This study introduces a new azobenzene-based amino acid, AMPO, for controlling β-turn and β-hairpin formation in polyQ peptides through light. The research aims to understand the role of β-hairpin structures in protein aggregation, particularly in Huntington's disease (HD) and other amyloid-related neurodegenerative disorders. β-hairpin formation is proposed as an early nucleation event in HD, contributing to the aggregation of mutant huntingtin protein fragments. Previous studies have used β-hairpin-stabilizing mutations to study aggregation kinetics and stability, but these approaches lack temporal control necessary for detailed mechanistic studies. The new azobenzene-based amino acid, AMPO, was designed to overcome limitations of previous azobenzene-based β-turn mimics, which had poor photochemical properties and imperfect structural compatibility with the desired β-turn structure. AMPO exhibits improved photochemical properties, including a longer half-life and higher photochemical efficiency, compared to previously reported systems. The cis isomer of AMPO was found to closely reproduce the spectral fingerprints of toxic β-hairpin-containing fibrils formed by mutant huntingtin protein fragments implicated in HD. The study used electron microscopy (EM) and solid-state NMR (ssNMR) to examine the structure of polyQ-AMPO aggregates formed by cis and trans configurations. The cis isomer was found to closely replicate the structure of the β-hairpin-containing fibrils, indicating its high structural compatibility with the polyQ β-hairpin fold. The results suggest that AMPO can be used to control the aggregation of polyQ peptides through light, providing a new tool for studying the role of β-hairpin structures in protein aggregation processes in HD and other amyloid-related neurodegenerative diseases. The findings have implications for the design of aggregation-inhibiting and -modulating drugs and treatments for protein misfolding diseases.This study introduces a new azobenzene-based amino acid, AMPO, for controlling β-turn and β-hairpin formation in polyQ peptides through light. The research aims to understand the role of β-hairpin structures in protein aggregation, particularly in Huntington's disease (HD) and other amyloid-related neurodegenerative disorders. β-hairpin formation is proposed as an early nucleation event in HD, contributing to the aggregation of mutant huntingtin protein fragments. Previous studies have used β-hairpin-stabilizing mutations to study aggregation kinetics and stability, but these approaches lack temporal control necessary for detailed mechanistic studies. The new azobenzene-based amino acid, AMPO, was designed to overcome limitations of previous azobenzene-based β-turn mimics, which had poor photochemical properties and imperfect structural compatibility with the desired β-turn structure. AMPO exhibits improved photochemical properties, including a longer half-life and higher photochemical efficiency, compared to previously reported systems. The cis isomer of AMPO was found to closely reproduce the spectral fingerprints of toxic β-hairpin-containing fibrils formed by mutant huntingtin protein fragments implicated in HD. The study used electron microscopy (EM) and solid-state NMR (ssNMR) to examine the structure of polyQ-AMPO aggregates formed by cis and trans configurations. The cis isomer was found to closely replicate the structure of the β-hairpin-containing fibrils, indicating its high structural compatibility with the polyQ β-hairpin fold. The results suggest that AMPO can be used to control the aggregation of polyQ peptides through light, providing a new tool for studying the role of β-hairpin structures in protein aggregation processes in HD and other amyloid-related neurodegenerative diseases. The findings have implications for the design of aggregation-inhibiting and -modulating drugs and treatments for protein misfolding diseases.