EAGER: Intra-Clay Trapping of Organic Molecules – A Key Step in the Chemical Evolution of Life?

大约40亿年前，地球是生命形成和进化的不适宜居住的环境。当时没有像我们今天这样保护我们免受猛烈、有害的紫外线辐射的臭氧层。考虑到火山过度活动的存在，气温可能非常高。在这种情况下，导致生命形成的化学反应不可能发生。那么，是什么让我们这个星球上的生命成为可能呢？一些科学家同意诺贝尔奖获得者、生物化学家罗杰·科恩伯格的观点，“生命只是化学。”然而，将生命的形成简单地理解为复杂的分子相互作用的过程，并不能充分解释地球早期的恶劣条件。它也没有解释是什么突然发生了变化，使生命在这些严酷的条件下形成成为可能。今天，人们知道生命的基石RNA和DNA受到一层细胞膜的保护，该细胞膜保护它们免受潜在的有害环境的影响，但这些细胞膜在40亿年前并不存在于地球上。一种基于地质学而非化学的科学假说表明，通常在沉积物和岩石中发现的粘土矿物的功能就像细胞膜一样，保护最终形成生命所必需的RNA和DNA的分子。研究人员建议研究粘土矿物的功能，就像容纳早期有机分子的细胞膜一样。简而言之，他们想要研究地质学在生命出现中的作用。更好地了解生命形成的地质维度可以改变人们对地球上生命起源的看法，并可能改变人们寻找和定义地球以外生命的方式。这一科学目标是美国国家科学基金会推动科学进步的使命的核心。这项提议的更广泛的影响部分是探索一个新的场所，以增加多样性和未被充分代表的群体参与地球科学研究生课程。研究人员建议与位于塔斯卡卢萨(AL)的HBCU机构斯蒂尔曼学院(Stillman College)合作，吸收化学和生物专业的本科生作为实验室研究助理，从事地球生物学和低温地球化学方面的研究。这将使这些学生接触到一种不同类型的地质学，而不是通常所认为的“只看岩石”，以及一种类似于研究生课程中的学术研究体验。最终目标是在加州大学和斯蒂尔曼学院之间建立长期的合作关系，并促进非裔美国学生获得地质学和其他STEM学科的研究生课程。生命的化学演化研究是自然科学中的一个基础跨学科研究课题。这项研究的一个基本方面是了解原始生物分子是如何在地球早期存在的恶劣环境条件下“生存下来”的。长期以来，矿物，特别是粘土，一直被认为是促进生物分子积累和聚合的有效吸附表面，以支持生命的进化。最近的一个假说甚至表明，粘土可能起到了限制结构的作用，类似于细胞膜，保护了这些原始的生物分子，同时促进了生化反应，最终导致了RNA和DNA的发展。这意味着生物分子必须被封闭在粘土的层间空间中；然而，没有对这种捕获机制的直接观察。这一提议的智力价值在于，该团队首次提出使用最先进的原子探针断层扫描(APT)技术，以三维方式显示粘土矿物层间区域是否存在有机分子。如果这些有机物“穿透”粘土结构，它们将证明粘土作为“细胞膜”的假说在生命起源于海底纪晚期或太古宙早期是可能的。这一奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

About 4 billion years ago, Earth was an inhospitable environment for the formation and evolution of life. There was no ozone layer like we have today protecting us from violent, harmful UV radiation. Temperatures likely were extremely high given the presence of excessive volcanic activity. Under these conditions, the chemical reactions that lead to the formation of life could not have occurred. So, what happened to make life possible on our planet? Some scientists agree with Nobel Prize winning biochemist Roger Kornberg in stating, “life is only chemistry.” However, to understand the formation of life as simply the process of complex molecular interactions does not adequately account for the early Earth's harsh conditions. Nor does it explain what changed to suddenly make it possible for life to form under those severe conditions. Today, it is known that RNA and DNA, the building blocks of life, are protected by a cell membrane that shields them from potentially harmful environments, but those cell membranes were not present on Earth 4 billion years ago. One scientific hypothesis, based on geology rather than chemistry, suggests that clay minerals, typically found in sediments and rocks, functioned like cell membranes, protecting the molecules that would eventually form the RNA and DNA that are essential to life. Investigators propose to examine the capacity of clay minerals to function like cell membranes that housed those early organic molecules. In short, they want to study the role of geology in the emergence of life. Understanding better the geological dimensions of life formation can change how one thinks about the beginnings of life on this planet and possibly alter the ways one looks for and define life beyond Earth. This scientific goal is at the core of NSF's mission to promote the progress of science. The Broader Impact component of this proposal is to explore a new venue to increase diversity and the participation of underrepresented groups in Geosciences graduate programs. Investigators propose to partner with Stillman College, a HBCU institution in Tuscaloosa (AL), to incorporate undergraduate students from Chemistry and Biology, as laboratory research assistants, to do research in geobiology and low-temperature geochemistry. This will expose these students to a different type of geology than the common perception of “just looking at rocks”, and to an academic research experience similar to that found in a graduate program. The ultimate goal is to establish a long-term collaboration between UA and Stillman College and to facilitate the access of African American students to graduate programs in Geology, and other STEM disciplines.The study of the chemical evolution of life is a fundamental interdisciplinary research topic in Natural Sciences. A fundamental aspect of this research is the understanding of how primitive biomolecules “survived” the harsh environmental conditions present on early Earth. Minerals, especially clays, have been long suggested as effective adsorption surface to promote the accumulation and polymerization of biomolecules to support the evolution of life. A more recent hypothesis even suggests that clays could have acted as confinement structures, similar to cell membranes, protecting these primitive biomolecules while promoting biochemical reactions ultimately leading to the development of RNA and DNA. This would imply that biomolecules had to be occluded within clays inter-layer spaces; however, there are no direct observations of this trapping mechanism. The Intellectual Merit of this proposal is that for the first time, the team proposes to visualize in three-dimensions whether organic molecules can be present within the interlayer regions of clays minerals using the state-of-the-art atom probe tomography (APT) technique. If these organics “penetrate” the clay structure, they would have demonstrated that the hypothesis of clays acting as "cell membranes" was a possibility during the life origin in the late Hadean or early Archean.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.