Sequence-Dependent Aggregation-Induced-Emission Characteristics of Tetraphenylethene-Containing π-Peptides

Four pH-responsive π-peptide macromolecules embedded with the known Aggregation Induced Emission chromophore (AIE-gen) tetraphenylethene (TPE) were examined to explore how peptide side chain composition influenced the nature of the AIE under aqueous conditions. These molecules were readily synthesized via standard solid-phase peptide synthesis (SPPS) followed by on-resin 4-fold conjugation with a functionalized TPE. The specific outcomes of the AIE upon π-peptide pH-driven assembly, as influenced by the nature of the peptide sequence, were characterized by ultraviolet–visible (UV–vis), photoluminescence (PL) and circular dichroism (CD) spectroscopies in aqueous media, along with transmission electron microscopy (TEM) to visualize nanomaterial morphologies resulting from the pH-triggered aggregation. Peptide side chains play a critical role in regulating emission in aggregated states. This study offers a new strategy for designing and modulating fluorescent molecules in aggregated states.