Picosecond Dynamics on the alpha-Helix Protein Analog: Acetanilide

Acetanilide (CH sub 3 CONHC sub 6 H sub 5) is a simple polypeptide analog to alpha-helix proteins for the study of energy transport and other biophysical problems. An exciting and controversial development in the experimental search for Davydov-like solitons to explain energy transport in proteins came from Careri, et. al. who proposed that self-trapped vibrational excitations could be photogenerated by infrared excitation of the amide I absorption band of acetanilide (ACN) at 1650 cm sup (-1). The unusual temperature dependence of this band can be fit to a modified soliton model where self-trapping is allowed by interaction with a ~ 1130 cm sup (-1) ACN crystal phonon. If the excitation is self-trapped, then its interaction with the lattice phonon bath would be weak and one might expect such soliton-like excitations to be relatively long-lived.