期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1982
卷号：79
期号：2
页码：386-389
DOI：10.1073/pnas.79.2.386
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have used 2H quadrupole-echo NMR spectroscopy to study the molecular dynamics of the leucine side chain in collagen fibrils labeled with [2H10]leucine. X-ray crystallographic studies of leucine and small leucyl-containing peptides and proteins [Benedetti, C. (1977) in Proceedings of the Fifth American Peptides Symposium, eds, Goodman, M. & Meienhofer, J. (Wiley, New York), pp. 257--274; Janin, J., Wodak, S., Levitt, M. & Maigret, B. (1978) J. Mol. Biol. 125, 357--386] show that the amino acid side chain exists predominantly in only two of the nine possible conformations. 2H NMR spectra of polycrystalline D,L [2H10]leucine obtained from -45 degrees C to +100 degrees C showed that interconversion of the two conformations did not take place on the 2H NMR timescale in this temperature range. In contrast, experimental lineshapes observed for [2H10]leucine-labeled collagen fibrils from -85 degrees C to +30 degrees C were simulated by using a model in which the side chain hops at various rates between the two predominant conformations found by the x-ray studies. A small difference between calculated and observed linewidths above the freezing point of water can be accounted for by backbone reorientation or by the presence of a small percentage of other side-chain conformations. Thus, these results provide strong evidence that the two predominant x-ray conformations not only exist in the fibrils as the preferred orientations but interconvert at rates that are proportional to temperature over the range - 85 degrees C to +30 degrees C. These observations concur with previous NNR studies of collagen fibrils that demonstrated a mobile contact region between collagen molecules.
