Hemoproteins, ligands, and quanta.

As with other quantitative subjects, there is no obvious end point in the study of heme-ligand interactions, which has advanced quickly following each technical innovation and slowly while waiting for significant new methods to appear. Major advances in laser technology in recent years have opened a new range of time scales in describing heme-ligand interactions. It lends a certain concreteness to recall that a flash lasting 1 ns is about a foot long, and so a picosecond flash is about 1/100 of an inch. The shortest flashes used so far with hemoproteins have been about 2/1000 of an inch long. These laser methods are about to be supplemented by the powerful tool of site-directed mutagenesis. At present then, one major advance has taken place, and another is just beginning. There is large literature on kinetics of hemoprotein reactions. The older literature should be accessible through the two reviews cited (Gibson, 1959, 1978), and the modern work from the reference lists of the handful of recent papers quoted. Recent progress in the field has not depended on the work of any single individual but derives from the accumulation of data by many investigators. In many cases, several workers might fairly be mentioned; in general, results have frequently been quoted without citation to avoid a large and perhaps unfair reference list.