Mansbach Rachael A, Ferguson Andrew L
Department of Physics, University of Illinois at Urbana-Champaign, 1110 W Green St, Urbana, IL 61801, USA.
Org Biomol Chem. 2017 Jul 5;15(26):5484-5502. doi: 10.1039/c7ob00923b.
Self-assembled nanoaggregates of π-conjugated peptides possess optoelectronic properties due to electron delocalization over the conjugated peptide groups that make them attractive candidates for the fabrication of bioelectronic materials. We present a computational and theoretical study to resolve the microscopic effects of pH and flow on the non-equilibrium morphology and kinetics of early-stage assembly of an experimentally-realizable optoelectronic peptide that displays pH triggerable assembly. Employing coarse-grained molecular dynamics simulations, we probe the effects of pH on growth kinetics and aggregate morphology to show that control of the peptide protonation state by pH can be used to modulate the assembly rates, degree of molecular alignment, and resulting morphologies within the self-assembling nanoaggregates. We also quantify the time and length scales at which convective flows employed in directed assembly compete with microscopic diffusion to show that flow influences cluster alignment and assembly rate during early-stage assembly only at extremely high shear rates. This suggests that observed improvements in optoelectronic properties at experimentally-accessible shear rates are due to the alignment of large aggregates of hundreds of monomers on time scales in excess of hundreds of nanoseconds. Our work provides new fundamental understanding of the effects of pH and flow to control the morphology and kinetics of early-stage assembly of π-conjugated peptides and lays the groundwork for the rational manipulation of environmental conditions to direct assembly and the attendant emergent optoelectronic properties.
π共轭肽的自组装纳米聚集体由于电子在共轭肽基团上的离域而具有光电特性，这使其成为制造生物电子材料的有吸引力的候选物。我们进行了一项计算和理论研究，以解决pH值和流动对一种可实验实现的、具有pH触发组装特性的光电肽早期组装的非平衡形态和动力学的微观影响。通过粗粒度分子动力学模拟，我们探究了pH值对生长动力学和聚集体形态的影响，结果表明，通过pH值控制肽的质子化状态可用于调节自组装纳米聚集体内的组装速率、分子排列程度和最终形态。我们还量化了定向组装中使用的对流流动与微观扩散竞争的时间和长度尺度，结果表明，流动仅在极高的剪切速率下才会影响早期组装过程中的团簇排列和组装速率。这表明，在实验可达到的剪切速率下观察到的光电性能改善是由于数百个单体的大聚集体在超过数百纳秒的时间尺度上的排列。我们的工作为理解pH值和流动对π共轭肽早期组装形态和动力学的影响提供了新的基础认识，并为合理控制环境条件以指导组装及随之产生的光电特性奠定了基础。
