7 Amino actinomycin D as a cytochemical probe. I. Spectral properties

Abstract

The optical absorption and fluorescence characteristics of 7 amino actinomycin D were determined to evaluate its potential as a fluorescent cytochemical probe. At pH 7.0, the absorption maximum and fluorescence excitation maximum are both at 503 nm; the fluorescence emission is at 675 nm. When this compound forms complexes with DNA in solution, the absorption and fluorescence excitation maxima shift to 543 nm and the fluorescence emission shifts to 655 nm. The fluorescenc quantum yield is 0.016 for 7 amino actinomycin D free in solution and 0.01-0.02 for complexes with native DNA. The 7 amino actinomycin D also exhibits fluorescence shifts characteristic of binding when put into solution with poly(dG dC) x poly(dG dC), but not with poly(dI dC) x poly(dI dC). The spectral characteristics are the same at pH 7.0 whether the solvent is 0.01 M PO4 with 0.0001 M EDTA or Earle's salts with 0.025 M N 2 hydroxyethylpiperazine N1 2 ethanesulfonic acid.