DAVYDOV SOLITON DYNAMICS IN PROTEINS .3. APPLICATIONS AND CALCULATIONOF VIBRATIONAL-SPECTRA

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 o scillators to acoustic phonons in a hydrogen bonded chain. Results as obtained with the usually used ansatze are discussed. The quality of t hese states for an approximate solution of the time-dependent Schrodin ger equation is investigated. It is found that the semiclassical ansat z is a poor approximation, while the more sophisticated lD(1)> state s eems to represent the exact dynamics quite well. This was shown by ext ensive calculations, both analytically and numerically in the two prec eding papers. Calculations at a temperature of 300K for one chain, as well as for three coupled ones (as they are present in an alpha-helix) are presented and discussed. From the calculations it is evident, tha t Davydov solitons are stable for reasonable parameter values at 300K for special initial excitations close to the terminal sites of the cha in. Further vibrational spectra are presented and discussed. Our resul ts suggest, that due to their strong dependence on the initial state, the Davydov lD(1)> model system might be a (quantum) chaotic one.