Heme-based sensors: theoretical modeling of heme-ligand-protein interactions.

Heme proteins are uniquely adapted to bind the important diatomic molecules O(2), NO and CO. An increasing number of heme proteins are being discovered that sense these molecules and thereby regulate a variety of biochemical responses. The interactions of diatomic molecules with heme, and with the surrounding protein, are therefore of great interest. Recent theoretical modeling, using density functional theory, captures many features of these interactions, as exemplified by the well-characterized heme protein myoglobin. Important details, however, especially the mutual influence of the bound diatomic molecule and the proximal ligand, remain to be clarified.