This book is concerned with the physical aspects of molecular and electronic tunneling in biological systems, and the extent to which protein structure controls these events. The scope is very broad and this volume could almost be a textbook in biophysics. Both fundamental processes and the extrapolation to physiological events are stressed. The discussion sections are remarkably frank and offer insight into the basic problems confronting physists and chemists as they seek to apply their techniques to biological systems. This book on the physics of biomolecules reflects recent progress in understanding the biological function of the key protein molecules from detailed knowledge of their physics. New and exciting are the glasslike aspects of protein structures and the discussion of proteins as fractals. Other topics dealt with are low-temperature kinetics and reactivity, structure and charge exchange, and charge separation in photosynthetic reaction centers.