Abstract
This study presents quasielastic neutron scattering data of the water-soluble chlorophyll-binding protein (WSCP) and the corresponding buffer solution at room temperature. The contributions of protein and buffer solution to the overall scattering are carefully separated. Otherwise, the fast water dynamics dominating the buffer contribution is likely to mask the slow protein dynamics. In the case of WSCP, the protein scattering can be described by two contributions: i) internal protein dynamics represented by a diffusion in a sphere with an average radius of 2.7 Å and ii) global (Brownian) diffusion of the WSCP macromolecule with an upper limit for the translational diffusion coefficient of 9.4 ⋅ 10−7 cm2/s.
Highlights
Protein dynamics due to stochastic structural fluctuations of small molecular subgroups on the picosecond time scale has been shown to play an important role in physiological processes in nature
In the case of photosystem II membrane fragments of green plants, quasielastic neutron scattering (QENS) has established that the onset of diffusive molecular motions at ∼240 K [4], and at a relative humidity of ∼45% [5] is strictly correlated with the temperature- and hydration-dependent electron transfer efficiency from an electron donor referred to as Q−A to a transiently bound acceptor molecule named QB
In the present study we address this problem by QENS experiments on WSCP and on the corresponding buffer solution at room temperature
Summary
Protein dynamics due to stochastic structural fluctuations of small molecular subgroups on the picosecond time scale has been shown to play an important role in physiological processes in nature. In the case of photosystem II membrane fragments of green plants, quasielastic neutron scattering (QENS) has established that the onset of diffusive molecular motions at ∼240 K [4], and at a relative humidity of ∼45% [5] is strictly correlated with the temperature- and hydration-dependent electron transfer efficiency from an electron donor referred to as Q−A to a transiently bound acceptor molecule named QB Such a characteristic dependence of a functional process on temperature and hydration may indicate a crucial role of molecular dynamics in the underlying molecular mechanism [4, 6]. WSCP has recently been established as a minimal, but naturally abundant model system for photosynthetic pigment-protein complexes [7], its own particular function is not yet clarified
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