2-Aminopurine (hydrochloride)

2-Aminopurine (hydrochloride) (CAS No.: 1428126-74-2) is a fluorescent purine analog widely employed in molecular and chemical biology as a sensitive probe for nucleic acid structure, dynamics, and interactions. Functionally analogous to guanine and adenine, it can be site-specifically incorporated into DNA or RNA, where its fluorescence properties are highly responsive to local base stacking, pairing, and conformational changes, typically exhibiting quenching upon incorporation into duplex nucleic acids. This feature enables detailed investigation of processes such as base pairing fidelity, helix stability, and enzyme-mediated DNA base flipping, including studies of methyltransferases and other nucleic acid–modifying proteins. It can form noncanonical and canonical base pairs, contributing to its versatility in probing nucleic acid geometry and dynamics under varying conditions. In addition to its biophysical applications, 2-aminopurine has been reported to inhibit double-stranded RNA-dependent protein kinase (PKR), implicating it in modulation of antiviral signaling and innate immune pathways, with activity generally observed in the low micromolar range. The compound is broadly utilized in fluorescence-based assays, high-resolution kinetic studies, and mechanistic investigations in cell-free and cellular systems, where experimental concentrations are selected according to assay sensitivity and biological context. Its dual utility as both a structural probe and a modulator of nucleic acid–associated signaling pathways makes it a valuable tool in nucleic acid research and early-stage drug discovery.