Biological signatures in clumped isotopes of O2
Biological signatures in clumped isotopes of O2
复制标题
DOI：
10.1126/science.aaa6284
复制
发表时间：
2015-04
期刊：
影响因子：
56.9
通讯作者：
L. Yeung;J. Ash;E. Young
中科院分区：
文献类型：
--
作者：
L. Yeung;J. Ash;E. Young
是什么控制着聚集的同位素？一个分子的稳定同位素可以以几种组合聚集在一起，这取决于它们的质量。即使是简单的分子，如O2，它可以包含16 O，17 O和18 O的各种组合，聚集的同位素可以潜在地揭示分子形成的温度。然而，在远离平衡的情况下，同位素聚集的模式可能反映了一系列复杂的过程。使用高分辨率气相质谱，Yeung等人发现生物因素影响光合作用过程中产生的氧的聚集同位素特征（参见Passey的Perspective）。类似地，Wang等人表明，远离平衡，导致同位素聚集的动力学效应可能导致高估微生物产生甲烷的温度。《科学》，本期第431页;第428页;另见第394页氧的生物循环在重同位素对中产生可识别的特征。[Also含有一种以上稀有同位素的分子丰度已被广泛应用于确定天然物质的形成温度。这些“聚集”同位素的应用依赖于这样的假设，即在这些材料的形成过程中达到或至少接近同位素交换平衡。在一个封闭系统的玻璃容器实验中，我们表明，生物氧（O2）循环驱动器的聚集同位素组成的O2远离同位素平衡。我们的系统模型表明，独特的生物特征存在于O2的聚集同位素中，而不是形成温度。光合O2是亏损的18 O 18 O和17 O 18 O相对于一个随机分布的同位素，不像在平衡，重同位素对富集。类似的特征可能在自然界中广泛存在，为生物和地球化学循环提供了新的示踪剂。
What controls clumped isotopes? Stable isotopes of a molecule can clump together in several combinations, depending on their mass. Even for simple molecules such as O2, which can contain 16O, 17O, and 18O in various combinations, clumped isotopes can potentially reveal the temperatures at which molecules form. Away from equilibrium, however, the pattern of clumped isotopes may reflect a complex array of processes. Using high-resolution gas-phase mass spectrometry, Yeung et al. found that biological factors influence the clumped isotope signature of oxygen produced during photosynthesis (see the Perspective by Passey). Similarly, Wang et al. showed that away from equilibrium, kinetic effects causing isotope clumping can lead to overestimation of the temperature at which microbially produced methane forms. Science, this issue p. 431; p. 428; see also p. 394 Biological cycling of oxygen yields identifiable signatures in heavy-isotope pairs. [Also see Perspective by Passey] The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures of natural materials. These applications of “clumped” isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during the formation of those materials. In a closed-system terrarium experiment, we demonstrate that biological oxygen (O2) cycling drives the clumped-isotope composition of O2 away from isotopic equilibrium. Our model of the system suggests that unique biological signatures are present in clumped isotopes of O2—and not formation temperatures. Photosynthetic O2 is depleted in 18O18O and 17O18O relative to a stochastic distribution of isotopes, unlike at equilibrium, where heavy-isotope pairs are enriched. Similar signatures may be widespread in nature, offering new tracers of biological and geochemical cycling.