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

由热响应性合成聚合物和生物聚合物组装而成的纳米结构广泛应用于传感器、电子器件、分子机器、药物输送系统和组织工程基质。这些聚合物的设计特点，如分子组成、序列、分子量和水溶液浓度，允许调整发生相变的温度。此外，已经证明，热响应性聚合物的共轭物提供了一种编码双热转变的手段；这种多温度响应性可以用来指导纳米结构在特定温度下的组装和拆卸，增加了它们的潜在应用范围。然而，对于这些热响应偶联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，缺乏基本的理解。发展这样的理解是在生化传感器、驱动、分子货物（如药物）递送和时空控制催化等应用中扩展热响应纳米结构的关键。利用小角度x射线和中子散射来表征纳米结构组装过程中的共轭物，再加上分析散射结果的先进计算方法，将为分子设计提供变革性的机会。本提案的总体目标是开发新的方法来询问分子相互作用，包装，以及在技术上有用的热响应偶联物组装和拆卸过程中的动力学。研究小组引入了双热响应弹性蛋白样肽偶联物，连接到棒状寡聚肽域。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。实验将与一个新的粗粒度模型和模拟相结合，该模型和模拟将预测肽偶联物的一系列分子设计在不同温度下的结构转变。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，以及潜在的最终组装结构，不一定服从规范的结构和形状因素，因此新的计算方法将阐明组装过程的分子基础。拟议的工作将利用从研究小组高级成员之间以前成功合作中获得的知识。通过这次合作，学生在实验和模拟方面的跨学科训练将得到丰富；通过提议的工作所取得的技术进步将被整合到课堂中。研究人员将以他们在招募和留住来自代表性不足的少数群体的学生方面的历史承诺为基础，为从中学到研究生阶段的课程和推广做出贡献。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.