Delayed fluorescence spectroscopy and mechanism of the 730 nm component of chloroplast
Cheng-long Wang, Da Xing, Duo-wang Fan, Long Qian, Mai Lu
Optoelectronics Letters ›› 2006, Vol. 2 ›› Issue (2) : 158-162.
Delayed fluorescence spectroscopy and mechanism of the 730 nm component of chloroplast
Charge recombination in reaction center (RC) of photosystem II(PS II) is regarded as the location of 685 nm delayed fluorescence (DF). The mechanism of 730 nm component appearing in the DF spectrum for chloroplast was studied by various spectral analysis methods. Experimental results of the DF spectrum at different chloroplast concentration show that the intensity of peaks at 685nm and 730 nm ascends with the chloroplast concentration increasing when the concentration is relatively low. When the concentration increases to the level of 7.8μg/ml, a maximum intensity of the peak at 685 nm appears but the intensity of 730 nm peak still increases. The peak at 730 nm finally reaches a maximum intensity at the chloroplast concentration of 31.2 μg/ml while the intensity of the 685 nm peak has apparently fallen down. The results of absorption spectrum show that the ratios of A685 to A730 keep almost constant with the increasing of chloroplast concentration. Furthermore, the excitation spectrum for 730 nm fluorescence shows that the 685nm light has high excitation efficiency. These results indicate that the 730 nm component of DF spectrum is the fluorescence of chlorophyll in PS I RC excited by 685 nm DF. Meanwhile, this can be further verified by the invariability of DF spectrum at different delay time (1 second∼9 seconds).
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