When isotopes don't clump .....

重稳定同位素如C13或O18倾向于随机分散在分子中，其分布代表其天然丰度。成团描述了一种现象，其中一个以上的重同位素以高于随机分布的频率出现在分子中。结块是由热力学驱动的，温度越低，结块越多。凝聚与温度之间的这种关系是凝聚同位素测温法的基础。最近的反结块的描述，其中一个以上的重同位素出现在一个分子中的频率低于该温度下的预测丰度，已被描述在呼出的二氧化碳，光合氧和微生物甲烷。这些生物成因的气体中的抗结块被认为是由酶活性引起的，其控制过程远离热力学平衡。我们有海洋生物矿物抗结块的初步证据。可以说，生物矿物形成过程中的酶活性应该会影响结块的程度，这一点并不奇怪，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，多晶型物和晶体学的生物控制非常精细。如果成团同位素要广泛用作温度计，就必须确定和了解反成团现象的发生。我们的首要任务是确定在生物矿物中发生反结块的情况。当热力学平衡不适用时，反结块发生在生物影响下。因此，虽然结块提供了重要的温度数据，但抗结块指示生物原性，并告诉我们更多信息，包括有关生物过程和来源的细节。反聚集与聚集一样信息丰富，如果不是更多的话。为了利用这些信息，我们必须能够在发生反聚集时识别它，并了解导致反聚集的过程。我们的第二个优先事项是在微型反应器中使用酶驱动的矿物形成来诱导抗结块，该反应器将精细控制与高通量能力结合起来。这种方法支持快速蛋白质筛选，并产生大量的材料用于聚集同位素测量。在量化了蛋白质在一系列条件下诱导的聚集程度后，将使用具有集成拉曼光谱的微流体平台来确定抗聚集的机制。我们的研究结果将确保准确的古气候和古生物学数据的检索，并通过理解聚集同位素中编码的生物和环境信号来识别现代过程和起源。该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.