# Charge Directed Selective Co‐Assembly of Ionic Complementary Peptide Binary Mixtures

## TL;DR

This paper shows how to control the assembly of complex peptide mixtures by adjusting their charge and environmental conditions, leading to precise material properties.

## Contribution

The study introduces a framework for selectively co-assembling ionic peptide mixtures by tuning charge complementarity, pH, and stoichiometry.

## Key findings

- Charge distribution controls β-sheet alignment, assembly kinetics, and hydrogel viscoelasticity.
- Co-assembly behavior and nanofiber morphology depend on pH and mixing stoichiometry.
- Selective co-assembly into hetero-aggregates occurs at pH 7 with equimolar mixtures.

## Abstract

Multicomponent peptide nanostructures offer a powerful platform for designing functional materials, yet controlling their co‐assembly remains a key challenge. Here, we harness electrostatic molecular recognition to drive the selective co‐assembly of five amphiphilic ionic peptide binary mixtures (M1–M5). Our results revealed that charge distribution governs β‐sheet strand alignment (parallel vs. antiparallel), assembly kinetics, and hydrogel viscoelasticity. Mixing stoichiometry and pH significantly influences co‐assembly behavior, nanofiber morphology, and network structure (self‐sorted vs. hetero‐aggregated). At pH 7, equimolar mixtures undergo nucleation‐driven co‐assembly into hetero‐aggregates, immediately forming well‐defined nanofibers, while non‐equimolar ratios yield altered morphologies. At a slightly acidic pH of 5–7, both E and K side chains are charged, enabling complementary ionic interactions that promote co‐assembly and gelation. Outside this pH range, co‐assembly is impaired. Notably, M1 forms β‐sheets and hydrogels at acidic pH (≤4) via independent self‐assembly of its components, suggesting self‐sorted fibers. Overall, we demonstrate that tuning charge complementarity, ionization state, and stoichiometry enables precise control over the molecular, nanoscale, and mechanical properties of multicomponent peptide assemblies, providing a framework for the rational design of advanced peptide‐based materials.

Multi‐component peptide systems enable the development of multi‐functional and tunable materials, yet, controlling the co‐assembly of such complex systems remains challenging. This study demonstrates that rational design of peptide charge distribution, together with controlling parameters (pH, stoichiometry, and concentration), can guide selective co‐assembly, allowing for governing β‐sheet alignment, co‐assembly kinetics, fiber nanomorphology, network structure, and mechanical properties of the resulting hydrogels.