No abstract

No abstract

No abstract

No abstract

During the course of investigations on the effects of thermal exposure upon rat skin and tail-tendon( 1), we had occasion to utilize the method of Neuman and Logan for the determination of hydroxyproline ( 2 ) as a measure of the collagen content ( 3 ) . In the application of this method considerable difficulty was experienced in obtaining reproducible, linear standard curves. Frequently, the standard curves would display the form of an exponential function, making the selection of suitable aliquots of an unknown troublesome. Consequently, the following study was undertaken in an effort to establish conditions which would consistently result in a linear proportionality between light absorption and known concent ra t ions of h ydroxyproline.Experimental. The colorimetric method of Xeuman and Logan (2) for the determination of hydroxyproline consists of the following steps: a ) oxidation of the hydroxyproline with peroxide in the presence of alkali and copper sulfate; b) removal of the excess peroxide by heating at 80°C for 5 minutes; and c) color development with p-dimethylaminobenzaldehydet in acid solution. If the excess peroxide is not removed, the color intensity is considerably decreased. I t was felt that the erratic results obtained in this laboratory might be related to the step involving removal of the excess peroxide. However, variations in temperature between 70" and 8OoC, and in the heating periods from two to ten minutes failed * This work performed under contract between Ithe U. S. -4tomic Energy Commission and Western Reserve University.t We have found that several commercial samples of p-dimethylamino-benzaldehyde have proved refractory to purification by the method of Adams and Coleman(4) even when repeated 3 times and followed by crystallization from warm aqueous ethanol. Recrystallization from other solvents was also ineffectual. It was subsequently found that a product from the Matheson Co. could be used without purification.