivatives as Biased Adenosine A1 Receptor Agonists. J. Med. Chem. 2018, 61, 2087–2103.
(1) Aurelio, L.; Baltos, J. A.; Ford, L.; Nguyen, A. T. N.; Jörg, M.; Devine, S. M.; Valant, C.; White, P. J.; Christopoulos, A.; May, L. T.; et al. A Structure-Activity Relationship Study of Bitopic N6-Substituted Adenosine Derivatives as Biased Adenosine A1 Receptor Agonists. J. Med. Chem. 2018, 61, 2087–2103.
Presented by
Kyle Awalt
Institution
Medicinal Chemistry and Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
Keywords
▼ Nanochemistry Back to top
Control over the reaction in Ag prisms with Au3+ ions through Plasmon-mediated chemical reaction (PCMR).
Sanje Mahasivam, Sushrut Bhanushali, Rajesh Ramanathan, Murali Sastry, Vipul Bansal,
Abstract
Surface plasmons are collective free electron oscillations exhibited by noble metals (such as Ag, Au, and Cu) at nanoscale dimensions. The external electromagnetic field interacts with the free electron and produces remarkable optoelectronic properties to the materials. Noble metals nanoparticles can concentrate incident electromagnetic waves and produce intense near field enhancement, hot carriers, and thermalization of these localised surface plasmon excitations have received significant attention by researchers to harness these phenomena for driving chemical reactions. Anisotropic nanoparticles such as nanoprisms exhibit multiple LSPR modes. These modes can selectively be photo-excited using narrow bandwidth of wavelengths which leads to localised hot spots within the nanoparticle. This avenue can be used as an approach to control the site selectivity of reactions on a nanoparticle. Galvanic replacement (GR) is a spontaneous reaction that occurs due to the difference in the standard electrode potential of two components leads to the oxidation of the component having the lower reduction potential, while reduction of the second component leading to interesting nanoparticle morphologies such as nanoshells, nanocages, nanoframes . We report selective photoexcitation of LSPR modes as a means to control the chemical reaction sites in silver nanoprisms by taking galvanic replacement as a probe the site-selectivity. We attribute this effect to the hot-electron injection process at the sub-particle sites (plasmonic ‘hot-spots’) where localised plasmon eigenmodes drive selective reactivity. Our approach allows the mapping of plasmon-driven sub-particle reactions with a high spatial resolution.
Presented by
Sanje Mahasivam
<s3696163@student.rmit.edu.au>
Institution
RMIT University
Keywords
silver nanoprisms, galvanic replacement reaction, plasmons, photomodulation, hot electrons, chemical reactions
METALLO-NANODROPLETS FOR CATALYSIS AND NANOSTRUCTURE FABRICATION
Lei Bao, Haitao Yu, Brendan Dyett, Miaosi Li
Abstract
Surface nanodroplets are referred to small droplets with attoliter to femtoliter in volume and immobilised on substrates in contact with an immiscible liquid phase. The unique microenvironment of surface nanodroplets renders advanced features for miniaturising process and reactions with high efficiency[1,2]. The liquid-liquid interface between nanodroplets and the surrounding phase allows for extended droplet lifetime as well as for reagents imparting from one phase to the other. Within droplets, reactions are compartmentalised and accelerated due to the high surface area-to-volume ratio of nanodroplets [3].
In this work, we show in situ formation and assembly of gold-thiolate nanostructures in surface nanodroplets. Each droplet served as a nanocompartment to confine the nucleation and growth of the gold nanomaterials. The as-formed gold-functionalised droplets can facilitate a catalytic reaction, leading to a fast fluorescent quench of Nile Red accumulated in droplets.
Moreover, we show that spontaneous assembly of gold(I)-thiolate complex occurred inside droplets. The composition of droplets and the substrate wettability are both key elements to alter these assemblies. The obtained gold-thiolate complex with active gold atoms can serve as scaffolds to enable the selective growth of gold spikes on the top, which have been regarded as favourable structures for surface-enhanced Raman scattering (SERS) substrates [4]. Our results herein highlight the potentials of surface nanodroplets as novel miniaturisation platforms for nanomaterial synthesis, nanostructure fabrication, and catalytic reaction in nanoscale.
References
[1] L. Bao, A. R. Rezk, L. Y. Yeo, X Zhang. Small, 2015, 11, 4850-4855. [2] X. Zhang, Z. Lu, H. Tan, L. Bao, Y. He, C. Sun, D. Lohse. Proc. Natl. Acad. Sci. U.S.A, 2017, 112, 9253-9257. [3] M. Li, B. Dyett, H. Yu, H. V. Bansal, X Zhang. Small, 2019, 15, 1804683. [4] Q. Shi, D. E.Gómez, D. Dong, D. Sikdar, R. Fu, Y. Liu, Y. Zhao, D-M. Smilgies, W. Cheng. Adv. Mater, 2019, 31, 1900989.
In this work, we show in situ formation and assembly of gold-thiolate nanostructures in surface nanodroplets. Each droplet served as a nanocompartment to confine the nucleation and growth of the gold nanomaterials. The as-formed gold-functionalised droplets can facilitate a catalytic reaction, leading to a fast fluorescent quench of Nile Red accumulated in droplets.
Moreover, we show that spontaneous assembly of gold(I)-thiolate complex occurred inside droplets. The composition of droplets and the substrate wettability are both key elements to alter these assemblies. The obtained gold-thiolate complex with active gold atoms can serve as scaffolds to enable the selective growth of gold spikes on the top, which have been regarded as favourable structures for surface-enhanced Raman scattering (SERS) substrates [4]. Our results herein highlight the potentials of surface nanodroplets as novel miniaturisation platforms for nanomaterial synthesis, nanostructure fabrication, and catalytic reaction in nanoscale.
References
[1] L. Bao, A. R. Rezk, L. Y. Yeo, X Zhang. Small, 2015, 11, 4850-4855. [2] X. Zhang, Z. Lu, H. Tan, L. Bao, Y. He, C. Sun, D. Lohse. Proc. Natl. Acad. Sci. U.S.A, 2017, 112, 9253-9257. [3] M. Li, B. Dyett, H. Yu, H. V. Bansal, X Zhang. Small, 2019, 15, 1804683. [4] Q. Shi, D. E.Gómez, D. Dong, D. Sikdar, R. Fu, Y. Liu, Y. Zhao, D-M. Smilgies, W. Cheng. Adv. Mater, 2019, 31, 1900989.
Presented by
Lei Bao
Institution
STEM College, RMIT University
Keywords
nanodroplets, self-assembly, nanostructures, gold, catalysis
Chat with Presenter
Available 5th July 2.30 to 3.30 pm
▼ Organic Chemistry Back to top
Synthesis of Acyl Phosphoramidates Employing a Modified Staudinger Reaction
Iain Currie,* and Brad E. Sleebs*
Abstract
A one step synthesis of acyl phosphoramidates from a variety of functionalized acyl azides has been developed employing trimethylsilyl chloride as an activating agent in a modified Staudinger reaction. The methodology was further adapted to include the in situ generation of the acyl azides from a diverse selection of carboxylic acids and hydrazide starting synthons. The reaction scope was extended to include the synthesis of imidodiphosphates and the natural product Microcin C
Presented by
Iain Currie
<currie.i@wehi.edu.au>
Institution
The Walter and Eliza Hall Institute of Medical Research, Wurundjeri land, Parkville, Victoria, 3052, Australia.
Keywords
acyl phosphoramidate, Staudinger reaction, azides, natural product, nucleoside antibiotic
▼ Peptide Chemistry Back to top
Peptide BDNF mimetics with central and peripheral nervous system actions
Susan E Northfield, Qingqing Lin, Simon S. Murray, Richard A. Hughes
Abstract
Neurotrophins are a family of growth factors consisting of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), and neurotrophin-4/5 (NT-4/5). They exert their effects as homodimers, via the pan-neurotrophic receptor p75NTR, and/or their respective tropomyosin-kinase related (Trk) receptor. Often, they are biased toward one receptor on a specific cell type, resulting in vastly different effects. For example, BDNF has a pro-myelinating effect in the peripheral nervous system (PNS) via the p75NTR receptor. However, in the CNS, BDNF elicits a comparable effect via its corresponding Trk receptor: TrkB. The effects of BDNF are mediated by distinct ‘loop regions’ of the BDNF homodimer interacting with the receptors. These multiple-receptor actions of BDNF, along with its unfavourable pharmacokinetic properties, have made it a poor candidate for therapeutic use. To overcome these difficulties, we have developed structural peptide mimetics of different loop-regions of BDNF, which are able to be produced in greater yields than the parent neurotrophin, are proteolytically stable, and importantly are selective for a single receptor subtype. This poster outlines the design, development and analysis of these peptide mimetics as potential therapeutic leads, but more immediately as chemical biology tools to study demyelinating diseases.
Presented by
Susan Northfield
<susan.northfield@unimelb.edu.au>
Institution
Department of Biochemistry & Pharmacology, The University of Melbourne
Keywords
Peptide Chemistry, Chemical Biology, Mimetics
Chat with Presenter
Available July 9th 1.30 - 2.30pm
Expanding the peptide synthesis toolkit to produce bicyclic peptide mimetics for drug discovery
Qingqing Lin, Denham Hopper, Haoyue Zhang, Jordan Syris Qoon, Zihan Shen, John A. Karas, Richard A. Hughes, Susan E. Northfield
Abstract
The design and synthesis of cyclic peptides is a widely established practice in the field of peptide chemistry. This has been further expanded by the development of orthogonal chemical reactions allowing for production of more chemically complex peptides. One such reaction is the use of 1,3-dichloroacetone (DCA) to selectively link free cysteine side-chains via an acetone bridge. Herein, we examine for the first time the utility of this reaction to synthesise bicyclic dimeric peptides.
We synthesised six head-to-tail cyclic peptides, each possessing a single cysteine residue, and created bicyclic dimeric peptides by linking two copies of the cyclic peptide together via an acetone linker using DCA. We systematically investigated a range of reaction conditions, including stoichiometry of reagents, peptide concentration, reaction pH and buffer composition. We were successfully able to identify the optimum conditions for peptide dimerisation for our six peptide sequences and have use these results to produce an overall guide for preparing acetone-linked bicyclic peptides. The peptides were subsequently analysed for proteolytic stability in human serum and were observed to still be fully intact after 48 hours. This study provides valuable insights into the use of DCA as a tool in peptide synthesis. The non-reducible nature of the acetone linker between pairs of cysteine residues makes the DCA dimerisation reaction attractive compared to the better-known disulfide bond approach.
We synthesised six head-to-tail cyclic peptides, each possessing a single cysteine residue, and created bicyclic dimeric peptides by linking two copies of the cyclic peptide together via an acetone linker using DCA. We systematically investigated a range of reaction conditions, including stoichiometry of reagents, peptide concentration, reaction pH and buffer composition. We were successfully able to identify the optimum conditions for peptide dimerisation for our six peptide sequences and have use these results to produce an overall guide for preparing acetone-linked bicyclic peptides. The peptides were subsequently analysed for proteolytic stability in human serum and were observed to still be fully intact after 48 hours. This study provides valuable insights into the use of DCA as a tool in peptide synthesis. The non-reducible nature of the acetone linker between pairs of cysteine residues makes the DCA dimerisation reaction attractive compared to the better-known disulfide bond approach.
Presented by
Qingqing Lin
Institution
The University of Melbourne, Department of Biochemistry & Pharmacology
Keywords
1,3-Dichloroacetone, multicyclic peptides, cysteine
▼ Structural biology Back to top
Inhibiting Glutathione Transferase P1 (GSTP1) with Ruthenium-based Metallodrugs: Do they work as designed?
Claire M. Weekley, Anthony Cerra, Paul J. Dyson, Craig J. Morton and Michael W. Parker
Abstract
Glutathione Transferase P1 (GSTP1) is a detoxification enzyme that conjugates glutathione to toxic molecules, marking them for cellular export. This process also removes drugs from cells, and GSTP1 has been identified as a factor in the development of resistance to chemotherapy, especially in ovarian cancer cells (1). Platinum (2) and ruthenium (3) drugs have been developed to inhibit GSTP1 and they have demonstrated efficacy in ovarian cancer cell lines. While metallodrugs have been designed to bind GSTP1 at its active sites, there is evidence that the protein also binds metals via cysteine residues at its dimer interface (4).
We have designed a ruthenium-based inhibitor of GSTP1 to bind multiple sites across the GSTP1 dimer, including at the dimer interface, with the aim of strengthening the drug-protein interaction and improving the inhibitory effect of ruthenium-based GSTP1 inhibitors. Here, we use biophysical and structural biology methods to characterise inhibitor-GSTP1 interactions and X-ray absorption spectroscopy to explore the cellular fates of the ruthenium drugs and determine if these inhibitors work as expected.
1. L Sawers et al. Br. J. Cancer 2014, 111, 1150–1158. 2. LJ Parker et al. Chem. Eur. J. 2011, 17, 7806–7816. 3. WH Ang et al. Angew. Chem., Int. Ed. 2009, 48, 3854–3857. 4. De Luca et al. PNAS 2019, 116, 13943-12951.
We have designed a ruthenium-based inhibitor of GSTP1 to bind multiple sites across the GSTP1 dimer, including at the dimer interface, with the aim of strengthening the drug-protein interaction and improving the inhibitory effect of ruthenium-based GSTP1 inhibitors. Here, we use biophysical and structural biology methods to characterise inhibitor-GSTP1 interactions and X-ray absorption spectroscopy to explore the cellular fates of the ruthenium drugs and determine if these inhibitors work as expected.
1. L Sawers et al. Br. J. Cancer 2014, 111, 1150–1158. 2. LJ Parker et al. Chem. Eur. J. 2011, 17, 7806–7816. 3. WH Ang et al. Angew. Chem., Int. Ed. 2009, 48, 3854–3857. 4. De Luca et al. PNAS 2019, 116, 13943-12951.
Presented by
Claire Weekley
Institution
Department of Biochemistry and Pharmacology, The University of Melbourne
Keywords
Metallodrugs, Structural Biology, Ruthenium,
Chat with Presenter
Available July 12, 2-3 pm
Discovery of new inhibitors of transthyretin via virtual screening of small molecules
Jia Truong, Samantha Richardson, Jessica Holien
Abstract
Transthyretin (TTR) distributes thyroid hormone around the body via blood and the brain via cerebrospinal fluid. As hypothyroidism being associated with hypomyelination of nerves, it was unexpected to find that TTR null mice display hypermyelination and increased oligodendrogenesis than in wildtype mice. Therefore, drugs that inhibit TTR may potentially become new treatments for demyelinating diseases, such as multiple sclerosis.
This study aims to identify small molecule inhibitors of TTR by virtual screening. Two druggable sites on the protein were identified and a virtual library of commercially available compounds was docked against these sites using a rigid docking algorithm. The top hits covering a large chemical space were purchased and will be tested for dose-response affinity to TTR via surface plasmon resonance. Compounds that show promise will be assayed in cell culture to test their effect on myelination of nerve cells.
This study aims to identify small molecule inhibitors of TTR by virtual screening. Two druggable sites on the protein were identified and a virtual library of commercially available compounds was docked against these sites using a rigid docking algorithm. The top hits covering a large chemical space were purchased and will be tested for dose-response affinity to TTR via surface plasmon resonance. Compounds that show promise will be assayed in cell culture to test their effect on myelination of nerve cells.
Presented by
Jia Quyen Truong
<jia.truong@rmit.edu.au>
Institution
School of Science, STEM College, RMIT University
Keywords
Demyelination disease, transthyretin, structure-based drug design, virtual screening, drug discovery
Chat with Presenter
Available July 12, 2-4 pm
Watch Presentation
Crystal structure of a complex between the electron-transfer partners arsenite oxidase and cytochrome c552, from the arsenite respiring bacterium Pseudorhizobium banfieldii str. NT-26 .
Nilakhi Poddar, Joanne M. Santini, Megan J. Maher.
Abstract
Arsenic is a widely distributed toxic metalloid that poses a great threat to human health by contaminating ground water systems [1]. Arsenic exists in inorganic forms: arsenite (AsO33-) and arsenate (AsO43-) are toxic. Although arsenic is hazardous to human health, some prokaryotes have developed unique mechanisms that utilise arsenite (AsO33-) and arsenate (AsO43-) for respiration.
Such prokaryotes can respire using toxic arsenic oxyanions as an energy source. For example, the organism Rhizobium sp. NT-26, respires with arsenite and employs the arsenite oxidase enzyme (Aio) for its crucial respiratory activity, which catalyzes the oxidation of arsenite (AsO33-) to arsenate (AsO43-). The Aio enzyme consists of a large catalytic subunit (AioA), which contains a molybdenum centre, 3Fe-4S cluster, and a small subunit (AioB) containing a Rieske 2Fe-2S cluster. Arsenite is oxidized to arsenate at the Mo site, concomitantly reducing Mo(VI) to Mo(IV) [2]. The electrons are passed to the 3Fe-4S cluster, the Rieske cluster and finally to an electron acceptor, which is cytochrome c552 (Cyt c552) [2-3]. Structures of interprotein transfer complexes form complexes via extensive electrostatic interaction and are very transient in nature [4]. To date, the structure of the Aio and Cyt c552 complex has not been investigated, and the kinetics and thermodynamics of Aio to Cyt c552 interaction are unknown. In this study, we describe the structure of the Aio/Cyt c552 complex, determined by X-ray crystallography. The structure provides insight into the mechanism and specificity between the partner proteins during electron transfer.
References [1] H. V. Aposhian, M. M. Aposhian. Arsenic toxicology: five questions. Chem Res Toxicol. 2006, 19, 1. [2] T. P. Warelow, M. Oke, B. Schoepp-Cothenet, J. U. Dahl, N. Bruselat, G. N. Sivalingam, et al. The respiratory arsenite oxidase: structure and the role of residues surrounding the rieske cluster. PLoS One. 2013, 8, e72535. [3] P. J. Ellis, T. Conrads, R. Hille, P. Kuhn. Crystal structure of the 100 kDa arsenite oxidase from Alcaligenes faecalis in two crystal forms at 1.64 Å and 2.03 Å. Structure. 2001, 9, 125. [4] D. Leys, N. S. Scrutton. Electrical circuitry in biology: emerging principles from protein structure. Curr Opin Struct Biol. 2004, 14, 642.
References [1] H. V. Aposhian, M. M. Aposhian. Arsenic toxicology: five questions. Chem Res Toxicol. 2006, 19, 1. [2] T. P. Warelow, M. Oke, B. Schoepp-Cothenet, J. U. Dahl, N. Bruselat, G. N. Sivalingam, et al. The respiratory arsenite oxidase: structure and the role of residues surrounding the rieske cluster. PLoS One. 2013, 8, e72535. [3] P. J. Ellis, T. Conrads, R. Hille, P. Kuhn. Crystal structure of the 100 kDa arsenite oxidase from Alcaligenes faecalis in two crystal forms at 1.64 Å and 2.03 Å. Structure. 2001, 9, 125. [4] D. Leys, N. S. Scrutton. Electrical circuitry in biology: emerging principles from protein structure. Curr Opin Struct Biol. 2004, 14, 642.
Presented by
NILAKHI PODDAR
Institution
School of Chemistry, Faculty of Science and The Bio21 Institute Molecular Science and Biotechnology Institute, The University of Melbourne.
Keywords
X-ray crystallography, electron transfer complex.