The composition of fossil oyster shell proteins.

Proceedings of the National Academy of Sciences of the United States of America

PubMedID: 5264151

Matter P, Davidson FD, Wyckoff RW. The composition of fossil oyster shell proteins. Proc Natl Acad Sci USA. 1969;64(3):970-2.
Analyses of the protein residues recovered from fossil oyster shells of ages from the Pleistocene through the Cretaceous show substantially the same amino acids as are present in modern proteins. The amount of these residues declines sharply to the Oligocene, after which it proceeds more slowly. These older proteins contain relatively less aspartic acid and glycine than do their younger counterparts.