von Holstein Isabella C C, von Tersch Matthew, Coutu Ashley N, Penkman Kirsty E H, Makarewicz Cheryl A, Collins Matthew J
BioArCh, Department of Archaeology, University of York, York, YO10 5DD, UK.
Institut für Ur- und Frühgeschichte, Christian-Albrechts-Universität, D-24098, Kiel, Germany.
Rapid Commun Mass Spectrom. 2018 Mar 30;32(6):523-534. doi: 10.1002/rcm.8064.
The oxygen (O) isotope composition of collagen proteins is a potential indicator of adult residential location, useful for provenancing in ecology, archaeology and forensics. In acidic solution, proteins can exchange O from carboxylic acid moieties with reagent O. This study investigated whether this exchange occurs during demineralisation and gelatinisation preparation of bone/ivory collagen.
EDTA and HCl demineralisation or gelatinisation reagents were made up in waters with different δ O values, and were used to extract collagen from four skeletal tissue samples. Aliquots of extracted collagen were exposed to two different atmospheric waters, at 120°C and ambient temperature, and subsequently dried in a vacuum oven at 40°C or by freeze drying. Sample δ O values were measured by HT-EA pyrolysis/IRMS using a zero-blank autosampler.
Collagen samples exchanged O with both reagent waters and atmospheric water, which altered sample δ O values. Exchange with reagent waters occurred in all extraction methods, but was greater at lower pH. Damage to the collagen samples during extraction increased O exchange. The nature of exchange of O with atmospheric water depended on the temperature of exposure: kinetic fractionation of O was identified at 120°C but not at ambient temperature. Exchange was difficult to quantify due to the high variability of δ O values between experimental replicates.
Studies of δ O values in collagen proteins should avoid extraction methods using acidic solutions.
胶原蛋白的氧（O）同位素组成是成人居住地点的潜在指标，可用于生态学、考古学和法医学的溯源。在酸性溶液中，蛋白质可与试剂氧发生羧酸部分的氧交换。本研究调查了这种交换是否在骨/象牙胶原蛋白的脱矿质和明胶化制备过程中发生。
用具有不同δO值的水配制乙二胺四乙酸（EDTA）和盐酸脱矿质或明胶化试剂，并用于从四个骨骼组织样本中提取胶原蛋白。将提取的胶原蛋白等分试样在120°C和环境温度下暴露于两种不同的大气水中，随后在40°C的真空烘箱中干燥或冷冻干燥。使用零空白自动进样器通过高温-元素分析仪热解/同位素比率质谱仪（HT-EA pyrolysis/IRMS）测量样品的δO值。
胶原蛋白样品与试剂水和大气水都发生了氧交换，这改变了样品的δO值。在所有提取方法中均发生了与试剂水的交换，但在较低pH值下交换量更大。提取过程中胶原蛋白样品的损伤增加了氧交换。与大气水的氧交换性质取决于暴露温度：在120°C时发现了氧的动力学分馏，但在环境温度下未发现。由于实验重复之间δO值的高度变异性，交换难以量化。
胶原蛋白中δO值的研究应避免使用酸性溶液的提取方法。
