Hydratwasseraustausch und Alkanol-induzierte Molekulare Umordnungen an Kollagen/Exchange of the Structural Water of Collagen and Alcanol-Induced Molecular Rearrangement

Abstract

The exchange of the structural water of collagen for alcanols was investigated using X -ray diffraction combined with mechanical measurements. The stepwise dehydration with methanol, ethanol or 1-propanol is reflected by the reversible loss of the characteristic equatorial reflexions of native rat tail tendons. The exchange for 1-alcanols in ascending homologous order is characterized by: 1. an increase in the distance between the axes of the triple helices depending on the number of carbon atoms of the alkyl chain, 2. a shortening of the long-spacing of 67 nm characteristic of native collagen and 3. the herewith correlated increase in tension on isometrically measured fibres. The stepwise dehydration with 2-propanol leads first to a loss of the equatorial reflexions that are characteristic of native collagen, then to their reappearance at smaller diffraction angles. The exchange for 2-alcanols in ascending homologous order is characterized by: 1. a splitted equatorial reflexion at 4.1 ± 0 .1 nm, that stays constant up to 2-nonanol, and moves to 4 .8 - 5 .0 ± 0 .1 nm with more than 9 carbon atoms in the alkyl chain, 2. a shortening of the long spacing of 67 nm characteristic of native collagen and 3. the herewith correlated increase in tension on isometrically measured fibres. Stereochemical requirements are discussed as well as consequences for the structural model of collagen.