Abstract
The methyl line of the proton magnetic resonance spectrum of acridine orange zinc trichloride, dissolved in heavy water, has been studied. This line consists of two overlapping components with different widths. A mathematical technique has been developed to resolve the two components quantitatively. Their relative proportion depends on the acid-base state of the molecular environment. If the stain is adsorbed on albumin the narrow component quickly disappears, while adsorption on RNA gives rise to a broadening of the narrow line. With large amounts of albumin or RNA, both components disappear. DNA strongly adsorbs acridine orange with complete disappearance of all NMR spectral lines. Mitochondria, submitochondrial particles and microsomes cause some broadening of the narrow component of the methyl line. Due to the obvious alterations of the NMR spectrum, in the circumstances mentioned, this type of spectroscopy may be used for the biophysical characterization of interaction mechanisms between acridine orange and various proteins, nucleic acids and cell fractions.