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Research Groups | |
The Thordarson Group - ResearchBio-mimetic ChemistryThe most complex and elegant examples of "nanotechnology" come from Nature. In our group we first look to Nature for inspiration when it comes to solving the problems we are currently dealing with in nanotechnology (e.g., biosensors or tissue engineering). This is the philosophy of bio-mimetic chemistry, which underpins most of the work in our group. OverviewOur main research interest are in the broader area of:
At the core of nearly all of our work is the art of synthetic organic chemistry, however, we also apply techniques from across the whole spectrum of chemistry (physical, inorganic, organic, supramolecular and surface chemistry) as well as biochemistry and biology. Methods (synthesis and/or self-assembly) to direct the assembly of functional molecules are of particular interest to us as are methods to analyse nanostructures, e.g. by the use of scanning probe microscopy (AFM and STM) and other advanced characterisation tools. BioelectronicsWe are developing novel ways to control the function of redox proteins using light as the external input signal. The focus will be on using synthetic chromophores, conjugated either to proteins (direct activation) or to biological co-factors such as NAD, nicotinamide adenine dinucleotides (indirect activation). In the second project, we have shown that our photocatalyst is capable of reducing NAD and we are now currently optimising its performance by synthesizing NAD modified with our photocatalyst.
[1] Joshua R. Peterson, Trevor A. Smith and Pall Thordarson, Photoinduced reduction of catalytically and biologically active Ru(II)bisterpyridine-cytochrome c bioconjugates, Chem. Commun., 2007, 1899-1901. Link Self-assembled gelsThe extra-cellular matrix (ECM) outside the cell in multi-cellular organisms is a gel-like material, consisting mostly of proteins such as elastin and collagen. Bio-mimetic materials that resemble the ECM are of particular interest as they can be designed to interact favourably with the surrounding tissue, e.g., by stimulating a particular type of cell growth. Self-assembed gels formed from low molecular-mass organic gelators (LMOG) seem to be superior to polymeric gels as bio-mimetic ECM materials for applications in tissue engineering and drug delivery.
We are now investigating how we can utilize the unique properties of our pyromellitamide LMOG to create a new type of “smart” gels for biomedical applications (e.g., cancer therapy). [2] James E. A. Webb, Maxwell J. Crossley, Peter Turner and Pall Thordarson, Pyromellitamide Aggregates and Their Response to Anion Stimuli, J. Am Chem. Soc., 2007, 129, 7155-7162. Link Applications of STM and AFMTo analyse chemical structures on the nanoscale (1-100 nm), we can no longer rely on traditional techniques such as NMR spectroscopy. We need to resort to the use of high-resolution microscopy, especially AFM and STM,[3] and we have several on-going projects in this area. We have several projects within this area, including: Molecular electronics (see below) Single molecule imaging of catalytic porphyrins (Crossley, Elemans)[4,5], STM imaging of self-assembled metallomacrocycles (Lindoy)[6] and electron microscopy (TEM and SEM) studies of self-assembled gels from small molecules (Braet). [3] Pall Thordarson, Rob Atkin, Wouter H. J. Kalle, Gregory G. Warr and Filip Braet, Developments in using Scanning Probe Microscopy to study Molecules on Surfaces - From Thin Films and Single-molecule Conductivity to Drug-living Cell Interactions, Aust. J. Chem., 2006, 59, 359-375. Link [4] Bas Hulsken, Richard van Hameren, Jan W. Gerritsen, Tony Khoury, Pall Thordarson, Maxwell J. Crossley, Alan E. Rowan, Roeland J. M. Nolte, Johannes A. A. W. Elemans and Sylvia Speller, Real-Time Single Molecule Imaging of Alkene Oxidation by Manganese Porphyrins at a Liquid-Solid Interface, Nature Nanotechnlogy, 2007, 2, 285-289. Link [5] Bas Hulsken, Richard van Hameren, Pall Thordarson, Jan W. Gerritsen, Roeland J. M. Nolte, Alan E. Rowan, Maxwell J. Crossley, Johannes A. A. W. Elemans and Sylvia Speller, Scanning Tunneling Microscopy and Spectroscopy Studies of Porphyrins at Solid-Liquid Interfaces, Jpn. J. Appl. Phys., 2006, 45, 1953-1955. Link [6] Jonathon E. Beves, Bodgan E. Chapman, Philip W. Kuchel, Leonard F. Lindoy, John McMurtrie, Mary McPartlin, Pall Thordarson and Gang Wei, New discrete metallocycles incorporating palladium(II) and platinum(II) corners and dipyridyldibenzotetra-aza[14]annulene side units, Dalton Trans., 2006, 744-750. Link Non-linear binding in supramolecular chemistry
We are now focusing on co-operativity in self-assembled systems, including self-assembled gels formed from pyromellitamides (see above). Work is on-going into better understanding how we can use small anions or other related ligands to control the assembly and dis-assembly of these and other aggregates. [7] Pall Thordarson, Edward J. A. Bijsterveld, Johannes A. A. W. Elemans, Peter Kasák, Roeland J. M. Nolte and Alan E. Rowan, Highly Negative Homotropic Allosteric Binding of Viologens to a Double-Cavity Porphyrin, J. Am. Chem. Soc., 2003, 125, 1186-1187. Link [8] Pall Thordarson, Ruud G. E. Coumans, Johannes A. A. W. Elemans, Paul J. Thomassen, Johan Visser, Alan E. Rowan and Roeland J. M. Nolte, Allosterically Driven Multi-Component Assembly, Angew. Chem. Int. Ed., 2004, 43, 4755-4759. Link Molecular electronicsThe Molecular Electronics Group (Crossley, Hush, Reimers and Thordarson) at the School of Chemistry, The University of Sydney, is currently undertaking a large project on creating a novel molecular memory device. This project received an ARC Linkage grant in 2004 and our work within this project is focused on developing the microscopy techniques (AFM and STM) that are necessary to characterize the molecular memory components. OpportunitiesIf you are interested in our work, please don't hesitate to contact us (see our contact page or give Palli a call on +61-(0)2-9385-4478). Ph.D. students: Interested students with Australian or New Zealand permanent residency and a first class BSc. Honours are most welcome to apply for a position in our group. International students are advised that fees for international students are currently above $22,000 and the competition for International Post-graduate Research Scholarships (IPRS) is extremely strong. That said, international students with interest in our work, top academic performance (at least >75% average for BSc), some research experience and good communication skills are encouraged to seek further information about research opportunities in our group. Records that include research publication(s) in internationally recognized journals will be considered most favourably. Collaboration/consultancy: We also have substantial experience in collaboration with industry and other research groups and we welcome inquiries about consultation or research collaboration. Research positions / post-doctoral fellowship: Currently we have no vacancies in our group, however, potential post-doctoral fellows or research associate are most welcome to contact us and leave their CV's for future reference. Candidates who can provide their own funding are most welcome to contact us. |
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In the first project we have synthesized a series of bioconjugates between synthetic donor chromophores (Ru-terpyridines) and a redox acceptor protein (cytochrome c). Using laser spectroscopy, we have been able to demonstrate that photoinduced electron transfer takes place between the donor and protein-acceptor upon excitation of the Ru-terpyridine.[1]
In both these project we will continue to develop the application of these conjugates in three areas: biosensing, synthesis, and single-molecule research.
We recently discovered a novel family of LMOG, the pyromellitamides that form gels in hexanes and other non-polar solvents that collapse upon addition of small anions such as Cl- and Br- but not larger ones like PF6-.[2] 
Non-linear (or co-opeartive, including allosteric) interactions are ubiquitous in Nature as a tool to regulate processes ranging from simple catalysis or transport (e.g., oxygen binding to hemoglobin) to life-and-death processes such as gene and cell-cycle regulation. Our previous work in this area (with 
We have shown that these molecules aggregate by intermolecular hydrogen bonding interactions with positive co-operativity. Furthermore, we also showed that the addition of small anions causes these aggregates to collapse (allosteric effect) and that these molecules binding to two anions with negative co-operativity.[2]