Amino acid racemization (AAR) is a geochronological method that uses the ratio of D- to L-configurations in optically active amino acids from carbonate fossils to determine the time elapsed since the death of an organism. Although AAR techniques have been widely applied to foraminiferal tests, there have been limited dedicated assessments of the potential of isolating a bleach-resistant, intra-crystalline fraction of proteins to improve the reliability of AAR in this biomineral system. In this study, we evaluate the effect of two oxidative pre-treatments (hydrogen peroxide and bleach) on amino acid concentrations and D/L values in sub-modern benthic foraminifers (Ammonia spp. and Haynesina germanica) and well-preserved mid Holocene and mid Pleistocene planktic foraminifers (Pulleniatina obliquiloculata, Globorotalia truncatulinoides, and Globorotalia tumida). The oxidative pre-treatments successfully reduced the amino acid content of the foraminiferal tests to a residual fraction, and with the exception of Ammonia spp., neither pre-treatment substantially affected the relative proportion of individual amino acids. The bleaching pre-treatment does not consistently alter D/L values when compared to peroxide pre-treatment, but it does tend to reduce the subsample variability in D/L values, albeit only to a small degree in an inconsistent fashion. Therefore, we recommend that a relatively weak oxidative pre-treatment with 3% hydrogen peroxide is sufficient for foraminifera-based AAR applications.

氨基酸消旋化 (AAR) 是一种地质年代学方法，它使用来自碳酸盐化石的光学活性氨基酸中 D-与 L-构型的比率来确定自生物体死亡以来经过的时间。尽管 AAR 技术已广泛应用于有孔虫测试，但对分离抗漂白的蛋白质晶体内部分以提高 AAR 在该生物矿物系统中的可靠性的潜力的专门评估有限。在这项研究中，我们评估了两种氧化预处理（过氧化氢和漂白剂）对亚现代底栖有孔虫（Ammonia spp. 和Haynesina Germanica）和保存完好的全新世中期和中更新世浮游有孔虫（Pulleniatina obliquiloculata、Globorotalia truncatulinoides和Globorotalia tumida )。氧化预处理成功地将有孔虫测试的氨基酸含量降低到残留部分，并且除了氨菌之外，任何预处理都不会显着影响单个氨基酸的相对比例。与过氧化物预处理相比，漂白预处理不会始终如一地改变 D/L 值，但它确实倾向于减少 D/L 值的子样本可变性，尽管以不一致的方式仅在很小程度上有所改变。因此，我们建议使用 3% 过氧化氢进行相对较弱的氧化预处理足以用于基于有孔虫的 AAR 应用。