While amino acid (AA) geochronology has been widely applied to foraminiferal biomineral proteins, there has been limited assessment of the potential of isolating an ‘intra-crystalline’ fraction of proteins to improve the reliability of AA geochronology for foraminifera. In this study, bleaching experiments were carried out on the foraminifer Neogloboquadrina pachyderma (sinistral) from an independently dated core from the south eastern Norwegian Sea spanning the last 120 ka. Results show that this species contains a bleach-resistant fraction of biomineral proteins, and that this intra-crystalline fraction may behave as a closed system. Racemisation in both the intra-crystalline and whole-protein fractions was found to systematically increase with time.

Isoleucine epimerisation showed reliable trends with depth when analysed by ion exchange chromatography (IEC); analysis by reverse-phase liquid chromatography (RP-HPLC) resulted in reliable age-D/L relationships for aspartic acid, glutamic acid and alanine.

Isolating the intra-crystalline fraction with a 48 h bleach treatment reduced the influence of contamination in younger material. Therefore, this paper recommends that the intra-crystalline approach is used when analysing Neogloboquadrina pachyderma (sinistral) for AA geochronology, especially for younger samples. Material-specific regression equations developed in this study successfully convert IEC A/I to RP-HPLC D/L values for aspartic acid, glutamic acid and alanine, enabling integration of geochronologies developed using different methods for this class of biomineral.

尽管氨基酸（AA）年代学已广泛应用于有孔虫生物矿物蛋白，但对分离蛋白质的“晶体内”级分以提高有孔虫的AA年代学可靠性的潜力的评估有限。在这项研究中，对有孔虫Neogloboquadrina pachyderma（正弦）的漂白实验是从挪威东南部的一个独立日期的岩心进行的，历时120 ka。结果表明，该物种包含生物矿物蛋白的抗漂白组分，并且该晶体内组分可能表现为封闭系统。发现结晶内和全蛋白组分中的外消旋作用均随着时间而系统地增加。

当通过离子交换色谱法（IEC）分析时，异亮氨酸差向异构显示出可靠的深度趋势。反相液相色谱（RP-HPLC）进行的分析表明，天冬氨酸，谷氨酸和丙氨酸的年龄D / L关系可靠。

通过48小时的漂白处理将结晶内的馏分分离，可以减少年轻材料中污染物的影响。因此，本文建议在分析Neogloboquadrina pachyderma（正弦）AA年代学（尤其是较年轻的样品）时，采用晶内方法。在这项研究中开发的特定于材料的回归方程式成功地将IEC A / I转换为RP-HPLC D / L值，包括天冬氨酸，谷氨酸和丙氨酸，从而可以整合使用不同方法开发的此类生物矿物的地质年代学。