Dielectric and conductivity measurements are reported for bovine serum albumin as a function of hydration. Strong evidence is found for the existence ofmobile charges whose short-and long-range hopping motion strongly depends on the physical state of the protein-bound water. These charges are considered to be protons. Insights into the nature of the electrical properties of protein-methylglyoxal complexes are provided, and the possibilities for correlated proton-electron motions are outlined.Modern biology is a molecular biology. The rates of most biological reactions are assumed to be limited by the classical concepts of mass action theories applicable to reacting molecules in solution. The main bearers oflife are the protein macromolecules, which are often to be found incorporated into membrane structures. This situation would appear to violate the physical basis ofclassical mass action theories and suggests that the functioning of such structural proteins is controlled at the submolecular level. The reactivity and subtlety that characterizes living systems also indicates that at its most fundamental level the "living state" operates at the submolecular level of nuclei and electrons (1). Such considerations ofthe reactivity of living systems led one of us to suggest nearly 40 years ago that the functioning of proteins should be understood by considering their submolecular properties. It was envisaged that one manifestation of such submolecular processes would be the ability of proteins to sustain electrical conductivity (2). However, as shown by the pioneering studies ofEley (3, 4), proteins isolated in their pure and dry condition are poor conductors. The basic reason for this is that the valence and conduction levels of extended electronic states of protein structures are separated by such a wide energy gap that at normal temperatures there is a negligible probability for the intrinsic generation of mobile charge carriers. Formation of charge-transfer complexes with electron-accepting molecules makes it possible for the electronic ground states ofa protein to become desaturated ofelectronic charge and lead to a conductivity sustained by positively charged electron "holes." Similarly, a charge-transfer interaction with an electron donor could result in the appearance of mobile electrons in the protein's conduction energy levels. The possibility that proteins can be so converted from insulators into conductors has been demonstrated by Eley and coworkers (5, 6) in conduction studies on complexes ofbovine plasma albumin with chloranil or chlorophyll, and our own studies (7-9) indicate the possibility that aldehydes such as methylglyoxal can act as electron acceptors in charge-transfer interactions with proteins. We believe that it is through such charge transfer that structural proteins are imbued with a submolecular reactivity that is essential for their full biological functioning.Our attempts to fully understand the basic process by which methylglyoxal, when incorporated into a protein's structure, in...