Tritium–hydrogen exchange in insoluble collagen

Abstract

The rate and extent of exchange of collagen fibers with tritiated water has been investigated under various conditions, and four classes of hydrogen atoms are distinguishable. Of these classes, one exchanges too rapidly to be measured by this technique, a second exhibits rate curves similar to those observed in the absorption of water vapor, and a third class of hydrogen atoms shows a pH dependence remarkably similar to that expected for the titration curve of collagen. Lithium bromide treatment releases the fourth class for exchange as it severs the hydrogen bonds and destroys the structural features of the collagen macromolecule. Comparison of exchange under moderate chemical conditions with the total exchange suggests that two out of three peptide imino hydrogens may be hydrogen bonded in insoluble collagen, as is also suggested by one of the models proposed for the structure of the collagen macromolecule.