The organic shell matrix of the freshwater snail Biomphalaria glabrata

The organic matrix of the aragonitic, cross-lamellar-structured shell of the freshwater snail Biomphalaria glabrata (Basommatophora, Pulmonata) has been investigated. The analysis of the water-soluble matrix components revealed protein as the main part of the matrix, followed by sulfate, neutral sugar, amino sugar, and small amounts of uronic acid and phosphate. In the amino acid analysis, glycine was the main amino acid of all matrix fractions. In the water soluble matrix, potentially acidic amino acids did not exceed 23%, while hydrophobic amino acids reached 37%. The SDS-electrophoretical separation gave a very prominent band at 19.6 kDa and several weaker bands of higher molecular weight. The 19.6 kDa protein had a pi of 7.4, and at the N-terminus a high amount of hydrophobic amino acids were found. Additionally, the organic matrix consists to a considerable amount of glycosaminoglycans or proteoglycanes of undetermined size. These Alcian Blue-and Stains all positive matrix constituents could be involved in the accumulation of calcium in the shell. (C) 1997 Elsevier Inc.