HAAC Ligation-Enabled Hierarchical Assembly: Deciphering the Synergy of α‑Hydroxyl Aldehydes and 2‑Aminooxazoles

We report α-hydroxyl aldehyde–2-aminooxazole
conjugation
(HAAC), a bioorthogonal ligation platform that enables selective biomolecular
labeling and functional modulation under physiological conditions
(pH 7.0, 37 °C). HAAC chemistry supports: (1) multiplexed fluorescent
labeling of proteins (demonstrated with BSA), (2) targeted cell-surface
engineering through αHA-functionalized cetuximab for precision
EGFR engagement, and (3) spatially controlled regulation of β-amyloid
levels in HEK293T cells via small-molecule triggers (e.g., tetra-N-butylammonium fluoride, TBAF). Leveraging this tunable
reactivity, we developed a chemoproteomic workflow for system-wide
profiling of sialoglycoproteins, identifying ANK3 and FBXL22 as novel
sialylated effectors through SA (sialic acid)-specific mass spectra
detection. As the first chemical biology strategy to directly interrogate
SA (sialic acid)-modified proteomes, α-hydroxyl aldehydes and
2-aminooxazoles conjugation (HAAC) uniquely bridges prebiotic reaction
principles with contemporary biomedical applications. This platform
establishes a versatile paradigm for precision glycoproteomics, targeted
protein degradation, and dynamic control of biological systems.