Dissipation of pH Gradients in Tonoplast Vesicles and Liposomes by Mixtures of Acridine Orange and Anions: Implications for the Use of Acridine Orange as a pH Probe
AUTOR(ES)
Pope, Andrew J.
RESUMO
Acridine orange altered the response to anions of both ATP and in-organic pyrophosphate-dependent pH gradient formation in tonoplast vesicles isolated from oat (Avena sativa L.) roots and red beet (Beta vulgaris L.) storage tissue. When used as a fluorescent pH probe in the presence of I−, ClO3−, NO3−, Br−, or SCN−, acridine orange reported lower pH gradients than either quinacrine or [14C]methylamine. Acridine orange, but not quinacrine, reduced [14C]methylamine accumulation when NO3− was present indicating that the effect was due to a real decrease in the size of the pH gradient, not a misreporting of the gradient by acridine orange. Other experiments indicated that acridine orange and NO3− increased the rate of pH gradient collapse both in tonoplast vesicles and in liposomes of phosphatidylcholine and that the effect in tonoplast vesicles was greater at 24°C than at 12°C. It is suggested that acridine orange and certain anions increase the permeability of membranes to H+, possibly because protonated acridine orange and the anions form a lipophilic ion pair within the vesicle which diffuses across the membrane thus discharging the pH gradient. The results are discussed in relation to the use of acridine orange as a pH probe. It is concluded that the recently published evidence for a NO3−/H+ symport involved in the export of NO3− from the vacuole is probably an artefact caused by acridine orange.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1054671Documentos Relacionados
- Decrease of pH Gradients in Tonoplast Vesicles by NO3− and Cl−: Evidence for H+-Coupled Anion Transport 1
- Fluorescence probe measurement of the intralysosomal pH in living cells and the perturbation of pH by various agents.
- Effect of H+ Excretion on the Surface pH of Corn Root Cells Evaluated by Using Weak Acid Influx as a pH Probe 1
- Acridine Binding by Escherichia coli: pH Dependency and Strain Differences
- Growth Rates of Lactobacillus and Leuconostoc Species in Orange Juice as Affected by pH and Juice Concentration