A Simple and Reliable Method for the Determination and Localization of Chitin in Abalone Nacre

We collected test reactions which can be applied in an easy and reproducible way to the chemical composition of the abalone organic matrix. Several chemical and biochemical test reactions were applied to the interlamellar organic matrix of abalone nacre to study the content and nature of polysaccharides. The preparation of the polysaccharide matrix was examined in parallel by light microscopy. The polysaccharide core is covered by a honeycomb-like structure, which can be completely removed by the protease subtilisin under release of the hydrophobic amino acid proline. The honeycomb pattern is in its size and its shape exactly the inverse matrix of the aragonite tablets, which are well-known to build up the nacreous layer of abalone shells. With this protocol we proved and verified in a straightforward and simple way the polysaccharides in abalone to be chitin. In addition, 1 H and 13 C NMR analysis of the interlamellar organic matrix of abalone nacre confirmed that it consists to a high extent of the polysaccharide chitosan or its partially/completely N -acetylated derivative chitin (β-(1→4)-2-acetamido-2-deoxy- d -glucose or N -acetyl- d -glucosamine).