Reverse engineering methods for elucidating the molecular assembly mechanisms of thermoresponsive peptide-based conjugates: computation and experiment

由温敏性合成和生物聚合物组装的纳米结构可广泛用作传感器、电子器件、分子机器、药物递送系统和组织工程基质。这些聚合物的设计特征，如分子组成、序列、分子量和水溶液浓度，允许调节发生相变的温度。此外，已经证明，热响应聚合物的缀合物提供了编码双重热转变的手段;这种多温度响应性可用于指导纳米结构在特定温度下的组装和拆卸，从而增加其潜在的应用范围。然而，缺乏对这些温敏缀合物的分子设计如何影响驱动多步骤纳米结构组装和拆卸过程的分子相互作用的基本理解。发展这样的理解是在诸如生物化学传感器、致动、分子货物（例如，药物）递送和时空控制催化。在纳米结构（反）组装过程中，使用小角度X射线和中子散射耦合到先进的计算方法分析散射结果的能力，共轭物将提供变革的机会，在分子design.The总体目标的建议是开发新的方法来询问分子的相互作用，包装，和动态组装和拆卸技术上有用的热敏共轭物。该研究小组已经引入了双重热响应弹性蛋白样肽缀合物，其与棒状寡聚肽结构域相连。这些分子将通过X射线和中子散射以及显微镜进行合成和表征。实验将耦合到一个新的，粗粒度的模型和模拟，将预测结构转变与不同的温度范围内的肽缀合物的分子设计。温度控制的小角度散射实验将探测组装路径中不同温度下的结构。中间结构，并可能最终组装的结构，将不一定服从规范的结构和形状因子，因此，将阐明组装过程的分子基础的新的计算方法将被开发。拟议的工作将利用研究小组高级成员以前成功合作所获得的知识。通过这种合作，将丰富学生在实验和模拟方面的跨学科培训;通过拟议工作取得的技术进步将被纳入课堂。研究人员将建立在他们的历史承诺，在招聘和保留学生的代表性不足的少数群体，有助于课程和推广从中学到研究生水平。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

Nanostructures assembled from thermoresponsive synthetic and biological polymers are widely applicable as sensors, electronic devices, molecular machines, drug delivery systems, and matrices for tissue engineering. The design features of these polymers, such as molecular composition, sequence, molecular weight, and aqueous solution concentration, permit tuning of the temperature at which phase transitions take place. Furthermore, it has been demonstrated that conjugates of thermoresponsive polymers provide a means of encoding dual thermal transitions; this multi-temperature responsiveness can be used to direct the assembly and disassembly of nanostructures at specific temperatures, increasing their potential range of applications. However, there is a lack of fundamental understanding of how the molecular design of these thermoresponsive conjugates affects the molecular interactions that drive the multi-step nanostructural assembly and disassembly processes. Developing such an understanding is key to expanding thermoresponsive nanostructures in applications such as biochemical sensors, actuation, molecular cargo (e.g., drug) delivery, and spatiotemporally controlled catalysis. The ability to characterize conjugates during nanostructure (dis)assembly using small-angle X-ray and neutron scattering coupled to advanced computational methods for analyzing the scattering results will provide transformative opportunities in molecular design.The overarching objective of this proposal is to develop new approaches to interrogate molecular interactions, packing, and dynamics during the assembly and disassembly of technologically useful thermoresponsive conjugates. The research team has introduced dually thermoresponsive elastin-like peptide conjugates tethered to rod-like, oligomeric peptide domains. These molecules will be synthesized and characterized via X-ray and neutron scattering and microscopy. Experiments will be coupled to a new, coarse-grained model and simulations that will predict structural transitions with varying temperature for a range of molecular designs of the peptide conjugates. Temperature-controlled small-angle scattering experiments will probe structures at various temperatures in the assembly pathway. The intermediate structures, and potentially the final assembled structures, will not necessarily obey canonical structure and form factors, thus new computational methods that will elucidate the molecular underpinnings of the assembly process will be developed. The proposed work will leverage the knowledge gained from previous successful collaborations between the senior members of the research team. Interdisciplinary training of students in experiments and simulations will be enriched through this collaboration; the technical advances made through the proposed work will be integrated into the classroom. The researchers will build on their historical commitment in recruitment and retention of students from under-represented minority groups, contributing to curricula and outreach from the secondary through graduate levels.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.