Abstract
Energy states of proteins are divided into configurational states, electronic states and vibrational/rotational states. The configurations of proteins in solution are described. A simple single configuration is not observed in general. Spectroscopic observations on the electronic ground states of groups in folded proteins shows that some are unusual. The rotational/vibrational energies of internal protein side chains are limited by packing but this is a highly selective property of different classes of protein. External side chains are very flexible. States of proteins in membranes are influenced by the energization of the membrane. Furthermore, owing to restrictions upon diffusion within the membrane, especially of charged groups, it is possible to energize proteins differentially within this phase. All the different energy states have been put to special functional use, for example in enzymic catalysis and within membranes in energy conversion from charge separation to ATP formation.