Binding of Aliphatic Dihydroxy Compounds to Collagen with X-ray Diffraction Evidence for the Vander Waals Bond

Abstract

AbstractPrevious work presented by the author at these conferences has been summarized by G.N. Ramachandran in “Treatise on Collagen I , 177-8”. Epitactic crystallization of amides and diols in the collagen lattice of formalinized rat tail tendon, with equatorial expansion of the collagen lattice, was used to visualize the core diameter of each coil in the triple spiral at 7A and the vertical repeat of the hydrogen-bonding unit at 5.2A. Expansion of the non - formalinized collagen lattice has been observed as high as 20.1A when 1, 4-trans-(bisamino-methyl) - cyclo-hexane was inserted between the hexagonal array of protein spirals in the collagen lattice, the length of the inserted molecule being 13A. With dimensions based on Fisher - Hirschfelder - Taylor atomic models, with maximum extension of the dihydroxy compounds, the a. parameter of the expanded collagen would be expected to increase from 16.5A in the case of glycol to 20.6A in the case of 1, 5 - pentanediol, but actually the parameter decreases from 18.3A in the case of glycol to 16.2A in the case of 1, 5 - pentanediol. The larger figure in the case of glycol is explained by its hydrogen bonded dimerization. 1,3 propanediol fits in to the collagen lattice as its extended form. In the case of the other compounds, the chains are folded and fit together with Vander Waals bonding, and produce progressively smaller parameters for the a axis in collagen. In this nonaqueous equilibrium the non - formalinized collagen core diameter averages 7.7A ±0.2 and the spacing of hydrogen bond contacts along the collagen fiber axis is 4.8 ±0.2A.