Thermodynamic Models for Macromolecular Crystallization

小行星9728240 目前研究的主要目标是建立一个可测试的热力学模型来描述大分子结晶。 这个项目将使用一个独特的七核苷酸晶体系统，因为结晶的热力学可以使用晶体滴定分析进行研究。 该实验系统是一系列形成双链体的七核苷酸。 单个链在晶格中是不同的，并且可以通过晶体学或色谱学精确定量。 通过改变结晶溶液中两条链的比例，我们可以确定结晶过程中双链体之间的相互作用能。 从最初的研究中观察到晶格类型之间的过渡是高度合作的。 因此，该测定导致对形成初始晶种的DNA双链体之间的相互作用的能量和协同性的估计。 建议的研究是推导出一个模型来准确地描述这种结晶滴定，准确地确定该模型的参数，然后将该模型扩展到更普遍适用于其他晶体系统。 将通过监测浓度对晶体链组成的影响来验证模型。 X射线晶体学对我们理解大分子的结构和功能做出了重大贡献，特别是在原子水平上。 然而，该方法完全依赖于生长衍射质量单晶的能力。 尽管最近已经开发了许多工具来促进大分子的结晶，但对结晶的实际过程仍然知之甚少。 建议的研究结果将是一个热力学模型，应该是有用的结晶研究的合理设计的工具。该模型通常可用作核酸和蛋白质结晶的预测工具。 该模型将结合分子的可测量性质来预测晶种形成与晶体生长的概率，以及可能有利于这两个过程的条件。

9728240 Ho The primary objective of the current research is to develop a testable thermodynamic model to describe macromolecular crystallization. This project will use a heptanucleotide crystal system that is unique, in that the thermodynamics of crystallization can be studied using a crystallographic titration assay. This experimental system is a series of heptanucleotides that form duplexes. The individual strands are distinct in the lattice, and can be accurately quantified crystallographically or chromatographically. By varying the ratio of the two strands in the crystallization solutions, we can determine the energies of interaction between duplexes during crystallization. Transitions between lattice types were observed from initial studies to be highly cooperative. Thus, the assay has led to estimates for the energies and cooperativity for interactions between the DNA duplexes that form the initial seed crystal. The proposed studies are to derive a model to accurately describe this crystallization titration, accurately determine the parameters for this model, then extend the model to be more generally applicable to other crystal systems. The models will be validated by monitoring the effects of concentrations on the strand compositions of the crystals. X-ray crystallography has contributed significantly to our understanding of macromolecular structure and function, particularly at the atomic level. However, the method is entirely dependent on the ability to grow diffraction quality single crystals. Although a number of recent tools have been developed to facilitate the crystallization of macromolecules, the actual process of crystallization remains poorly understood. The result of the proposed studies will be a thermodynamic model that should be useful as a tool for the rational design of crystallization studies. The model will be generally useful as a predictive tool for crystallizing nucleic acids and proteins. The model will incorporate measurable properties of mo lecules to predict the probabilities for seed formation versus crystal growth, and conditions that may favor these two processes.