Mollusk shells, especially the nacre, are of commercial interest as well as palaeoenvironmental proxies. They are also investigated as biomaterials for medical purposes and biomimetics. Although the mineralogy is well-known and unique (aragonite tablets), the organic components are various. However, determination of the precise composition of the soluble organic matrix (SOM) of the nacreous layer is difficult. Among the range of possible techniques, 1D electrophoresis and High-performance liquid chromatography (HPLC) have previously been applied separately to differentiate pI and molecular weights. To date, no clear correlation has been established between the two parameters obtained in such conditions. Here, we report the use of preparative electrophoresis, coupled with HPLC, to determine the molecular weights of the pI fractions. The results are compared with 2D gel electrophoresis. It is shown that both methods have drawbacks and advantages, and are not redundant. The complexity of the composition of the nacreous tablet shown by scanning electron microscope (SEM) and Atomic Force Microscope (AFM) observations is also evidenced by electrophoresis and？HPLC.
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