CV and list of publications

Research

The research in my group uses a variety of techniques in laser spectroscopy to study the structure and dynamics of biological molecules. We are also developing a new experimental tool in the area of single-molecule spectroscopy to reveal the diffusion and conformation of an individual molecule in solution.

The isolation of molecules under cold conditions in vacuo provides a way to use laser spectroscopy to investigate various aspects of structure and dynamics. We apply this approach to study the electronic and nuclear states of important functional groups in proteins. Presently, we are interested in the derivatives of porphyrin – related to the functional groups of haemoglobin (oxygen transport in blood) and chlorophyll (light harvesting in plants). Multi-photon ionization and hole-burning methods are used in the first instance to identify the various conformational states of the porphyrin under isolated conditions. Other methods are then used to obtain an insight into pathways for structural isomerisation and electronic decay from photoexcited states of these groups.

Differences in chemical reactivity might arise from small variations in the tertiary structure of a protein (the 3D folding). However, the molecular dynamics of individual copies of a protein are not revealed in the majority of experimental measurements. Instead, the results will usually reflect the ensemble average across the entire population of molecules in a sample. It is the objective of single-molecule research to reveal the differences (i.e. heterogeneity) in an ensemble and we are using various techniques in fluorescence spectroscopy to examine important reaction mechanisms in biology. In collaborations with researchers from the Dept. of Biochemistry, we are investigating the repair of damaged DNA initiated by helicase/nuclease enzymes (with Dr Dillingham), and the stepwise displacement of molecular motors transporting cargo along microtubules in the human cell (with Dr Stephens).

Optical forces can be used to manipulate particles in an aerosol and it is possible to suspend a single droplet of liquid in the waist of a tightly-focussed beam from a laser. This technique is referred to as optical tweezing and, in collaboration with Dr Reid, we are using it to characterise the properties of single droplets from an aerosol containing a mixture of aqueous and organic components. This has led to the development of novels methods for spectroscopic analysis and imaging of microparticles. In addition, our group has combined optical tweezing of liquid microparticles with methods for sensitive detection of the fluorescence from a single molecule. We intend to use this approach to investigate Brownian motion of molecules in different liquid droplets and the conformational dynamics of a single copy of a protein in a confined volume of solvent.