Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
-casein micelles using neutron spectroscopyNakagawa, Hiroshi; Appavou, M.-S.*; Wuttke, J.*; Zamponi, M.*; Holderer, O.*; Schrader, T.*; Richter, D.*; Doster, W.*
Joint Annual Report 2021 of the MLZ and FRM II, P. 55, 2022/00
Times Cited Count：0 Percentile：0.01(Biophysics)-casein undergoes a reversible endothermic self-association with increasing temperature, forming micelles of limited size. We characterize the structural flexibility in terms of nano-second molecular motions. We report on two relaxation processes on a nano-second and a sub-nano-second time scale for -casein in solution. Both processes are analyzed by Brownian Oscillator model, by which the spring constant can be defined in the isotropic parabolic potential. The slower process seems a characteristic feature of the unfolded structure, and dividing the relaxation time by the solvent viscosity removes most of the temperature dependence, indicating that indicates, the process involves density fluctuations of the solvent. The faster process has a smaller amplitude and requires hydration water. The flexibility of a -casein monomer is preserved in the micelle.
-casein micelles by neutron spectroscopyNakagawa, Hiroshi; Appavou, M.-S.*; Wuttke, J.*; Zamponi, M.*; Holderer, O.*; Schrader, T. E.*; Richter, D.*; Doster, W.*
Biophysical Journal, 120(23), p.5408 - 5420, 2021/12
Times Cited Count：1 Percentile：7.79(Biophysics)Casein proteins are characterized by its extended structural features and its dynamics, which are different from those of typical folded proteins, due to a large number of proline residues. We were able to describe the unique structural dynamics by Orenstein-Uhlenbeck Brownian oscillator model by several types of QENS experiments with wide time-scales. The characterized dynamics also allowed us to discuss the effective sequestration of calcium phosphate in terms of its unique dynamical structure. The biological role of the physical processes of the proteins on the nanosecond order on the biological functions is presented.
Doster, W.*; Nakagawa, Hiroshi; Appavou, M. S.*
Journal of Chemical Physics, 139(4), p.045105_1 - 045105_16, 2013/07
Times Cited Count：25 Percentile：68.21(Chemistry, Physical)Numerous neutron scattering studies of bio-molecular dynamics employ a qualitative analysis of elastic scattering data and atomic mean square displacements. We provide a new quantitative approach, showing, that the intensity at zero energy exchange can be a rich source of information of bio-structural fluctuations on a pico- to nano-second time scale. Elastic intensity scans performed either as a function of the temperature and /or by varying the instrumental resolution yield the activation parameters of molecular motions and the approximate structural correlation function in the time domain. The two methods are unified by a scaling function. The complete elastic scattering function versus temperature, momentum exchange and instrumental resolution is analyzed instead of focusing on a single cross-over temperature of mean square displacements at the apparent onset temperature of an-harmonic motions. Our method predicts the protein dynamical transition (PDT) at Td from the collective alpha-structural relaxation rates of the solvation shell as input. By contrast the secondary beta-relaxation enhances the amplitude of fast local motions in the vicinity of the glass temperature Tg.
