The pi-Cation Radical of Chlorophyll a.
Proceedings of the National Academy of Sciences of the United States of America
confidence
Key findings
Physical chemistry study on one-electron oxidation of chlorophyll a; identifies pi-cation radical; no clinical or biological endpoints.
View source on PubMed (PMID 16591873) ↗
- Sample size
- Not applicable
- Population
- Not applicable (physical chemistry study)
- Dosing
- Not applicable
- Duration
- Not applicable
- Route
- Not applicable
- Blinding
- not_reported
- Controls
- none
- Drug class
- porphyrin pigment
Full abstract
Chlorophyll a undergoes reversible one-electron oxidation in dichloromethane and butyronitrile. Removal of the electron by controlled potential electrolysis or by stoichiometric charge transfer to a known cation radical yields a radical (epr line width = 9 gauss, g = 2.0025 +/- 0.0001) whose optical spectrum is bleached relative to that of chlorophyll. Upon electrophoresis this bleached species behaves as a cation. By comparison with the known properties of pi-cation radicals of porphyrins and chlorins, the chlorophyll radical is also identified as a pi-cation. Further correlation of optical and epr properties with published studies on photosynthesis leads to the conclusion that oxidized P700, the first photochemical product of photosystem I in green plants, contains a pi-cation radical of the chlorin component of chlorophyll a. This radical is the likely source of the rapidly-decaying, narrow epr signal of photosynthesis.