MOLECULAR-SIZE AND CONFORMATION OF PROTEIN RECOVERED FROM CHROME SHAVINGS

Partially hydrolyzed collagen is one product of the treatment for chro me shavings developed in this laboratory. The value of this process to the tanner depends, in part, on the market value of this proteinaceou s material. Modification of the process at any of several points may a lter the characteristics of the protein product and thus improve its m arket potential. The molecular size of the collagen fragments and ther mal stability of collagen-like conformations are both factors in deter mining possible uses for this material. Polyacrylamide gel electrophor esis (SDS-PAGE) was used to analyze the protein fragments. These fragm ents were extracted from chrome shavings with MgO alone or in combinat ion with NaOH, KOH or the respective carbonates. Results of these anal yses showed a wide dispersion of molecular weights in all of the sampl es with the heaviest concentrations in the 100-200 kDa and 50-100 kDa fractions. About 25% of the protein was degraded into fragments less t han or equal to 50 kDa and a smaller portion was in the form of aggreg ates greater than or equal to 200 kDa. When aqueous solutions were hel d at 5 degrees C for at least 15 hrs, these protein fractions develope d 30-60% of the triple helical conformation of a comparable concentrat ion of native collagen as measured by circular dichroism. All fraction s extracted with MgO/carbonate mixtures developed more than 50% helica l structure while those extracted with MgO/hydroxide mixtures develope d 30-50% helix. Melting points for the helix to coil transition were 2 2 degrees C +/- 2 degrees C for all samples studied.