SynopsisInteractions of glutaraldehyde with either n-butylamine, poly(a,L-lysine), or collagen resulted in a fast release of protons in dilute aqueous solutions a t various pH values, followed by much slower changes. The latter reactions, which extended over hours and days, were followed spectrophotometrically and revealed the formation of distinct absorption bands in the visible and near-ultraviolet regions in all the above systems. The visible-range bands disappeared upon treatment with sodium borohydride. A qualitative relationship between oxygen uptake by the system n-butylamine-glutaraldehyde and the slow formation of colored products has been established, while the chemical nature of the reaction products has not been determined.Sedimentation velocity, viscosity, and optical rotation measurements on the products of interaction between poly(L-lysine) and glutaraldehyde in aqueous solution indicated large conformational changes in the polyamino acid present in excess (in residues) over the dialdehyde. In particular, the intrinsic viscosity dropped considerably after interaction, indicating intramolecular crosslinking. At molar ratios of 1:1 between polylysine residues and aldehyde groups, intermolecular crosslinking of polylysine was obtained a t pH 8.6.Electron microscopic examidations of collagen samples treated by glutaraldehyde a t various pH values indicated changes from unordered to more ordered structures upon treatment with glutaraldehyde, in particular a t pH 10.The present structural and optical investigations are considered to be relevant to tanning processes of hides and to fixation procedures.

SynopsisThe interaction between poly(a,L-lysine) (G = 180) and glutaraldehyde was investigated in dilute aqueous solution by measurement of the kinetics of proton release a t constant pH and temperature and a t various concentrations of the reaction components. Under various conditions, the release of protons a t constant pH appeared kinetically to be composed of a t least two steps: an initial zero-order reaction, followed by a slower reaction.At excess of polylysine amino groups, the pH optimum for the rates of reaction was at pH 9-10 (24-25OC). Under the conditions used and a t pH 8, the initial rate of the second kinetic step was proportional to the glutaraldehyde concentration and was practically independent of polylysine concentration a t pH 8 and 8.6, a t an excess of amino groups. At pH values of 7, 8, and 8.6 the apparent overall energy of activation for the second kinetic step was 18-19 kcal/mole (temp. range 4-40"C). Comparing acetaldehyde with the difunctional glutaraldehyde, it was found that the rate of proton release was much smaller in the case of acetaldehyde. Comparing n-butylamine with the macromolecular polylysine a t equal concentrations of amino groups, the rates of proton release were much smaller in the case of n-butylamine. Collagen in aqueous medium also interacted with glutaraldehyde in a manner analogous to polylysine, although the conditions were not quite comparable. In the case of collagen, the initial fast proton liberation step was relatively much larger than in the case of polylysine.A reaction scheme for the initial reaction steps is being proposed which includes primary complex formation between glutaraldehyde and polylysine. This dialdehyde-polyamino acid system is considered to serve as a model for tanning processes of hides and for fixation procedures.

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