The transfer of light energy from phycobilisomes (PBS) to photosystem II (PSII) reaction centers is vital for photosynthesis in cyanobacteria and red algae. To investigate the relationship between PBS and PSII and to optimize the energy transfer efficiency from PBS to PSII, isolation of the PBS-PSII supercomplex is necessary. SPC (sucrose/phosphate/citrate) is a conventional buffer for isolating PBS-PSII supercomplex in cyanobacteria. However, the energy transfer occurring in the supercomplex is poor. Here, we developed a new buffer named SGB by adding 1M glycinebetaine and additional sucrose to SPC buffer. Compared to SPC, the newly developed SGB buffer greatly enhanced the associated populations of PBS with thylakoid membranes and PSII and further improved the energy transfer efficiency from PBS to PSII reaction centers in cyanobacteria in vitro. Therefore, we conclude that SGB is an excellent buffer for isolating the PBS-PSII supercomplex and for enhancing the energy transfer efficiency from PBS to PSII reaction centers in cyanobacteria in vitro., L. P. Chen, Q. X. Wang, W. M. Ma., and Obsahuje bibliografii
In order to study photosynthetic characteristics, phosphoenolpyruvate carboxylase (PEPC) and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activities as well as soluble protein and chlorophyll contents were determined in leaf and fruit pericarp samples from diverse coffee genotypes (Coffea arabica cv. Colombia, Caturra, Caturra Erecta, San Pacho, Tipica, C. stenophylla, C. eugenioides, C. congensis, C. canephora, C. canephora cv. Arabusta, C. arabica cv. Caturra×C. canephora and Hibrido de Timor. We found a slightly higher PEPC activity in fruit pericarp than in leaves, while RuBPCO activity was much lower in pericarp than leaf tissue. Partial purification of PEPC and RuBPCO was carried out from leaves of C. arabica cv. Caturra and Michaelis-Menten kinetics for RuBPCO (Km CO2 = 5.34 µM), (Km RuBP = 9.09 µM) and PEPC (Km PEP = 19.5 µM) were determined. Leaf tissues of Colombia, Hibrido de Timor, and Caturra consistently showed higher content of protein [55.4-64.4 g kg-1 (f.m.)] than San Pacho, C. stenophylla, Tipica, Caturra Erecta, and Caturra×C. canephora [25.6-36.9 g kg-1 (f.m.)] and C. canephora cv. Arabusta, Borbon, C. congensis, C. eugenioides, and C. canephora [16.1-21.1 g kg-1 (f.m.)]. and Y. Lopez ... [et al.].
During batch culture of Haslea ostrearia the highest carbon (14C) fixation rate was found in vivo in cells that did not accumulate the blue pigment marennine (green form). This fixation rate decreased concomitantly with the accumulation of marennine. In vitro, no phosphoenolpyruvate carboxylase (PEPC) activity was detected, but nearly equivalent activities of ribulose-1,5-bisphosphate carboxylase (RuBPC) and phosphoenolpyruvate carboxykinase (PEPCK) were found in the green form. However, the activity of RuBPC was lower than that of PEPCK during marennine accumulation. In vitro carboxylase activities were strongly inhibited by the addition of a marennine extract. A full description of this inhibition could not be confirmed within the cells because marennine accumulates in small cytoplasmic vesicles. and G. Tremblin, J.-M. Robert.
Calamagrostis arundinacea L. (Roth.) and C. villosa (Chaix.) J.F. Gmel are two grass species substituting forest communities on deforested areas in Central Europe. They were exposed to enhanced ultraviolet-B (UV-B, λ = 290-320 nm) radiation during 22 weeks. A system of modulated lamps operating under field conditions was used to simulate a 25 % increase of incident UV-B radiation. CO2 assimilation seemed to be limited by a decrease of stomatal conductance (gs) in C. arundinacea, whereas carboxylation activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) was not affected. On the contrary, gs and RuBPCO activity decreased in C. villosa. These physiological adjustments resulted in growth changes; above-ground biomass decreased in C. villosa (prevailing negative effect) and significantly increased in C. arundinacea (prevailing positive effect) in response to enhanced UV-B radiation. and O. Urban ... [et al.].
The oligomeric state of photosystem 2 (PS2) complex in soybean leaves treated with saturating irradiance was studied by non-denaturing polyacrylamide gel electrophoresis (PAGE) and gel filtration chromatography. PS2 dimers resolved by non-denaturing PAGE accounted for about 75 % of total PS2 complex and there was no significant difference in the ratio of PS2 dimer to monomer between samples from saturating irradiance-treated and fully dark-adapted leaves. Furthermore, BBY particles were resolved into four chlorophyll-enriched fractions by gel filtration chromatography. From their molecular masses and protein components, these fractions were deduced to be PS2 dimer, PS2 monomer, oligomeric light-harvesting complex 2 (LHC2), and monomeric LHC2. Also, no change in the proportion of PS2 dimer in total PS2 was observed in the granal region of thylakoid membranes from soybean leaves after saturating irradiation. Hence the dimer is the predominant natural form of PS2 in vivo and no monomerisation of PS2 dimer occurs during saturating irradiance-induced photoinhibition in soybean leaves. and Shi-Qing Cai ... [et al.].