Boosting wet adhesion of a genetically engineered glue from supercharged polypeptides employing a combination of computational and experimental methods

尽管在身体的动态和潮湿环境中的粘附在诸如外科手术的临床应用中是最重要的，但它仍然是一个技术挑战。天然海洋生物为开发水下胶水提供了灵感，这些胶水可以融合高机械稳定性和高柔性，以抵抗动态流体和表面存在下的连续机械应力和高离子强度以及pH值。尽管有复杂的生物机械和化学，海洋生物中粘附的主要基本机制是基于复杂的凝聚-由静电相互作用驱动，然后成熟为固相-由短程相互作用驱动。当两种带相反电荷的聚电解质混合时发生复凝聚，其经历液-液相转变。合成聚电解质和天然或重组蛋白质已被广泛研究，以模拟这种天然机制。然而，它们通常不能在环境条件下提供强的粘合强度。这主要是由于低程度的结构可调性，包括电荷密度和分布或分子相互作用的精确调节等，从而加深了我们对分子尺度上的粘附力的理解。为了克服这些挑战，我们介绍了一个家庭的序列定义的超荷电多肽（SUPs）和调查的结构要求，以提高其粘合性能。SUPs由每个重复序列中含有一个带电残基（X）的重复氨基酸序列组成（（VPGXG）n X：赖氨酸或精氨酸）。我们的目标是展示如何改变SUPs的结构和组成影响其机械性能，并优化这些功能，以提高水下附着力。这需要在不同类型的分子相互作用之间在几个时间和长度尺度上保持微妙的平衡。该项目分为三个主要目标：（1）合成SUPs并编码其结构中不同类型的分子相互作用，（2）在宏观尺度上研究基于SUP的复合凝聚层的粘附性能，（3）在分子水平上阐明粘附机制并通过合成，表征和计算机模拟之间的重复反馈来改善粘附。我们的目标是精确控制SUPs的分子参数，包括摩尔质量，电荷密度和电荷梯度，拓扑结构以及化学，以开发一个全面的模型，并预测湿粘附性能。

Although adhesion in dynamic and wet environments of the body is of prime importance in clinical applications such as surgery, it is still a technical challenge. Natural marine organisms have provided inspiration to develop underwater glues that can amalgamate high mechanical stability and high flexibility to resist continuous mechanical stresses and high ionic strength as well as pH in the presence of dynamic fluids and surfaces. In spite of the intricate biological machinery and chemistry, the primary underlying mechanism for adhesion in marine organisms is based on complex coacervation – driven by electrostatic interactions, followed by maturation into a solid phase – driven by short-range interactions. Complex coacervation occurs upon mixing of two oppositely charged polyelectrolytes, which undergo a liquid-liquid phase transition. Synthetic polyelectrolytes and natural or recombinant proteins have been extensively investigated to mimic this natural mechanism. However, they often failed to deliver strong adhesion strengths under ambient conditions. This is mainly due to the low degree of structural tunability, including charge density and distribution or the precise adjustment of molecular interactions etc., which imped our understanding about adhesion at the molecular scale. To overcome these challenges, we introduce a family of sequence-defined supercharged polypeptides (SUPs) and investigate the structural requirements to enhance their adhesive performance. SUPs consist of a repetitive amino acid sequence containing one charged residue (X) in every repeat ((VPGXG)n X:lysine or arginine). Our goal is to show how altering the architecture and composition of SUPs affect their mechanical properties and to optimize these features to improve underwater adhesion. This requires a delicate balance, at several time- and length-scales, between different types of molecular interactions. The project is divided into three main objectives: (1) synthesis of SUPs and encoding different types of molecular interactions in their structures, (2) investigation of adhesion performance of SUP-based complex coacervates at macroscopic scale and (3) elucidating the adhesion mechanism at the molecular level and improving the adhesion by a repetitive feedback between synthesis, characterization and computer simulation. We are aiming for precisely controlling the molecular parameters of SUPs including molar mass, charge density and charge gradients, topology as well as chemistry to develop a comprehensive model and to predict the wet adhesion properties.