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A fluorescence lifetime study of virginiamycin S using multifrequency phase fluorometry.
K Clays1, M Di Giambattista, A Persoons
1Laboratory of Chemical and Biological Dynamics, University of Leuven, Belgium.
Biochemistry
|July 23, 1991
Summary
Fluorescence lifetimes of the antibiotic virginiamycin S were determined for its various protolytic forms. Divalent cations significantly alter fluorescence lifetimes, while monovalent cations do not.
Area of Science:
- Biophysical Chemistry
- Photochemistry
- Antibiotic Research
Background:
- Virginiamycin S is an antibiotic with complex protolytic forms.
- Understanding its photophysical properties is crucial for its application and study.
- Fluorescence lifetime is a key parameter sensitive to molecular environment and charge.
Purpose of the Study:
- To assign specific fluorescence lifetimes to different protolytic forms of virginiamycin S.
- To investigate the influence of pH, solvent, and cations on these lifetimes.
- To elucidate the role of excited-state proton transfer in the fluorescence behavior.
Main Methods:
- Multifrequency phase fluorometry was employed to measure fluorescence lifetimes.
- Measurements were conducted across a range of pH values and ethanol concentrations.
- The effect of various monovalent and divalent cations was analyzed.
Main Results:
- Distinct fluorescence lifetimes were assigned to uncharged, zwitterionic, singly, and doubly negatively charged forms.
- Excited-state proton transfer was observed to be complete at low pH.
- Divalent cations (Mg2+, Ca2+, Ba2+) significantly increased fluorescence lifetimes of the negatively charged form, with cation-specific effects.
Conclusions:
- The study successfully characterized the fluorescence lifetimes of virginiamycin S protolytic forms.
- Cation binding, particularly by divalent cations, modulates the photophysical properties of virginiamycin S.
- These findings provide insights into the molecular interactions and fluorescence mechanisms of this antibiotic.