The mechanism for energy and signal transport in proteins as suggested by Davydov is discussed. The idea is based on a coupling of amide-I oscillators to acoustic phonons in a hydrogen-bonded chain. Results as obtained with the usually used ansatze are discussed. The quality of these states for an approximate solution of the ẗime-dependent Schrodinger equation is investigated. It is found that the semiclassical ¨< :
ansatz is a poor approximation, while the more sophisticated D state seems to 1 represent the exact dynamics quite well. Calculations at a temperature of 300 K for one Ž . chain, as well as for three coupled ones as they are present in an ␣-helix , are presented and discussed. From the calculations, it is evident that Davydov solitons are stable for reasonable parameter values at 300 K only for special initial excitations close to the terminal sites of the chain. However, for soliton formation, it is not necessary that the initial excitation occurs at the chain end which has its CϭO group directly coupled to the lattice as it is the case for T s 0 K. At higher temperatures, solitary waves can be formed from both chain ends. Since the model for temperature effects used was criticized from the theoretical point of view, we suggest an improved theory for temperature effects. Finally, we discuss recent experimental findings which indicate that normal modes describing the N-H stretch and its coupling to the hydrogen bonds should be considered in addition to the amide-I vibration.