“Switchable and Sensory Interfaces: molecular scale analysis and near field chemistry”

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• Dr Jason Davis - University of Oxford
• Tuesday 27 October 2009, 16:15-17:15
• Pfizer Lecture Theatre, Department of Chemistry.

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Switchable and Sensory Interfaces: molecular scale analyses and near field chemistry

The talk with focus on the integration of biological and redox active molecules with electrode surfaces, derived sensory applications and conductance switching. Analyses are routinely carried out at molecular scales (using both near and far field imaging technologies) where dispersion characteristics are resolvable. The group have also developed the application of imaging (AFM) probes as catalytically active entities in which chemical conversion/molecular coupling at such interfaces can be induced with very high spatial definition.

Bioelectronics; the controlled interfacing of bioelectrochemical molecules with electrode surfaces facilities insight into natural electron transfer processes, interfacial design, and enables to construction of derived biosensors. Standard voltammetric assessments are globally averaging and not able to resolve thermodynamic or kinetic dispersion within any given surface-confined population of molecules (be it inherent in the molecule or surface induced). Current limitations prohibit an electrochemical assessment at the single molecule level. In coupling optical and electron transfer processes it is, however, possible to use standard fluorescence microscopy methods to access redox processes at truly molecular levels and, in so doing, directly observe (for the first time), the dispersion in molecular electron transfer characteristics within a given surface confined population of proteins (or indeed enzymes). The detection and quantification of protein biomarkers in biological samples lies central to proteomics, drug design, disease diagnosis and therapeutic development. In interfacing protein receptive molecules to electrodes a host of potentially highly sensitive assays can be developed. Current techniques are largely dominated by the use of antibodies. Peptide aptamers are defined as peptide recognition moieties that are presented in, and conformationally constrained by, an engineered non-antibody scaffold. They are more stable, more specific and potentially more conformationally sensitive than antibodies. In recent work we have reported the controlled and orientated surface assembly of these molecules on optical and electroactive surfaces in the establishment of sensitive and highly specific protein detection assays. We have recently reported the application of these assays to the detection of Cyclin-dependent protein kinases (CDKs) whose activity is important in proliferating and cancerous cells. The design and use of these aptamer interfaces in protein detection will be briefly discussed. Significantly, some of these interfaces are able to detect subtle changes in the conformation of CDK2 associated with activation of its catalytic activity that may be caused by the phosphorylation of a single amino acid (threonine 160).

Conductance switches; in confining redox molecules to an electrode and engaging them with a conductive proximal probe from above, single molecule conductance can be measured. In the case of electroactive molecules an appreciable amount of current can be tuned to flow via the metallic redox site under specific conditions. It is specifically possible to gate single molecule conductance and, in so doing, shed light on both the thermodynamics and kinetics of the molecules electrochemical coupling to the supporting planar electrode. Recent work has, additionally, indictaed that the size of this conductance switch scales with electron transfer kinetics as assessed electrochemically.

Molecular Scale Chemical Conversion; finally, a brief look at the use of near field (Proximal probe) methods in switching locally chemical characteristics on surfaces (in inducing molecular scale chemical change) will be presented.

Brief Biog:

Jason Davis studied Chemistry at Kings College London, where he was awarded The Victor Gold Prize for Chemistry in 1991, The Ivor John Prize for Organic Chemistry in 1992, and The Robert Wakeford Memorial Prize in Chemistry and a first class honours degree in 1993. He moved to the Inorganic Chemistry Laboratory at the University of Oxford in 1994. After obtaining a PhD and postdoctoral research on carbon nanotubes, electroanalysis and scanning probe microscopy he was elected to an Extraordinary Junior Research Fellowship at The Queens College in 1998, a Ramsey Fellowship and a Royal Society University Research Fellowship in 1999 and a Lectureship in Chemistry at Jesus College, Oxford, in 2001. He was made a University Lecturer and Official Student and Tutor in Chemistry at Christ Church in 2003. He became Senior Subject Tutor in 2006 and was made a University Reader in Chemistry in September 2008. His work has focused on the molecular and nanometre-scale construction and analysis of bioinorganic, sensory, electronic and optical systems. He has published extensively on biomolecular electronics, molecular imaging, carbon nanotubes, nanoparticles, and biological and molecular sensing.

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