Unraveling the Complexity of Biosilicification Processes: Kinetic and Thermodynamic Controls of Organic Substrates on the Nucleation of Amorphous Silica

揭示生物硅化过程的复杂性：有机基质对无定形二氧化硅成核的动力学和热力学控制

• 批准号: 0545166
• 负责人: Patricia Dove
• 金额: $ 21.98万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-15 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0545166&HistoricalAwards=false
• 关键词: Unraveling; Complexity; Biosilicification; Processes; Kinetic

EAR-0545166DOVEIntellectual Merit: With the recognition that silicon is a highly biological element, its roles in controlling the global biogeochemistry of both silicon and carbon have emerged as a forefront of scientific investigation. Of particular interest is to learn the biomineralization processes that readily produce the highly reactive pool of Si as amorphous hydrated silicas, also referred to as biogenic silica. Extensive morphological studies of biogenic silicas produced by marine and terrestrial silicifiers (ex. diatoms, choanoflagellates, vascular plants) show that many organisms share commonalities in their approaches to mineralization. This and evidence from the phylogenetic record have led to suggestions that underlying principles must exist to control biosilica formation (and other biominerals) by 'off the shelf' biochemical processes that direct a given type of mineralization again and again across multiple kingdoms and phyla. While the literature abounds in phenomenological characterizations of biological silicas, they cannot, by themselves, yield fundamental laws of biosilicification processes. Advances will require understanding the nucleation and growth processes taking place at the molecular level. This research area is ripe for advancement and this proposal describes a plan that takes advantage of the PI's unique experience in silica geochemistry and nanoscale model studies of mineral nucleation and growth in biomineralizing systems.Objectives, Methods: The project will use novel model biosubstrates to determine how the biochemistry of interfaces in biosilicification environments control the timing (kinetics) and extent/location (thermodynamics) of silica nucleation. The project will: 1) test hypotheses aimed at discovering how biochemical interfaces govern the nucleation step and early growth; and 2) quantify assertions that key functional groups associated with membranes promote the formation of hydrated silicas by modulating interfacial energy and attachment/detachment kinetics. This will also allow a direct test of the Gibbs-Thomson relation, a fundamental thermodynamic principle long believed to determine the spontaneous onset of mineral nucleation.This project is unique from previous studies by our focus on biochemical interfaces and our analysis by in situ nanoscale methods to measure and characterize the products. Applying methods in use in our laboratory, model membranes will be prepared as nanoscale chemical templates. The kinetic, thermodynamic, and characterization studies of nucleation will use insitu fluid tapping AFM and confocal Surface Enhanced Raman spectroscopy. Results will be analyzed within the framework of classical nucleation and growth theories. This basic science study will establish factors that promote and retard silicification in organic-rich environments. In quantifying these organic controls, an understanding of the relative importance of thermodynamic drivers and kinetic factors in inducing nucleation will emerge.Broader Impacts: The outcomes will benefit forefront research questions in many disciplines.1) How do microbes (passively or actively?) promote extensive silicification in hydrothermal springs? 2) Under what conditions could the onset of phosphate-based mineralization be determined by an initial silicification step? 3) What are the kinetic and thermodynamic controls on the formation of silica precipitates/scales in earth/industrial systems? 4) How do silicifying organisms utilize environmentally benign conditions to initiate and mold elaborate structures? The world of minerals and organisms is naturally exciting for outreach and education. The fascinating linkages between these two areas will be the focus of a second 'Biominerals- Earth to Life' activity. We will build a new module that integrates minerals, amorphous silica gels, and silicifying organisms to develop an interactive activity targeted to middle school students.

EAR-0545166DoveIntelectual功绩：认识到硅是一种高度生物学元素，其在控制硅和碳全球生物地球化学方面的作用已成为科学研究的前沿。特别有趣的是学习生物矿化过程，这些过程易于产生高度反应性的Si作为无定形水合硅，也称为生物二氧化硅。海洋和陆生硅化剂（例如硅藻，choanoflagellates，discular植物）生成的生物硅对生物硅的广泛形态学研究表明，许多生物体在其矿化方法中具有共同点。从系统发育记录中的这一证据和证据提出了建议，即必须存在基本原则来控制生物硅硅氧基菌形成（和其他生物矿物质），这是通过“搁置”的生化过程，这些过程一次又一次地引导给定类型的矿化类型的矿化类型。尽管文献在生物硅的现象学特征中遍布，但它们本身不能产生生物硅化过程的基本定律。进步将需要了解分子水平上发生的成核和生长过程。 This research area is ripe for advancement and this proposal describes a plan that takes advantage of the PI's unique experience in silica geochemistry and nanoscale model studies of mineral nucleation and growth in biomineralizing systems.Objectives, Methods: The project will use novel model biosubstrates to determine how the biochemistry of interfaces in biosilicification environments control the timing (kinetics) and extent/location (thermodynamics)二氧化硅成核。该项目将：1）旨在发现生化界面如何控制成核步骤和早期生长的测试假设； 2）量化与膜相关的关键官能团通过调节界面能量和附着/脱离动力学来促进水合硅的形成。这还将允许直接测试Gibbs-Thomson关系，这是一种基本的热力学原理，据信据信确定矿物质成核的自发发作。这是我们对生物化学界面的重点是以前的研究，并且我们通过现场纳米级方法进行了测量和表征产品的分析。在我们的实验室中使用的方法，将作为纳米级化学模板制备模型膜。成核的动力学，热力学研究和表征研究将使用滴滴液体敲击AFM和共聚焦表面增强的拉曼光谱。结果将在经典成核和生长理论的框架内进行分析。这项基础科学研究将建立在有机富裕环境中促进和推迟硅化的因素。在量化这些有机控制的过程中，了解热力学驱动因素和动力学因素在诱导成核中的相对重要性将出现。Broader的影响：结果将使许多学科中的前沿研究问题受益。1）1）微生物（被动或主动？ 2）在什么条件下，可以通过初始硅化步骤确定基于磷酸盐的矿化的发作？ 3）关于地球/工业系统中二氧化硅沉淀/尺度的形成的动力学控制和热力学控制是什么？ 4）如何利用环境良性条件来启动和塑造精心制作的结构？矿物质和生物的世界对于外展和教育而言自然是令人兴奋的。这两个领域之间引人入胜的联系将是第二个“生物地球到生命”活动的重点。我们将建立一个新的模块，该模块整合矿物质，无定形硅胶和硅化生物，以开发针对中学生的互动活动。