'WET' ELECTROSTATICS AND BIOMOLECULAR SELF-ASSEMBLY

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 “湿”静电相互作用知之甚少，往往表现出违反直觉的行为。例如，在水溶液中，两个带相同电荷的大分子会互相排斥，这基本上是流行的平均场理论的预测。然而，在多价离子的存在下，许多生物聚合物实际上相互吸引并凝聚成紧凑的有序状态。例子包括染色体中带电组蛋白的DNA浓缩，以及细菌和病毒衣壳中多价鱼精蛋白的DNA包装。在我们以前在SSRL的工作中，我们直接观察到的棒状聚电解质之间的吸引力的分子机制，通过观察counterweight组织。目前提出的计划的目的是发展我们的直觉更复杂的形式的静电组装。我们将研究一系列简单的几何物体之间的相互作用的范例，如复合物之间形成的带电荷的杆和片（阴离子DNA和阴离子膜），或复合物之间形成的带相反电荷的杆和球状体（F-肌动蛋白和单分散阳离子球状蛋白（溶菌酶，乳铁蛋白））在存在的盐的不同价。特别是，我们将利用基因工程技术，使突变蛋白质具有基本相同的大小，但不同的净电荷和电荷分布，并研究这些变化如何影响其自组装行为。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 'Wet' electrostatic interactions are poorly understood and often exhibit counterintuitive behavior. For example, two like-charged macromolecules in aqueous solution are expected to repel one another, which is essentially the prediction of prevailing mean-field theories. In the presence of multivalent ions, however, many biopolymers actually attract one another and condense into compact, ordered states. Examples include DNA condensation by charged histones in chromosomes, and DNA packaging by multivalent protamines in bacteria and viral capsids. In our previous work at SSRL, we have directly observed a molecular mechanism for attractions between rod-like polyelectrolytes by observing counterion organization. The aim of the present proposed program is to develop our intuition for more complex forms of electrostatic assembly. We will examine a series of paradigmatic examples of interactions between simple geometric objects, such as complexes formed between like-charged rods and sheets (anionic DNA and anionic membranes), or complexes formed between oppositely charged rods and spheroids (F-actin and monodisperse cationic globular proteins (lysozyme, lactoferrin)) in the presence of salts of different valence. In particular, we will take advantage of genetic engineering techniques to make mutant proteins with essentially the same size but with different net charges and charge distributions, and examine how these changes impinge on their self-assembly behavior.