A novel approach is described to analyze NMR relaxation data on proteins. This method introduces the frequency-dependent order parameter, S2(ω), in order to estimate contributions to the generalized order parameter S2 from different motional frequencies occurring on the picosecond to nanosecond time scales. S2(ω) is defined as the sum of a specified set of weighting coefficients from the Lorentzian expansion of the spectral density function. 15N NMR relaxation data (500, 600, and 800MHz) on protein GB1 exemplify the method. Using this approach provides information on motional restrictions over specific frequency or time scale ranges and provides a normalized comparison of motional restrictions between proteins having different overall tumbling correlation times.
Bibliographical noteFunding Information:
This work was supported by a research grant from the National Institutes of Health (NIH, GM-58008) and benefited from use of the high field NMR facility at the University of Minnesota. We would like to thank Judy Haseman for preparing 15 N -enriched samples of protein GB1.
- Molecular dynamics
- N relaxation