Soluble Organic Matrices of the Calcitic Prismatic Shell Layers of Two Pteriomorphid Bivalves: PINNA NOBILIS AND PINCTADA MARGARITIFERA

Yannicke Dauphin

doi:10.1074/jbc.m204375200

Abstract

The calcitic prisms of the shells of two bivalves, Pinna and Pinctada, are considered simple prisms according to some morphological and mineralogical characteristics. Scanning electron microscopic and atomic force microscopic studies show that the microstructures and nanostructures of these two shells are different. Pinna prisms are monocrystalline, whereas Pinctada prisms are not. Moreover, intraprismatic membranes are present only in the Pinctada prisms. The soluble organic matrices extracted from these prisms are acidic, but their bulk compositions differ. Ultraviolet and infrared spectrometries, fluorescence, high pressure liquid chromatography, and electrophoresis show that the sugar-protein ratios and the molecular weights are different. Sulfur is mainly associated with acidic sulfated sugars, not with amino acids, and the role of acidic sulfated sugars is still underestimated. Thus, the simple prism concept is not a relevant model for the biomineralization processes in the calcitic prismatic layer of mollusk shells.

Highlights

The calcitic prisms of the shells of two bivalves, Pinna and Pinctada, are considered simple prisms according to some morphological and mineralogical characteristics
Ultraviolet and infrared spectrometries, fluorescence, high pressure liquid chromatography, and electrophoresis show that the sugarprotein ratios and the molecular weights are different
Much of what is known about biominerals is deduced from the nacreous layers of mollusks, and it is believed that the organic matrix serves as a guide for crystal growth [1, 2]

Summary

Introduction

The calcitic prisms of the shells of two bivalves, Pinna and Pinctada, are considered simple prisms according to some morphological and mineralogical characteristics. Among more than 60 known different biominerals, calcium minerals are the most abundant These exoskeletons ( called hard tissues or shells) have morphological, chemical, and physical properties that are never shown by the corresponding abiotic crystals. Pinna nobilis and Pinctada margaritifera are two modern pteriomorphid bivalves with shells composed of an outer calcitic prismatic layer and an inner aragonitic nacreous layer Their calcitic prisms offer remarkable advantages to investigate the organization of biocrystals. Illustrations of a transverse section of the prisms of Pinctada by Wise [12] are similar to those of Taylor et al [11] and follow the simple prism concept These calcitic layers have high S and magnesium contents [13,14,15,16]. The location of the organic matrices and the presence of sugars are considered

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Conclusion