Protein and solvent dynamics as studied by QENS and dielectric spectroscopy

• Published in: Journal of non-crystalline solids Vol. 352; no. 42-49; pp. 4410 - 4416
• Main Authors: Jansson, Helén, Bergman, Rikard, Swenson, Jan
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.11.2006; Elsevier
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; Biological systems; Fundamental and applied biological sciences. Psychology; Miscellaneous; Proteins; 77.22.Gm; 61.12.Ex; 87.68.+z; 87.14.Ee; Biological systems; Quasi elastic scattering; Solvent effect; Molecular motion; Root mean square displacement; Protein; Dielectric relaxation; Neutron scattering; Hemoglobin
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2006.03.120

We have investigated the dynamics of a protein (hemoglobin) in three different solvents by broadband dielectric spectroscopy and quasi-elastic neutron scattering (QENS). The solvents used were water, glycerol and methanol. From the dielectric measurements we were able to extract four relaxation processes, where the fastest process is due to solvent dynamics, and the three slower processes arise from protein motions of a different nature, and hence, visible on different time and temperature scales. The results from the mean square displacement (MSD) obtained by quasi-elastic neutron scattering indicate that the fast and local protein motions are strongly related (slaved) by the fastest and most local solvent motions in the case of water and glycerol. In contrast, for methanol we found the low temperature dynamics are dominated by the CH3 group rotation, which does not promote any protein dynamics.