Scaling analysis of bio-molecular dynamics derived from elastic incoherent neutron scattering experiments

Journal Article · Sun Jul 28 04:00:00 EDT 2013 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4816513· OSTI ID:22224181

Doster, W. ^[1]; Nakagawa, H. ^[2]; Appavou, M. S. ^[2]

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1. Physik-Department, Technische Universität München, D-85748 Garching (Germany)
2. Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, Outstation at MLZ, Lichtenbergstraße 1, 85747 Garching (Germany)

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 (back-scattering) and/or by varying the instrumental resolution (time of flight spectroscopy) 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, which depends on the ratio of correlation time and instrumental resolution time. The elastic scattering concept is illustrated with a dynamic characterization of alanine-dipeptide, protein hydration water, and water-coupled protein motions of lysozyme, per-deuterated c-phycocyanin (CPC) and hydrated myoglobin. 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 T{sub d} from the collective (α) structural relaxation rates of the solvation shell as input. By contrast, the secondary (β) relaxation enhances the amplitude of fast local motions in the vicinity of the glass temperature T{sub g}. The PDT is specified by step function in the elastic intensity leading from elastic to viscoelastic dynamic behavior at a transition temperature T{sub d}.

• OSTI ID: 22224181
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 4 Vol. 139; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALANINES
BACKSCATTERING
CORRELATION FUNCTIONS
ELASTIC SCATTERING
ENERGY TRANSFER
HYDRATION
LYSOZYME
MOLECULAR DYNAMICS METHOD
MYOGLOBIN
NEUTRON DIFFRACTION
PHYCOCYANIN
RELAXATION
SHELLS
SPECTROSCOPY
TRANSITION TEMPERATURE