Estimation of Collagen in Hard Tissues

Abstract

IN analysing the protein constituents of connective tissues, it is usually assumed that collagen is represented by a fraction of the total nitrogen which is precipitable by tannic acid after autoclaving the washed sample. The existing procedure for the determination of this protein in bone¹ was applied to dentine², but later shown to be unsatisfactory. Preparation of the powdered sample by grinding results in the conversion of at least one-tenth of the collagen to gelatin. Drastic autoclaving conditions account for the failure to precipitate a similar fraction of the protein thus made soluble, while somewhat more of the gelatin remains adsorbed on the autoclaved dentine powder even after washing with boiling water. These facts became apparent when a purified hide collagen sample³ was mixed with the correct proportion of the residue prepared by extracting dentine with boiling alkaline ethylene glycol and analysed under the same conditions.