title: 9-Aminoacridine as a fluorescent probe of the electrical diffuse layer associated with the membranes of plant mitochondria.
abstract: 1. Mitochondria from Jerusalem artichoke (Helianthus tuberosus) tubers and Arum maculatum spadices caused a quenching of the fluorescence of 9-aminoacridine when mixed in a low-cation medium (approximately 1 mM-K+) and addition of chelators further decreased the fluorescence. Salts released the quenching of the 9-aminoacridine fluorescence and the efficiency of the release appeared to be mainly dependent on the valency of the cation (C3+ greater than C2+ greater than C+). 2. The results are consistent with the theory of charge screening and demonstrate that 9-aminoacridine is a convenient probe of the behaviour of cations on the membranes of mitochondria and in the diffuse layer associated with these membranes. 3. The concentration of salt required to achieve half-maximal release of quenching of 9-aminoacridine fluorescence was proportional to the concentration of mitochondria in the solution and theoretical considerations show this effect to be inherent in the Gouy-Chapman theory. 4. 9-Aminoacridine was removed from the bulk of the solution by the mitochondria to a far greater extent than was Na+ or K+, which is suggested to be due to the formation of bi- and poly-valent cations by aggregation of 9-aminoacridine molecules in the diffuse layer. This would have implications for the use of 9-aminoacridine to determine delta pH across membranes. 5. Jerusalem-artichoke mitochondria removed from 9-aminoacridine and Ca2+ from the bulk of the solution and required more ions to screen the membranes than did an equal concentration (mg of protein/ml) of Arum mitochondria, indicating that Jerusalem-artichoke mitochondria contain more negative charges per mg of protein.
mesh_terms: D000585:Aminacrine; D000609:Aminoacridines; D002412:Cations / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D005456:Fluorescent Dyes; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D010944:Plants / Q000378:metabolism*
chemical_list: D000609:Aminoacridines; D002412:Cations; D002614:Chelating Agents; D005456:Fluorescent Dyes; D010940:Plant Proteins; D000585:Aminacrine