Arctica islandica (Linnaeus, 1767) is a bivalve mollusk with a lifespan of up to 500 years. Its shell is a complex inorganic-organic nanocomposite, which is still not fully characterized. Here, we used Optical Photothermal Infrared (O-PTIR) microspectroscopy to characterize its organic phase, i.e. the hydrophobic insoluble extracts of both modern and fossil A. islandica shells. We compared the spectra from O-PTIR technique with those obtained from microRaman, microFTIR and ATR-FTIR spectroscopies. The structure of the shells was also studied using scanning electron microscope imaging. The spectroscopic techniques confirmed the presence of β-chitin and chitin-binding protein in the hydrophobic insoluble organic matrix. The results of element and light stable isotope analyses (δ13C, δ15N) from the hydrophobic insoluble extracts of both the modern and fossil shells were consistent with a shallow marine environment. The results demonstrate how O-PTIR can be applied in-situ for the study of biomaterials in shells, and points towards how it can be applied for the elucidation of intricate structure-function relationships. Furthermore, the approach of using the hydrophobic insoluble extracts to probe conditions and the nature of organic remains in fossil shells demonstrate an alternative to the use of soft tissues in isotopic studies and hence opens new possibilities for environmental reconstruction using fossil material when soft tissues are unavailable.

中文翻译：

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Arctica islandica 贝壳中微米和亚微米尺度生物大分子的分子特征


Arctica islandica （Linnaeus， 1767） 是一种双壳类软体动物，寿命长达 500 年。它的壳是一种复杂的无机-有机纳米复合材料，仍未完全表征。在这里，我们使用光学光热红外 （O-PTIR） 显微光谱来表征其有机相，即现代和化石 A. islandica 贝壳的疏水性不溶性提取物。我们将 O-PTIR 技术的光谱与从微拉曼、microFTIR 和 ATR-FTIR 光谱获得的光谱进行了比较。还使用扫描电子显微镜成像研究了壳的结构。光谱技术证实了疏水性不溶性有机基质中存在β-几丁质和几丁质结合蛋白。现代贝壳和化石贝壳的疏水不溶性提取物的元素和光稳定同位素分析结果（δ13C、δ15N）与浅海环境一致。结果展示了 O-PTIR 如何原位应用于壳中的生物材料研究，并指出了如何将其应用于阐明复杂的结构-功能关系。此外，使用疏水性不溶性提取物来探测化石壳中有机遗骸的条件和性质的方法证明了在同位素研究中使用软组织的替代方案，因此在软组织不可用时使用化石材料进行环境重建开辟了新的可能性。