Abstract
Based on the fiber diffraction data from native collagen, Rich and Crick proposed the 10/3‐helical model with a 28.6 Å axial repeat in 1955 (Rich A.; Crick, F. H. C. Nature (Lond) 1955, 176, 915–916). We obtained the 7/2‐helical structure with a 20 Å axial repeat from the single crystal analysis of (Pro–Pro–Gly)~10~. Since the latter structure could explain fiber diffraction patterns from native collagen, we proposed this structure as a new model for collagen in 1977 (Okuyama et al., Polym J 1977, 9, 341–343). These two structural models were refined against observed continuous intensity data from native collagen using a linked‐atom least‐squares method. It was found that the diffraction data from native collagen could be explained by the 7/2‐helical model better than, or at least the same as, the prevailing 10/3‐helical model. Together with the evidence that recent single crystal analyses of many model peptides have supported the 7/2‐helical model and there was no such active support for the 10/3‐helical model, it was concluded that the average molecular structure of native collagen seems to be closer to the 7/2‐helical symmetry than the other one. © 2005 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 84: 181–191, 2006
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