The Chlorophyll a Fluorescence Modulated by All-Trans-β-Carotene in the Process of Photosystem II

Modulating the chlorophyll a (Chl-a) fluorescence by all-trans-β-Carotene (β-Car) in the polarity and non-polarity solutions was investigated. The fluorescence intensity of Chl-a decreased as the concentration of β-Car increased. The excited electronic levels of Chl-a and β-Car became much closer owing to the solvent effect, which led to the electron transfer between both two molecules. A electron-separated pair Chl(−)·Chl(+) that is not luminous was formed due to electron transfer. The solution of Chl-a and β-car in C(3)H(6)O was similar to the internal environment of chloroplast. We conclude that the polar solvent is good for the fluorescent modulation in photosystem II.