High-light induced superoxide radical formation in cytochrome b₆f complex from Bryopsis corticulans as detected by EPR spectroscopy.

The generation of superoxide radical (O₂·⁻) in Cyt b₆f of Bryopsis corticulans under high light illumination was studied using electron paramagnetic resonance (EPR) spectroscopy. This could be evidenced by the addition of SOD which specifically reacted with O₂·⁻. The generation of O₂·⁻ was lost in the absence of oxygen and was found to be suppressed in the presence of NaN₃ and be scavenged by extraneous antioxidants such as ascorbate, β-carotene and glutathione which could also scavenged ¹O₂*.

High-light induced singlet oxygen formation in cytochrome b(6)f complex from Bryopsis corticulans as detected by EPR spectroscopy.

Electron paramagnetic resonance (EPR) spectroscopy was used to detect the light-induced formation of singlet oxygen ((1)O(2)*) in the intact and the Rieske-depleted cytochrome b(6)f complexes (Cyt b(6)f) from Bryopsis corticulans, as well as in the isolated Rieske Fe-S protein. It is shown that, under white-light illumination and aerobic conditions, chlorophyll a (Chl a) bound in the intact Cyt b(6)f can be bleached by light-induced (1)O(2)*, and that the (1)O(2)* production can be promoted by D(2)O or scavenged by extraneous antioxidants such as l-histidine, ascorbate, beta-carotene and glutathione. Under similar experimental conditions, (1)O(2)* was also detected in the Rieske-depleted Cyt b(6)f complex, but not in the isolated Rieske Fe-S protein.

Singlet oxygen formation and chlorophyll a triplet excited state deactivation in the cytochrome b6f complex from Bryopsis corticulans.

We have attempted to investigate the correlation between the detergent-perturbed structural integrity of the Cyt b (6) f complex from the marine green alga Bryopsis corticulans and its photo-protective properties, for which the nonionic detergents n-octyl-beta-D-glucopyranoside (beta-OG) and n-dodecyl-beta-D-maltoside (beta-DM), respectively, were used for the preparation of Cyt b (6) f, and the singlet oxygen ((1)O(2)*) production as well as the triplet excited-state chlorophyll a ((3)Chl a*) formation and deactivation were examined by spectroscopic means. Near-infrared luminescence of (1)O(2)* (approximately 1,270 nm) on photo-irradiation was detected for the beta-OG preparation where the complex is mainly in oligomeric state, but not for the beta-DM one in which the complex exists in dimeric form. Under anaerobic condition, photo-excitation of Chl a in the beta-DM preparation generated (3)Chl a* with a lower quantum yield of Phi(T) approximately 0.

Relationship between leaf photosynthetic function at grain filling stage and yield in super high-yielding hybrid rice (Oryza sativa. L).

The characteristics of dry matter production before and after heading and the relationships between photosynthesis of flag leaves and dry matter accumulation in panicles were investigated on super high-yielding rice cv. Xieyou 9308 (the yield of up to 12 t/ha) with rice cv. Xieyou 63 as a control.

Characterization of chlorophyll-protein complexes isolated from a Siphonous green alga, Bryopsis corticulans.

Six chlorophyll-protein complexes are isolated from thylakoid membranes of Bryopsis corticulans by dodecyl-beta-D: -maltoside polyacrylamide gel electrophoresis. Unlike that of higher plants, the 77 K fluorescence emission spectrum of the CP1 band, the PSI core complexes of B. corticulans, presents two peaks, one at 675 nm and the other at 715-717 nm.

Thermal denaturation of CP43 studied by Fourier transform-infrared spectroscopy and terahertz time-domain spectroscopy.

Thermal denaturation of CP43 was studied by Fourier transform-infrared (FT-IR) spectroscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and terahertz time-domain spectroscopy (THz-TDS). Under heat treatment, the secondary structure of CP43 changed, and the main thermal transition occurred at 59 degrees C. During the process, CP43 aggregated at first, and then with increasing temperature degraded.

The effects of detergents DDM and beta-OG on the singlet excited state lifetime of the chlorophyll a in cytochrome b6f complex from spinach chloroplasts.

The singlet excited state lifetime of the chlorophyll a (Chl a) in cytochrome b(6)f (Cyt b(6)f) complex was reported to be shorter than that of free Chl a in methanol, but the value was different for Cyt b(6)f complexes from different sources ( approximately 200 and approximately 600 ps are the two measured results). The present study demonstrated that the singlet excited state lifetime is associated with the detergents n-dodecyl-beta-D-maltoside (DDM) and n-octyl-beta-D-glucopyranoside (beta-OG), but has nothing to do with the different sources of Cyt b(6)f complexes. Compared with the Cyt b(6)f dissolved in beta-OG, the Cyt b(6)f in DDM had a lower fluorescence yield, a lower photodegradation rate of Chl a, and a shorter lifetime of Chl a excited state.

The guanidine hydrochloride-induced denaturation of CP43 and CP47 studied by terahertz time-domain spectroscopy.

Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the denaturation of two photosynthesis membrane proteins: CP43 and CP47. THz-TDS was proven to be useful in discriminating the different conformational states of given proteins with similar structure and in monitoring the denaturation process of proteins.

Rapid purification of photosystem I chlorophyll-binding proteins by differential centrifugation and vertical rotor.

Photosystem I (PSI), which consists of a core complex and light-harvesting complex I (LHCI), is an important multisubunit pigment-protein complex located in the photosynthetic membranes of cyanobacteria, algae and plants. In the present study, we described a rapid method for isolation and purification of PSI and its subfractions. For purification of PSI, crude PSI was first prepared by differential centrifugation, which was applicable on a large scale at low cost.

Hydrogen peroxide-induced chlorophyll a bleaching in the cytochrome b6f complex: a simple and effective assay for stability of the complex in detergent solutions.

The instability of cytochrome b ( 6 ) f complex in detergent solutions is a well-known problem that has been studied extensively, but without finding a satisfactory solution. One of the important reasons can be short of the useful method to verify whether the complex suspended in different detergent is in an intact state or not. In this article, a simple and effective assay for stability of the complex was proposed based on the investigation on the different effects of the two detergents, n-octyl-beta-D: -glucopyranoside (OG) and dodecyl-beta-D: -maltoside (DDM), on the properties of the complex.

Study on energy transfer between carotenoid and chlorophyll a in cytochrome b6f complex from Bryopsis corticulans.

The excitation energy transfer between carotenoid and chlorophyll (Chl) in the cytochrome b ( 6 ) f complex from Bryopsis corticulans (B. corticulans), in which the carotenoid is 9-cis-alpha-carotene, was investigated by means of fluorescence excitation and sub-microsecond time-resolved absorption spectroscopies. The presence of efficient singlet excitation transfer from alpha-carotene to Chl a was found with an overall efficiency as high as approximately approximately 24%, meanwhile the Chl a-to-alpha-carotene triplet excitation transfer was also evidenced.

Ultrafast carotenoid-to-chlorophyll singlet energy transfer in the cytochrome b6f complex from Bryopsis corticulans.

Ultrafast carotenoid-to-chlorophyll (Car-to-Chl) singlet excitation energy transfer in the cytochrome b(6)f (Cyt b(6)f) complex from Bryopsis corticulans is investigated by the use of femtosecond time-resolved absorption spectroscopy. For all-trans-alpha-carotene free in n-hexane, the lifetimes of the two low-lying singlet excited states, S(1)(2A(g)(-)) and S(2)(1B(u)(+)), are determined to be 14.3 +/- 0.

Photosynthesis research in the People's Republic of China.

The first research paper on photosynthesis in China was published by T.T. Li(2) in 1929.

Characterization of the cytochrome b(6)f complex from marine green alga, Bryopsis corticulans.

A pure, active cytochrome b(6)f was isolated from the chloroplasts of the marine green alga, Bryopsis corticulans. To investigate and characterize this cytochrome b(6)f complex, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), absorption spectra measurement and HPLC were employed. It was shown that this purified complex contained four large subunits with apparent molecular masses of 34.

[Effects of Triton X-100 on the oxygen uptake rate of photosystem I particles treated at 70 degrees C].

The characteristics including oxygen uptake rates, fluorescence spectra and absorption spectra of photosystem I particles with or without Triton-X 100 treatment before or after the incubation at 70 degrees C for 10 min were compared. The oxygen uptake rates of photosystem I particles decreased after being incubated at 70 degrees C for 10 min, which could be recovered by the addition of Triton-X 100. Singlet oxygen was formed when the light-harvesting complex I was separated from the core complex of photosystem I, which resulted in high oxygen uptake rate.

Effects of acid and alkali on the light absorption, energy transfer and protein secondary structures of core antenna subunits CP43 and CP47 of photosystem II.

The effects of acid and alkali treatment on the light absorption, energy transfer and protein secondary structure of the photosystem II core antenna CP43 and CP47 of spinach were investigated by the absorption spectra, fluorescence emission spectra and circular dichroism spectra. It has been found that acid treatment caused the appearance of absorption characteristic of pheophytin a (Pheo a), whereas alkali treatment induced a new absorption peak at 642 nm. The energy transfer between beta-carotene and chlorophyll a (Chl a) in CP43 was easily disturbed by alkali, whereas in CP47 was readily affected by acid.

The composition and spectral properties of three different forms of light-harvesting complex II.

Different aggregates of LHC II play a very important role in regulating the light absorption and excitation energy transfer of plant. Trimeric LHC II was purified from spinach thylakoid membrane. In order to obtain the dimeric and monomeric LHC II, the trimer was treated with the mixture of 2% OGP and 10 microg/mL PLA(2), then loaded onto the sucrose density gradient in the presence of 0.

Effect of various temperatures on phosphatidylglycerol biosynthesis in thylakoid membranes.

Lipid unsaturation, the major factor to maintain thylakoid membrane fluidity, is affected by temperature. In this work, we analysed the molecular species composition of phosphatidylglycerol (PG) in thylakoid membranes during spinach (Spinacia oleracea) and squash (Cucurbita pepo) cotyledon growth to investigate how the growth temperature affects the PG biosynthesis. Of the 10 molecular species detected, temperature affected mainly the relative content of molecular species containing linolenic acid (18:3) and those containing palmitic acid (16:0) at the sn-1 position of glycerol backbone.