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Britton Chance: An Appreciation

R.J.P. Williams

14 February 2011

Brit was a highly refined innovator in experimental spectroscopy of rates of chemical change who for me provided especially two deep insights into mechanisms associated with electron transfer in biological metabolism. One of them led to the use of Marcus theory of electron tunnelling and the other to understanding of energy transduction in both oxidative and photo synthesis of pyrophosphate (ATP). The understanding of electron transfer over large distances through a particular protein matrix by quantum mechanical tunnelling was put forward by Brit with the assistance of De Vault. I have played a minor part in exploiting the idea to the general way electron transfer in proteins could be related to the distance of separation of reaction centres. By far the major contribution came from my other colleague and friend in the Biochemistry Department of the University of Pennsylvania, Leslie Dutton. The success of the work is well-known worldwide. The second insight by Brit and his colleagues was in the study of oxidative and photosynthesis energy transduction on using analysis of the succession of electron transfer and other steps of an unknown chemical character by a long series of sophisticated spectroscopic observations. Brit succeeded in resolving and analysing experiments between 1950 and 1980. The finding in the work which intrigued me was the fact that there were certain spectral “cross-over” points in the series of steps which could be related in certain chemical events in the sequence. Wondering about the steps I came to the conclusion that the chemical nature of the cross-over points had to refer to the common production of chemical intermediates as each one contributed to the transduction of electron flow to energy conservation in pyrophosphate (ATP). The singular intermediate which satisfied the chemical and spectral data was a proton gradient. Shortly afterwards Mitchell developed a similar hypothesis of protons based on a much simpler description readily understandable by biologists but very unsatisfactory chemically. The development of Mitchell’s description led to the award of the Nobel Prize many years later. As a consequence the very sophisticated spectroscopic study by Brit and the insight shown are rarely mentioned. I doubt that many understood his experiments or my interpretation.

Brit was a serious man in his science but he had a lighthearted touch coloured by somewhat sharp humour. When he first heard Mitchell’s and my views at closely the same time around 1965 he remarked to me, ‘It is strange RJP (he always addressed me by my initials) that you and Mitchell look alike’ (we both had long hair then). Very touchingly and much later he proposed that the general idea of proton gradient energy transduction should be called the Mitchell/Williams hypothesis. Kind thought that it was I did not believe it would catch on as Mitchell’s name, not mine, by that time dominated the textbooks.

In closing let me say that I always respected Brit’s ability and achievements and much enjoyed the exchange of banter with him. Your University will find it hard to replace a man of his talent who gave so much of his time to science within it.

– R.J.P. Williams