The basis for the correlation between fluorescence changes of 8-anilino-1-naphthalene sulfonate (ANS3 3 Abbreviations used: ETPh, phosphorylating submitochondrial particles; ANS, 8-anilino-1-naphthalene sulfonate.) with changes of the functional state of submitochondrial particles has been investigated. Evidence is presented which suggests that under the conditions studied initiation of electron transfer does not result in an increase in the quantum yield of ANS fluorescence. More apparent was a dramatic increase in the binding affinity of the "energized" membrane for the fluorochrome. Some pH-dependent increase in the binding capacity of the membrane was also observed. In contrast, the number of apparent binding sites was increased without changing the affinity of the membrane for ANS by either lowering the pH of the medium or adding the lipophilic cation ketamine. At the concentrations studied, oleate noncompetitively inhibited ANS binding to submitochondrial particles, but competitively inhibited ANS binding to phospholipid micelles. The binding characteristics for ANS of "lipid-depleted" submitochondrial particles were somewhat similar to those of submitochondrial particles oxidizing succinate. The evidence suggests that generation of the "energized" state produces either a potential gradient or a conformational change of protein components which results in an increase in binding affinity of the membrane for ANS. A marked change in the hydrophobicity of the binding site for ANS does not appear to occur.
ASJC Scopus subject areas
- Molecular Biology