ATOMIC-FORCE MICROSCOPY AND ENZYMATIC DEGRADATION OF OYSTER SHELL PROTEIN AND POLY(ASPARTATE)

Oyster shell protein (OSP), an aspartate-enriched regulator of crystal lization, was readily observed in its natural condition by atomic forc e microscopy (AFM) of fragments of oyster shell. The fragments of shel l consisted of layers of calcite mineral, termed folia, to which array s of protein molecules are attached. Modification and removal of the O SP following treatment with several proteolytic enzymes such as subtil isin, carboxypeptidase B, and endoproteinase Glu-C were also observed by AFM. Similarly, poly(aspartate), a polypeptide analog of the OSP, w as visualized by AFM on both calcite and mica. Images of poly(aspartat e) before and after treatment with lipase demonstrated the potential u tility of AFM in degradation studies. The mechanism of hydrolysis is n ot clear in that lipase normally is considered to be an esterase and n ot a peptidase.