Harry B. Gray
Wolf Prize Laureate in Chemistry 2004
Harry B. Gray
Affiliation at the time of the award:
California Institute of Technology, USA
“for pioneering work in bio-inorganic chemistry, unravelling novel principles of structure and long-range electron transfer in proteins”.
A pioneer of bio-inorganic chemistry, Professor Harry Gray has made a critical contribution to our understanding of electron transfer in proteins and their folding.
To work its decipherable miracles, to effect change, and to create complexity and difference, life needs electrons, ions, atoms, and energy. From these, it constructs molecules of defined shapes and precise functions. The critical role of inorganic chemistry in these processes was recognized only recently.
In biological systems, inorganic components are essential. In hemoglobin, out of a total 9,072 atoms, there are only four iron atoms. These, however, play a critical role. Similarly, minute amounts of zinc, magnesium, calcium, copper and manganese, as well as other metal ions, play critical roles. When nature needs to accomplish a task that requires electron transfer, or where big energy jumps are essential, this is made possible by metal ion chemistry. From hemoglobin to chlorophyll, from zinc fingers to respiration, one finds important bio-inorganic chemistry in the service of life. Electron transfer reactions in proteins provide the basis for energy production and much of the intermediary metabolism in cells of all living organisms and plants. Until Gray’s work, little was known about the chemical factors, which govern electron transfer in biological systems.
Gray has made seminal contributions to the understanding of chemical bonding of metal complexes, mechanisms of inorganic reactions, spectroscopy and magneto-chemistry of inorganic compounds. His study of the first trigonal prismatic complexes is one such example. Through these achievements alone, coupled with a vivacious, interactive personality (that has also served him well as he brought, with enthusiasm, chemistry to the general public), he has established himself as one of the world’s leading chemists.
But Harry Gray’s most significant work lies at the interface between chemistry and biology. As a pioneer of the important and thriving field of bio-inorganic chemistry, he has made many key contributions, the most important of which is the development of fundamental understanding of electron transfer in biological systems, at the atomic level.
Harry Gray has developed methods for binding electron transfer-active metal complexes to the surface of proteins and has prepared proteins (variants of myoglobin and cytochromes) in which ruthenium complexes, amenable to activation by light, were placed at defined locations. Using these systems, he reported the first measurement of an electron transfer rate between two sites located at a fixed known distance in a protein; and has. systematically investigated the distance dependence of long range protein electron transfer and its free energy dependence. Gray has experimentally established, the mechanism of tunnelling as the transport of holes through the protein’s covalent bonds. He has demonstrated that electron transfer in proteins can occur with significant rates between centers separated by distances of up to 20 Ångströms. Gray’s work has provided insight into how the electron transfer rate depends on the separation of the redox centers and on the composition of the intervening material. Further, using laser-induced electron transfer as a tool, he has developed a method for triggering protein folding by light, enabling the study of early events of protein folding, which is central to protein structure and function. Gray’s work on electron transfer in biomolecules, is a striking demonstration of the power of modern physical tools and inorganic chemistry, applied to a critical biological problem. Ingenious chemistry, meticulously executed, has given us real understanding, for the first time, of biological processes of great significance for life.