Photodamage of some pigments in the isolated photosystem Ⅱ (PS Ⅱ) reaction center D1/D2/Cyt b559 complex from spinach has been investigated by means of high performance liquid chromatography. The light induced damag...Photodamage of some pigments in the isolated photosystem Ⅱ (PS Ⅱ) reaction center D1/D2/Cyt b559 complex from spinach has been investigated by means of high performance liquid chromatography. The light induced damage of pheophytin a (pheo a) in the complex was observed for the first time. The content of pheo a decreased about 47% by illumination, suggesting only one of the two pheo a molecules in the PSⅡ reaction center complex was damaged. No damage of β carotene was found.展开更多
Photodamage of pheophytin a (pheo a) in the isolated photosystem Ⅱ (PSⅡ) reaction center D1/D2/Cyt b559 complex from spinach has been investigated by high performance liquid chromatographic method in detail. The res...Photodamage of pheophytin a (pheo a) in the isolated photosystem Ⅱ (PSⅡ) reaction center D1/D2/Cyt b559 complex from spinach has been investigated by high performance liquid chromatographic method in detail. The results showed that: (1) There is one pheo a molecule which is not associated with the primary photochemistry in the PSⅡ reaction center complex. It may be considered that there are two different electron transfer branches in the PSⅡ reaction center just as in the purple bacterium photosynthetic reaction center. (2) The damaged pheo a may be attributed to the one bonding to the D2 protein comparing the D2 subunit in the PSⅡ reaction center with M subunit in the purple bacterium photosynthetic reaction center. (3) A possible arrangement model of redox cofactors in the PSⅡ reaction center was proposed based on our experiment.展开更多
IN recent years,magnetic circular dichroism(MCD)demonstrated its unique advantages inanalysis of metal porphyrin and its interaction with protein.However,there were few re-ports about the application of MCD method in ...IN recent years,magnetic circular dichroism(MCD)demonstrated its unique advantages inanalysis of metal porphyrin and its interaction with protein.However,there were few re-ports about the application of MCD method in photosynthesis field.It is known that most pig-ments in PS Ⅱ-RC are metal porphyrin type.This note reports the MCD spectrum of PS Ⅱ-展开更多
An Isolated photosystem （PS） II reaction center （RC） with altered pigment content was obtained by chemical exchange of native chlorophyll a （Chl） with externally added Cu-Chl a （Cu-Chl）. Pigment composition an...An Isolated photosystem （PS） II reaction center （RC） with altered pigment content was obtained by chemical exchange of native chlorophyll a （Chl） with externally added Cu-Chl a （Cu-Chl）. Pigment composition and spectroscopic properties of the RC exchanged with Cu-Chl were compared with native RC and RC treated with Chl In the same way. High-performance liquid chromatography analysis showed approximately 0.5 Cu-Chl per two pheophytln in the Cu-Chl-reconstltuted RC preparation. Insertion of Cu-Chl resulted in a decrease In absorption at 670 nm and an Increase at 660 nm, suggesting that the peripheral Chl may have been displaced. Fluorescence emission spectra of the Cu-Chl-reconstituted RC displayed a marked decrease In fluorescence yield and a blue shift of the band maximum, accompanied by the appearance of a broad peak at a shorter wavelength, Indicating that energy transfer In the modified RC was disturbed by Cu-Chl, a quencher of the excited state. However, there were few differences in the circular dichrolsm （CD） spectra, suggesting that the arrangement of pigments and proteins responsible for the CD signal was not significantly affected. In addition, no obvious change In peptlde components was found after the exchange procedure.展开更多
Strong light （800μmol photons/m^2 per s）-induced bleaching of the pigment in the isolated photosystem Ⅱ reaction center （PSII RC） under aerobic conditions （in the absence of electron donors or acceptors） was s...Strong light （800μmol photons/m^2 per s）-induced bleaching of the pigment in the isolated photosystem Ⅱ reaction center （PSII RC） under aerobic conditions （in the absence of electron donors or acceptors） was studied using high-pressure liquid chromatography （HPLC）, absorption spectra, 77K fluorescence spectra and resonance Raman spectra. Changes in pigment composition of the PSII RC as determined by HPLC after light treatment were as follows： with Increasing illumination time chlorophyll （Chl） a and β-carotene （β-car） content decreased. However, decreases in pheophytin （Pheo） could not be observed because of the mixture of the Pheo formed by degraded chlorophyll possibly. On the basis of absorption spectra, it was determined that, with a short time of illuminatlon, the initial bleaching occurred maximally at 680 nm but that with Increasing Illumination time there was a blue shift to 678 nm. It was suggested that P680 was destroyed Initially, followed by the accessory chlorophyll. The activity of P680 was almost lost after 10 mln light treatment. Moreover, the bleaching of Pheo and β-car was observed at the beginning of illumination. After Illumination, the fluorescence emission Intensity changed and the fluorescence maximum blue shifted, showing that energy transfer was disturbed. Resonance Raman spectra of the PSII RC excited at 488.0 and 514.5 nm showed four main bands, peaking at 1 527 cm^-1 （υ101）, 1 159 cm^-1 （υ2）, 1 006 cm^-1 （υ3）, 966 cm^-1 （υ4） for 488.0 nm excitation and 1 525 cm^-1 （υ1）, 1 159 cm^-1 （υ2）, 1 007 cm^-1 （υ3）, 968 cm^-1 （υ4） for 514.5 nm excitation. It was confirmed that two spectroscopically different β-car molecules exist In the PSII RC. After light treatment for 20 mln, band positions and bandwidths were unchanged. This indicates that carotenoid configuration Is not the parameter that regulates photoprotectlon in the PSII RC.展开更多
文摘Photodamage of some pigments in the isolated photosystem Ⅱ (PS Ⅱ) reaction center D1/D2/Cyt b559 complex from spinach has been investigated by means of high performance liquid chromatography. The light induced damage of pheophytin a (pheo a) in the complex was observed for the first time. The content of pheo a decreased about 47% by illumination, suggesting only one of the two pheo a molecules in the PSⅡ reaction center complex was damaged. No damage of β carotene was found.
文摘Photodamage of pheophytin a (pheo a) in the isolated photosystem Ⅱ (PSⅡ) reaction center D1/D2/Cyt b559 complex from spinach has been investigated by high performance liquid chromatographic method in detail. The results showed that: (1) There is one pheo a molecule which is not associated with the primary photochemistry in the PSⅡ reaction center complex. It may be considered that there are two different electron transfer branches in the PSⅡ reaction center just as in the purple bacterium photosynthetic reaction center. (2) The damaged pheo a may be attributed to the one bonding to the D2 protein comparing the D2 subunit in the PSⅡ reaction center with M subunit in the purple bacterium photosynthetic reaction center. (3) A possible arrangement model of redox cofactors in the PSⅡ reaction center was proposed based on our experiment.
文摘IN recent years,magnetic circular dichroism(MCD)demonstrated its unique advantages inanalysis of metal porphyrin and its interaction with protein.However,there were few re-ports about the application of MCD method in photosynthesis field.It is known that most pig-ments in PS Ⅱ-RC are metal porphyrin type.This note reports the MCD spectrum of PS Ⅱ-
文摘An Isolated photosystem （PS） II reaction center （RC） with altered pigment content was obtained by chemical exchange of native chlorophyll a （Chl） with externally added Cu-Chl a （Cu-Chl）. Pigment composition and spectroscopic properties of the RC exchanged with Cu-Chl were compared with native RC and RC treated with Chl In the same way. High-performance liquid chromatography analysis showed approximately 0.5 Cu-Chl per two pheophytln in the Cu-Chl-reconstltuted RC preparation. Insertion of Cu-Chl resulted in a decrease In absorption at 670 nm and an Increase at 660 nm, suggesting that the peripheral Chl may have been displaced. Fluorescence emission spectra of the Cu-Chl-reconstituted RC displayed a marked decrease In fluorescence yield and a blue shift of the band maximum, accompanied by the appearance of a broad peak at a shorter wavelength, Indicating that energy transfer In the modified RC was disturbed by Cu-Chl, a quencher of the excited state. However, there were few differences in the circular dichrolsm （CD） spectra, suggesting that the arrangement of pigments and proteins responsible for the CD signal was not significantly affected. In addition, no obvious change In peptlde components was found after the exchange procedure.
文摘Strong light （800μmol photons/m^2 per s）-induced bleaching of the pigment in the isolated photosystem Ⅱ reaction center （PSII RC） under aerobic conditions （in the absence of electron donors or acceptors） was studied using high-pressure liquid chromatography （HPLC）, absorption spectra, 77K fluorescence spectra and resonance Raman spectra. Changes in pigment composition of the PSII RC as determined by HPLC after light treatment were as follows： with Increasing illumination time chlorophyll （Chl） a and β-carotene （β-car） content decreased. However, decreases in pheophytin （Pheo） could not be observed because of the mixture of the Pheo formed by degraded chlorophyll possibly. On the basis of absorption spectra, it was determined that, with a short time of illuminatlon, the initial bleaching occurred maximally at 680 nm but that with Increasing Illumination time there was a blue shift to 678 nm. It was suggested that P680 was destroyed Initially, followed by the accessory chlorophyll. The activity of P680 was almost lost after 10 mln light treatment. Moreover, the bleaching of Pheo and β-car was observed at the beginning of illumination. After Illumination, the fluorescence emission Intensity changed and the fluorescence maximum blue shifted, showing that energy transfer was disturbed. Resonance Raman spectra of the PSII RC excited at 488.0 and 514.5 nm showed four main bands, peaking at 1 527 cm^-1 （υ101）, 1 159 cm^-1 （υ2）, 1 006 cm^-1 （υ3）, 966 cm^-1 （υ4） for 488.0 nm excitation and 1 525 cm^-1 （υ1）, 1 159 cm^-1 （υ2）, 1 007 cm^-1 （υ3）, 968 cm^-1 （υ4） for 514.5 nm excitation. It was confirmed that two spectroscopically different β-car molecules exist In the PSII RC. After light treatment for 20 mln, band positions and bandwidths were unchanged. This indicates that carotenoid configuration Is not the parameter that regulates photoprotectlon in the PSII RC.
