Timothy Havel, Igor Najfeld, Kwaku Dayie, and Gerhard Wagner
BCMP, Harvard Medical School, Boston MA 02115, USA
Measurements of amide spin order relaxation rates in proteins enable one to map the spectral density functions along the polypeptide backbone, which in turn is a measure of motional amplitude as a function of frequency (Wagner, 1993). We have developed a new method for estimating the relaxation rate between the <Nx> and the <2 Iz Nx> spin orders of protein amide groups (Havel et al, poster presented at ISMAR-95), and have applied this method to Villin 14T, a domain conserved among actin-severing proteins. This method does not assume the suppression of competing coherence transfer pathways, avoids most of the ill-conditioning problems that plague exponential fits. The results provide us with an estimate of the low-frequency components of the spectral density function J(0) and J([[omega]]N), as well as the angle between the chemical shift anisotropy tensor and the N-H bond.
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