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Aspects of the Biochemistry of the Organic Matrix of Extant and Fossil Mollusks


Weiner, Stephen (1977) Aspects of the Biochemistry of the Organic Matrix of Extant and Fossil Mollusks. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Q5CV-RC94.


The biochemistry of the organic matrix of mollusks is investigated to improve our understanding of the function of this material in shell formation and to explore the possibility of using fossil organic matrix components to study aspects of molecular evolution.

The soluble fractions of the organic matrices of nine species of mollusks representing the three major classes of the phylum have been investigated. However, the organic matrix of the clam, Mercenaria mercenaria, has been studied in greatest detail. It is composed of protein with covalently bound carbohydrate. The protein-carbohydrate linkage is probably through serine and/or threonine residues. The organic matrix components vary greatly in their protein-carbohydrate proportions, amino acid compositions and hydrodynamic size.

The discrete molecular weight components of the nine species of mollusks investigated exhibit great heterogeneity above the species level. A particular repeating amino acid sequence in which every second amino acid is an aspartic acid separated by either glycine or serine, is present in all mollusks examined to date. It is suggested that this amino acid sequence is a potential template for crystal nucleation.

The organic matrix of an 80 million year old clam, Scabrotrigonia thoracica, still contains the repeating aspartic acid sequence and discrete molecular weight components, indicating that this material is unusually well preserved, and therefore could be of use in future studies of molecular evolution based on material derived from the fossil record. The glycine content of the organic matrices of eight of these fossil shells is a sensitive indicator of early diagenesis. The alloisoleucine/isoleucine ratios of the shell protein ranged from the equilibrium value to extremely low values. The potential uses of fossil organic matrices in evolution studies are discussed.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Geobiology
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geobiology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Unknown, Unknown
Thesis Committee:
  • Unknown, Unknown
Defense Date:18 October 1976
Funding AgencyGrant Number
NSFDES 75-08659
NSFPCM 71-00770
Record Number:CaltechTHESIS:11112019-161331927
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Appendix. adapted for Appendix.
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13565
Deposited By: Mel Ray
Deposited On:12 Nov 2019 01:06
Last Modified:20 Dec 2019 19:55

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