Effect of ionic residue sequence on polyampholyte interactions, molecular recognition and phase separation

该项目的总体目标是了解带电两性大分子中的序列编码信息如何实现分子识别并驱动多个非混合相分离液相的形成。液-液相分离的大分子以高度带电的固有无序蛋白质结构域的形式存在于非常不同的生物实体中，例如蜘蛛丝纤维、贻贝胶或无膜细胞内细胞器的前体。因此，这种凝聚相表现出令人印象深刻的功能，例如，生物活性分子的分配，坚韧纤维的合成或特异性粘附。这些功能是由于带电序列的明确定义的相互作用和分子识别，这可能是由带电残基沿大分子链沿着的图案化控制。可以假设，对于带电序列和下游功能（如液-液相分离）之间的这种分子识别，确实需要对沿着链的许多电荷-电荷相互作用沿着进行精细控制。随着序列控制聚合物的出现，可以实现这种控制，并且能够用合成聚合物模拟这些功能将是有趣的。然而，更多的知识如何带电聚合物利用多价离子相互作用，以驱动相分离必须首先获得。为了实现这一目标，高通量筛选技术，定量粘附测量与软胶体探针，并通过AFM单分子力光谱将用于破译分子识别模式的序列定义的两性肽（A部分：相互作用）。这些定量相互作用研究将与使用荧光技术和拉曼光谱的液-液相分离研究相结合，以确定凝聚相的组成和结构（部分B：相分离）。一个具体的目的是通过将不同的序列与A部分中确定的不同的自相互作用组合来实现多个非混合分离相。为了更接近地模拟天然内在无序蛋白质的相分离性质，将制备由序列限定的肽组成的高分子量结构。在这里，我们提出了聚合物类似物反应对这样的高分子量的系统，这是很容易获得的，同时保持带电残基的序列定义的介绍。总的来说，这个项目将使广泛的了解序列的作用，相互作用和两性聚电解质之间的识别，他们的相行为，亚相的形成等，这导致超越国家的最先进的这些新的见解可能会激发一类新的材料，模仿一个有趣的蛋白质性质：进行功能相分离的能力。

The overall aim of this project is to understand how sequence-encoded information in charged ampholytic macromolecules achieves molecular recognition and drives the formation of multiple non-mixing phase-separated liquid phases. Liquid-liquid phase-separated macromolecules are present in form of highly charged intrinsically disordered protein domains in vastly different biological entities such as precursors of spider silk fibers, mussel glue or membraneless intracellular organelles. Therefore, such coacervate phases exhibit an impressive array of functions, for example, partitioning of bioactive molecules, synthesis of tough fibers, or specific adhesion. These functions are due to well-defined interactions and molecular recognition of the charged sequences, which is likely controlled by the patterning of charged residues along the macromolecule chain. It can be assumed that fine control over many charge-charge interactions along a chain is indeed required for such molecular recognition among charged sequences and downstream functions, like liquid-liquid phase separation. With the advent of sequence-controlled polymers, such control can be achieved and it would be intriguing to be able to emulate these functions with synthetic polymers. However, more knowledge on how charged polymers take advantage of multivalent ionic interactions to drive phase separation must first be acquired. To achieve this goal, high-throughput screening techniques, quantitative adhesion measurements with soft colloidal probes, and single molecule force spectroscopy via AFM will be used to decipher molecular recognition modes on sequence-defined ampholytic peptides (part A: interactions). These quantitative interaction studies will be combined with liquid-liquid phase separation studies using fluorescent techniques and Raman spectroscopy to determine the composition and structure of the coacervate phases (part B: phase separation). A specific aim is to achieve multiple non-mixing separated phases by combining different sequences with varying self-interactions as determined in part A. In order to more closely mimic the phase separation properties of natural intrinsically disordered proteins, high-molecular-weight structures composed of sequence defined peptides will be prepared. Here, we propose polymer analogue reactions toward such high-molecular-weight systems, which are readily accessible while the sequence defined presentation of charged residues is maintained. Overall, this project will enable a broad understanding of the role of sequence on the mutual interactions and recognition among polyampholytes, their phase behavior, the formation of subphases, etc. which leads beyond the state-of-the-art. These new insights may inspire a new class of materials that mimic an intriguing protein property: the ability to undergo functional phase separation.