在生物系统中，金属/金属类同位素分馏是一个新兴的研究领域，它需要应用先进的分析化学工具，并提供与生命科学相关的数据。本研究测量了面包酵母（酿酒酵母）（Saccharomyces cerevisiae）富集硒和硒同位素分馏过程，该产品被广泛用于膳食补硒和癌症预防。另一方面，15N代谢标记是基于质谱的比较蛋白质组学中的有价值的工具。对于硒酵母来说，这种标记将有助于评估硒对酵母蛋白质组的影响；然而，一个问题是微生物体中的15N是否会影响硒的吸收和同位素分馏。为了解决上述问题，我们使用了产氢-多收集器电感耦合等离子体质谱仪（HG MC ICP-MS）进行了对细胞外还原的硒和细胞内硒的分析。发现细胞外还原的硒富集了轻同位素；而对于细胞内硒，这种变化更加明显，这为生物亚硒酸盐还原过程中的质量分馏提供了新的证据。在15N存在的情况下，细胞外和细胞内硒对轻同位素的偏好较弱。此外，与14N生物组相比，发现15N的硒摄取显著增加，并且产生了产氢微波等离子体原子发射光谱法（HG MP-AES）和四极杆ICP-MS结果之间的良好一致性。重氮的生物效应表明15N驱动了蛋白质组水平的变化，有利于硒透入细胞，并且对轻同位素的偏好降低。 © 2023. 作者，独家授权给生物无机化学学会（SBIC）。

Isotope fractionation of metals/metalloids in biological systems is an emerging research area that demands the application of state-of-the-art analytical chemistry tools and provides data of relevance to life sciences. In this work, Se uptake and Se isotope fractionation were measured during the biofortification of baker's yeast (Saccharomyces cerevisiae)-a product widely used in dietary Se supplementation and in cancer prevention. On the other hand, metabolic labeling with 15N is a valuable tool in mass spectrometry-based comparative proteomics. For Se-yeast, such labeling would facilitate the assessment of Se impact on yeast proteome; however, the question arises whether the presence of 15N in the microorganisms affects Se uptake and its isotope fractionation. To address the above-mentioned aspects, extracellularly reduced and cell-incorporated Se fractions were analyzed by hydride generation-multi-collector inductively coupled plasma-mass spectrometry (HG MC ICP-MS). It was found that extracellularly reduced Se was enriched in light isotopes; for cell-incorporated Se, the change was even more pronounced, which provides new evidence of mass fractionation during biological selenite reduction. In the presence of 15N, a weaker preference for light isotopes was observed in both, extracellular and cell-incorporated Se. Furthermore, a significant increase in Se uptake for 15N compared to 14N biomass was found, with good agreement between hydride generation microwave plasma-atomic emission spectrometry (HG MP-AES) and quadrupole ICP-MS results. Biological effects observed for heavy nitrogen suggest 15N-driven alteration at the proteome level, which facilitated Se access to cells with decreased preference for light isotopes.© 2023. The Author(s), under exclusive licence to Society for Biological Inorganic Chemistry (SBIC).