title: Nanosecond Dynamics of InfluenzaA/M2TM and an Amantadine Resistant Mutant Probed by Time-Dependent Red Shifts of a Native Tryptophan.
abstract: Proteins involved in functions such as electron transfer or ion transport must be capable of stabilizing transient charged species on time scales ranging from picoseconds to microseconds. We study the influenza A M2 proton channel, containing a tryptophan residue that serves as an essential part of the proton conduction pathway. We induce a transition dipole in tryptophan by photoexcitation, and then probe the dielectric stabilization of its excited state. The magnitude of the stabilization over this time regime was larger than that generally found for tryptophan in membrane or protein environments. M2 achieves a water-like stabilization over a 25 nanosecond time scale, slower than that of bulk water, but sufficiently rapid to contribute to stabilization of charge as protons diffuse through the channel. These measurements should stimulate future MD studies to clarify the role of sidechain versus non-bulk water in defining the process of relaxation.
authors.affiliation: Center for Advanced Biotechnology and Medicine, Robert Wood Johnson Medical School - UMDNJ, Piscataway, New Jersey 08854 ; Department of Biochemistry, Robert Wood Johnson Medical School - UMDNJ, Piscataway, New Jersey 08854.
authors.forename: Vikas
authors.initials: V
authors.lastname: Nanda
authors.forename: Lidia
authors.initials: L
authors.lastname: Cristian
authors.forename: Dmitri
authors.initials: D
authors.lastname: Toptygin
authors.forename: Ludwig
authors.initials: L
authors.lastname: Brand
authors.forename: William F
authors.initials: WF
authors.lastname: Degrado