The Low-Temperature Inflection Observed in Neutron Scattering Measurements of Proteins Is Due to Methyl Rotation: Direct Evidence Using Isotope Labeling and Molecular Dynamics Simulations

• DOI: 10.1021/ja910502g
• Publication Date: 2010-03-19T15:20:52Z
• Authors: Kathleen Wood; Douglas J. Tobias; Brigitte Kessler; Frank Gabel; Dieter Oesterhelt; Frans A. A. Mulder; Giuseppe Zaccai; Martin Weik
• Keywords: Methyl group; Inflection point

There is increasing interest in the contribution of methyl groups to overall dynamics measured by neutron scattering experiments proteins. In particular an inflection observed atomic mean square displacements as a function temperature on high resolution spectrometers (approximately 1 microeV) was explained onset group rotations. By specifically labeling non-methyl-containing side-chain native protein system, purple membrane, and performing measurements, we here provide direct experimental evidence that indeed due Molecular simulations reproduce data, their analysis suggests apparent transition rotation entering finite instrumental spectrometer. Methyl correlation times solid state NMR taken from previous work, support interpretation.