Peptide therapeutics have the potential to self-associate, leading to aggregation and fibrillation. Noncovalent PEGylation offers a strategy to improve their physical stability; an understanding of the behavior of the resulting polymer/peptide complexes is, however, required. In this study, we have performed a set of experiments with additional mechanistic insight provided by in silico simulations to characterize the molecular organization of these complexes. We used palmitoylated vasoactive intestinal peptide (VIP-palm) stabilized by methoxy-poly(ethylene glycol)_5kDa-cholane (PEG-cholane) as our model system. Homogeneous supramolecular assemblies were found only when complexes of PEG-cholane/VIP-palm exceeded a molar ratio of 2:1; at and above this ratio, the simulations showed minimal exposure of VIP-palm to the solvent. Supramolecular assemblies formed, composed of, on average, 9–11 PEG-cholane/VIP-palm complexes with 2:1 stoichiometry. Our in silico results showed the structural content of the helical conformation in VIP-palm increases when it is complexed with the PEG-cholane molecule; this behavior becomes yet more pronounced when these complexes assemble into larger supramolecular assemblies. Our experimental results support this: the extent to which VIP-palm loses helical structure as a result of thermal denaturation was inversely related to the PEG-cholane:VIP-palm molar ratio. The addition of divalent buffer species and increasing the ionic strength of the solution both accelerate the formation of VIP-palm fibrils, which was partially and fully suppressed by 2 and >4 mol equivalents of PEG-cholane, respectively. We conclude that the relative freedom of the VIP-palm backbone to adopt nonhelical conformations is a key step in the aggregation pathway.

中文翻译：

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通过物理PEG化控制肽的聚集和原纤化

肽治疗剂具有自我缔合的潜力，从而导致聚集和原纤维形成。非共价PEG化提供了改善其物理稳定性的策略；但是，需要了解所得聚合物/肽复合物的行为。在这项研究中，我们进行了一系列实验，并通过计算机模拟提供了更多的机械洞察力，以表征这些配合物的分子组织。我们使用由_5kDa甲氧基聚乙二醇稳定的棕榈酰化血管活性肠肽（VIP-palm）-cholane（PEG-cholane）作为我们的模型系统。仅当PEG-胆烷/ VIP-棕榈的复合物的摩尔比超过2：1时，才发现均相的超分子组装。在此比率以上，模拟显示VIP棕榈对溶剂的暴露最少。超分子组装体形成，平均由化学计量比为2：1的9-11 PEG-胆烷/ VIP-棕榈复合物组成。我们的计算机分析结果表明，当与PEG-胆烷分子复合时，VIP-棕榈中螺旋构象的结构含量增加；当这些络合物组装成更大的超分子组装体时，这种行为变得更加明显。我们的实验结果证明了这一点：由于热变性，VIP-棕榈失去螺旋结构的程度与PEG-胆烷：VIP-棕榈的摩尔比成反比。添加二价缓冲剂种类和增加溶液的离子强度都加速了VIP-棕榈原纤维的形成，这分别被2摩尔当量和> 4摩尔当量的PEG-胆烷所部分和完全抑制了。我们得出结论，VIP棕榈骨架采用相对非螺旋构象的相对自由度是聚合途径中的关键步骤。