| Citation | Professor Andrew Thomson has pioneered a number of advances in magnetic circular dichroism (MCD) and has made widespread applications of this technique to solve problems of molecular structure.
The earlier work on the MCD spectra of matrix-isolated species (with R. Grinter) gave for the first time definitive assignments for some of the electronic transitions of such simple and important molecules as benzene and oxygen and enabled the magnetic properties of unstable species such as Fe(CO)4 to be measured. This was followed by the formulation of symmetry-based selection rules for radiationless processes in transition-metal complexes. Ultra-low temperature (<1.5K) MCD spectroscopy was next developed as a powerful means of characterising individual centres of multi-metal proteins through their ground-state magnetic parameters and optical properties. Applications include the study of cytochrome c oxidase (with C. Greenwood) to provide the first identification of the di-oxygen reaction site lying between one haem and one copper ion; the demonstration that [4FE-4S] clusters in proteins can be oxidatively transformed into [3Fe-4S] which was crucial to understand the active site of the enzyme aconitase (with H. Beinert); the characterisation of the two principal metal cluster groups in the enzyme nitrogenase (with B.E. Smith); identification of the mechanism of the redox triggered activation of a di-haem peroxidase enzyme (with C. Greenwood). A recent development is the use of MCD detection of ground state microwave resonance to provide more highly selective detection of individual metal centres and, via the line shape, information about the angular orientation of metal ligands in proteins. In the hands of Thomson, MCD has become an extremely valuable method for the analysis of the states of metal ions in biological systems.
Other work includes the discovery of cis-Pt(NH3)2Cl2, as a bacterial filamenting agent which led to Rosenburg's discovery of its anti-tumour properties. |