Micro-XANES mapping of sulphur and its association with magnesium and phosphorus in the shell of the brachiopod, Terebratulina retusa

Cusack, M. , Dauphin, Y., Cuif, J.P., Salomé, M., Freer, A. and Yin, H. (2008) Micro-XANES mapping of sulphur and its association with magnesium and phosphorus in the shell of the brachiopod, Terebratulina retusa. Chemical Geology, 253(3-4), pp. 172-179. (doi: 10.1016/j.chemgeo.2008.05.007)

Abstract

Biominerals are natural composite materials comprising organic and inorganic components. Detailed knowledge of the nature and distribution of both components is a crucial requirement in order to advance our understanding of biomineral formation, their material properties and preservation potential as well as the interpretation of environmental data. Detailed chemical data are essential for our understanding of the nature and distribution of such components. Micro-XANES mapping at the sulphur K-edge reveals that, in the brachiopod <i>Terebratulina retusa</i>, the sulphate concentration is higher in the outer (primary) layer than in the calcite fibres of the secondary layer. This is co-incident with a higher magnesium concentration. In contrast, the sheaths surrounding the calcite fibres contain sulphur as thiol, confirming the presence of protein while, the sulphur within the fibres themselves, occurs as sulphate. Micro-XANES analysis of the insoluble organic extract from <i>T. retusa</i> indicates the presence of organic sulphate while Micro-Raman spectroscopy confirms that structurally substituted sulphate (SSS) is also present although semi-quantitative Raman spectroscopy carried out in this spectral region (wavenumbers 900–1200) indicates that the sulphate present is at the threshold of detection by Raman spectroscopy. The distribution of phosphorus in the shell of <i>T. retusa</i> correlates well with that of protein indicating the presence of phosphorylated proteins in the periostracum, the sheaths surrounding the calcite fibres and the interface between the primary and secondary layer.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Yin, Professor Huabing and Cusack, Professor Maggie
• Authors: Cusack, M., Dauphin, Y., Cuif, J.P., Salomé, M., Freer, A., and Yin, H.
• College/School: College of Science and Engineering > School of Engineering > Biomedical Engineering; College of Science and Engineering > School of Geographical and Earth Sciences
• Journal Name: Chemical Geology
• ISSN: 0009-2541
• ISSN (Online): 1872-6836
• Published Online: 28 May 2008