School of Chemistry, Pharmacy and Food Biosciences, University of Reading, Whiteknights, Reading RG6 6AD, U.K.
School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6AH, U.K.
ACS Appl Bio Mater. 2024 Aug 19;7(8):5553-5565. doi: 10.1021/acsabm.4c00664. Epub 2024 Jul 23.
Chirality plays a crucial role in the self-assembly of biomolecules in nature. Peptides show chirality-dependent conformation and self-assembly. Lipidation of peptides occurs in vivo and has recently been exploited in designed conjugates to drive self-assembly and enhance bioactivity. Here, a library of pH-responsive homochiral and heterochiral lipidated tripeptides has been designed. The designed lipopeptides comprise homochiral C-YKK or C-WKK (where all the amino acids are l-isomers), and two heterochiral conjugates C-Ykk and C-Wkk (where the two lysines are d-isomers). The self-assembly of all the synthesized lipopeptides in aqueous solution was examined using a combination of spectroscopic methods along with cryogenic-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS). Interestingly, it was observed that at acidic pH all the lipopeptides self-assemble into micelles, whereas at basic pH the homochiral lipopeptides self-assemble into nanofibers, whereas the heterochiral lipopeptides self-assemble into nanotapes and nanotubes. A pH switch was demonstrated using a thioflavin T fluorescence probe of β-sheet structure present in the extended structures at pH 8. We demonstrate that both chirality and pH in lipopeptides influence the self-assembly behavior of the model tripeptides, which also show promising bioactivity. Good cytocompatibility is observed in hemolytic assays and antimicrobial activity against both Gram-negative and Gram-positive bacteria is shown through the determination of minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) values and live/dead bacteria staining assay.
手性在自然界中生物分子的自组装中起着至关重要的作用。肽表现出依赖手性的构象和自组装。肽的脂质化在体内发生，并在最近被用于设计的缀合物中，以驱动自组装和增强生物活性。在这里，设计了一组 pH 响应的同手性和异手性脂质化三肽库。设计的脂肽包括同手性 C-YKK 或 C-WKK（其中所有氨基酸均为 l-异构体），以及两种异手性缀合物 C-Ykk 和 C-Wkk（其中两个赖氨酸为 d-异构体）。使用光谱学方法以及低温透射电子显微镜（cryo-TEM）和小角 X 射线散射（SAXS）的组合，研究了所有合成脂肽在水溶液中的自组装。有趣的是，观察到在酸性 pH 下，所有脂肽都自组装成胶束，而在碱性 pH 下，同手性脂肽自组装成纳米纤维，而异手性脂肽自组装成纳米带和纳米管。使用存在于扩展结构中的硫代黄素 T 荧光探针证明了 pH 开关β-片结构在 pH 8 下。我们证明了手性和 pH 都会影响模型三肽的自组装行为，这些三肽也表现出有前途的生物活性。溶血试验中观察到良好的细胞相容性，通过测定最小抑制浓度（MIC）和最小杀菌浓度（MBC）值以及活菌/死菌染色试验，显示对革兰氏阴性和革兰氏阳性菌均具有抗菌活性。
