Design and synthesis
of NS560 as a pan-specific amino acid probe.
(A) Incubation of NS560 with free amino acids results in reversible
covalent attachment of the N and C termini to the aldehyde and boronic
acid, respectively, producing a fluorescent adduct. (B) Synthesis
of NS560. (C) In vitro incubation of NS560 with proteinogenic amino
acids leads to metabolite binding and fluorescence increase. Fluorescence
enhancement was determined by taking the ratio of saturated over control
fluorescence signal (10 μM NS560, 25 mM HEPES, 50 mM Na2S2O3, 1% DMSO, pH 7.4, λex = 488 nm, λem = 560 nm). The fluorescence of Tyr
was estimated due to low solubility.