The swelling of collagen in alkaline solutions. 2. Swelling in solutions of univalent bases

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Abstract
The swelling of ox-hide collagen in solns. of strong and weak bases was studied. Differences in swelling at pH up to 12.5 are ascribed to variations in the affinity of the cations for the collagen. The swelling curves obtained with tetra-methylammonium hydroxide and guanidine were of the same general shape as the curve obtained with NaOH, suggesting that the increased swelling at high pH values is due to increase in the hydroxyl ion concn. rather than to any specific effect of the Na ion. With weak bases swelling decreased at pH values above 12.5 in apparent accordance with the Donnan theory. Curves of similar shape were obtained by the addition of increasing amts. of neutral organic solvent, and it is concluded that the decrease in swelling is due to the progressive departure from an aqueous medium. There were also specific effects due to the different bases. The effect of the organic solvents was presumably due to decrease in the swelling pressure rather than to increase in cohesion, since their presence was found to favor solution of the collagen. The results are consistent with the view that decrease in the cohesion of collagen at high pH values is due to breaking of inter molecular linkages. The possible nature of these linkages is discussed.
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