9-Amino-6-chloro-2-methoxyacridine

9-Amino-6-chloro-2-methoxyacridine (ACMA) is a cell-permeable ph-sensitive fluorescent probe that intercalates into DNA. It selectively binds to poly(dA-dT) sequences with the fluorescence lifetime decreasing with incorporation of guanosine. It is used for nucleic acid staining/labeling. ACMA fluorescence is pH-dependent and is quenched when a pH gradient is established. Spectral Data: lambdaex 411nm, lambdaem 475nm (in methanol). Excitation of the ACMA-DNA complex (excitation/emission maxima lambda419/483 nm) is possible with most UV-light sources, making it compatible for use with both shorter- and longer-wavelength dyes. ACMA also apparently binds to membranes in the energized state and becomes quenched if a pH gradient forms. It has been extensively employed to follow cation and anion movement across membranes and to study the proton-pumping activity of various membrane-bound ATPases. ACMA also inhibits acetylcholinesterase.