Living With Metals

by Prof. Gerard W. Canters (Leiden Institute of Physics and Leiden Institute of Chemistry, The Netherlands)

Monday, January 30, 2012 from 16:00 to 17:00 (Asia/Kolkata)
at Colaba Campus ( AG-66 )

TIFR, Colaba Mumbai 400005

Description

Metals play an indispensable role in the processes that keep a living cell alive. They are involved in cellular metabolism and processes like cell division and cell differentiation. As the daily requirements by a cell for a particular metal often do not match the environmental availability, uptake and secretion of metals need to be carefully regulated and orchestrated. Moreover, once taken up by the cell the metals need to be delivered at the right cellular location and incorporated in the appropriate macromolecular structures within the cell. To some extent the environmental availability of a particular metal is reflected in the role it plays in the cellular machinery. A changing availability as a result of evolutionary changes in the atmosphere, the oceans and the earth’s crust, sometimes can be traced back in the elemental make-up of a cell. Copper, for instance, became available relatively late in the development of life on earth and consequently plays a minor role as compared to Fe and Zn. Its rising availability was a direct consequence of the development of an oxygenic atmosphere and its use, thus, is primarily restricted to extra-cellular proteins involved in electron transfer reactions and the catalysis of oxygen chemistry. The electron transfer character of some copper proteins has inspired research into their conducting properties. Is it possible to see electron tunneling events within proteins? Can copper proteins be employed in the construction of protein transistors?

The crucial role copper appears to play in such varied diseases as Wilson’s disease, Menkes disease, Alzheimer and Parkinson’s diseases and prion diseases have led to the realization that chemical processes taking place in the cell need to be studied within the cell itself, preferably in vivo. There we are confronted with the notion that a different approach is needed than we are used to. While normally in studying chemical reactions we are dealing with numbers aptly symbolized by Avogadro’s number, cellular components may run in the thousands or less copies per cell the ultimate limit being exemplified by the DNA molecule of which only a single copy exists in the bacterial cell. It means that cellular processes may exhibit stochastic variations and need to be studied at the level of the single molecule.

The role of metals in life will be briefly reviewed, with emphasis on the role of copper. The role of copper proteins in biological electron transfer will be discussed as well as their characterization in terms of the physics of electronic conduction. Manifestations of the stochastic variation in enzyme properties as evidenced by single molecule studies will be discussed.