D.L. Stein: Research on Biophysics
for Non-Physicists

Physical analysis of biological problems, and - in the opposite direction - biological inspiration of new physical and mathematical problems, go back a very long way. However, the previous few decades have seen an unprecedented growth of biological physics.

My work covers only a tiny part of the large spectrum of activities in the field. My research in other areas has naturally led me to pursue some of the many problems in biology where random processes play an important role. Of these, one of the more intriguing (to me, anyway) is the process by which a molecule of oxygen finds its way from the outside of a hemoglobin molecule (in a red blood cell) to the iron-containing heme group deep in the interior, to which the oxygen molecule binds. Although the hemoglobin molecule (a protein) is much larger than an oxygen molecule, it is tightly packed in most places. So, if the protein remained perfectly rigid, the oxygen could never enter very far (and we'd all be dead).

It turns out that getting the oxygen molecule to the deep interior of the protein, where it binds to the heme group, depends on the rapid fluctuations of the protein. At physiological temperatures, hemoglobin and many other proteins continually flit in and out of different spatial conformations. In the present example, this creates (momentarily, and at sort of random locations) large enough holes for the oxygen molecule to diffuse through.

 

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