Quantifying and monitoring functional photosystem II and the stoichiometry of the two photosystems in leaf segments: approaches and approximations.

Given its unique function in light-induced water oxidation and its susceptibility to photoinactivation during photosynthesis, photosystem II (PS II) is often the focus of studies of photosynthetic structure and function, particularly in environmental stress conditions. Here we review four approaches for quantifying or monitoring PS II functionality or the stoichiometry of the two photosystems in leaf segments, scrutinizing the approximations in each approach. (1) Chlorophyll fluorescence parameters are convenient to derive, but the information-rich signal suffers from the localized nature of its detection in leaf tissue.

Evaluation of the quality of deep frying oils with Fourier transform near-infrared and mid-infrared spectroscopy.

Deep frying oils are subjected to high temperature and prolonged heating that may lead to a series of quality and safety problems for fried foods. This study evaluated the quality of deep frying oils collected from a local college canteen (n = 132) with Fourier transform mid-infrared (FT-IR) and Fourier transform near-infrared (FT-NIR) spectroscopy. Partial least squares (PLS) regression was used to correlate spectral data with free fatty acids (FFA) and peroxide (PO) values of frying oils.

[The progress in research on the reduced nicotinamide adenine di(tri)-nucleotide phosophate [NAD(P)H] dehydrogenase complex and chlororespiration].

Besides the non-cyclic electron transport driven by the two photosystems (PSII and PSI), the cyclic electron transport pathways around PSI are also essential for efficient photosynthesis. As one of these pathways, the NAD(P)H dehydrogenase complex (NDH complex) mediated cyclic electron transport has been well studied. Along with the identification of the plastid terminal oxydase (PTOX), the functions of NDH-mediated cyclic and chlororepiratory electron transport in energy supply for photosynthesis as well as in the resistance to photooxidative stress have increasingly been brought to the researchers' attention.

Changes in cyclic and respiratory electron transport by the movement of phycobilisomes in the cyanobacterium Synechocystis sp. strain PCC 6803.

Phycobilisomes (PBS) are the major accessory light-harvesting complexes in cyanobacteria and their mobility affects the light energy distribution between the two photosystems. We investigated the effect of PBS mobility on state transitions, photosynthetic and respiratory electron transport, and various fluorescence parameters in Synechocystis sp. strain PCC 6803, using glycinebetaine to immobilize and couple PBS to photosystem II (PSII) or photosystem I (PSI) by applying under far-red or green light, respectively.

The role of chloroplast NAD(P)H dehydrogenase in protection of tobacco plant against heat stress.

After incubation at 42 degrees C for more than 48 h, brown damages occurred on the stems of tobacco (Nicotiana tabacum L.) ndhC-ndhK-ndhJ deletion mutant (deltandhCKJ), followed by wilt of the leaves, while less the phenotype was found in its wild type (WT). Analysis of the kinetics of post-illumination rise in chlorophyll fluorescence indicated that the PSI cyclic electron flow and the chlororespiration mediated by NAD(P)H dehydrogenase (NDH) was significantly enhanced in WT under the high temperature.

[Environmental regulation of Citrus photosynthesis].

Recent researches on the mechanisms of environmental regulation of citrus photosynthesis showed that the photoinhibition of photosynthesis induced by strong light or ultraviolet radiation was related to the inactiveness of PS II reaction center, and photorespiration and xanthophyll cycle played a pivotal role in protecting photosynthetic apparatus. Under temperature stress, lower CO2 assimilation was mainly due to the decrease of RuBPCase activity and the inactiveness of PS II reaction center, and species sensitivity existed. The decline of photosynthetic CO2 assimilation under high water stress was due to non-stomatal limitation, while that under low water stress was due to stomatal limitation.

[State transition of the photosynthetic apparatus in plant].

State transition of the photosynthetic apparatus in plants is a short-term adaptation mediated mainly by the reversible phosphorylation of the main light-harvesting complex protein (LHCII) and its migration between photosystem I (PSI) and photosystem II (PSII). In higher plants and Chlamydomonas, LHCII phosphorylation is mainly controlled by the redox state of plastoquinone pool and cytochrome b(6)f complex, while salt could induce a redox-independent LHCII phosphorylation via transient changes in ion concentrations in Dunaliella. State transition can balance the distribution of excitation energy between PSII and PSI by changes in light absorption cross section and excitation energy spillover between the two photosystems.

Transient decrease of light-harvesting complex II phosphorylation level by hypoosmotic shock in dark-adapted Dunaliella salina.

This study investigated the regulation of major light harvesting chlorophyll a/b protein (LHCII) phosphorylation by hypoosmotic shock in dark-adapted Dunaliella salina cells. When the external NaCl concentration decreased in darkness, D. salina LHCII phosphorylation levels transiently dropped within 20 min and then restored gradually to basal levels.

Effects of site-directed mutation on the function of the chloroplast ATP synthase epsilon subunit.

The previous work in our lab showed that the spinach chloroplast ATP synthase epsilon mutant with 3 amino acid residues deleted from the N-terminus had much lower ability to inhibit ATP hydrolysis and block proton leakage in comparison to a mutant with 1 or 2 residues deleted from the N-terminus. The present study aimed at determining whether there is special importance in the structure and function of the N-terminal third residue of the chloroplast epsilon subunit. The leucine residue at the N-terminal third site (Leu3) of the spinach chloroplast epsilon subunit was replaced with Ile, Phe, Thr, Arg, Glu or Pro by site-directed mutagenesis, forming mutants epsilonL3I, epsilonL3F, epsilonL3T, epsilonL3R, epsilonL3E and epsilonL3P, respectively.

[Changes in trans-thylakoid membrane proton motive force induced by treatments with red and far-red light in Dunaliella salina].

The changes in trans-thylakoid membrane proton motive force caused by red light and caused by far-red light in the halotolerant green alga, Dunaliella salina are investigated. Irradiation with red light decreased the intensity of the fast phase of millisecond delayed light emission (ms-DLE) in D. salina, and far-red light led to the opposite effects.

Salt-induced redox-independent phosphorylation of light harvesting chlorophyll a/b proteins in Dunaliella salina thylakoid membranes.

This study investigated the regulation of the major light harvesting chlorophyll a/b protein (LHCII) phosphorylation in Dunaliella salina thylakoid membranes. We found that both light and NaCl could induce LHCII phosphorylation in D. salina thylakoid membranes.

NaCl-induced phosphorylation of light harvesting chlorophyll a/b proteins in thylakoid membranes from the halotolerant green alga, Dunaliella salina.

Light could induce phosphorylation of light harvesting chlorophyll a/b binding proteins (LHCII) in Dunaliella salina and spinach thylakoid membranes. We found that neither phosphorylation was affected by glycerol, whereas treatment with NaCl significantly enhanced light-induced LHCII phosphorylation in D. salina thylakoid membranes and inhibited that in spinach.

[Fourier transform infrared spectroscopy study on the protein secondary structure of photosystem II reaction center].

A successful study on the secondary structure of the isolated photosystem II (PSII) particles with the Fourier transform infrared spectroscopy is reported in this paper. The beta condensation effect is obviously characterized by infrared absorption spectra. The infrared spectra of both living protein and beta condensed protein samples are measured at room temperature.

[Separation of hydrophobic NAD(P)H dehydrogenase subcomplexes from cyanobacterium Synechocystis PCC6803].

Many efforts have been paid to the separation of an integrated NA(D)PH dehydrogenase (NDH) complex. Several hydrophilic subcomplexes of NDH have been purified from the cyanobacterium Synechocystis PCC6803. However, no hydrophobic NDH subcomplex has ever been separated from cyanobacteria yet.

The Photochemical Change in Photosynthetic Reaction Center of Purple Bacterium with Pheophytin Substitution.

The reaction centers are isolated from chromatophores of Rhodobacter sphaeroides 601 by detergent LDAO, and purified by chromatography on a DEAE-52 cellulose column. In the presence of acetone and an access of free pheophytins (Phes), bacteriopheophytins (Bphes) in reaction centers are replaced by pheophytins at sites H(A) and H(B) when incubated under high temperature. The substituting amounts are about 50% and 71% Bphes in reaction centers with incubation of fifteen and sixty minutes respectively.

The Involvement of Plastoquinone in the Pyocyanine-mediated Cyclic Electron Transport around Photosystem I.

2,5 dibromo-3-methyl-5-isopropyl-p-benzoquinone (DBMIB), an inhibitor of plastoquinone, inhibited photosystem I cyclic electron transport mediated by pyocyanine of low concentration, but had no effect on that mediated by phenazine methosulphate (PMS). In the presence of pyocyanine, the thylakoids displayed a transient post-illumination increase in chlorophyll fluorescence which resembled that displayed in leaves. The above results indicate the involvement of plastoquinone in the pyocyanine-mediated cyclic electron transport around photosystem I.

Expression of the atpE Gene Coding for the epsilon Subunit of Maize Chloroplast Coupling Factor.

The entire atpE gene of the maize chloroplast coupling factor was inserted into the polylinker region of vectors pJLA505 and pWA to form recombinant plasmids pJLA505-atpE and pWA-atpE respectively. These expression plasmids were transformed into E. coli NM522 which induced at 42 degrees.