Side‐Chain Chemistry Governs Hierarchical Order of Charge‐Complementary β‐sheet Peptide Coassemblies

Self‐assembly of proteinaceous biomolecules into functional materials with ordered structures that span length scales is common in nature yet remains a challenge with designer peptides under ambient conditions. This report demonstrates how charged side‐chain chemistry affects the hierarchical co‐assembly of a family of charge‐complementary β‐sheet‐forming peptide pairs known as CATCH(X+/Y‐) at physiologic pH and ionic strength in water. In a concentration‐dependent manner, the CATCH(6K+) (Ac‐KQKFKFKFKQK‐Am) and CATCH(6D‐) (Ac‐DQDFDFDFDQD‐Am) pair formed either β‐sheet‐rich microspheres or β‐sheet‐rich gels with a micron‐scale plate‐like morphology, which were not observed with other CATCH(X+/Y‐) pairs. This hierarchical order was disrupted by replacing D with E, which increased fibril twisting. Replacing K with R, or mutating the N‐ and C‐terminal amino acids in CATCH(6K+) and CATCH(6D‐) to Qs, increased observed co‐assembly kinetics, which also disrupted hierarchical order. Due to the ambient assembly conditions, active CATCH(6K+)‐green fluorescent protein fusions could be incorporated into the β‐sheet plates and microspheres formed by the CATCH(6K+/6D‐) pair, demonstrating the potential to endow functionality.