Jiangxi Provincial Key Laboratory of Genesis and Remediation of Groundwater Pollution, East China University of Technology, Nanchang, 330013, China.
School of Water Resources and Environmental Engineering, East China University of Technology, Nanchang, 330013, China.
Sci Rep. 2024 Jun 24;14(1):14559. doi: 10.1038/s41598-024-65544-w.
Understanding the nitrogen isotopic variations of individual amino acids (AAs) is essential for utilizing the nitrogen isotope values of individual amino acids (δN-AA) as source indicators to identify proteinaceous matter originating from biomass combustion processes. However, the nitrogen isotope effects (ε) associated with the degradation of individual amino acids during combustion processes have not been previously explored. In this study, we measured the nitrogen isotope values of residual free amino acids -following a series of controlled combustion experiments at temperatures of 160-240 °C and durations of 2 min to 8 h, as described in Part 1. δN values of proline, aspartate, alanine, valine, glycine, leucine, and isoleucine are more positive than their initial δN values after prolonged combustion. Variations in δN values of the most AAs conform to the Rayleigh fractionation during combustion and their nitrogen isotope effects (ε) are greatly impacted by their respective combustion degradation pathways. This is the first time the ε values associated with the degradation pathways of AAs during combustion have been characterized. Only the ε values associated with Pathway 1 (dehydration to form dipeptide) and 2 (simultaneous deamination and decarboxylation) are found to be significant and temperature-dependent, ranging from + 2.9 to 6.4‰ and + 0.9‰ to + 3.8‰, respectively. Conversely, ε values associated with other pathways are minor. This improves the current understanding on the degradation mechanisms of protein nitrogen during biomass burning.
理解单个氨基酸（AAs）的氮同位素变化对于利用单个氨基酸的氮同位素值（δN-AA）作为源示踪剂来识别源自生物质燃烧过程的蛋白质物质至关重要。然而，在燃烧过程中单个氨基酸降解的氮同位素效应（ε）尚未得到探索。在这项研究中，我们在 160-240°C 的温度下进行了一系列受控燃烧实验，持续时间从 2 分钟到 8 小时，并测量了残留游离氨基酸的氮同位素值，如第 1 部分所述。脯氨酸、天冬氨酸、丙氨酸、缬氨酸、甘氨酸、亮氨酸和异亮氨酸的 δN 值在长时间燃烧后比其初始 δN 值更正。大多数氨基酸的 δN 值变化符合燃烧过程中的瑞利分馏，它们的氮同位素效应（ε）受各自的燃烧降解途径的影响很大。这是首次对燃烧过程中氨基酸降解途径相关的 ε 值进行了描述。只有与途径 1（脱水形成二肽）和 2（同时脱氨和脱羧）相关的 ε 值被发现是显著的且与温度相关，范围分别为+2.9 到 6.4‰和+0.9‰到+3.8‰。相反，与其他途径相关的 ε 值较小。这提高了对生物质燃烧过程中蛋白质氮降解机制的现有理解。
