Studies of Phononlike Low-Energy Excitations of Protein Molecules by Inelastic X-Ray Scattering

Dazhi Liu, Xiang-qiang Chu, Marco Lagi, Yang Zhang, Emiliano Fratini, Piero Baglioni, Ahmet Alatas, Ayman Said, Ercan Alp, and Sow-Hsin Chen

Phys. Rev. Lett. 101, 135501 – Published 24 September 2008

Abstract

Molecular dynamics simulations and neutron scattering experiments have shown that many hydrated globular proteins exhibit a universal dynamic transition at $T_{D} = 220 K$ , below which the biological activity of a protein sharply diminishes. We studied the phononlike low-energy excitations of two structurally very different proteins, lysozyme and bovine serum albumin, using inelastic x-ray scattering above and below $T_{D}$ . We found that the excitation energies of the high- $Q$ phonons show a marked softening above $T_{D}$ . This suggests that the large amplitude motions of wavelengths corresponding to this specific $Q$ range are intimately correlated with the increase of biological activities of the proteins.

Received 25 June 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.135501

Authors & Affiliations

Dazhi Liu¹, Xiang-qiang Chu¹, Marco Lagi^1,2, Yang Zhang¹, Emiliano Fratini², Piero Baglioni², Ahmet Alatas³, Ayman Said³, Ercan Alp³, and Sow-Hsin Chen^1,*

¹Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
²Department of Chemistry and CSGI, University of Florence, Sesto F.no, Florence, I-50019
³Advanced Photon Source, Argonne National Lab, Argonne, Illinois 60439

^*Author to whom correspondence should be addressed. sowhsin@mit.edu

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Vol. 101, Iss. 13 — 26 September 2008

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