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Chlorophyll destruction by the bisulfite-oxygen system.
1Department of Vegetable Crops, University of California, Davis, California 95616.
Plant Physiology
|August 1, 1977
Summary
Bisulfite causes chlorophyll destruction in two systems, one light-dependent and one dark-dependent. Free radicals, likely superoxide, are implicated in this process, as shown by inhibition with radical scavengers.
Area of Science:
- Biochemistry
- Photochemistry
Background:
- Chlorophyll is a vital pigment in photosynthesis.
- Understanding chlorophyll degradation is crucial for various biological and chemical processes.
Purpose of the Study:
- To investigate the mechanisms of chlorophyll destruction in vitro.
- To identify the reactive species involved in bisulfite-induced chlorophyll degradation.
Main Methods:
- Two in vitro systems were used: one light-dependent and one dark-dependent, both involving bisulfite in 76% ethanol.
- Chlorophyll destruction was monitored by absorbance at 665 nm.
- Inhibition studies were performed using free radical and singlet oxygen scavengers.
Main Results:
- Chlorophyll destruction occurred in both systems, linked to bisulfite oxidation.
- The light system required light, O(2), and bisulfite (optimum pH 4), with rapid destruction under irradiation.
- The dark system required Mn(2+), O(2), glycine, and bisulfite, showing even faster chlorophyll destruction.
- Free radical scavengers effectively inhibited chlorophyll destruction in both systems.
- Singlet oxygen scavengers showed minimal to no inhibition, suggesting a free radical mechanism.
Conclusions:
- Chlorophyll destruction in these systems is mediated by free radicals, likely superoxide radicals.
- The aerobic oxidation of bisulfite is the source of these damaging free radicals.