title: Relationship between structure, dynamics and function of hydrated purple membrane investigated by neutron scattering and dielectric spectroscopy.
abstract: We investigated the influence of hydration water on the relationship between structure, dynamics and function in a biological membrane system. For the example of the purple membrane (PM) with its protein bacteriorhodopsin (BR), a light-driven proton pump, complementary information from neutron diffraction, quasi-elastic neutron scattering (QENS) and dielectric spectroscopy will form a comprehensive picture of the structural and dynamic behavior of the PM in the temperature range between 150 and 290 K. Temperature- and humidity-dependent changes in the membrane system influence the accessibility of the different photocycle intermediates of BR. The melting of the 'freezing bound water' between 220 and 250 K could be related to the transition from the M1 to the M2 intermediate, which represents the key step in the photocycle. The dynamic transition in the vicinity of 180 K was shown to be necessary to ensure that the M1 intermediate can be populated and that the melting of crystallized bulk water above 255 K enables the completion of the photocycle.
authors.affiliation: Hahn-Meitner-Institut Berlin, Glienicker Str. 100, D-14109 Berlin, Germany. buchsteiner@hmi.de
authors.forename: Alexandra
authors.initials: A
authors.lastname: Buchsteiner
authors.forename: Ruep E
authors.initials: RE
authors.lastname: Lechner
authors.forename: Thomas
authors.initials: T
authors.lastname: Hauss
authors.forename: Norbert A
authors.initials: NA
authors.lastname: Dencher
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry / Q000378:metabolism; D004583:Electrons; D019617:Halobacterium salinarum / Q000737:chemistry / Q000378:metabolism; D033363:Neutron Diffraction; D018717:Purple Membrane / Q000737:chemistry* / Q000378:metabolism*; D013053:Spectrophotometry; D013696:Temperature; D014867:Water / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D014867:Water; D001436:Bacteriorhodopsins