When isotopes don't clump .....

重稳定同位素如C13或O18倾向于随机分布在分子中，以代表其自然丰度的分布。团块现象描述了一个分子中多个重同位素以高于随机分布的频率出现的现象。结块是由热力学驱动的，较低的温度导致更多的结块。这种团块与温度的关系是团块同位素测温的基础。最近对反团块的描述，即一个分子中不止一种重同位素以低于该温度下预测丰度的频率出现，已经在呼出的二氧化碳、光合氧气和微生物甲烷中被描述。这些生物气体中的抗结块被认为是酶活性的结果，控制过程远离热力学平衡。我们有初步证据表明海洋生物矿物具有抗结块作用。可以说，生物矿物形成过程中的酶活性应该影响结块的程度，这并不奇怪，也许生物矿化可以完全由热力学驱动的想法是一个更具挑战性的概念，因为生物矿物结构、多晶型和晶体学的精细生物控制。如果团块同位素要广泛应用于温度计，就必须确定和了解反团块现象。我们的首要任务是确定生物矿物中抗结块发生的情况。当热力学平衡不适用时，在生物影响下会发生反结块。因此，虽然结块提供了重要的温度数据，但抗结块指示了生物原性，并告诉我们更多的信息，包括所涉及的生物过程和来源的细节。反结块与结块一样信息丰富，如果不是更丰富的话。为了充分利用这些信息，我们必须能够在发生反结块时识别它，并了解导致反结块的过程。我们的第二个重点是在结合精细控制和高通量能力的微反应器中利用酶驱动的矿物形成诱导抗结块。这种方法支持快速蛋白质筛选，并为团块同位素测量提供了丰富的材料。在量化了蛋白质在一系列条件下诱导的结块程度后，将使用集成拉曼光谱的微流体平台来确定抗结块的机制。我们的发现将确保准确的古气候和古生物学数据的检索，并通过理解在团块同位素中编码的生物和环境信号来实现现代过程和物源的指纹识别。这个项目将充分发挥这一新兴领域的潜力。

Heavy stable isotopes such as C13 or O18 tend to be randomly dispersed among molecules in a distribution that represents their natural abundances. Clumping describes the phenomenon where more than one heavy isotope occurs in a molecule at a frequency that is higher than a stochastic distribution. Clumping is driven by thermodynamics and lower temperatures result in more clumping. This relationship between clumping and temperature is the basis of clumped isotope thermometry. Recent descriptions of anti-clumping, where more than one heavy isotope occurs in a molecule at a frequency that is lower than the predicted abundance for that temperature, have been described in CO2 of exhaled breath, photosynthetic oxygen and microbial methane. Anti-clumping in these biogenic gases is suggested to result from enzyme activity, controlling the processes well away from thermodynamic equilibrium. We have preliminary evidence of anti-clumping in marine biominerals. Arguably, it should not be surprising that enzyme activity during biomineral formation should influence the extent of clumping and perhaps the idea that biomineralisation could be driven solely by thermodynamics is a more challenging concept in light of the exquisite biological control on biomineral structure, polymorphs and crystallography. It is imperative that the occurrences of anti-clumping are identified and understood if clumped isotopes are to have widespread application as thermometers. Our first priority is to identify the circumstances in which anti-clumping occurs in biominerals.Anti-clumping occurs under biological influence when thermodynamic equilibrium does not apply. Therefore, while clumping provides important temperature data, anti-clumping is indicative of biogenicity and tells us much more including details on the biological processes involved and the provenance. Anti-clumping is as information-rich, if not more so, than clumping. To tap into this information, we must be able to identify anti-clumping when it occurs and to understand the processes that result in anti-clumping. Our second priority is to induce anti-clumping using enzyme-driven mineral formation in a microreactor which combines fine control with high throughput capability. This approach supports rapid protein screening and produces plentiful material for clumped isotope measurements. Having quantified the degree of clumping that the proteins induce in a range of conditions, a microfluidics platform with integrated Raman spectroscopy will be used to determine the mechanism of anti-clumping. Our findings will ensure the retrieval of accurate palaeoclimate and palaeobiological data and enable fingerprinting of modern processes and provenance by understanding biological and environmental signals encoded in clumped isotopes. This project will realise the full potential of this emerging field.