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

由热敏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的基质。这些聚合物的设计特征，如分子组成、序列、相对分子质量和水溶液浓度，允许调节发生相变的温度。此外，已经证明，热响应性聚合物的共轭提供了一种编码双重热转变的方法；这种多温度响应性可以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，对于这些热响应性共轭化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，缺乏基本的了解。发展这样的理解是扩大热响应纳米结构在生物化学传感器、驱动、分子货物(例如药物)输送和时空控制催化等应用中的关键。将小角X射线和中子散射与分析散射结果的高级计算方法相结合，在纳米结构(DIS)组装过程中表征偶联物的能力将为分子设计提供变革性的机会。该提议的总体目标是开发新的方法来询问在技术上有用的热响应偶联物的组装和拆卸过程中的分子相互作用、堆积和动力学。该研究小组引入了与杆状寡聚多肽结构域相连的双重热响应性弹性蛋白样肽结合物。这些分子将通过X射线、中子散射和显微镜进行合成和表征。实验将与一种新的粗粒度模型和模拟相结合，该模型和模拟将预测一系列多肽结合物的分子设计的结构转变随温度的变化。温控小角散射实验将探测组装路径中不同温度下的结构。中间结构，潜在的最终组装结构，不一定服从正则结构和形状因子，因此将发展新的计算方法，以阐明组装过程的分子基础。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。通过这一合作，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纳入课堂。研究人员将在他们历史承诺的基础上，从代表不足的少数群体招收和留住学生，为从中学到研究生的课程和推广做出贡献。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.