Methanol as a probe to investigate the relationship between the secondary electron donor TyrZ and the substrate water molecules in active photosystem Ⅱ

The secondary electron donor, TyrZ, is implicated in tuning the primary charge separation and the water oxidation in active pho-tosystem II (PSII). Two types of mechanisms have been proposed to explain the function of TyrZ. One is that TyrZ tunes the water oxidation through the direct interaction with substrate water molecules; the other is that TyrZ is located in a hydrophobic envi-ronment without interacting with H2O, and controls the water oxidation by tuning the strength of the hydrogen bond between Tyr...     

Effect of Mn cluster on the formation of superoxide radicals in photoinhibition of photosystem Ⅱ

To further realize the action of superoxide radicals (O₂^{− .}) in photoinhibition of photosystem Ⅱ (PSⅡ), we employed 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap, associated with EPR spectroscopy, to study the effect of illumination time on O₂^{− .} formation during high light photoinhibition in PSⅡ membranes and Mn-depleted PSⅡ membranes. Results indicated that the removal of Mn cluster from PS
membranes has a strong influence on the dynamics of superoxide formation. The relative mechanism was also discussed. These novel findings may further promote the studies of the structure and function of PSⅡ and the mechanism of photoinhibition.     

Thermal stability of oxygen evolution in photosystem Ⅱ core complex in the presence of digalactosyl diacylglyceroli

The influence of digalactosyldiacylglycerol (DGDG), one of the photosynthetic membrane lipids, on heat inactivation of the process of oxygen evolution has been studied in vitro in photosystem Ⅱ (PSⅡ) core complex. It was found that the temperature of semi-inactivation of oxygen evolution in the complex increased from 40.0 to about 43.0℃ in the presence of DGDG with 5-min heat treatment in the dark. Furthermore, when PSⅡ core complex was incubated for 5 min at 45.0℃, the oxygen evolution in the complex was completely lost, whilst the DGDG-complexed PSⅡ core complex still retained a 16% of activity (100% for 25.0℃). In addition, a 1-h incubation at 38.0℃ inactivated absolutely the oxygen evolution for the PSⅡ core complex. By contrast, there remained about 20% of activity (zero time for 100%) for the complex in the presence of DGDG under the same condition. These results indicate a new role of DGDG in the protection of PSⅡ core complex against the deleterious effects of temperature. It was most likely that DGDG-mediated stability toward thermal denaturation of oxygen evolution in PSⅡ core complex is due to the protective effect of DGDG on the release of the 33 kD protein from PSⅡ core complex.     

Depletion of phosphatidyl-glycerol head-group induces changes in oxygen evolution and protein secondary struc-tures of photosystem Ⅱ

The techniques of oxygen electrode polarogra-phy and Fourier transform infrared (FT-IR) spectroscopy were employed to explore the roles of polar head-group of phosphatidylglycerol (PG) molecules in the functional and structural aspects of photosystem Ⅱ (PS Ⅱ) through enzymatic approach. It was shown that the depletion of PG by treatment of phospholipase C (PLC) on PS Ⅱ particles caused the inhibition of oxygen evolving activity in PS Ⅱ. This effect also gave rise to changes in the protein secondary structures of PS Ⅱ, that is, an increase in a-helical conformation which is compensated by the loss of p-strand structures. It revealed that the head-group of PG molecules plays an important structural role in the maintenance of normal structure of PS Ⅱ proteins, which is required to maintain the appropriate physiological activity of the PS Ⅱ complex such as the oxygen evolving activity. It is suggested that there most probably exist hydrogen-bonding interactions between PG molecules and PS Ⅱ proteins.     

Node ordinal encoded genetic algorithm for the optimal allocation of water resources

A new method, node ordinal encoded genetic algorithm (NOEGA), is proposed for solving water resources optimal allocation problems, in which the capacity of water resources is split into a number of smaller parts so that successive operations can be overlapped. Our objective is to maximize the whole benefit function. To overcome the “dimensionality and algorithm complexity curse” while searching for solutions and looking for an optimal solution, the operations of one-point crossover operator, gene exchange operator, gene random operator, gene shift operator and node ordinal strings are established. It is proved to be an effective optimal method in searching for global solutions. The NOEGA does not need a diversity of initial population, and it does not have the problem of immature convergence. The results of two cases show that using NOEGA to solve the optimal allocation model is very efficient and robust. In addition, the algorithm complexity of NOEGA is discussed.     

The altitude effect of δ 18O in precipitation and river water in the Southern Himalayas

The lapse rate of water isotopes is used in the study of the hydrologic cycle as well as in the estimation of uplift of the Tibetan Plateau.The greater elevation contrast in the Southern Himalayas allows for a detailed discussion about this lapse rate.We analyze variations of 18δO in precipitation and river water between 1320 m and 6700 m elevations in the Southern Himalayas,and calculate the specific lapse rate of water 18δO.The results show that the multi-year average lapse rate in precipitation over this region is 0.15‰/100 m.The one-year average lapse rate is 0.17‰/100 m from three sites along the Southern Himalayas.The two results agree,but are much lower than the global average of 0.28‰/100 m.This work also shows that there is a difference in precipitation 18δO lapse rate between the monsoon and non-monsoon seasons.The calculated precipitation lapse rate is much lower than that in surface water.     

Isotopic composition of atmospheric water vapor before and after the monsoon’s end in the Nagqu River Basin

Stable isotopes of water are widely used in scientific research to reconstruct paleoclimate and paleoenviron- ment variations[1―4]. Atmospheric water vapor plays a keyrole in the precipitation events. Therefore, the isotopic composition of atmospheric water vapor has a direct effect upon that of precipitation[5,6]. Observation of stable isotope variation of atmospheric water vapor has an important significance to indicate the moisture origins andmoisture transport in the study area. Based on …     

Characteristics of δ~(18)O in precipitation over Eastern Monsoon China and the water vapor sources

Monsoon circulation is an important carrier of water vapor transport, and it impacts the precipitation of the monsoonal regions through the constraints and controls of large-scale water vapor transport and distributions as well as the water vapor balance. An overall research on stable Hydrogen and Oxygen isotopes in precipitation over Eastern Monsoon China could benefit a comprehensive understanding of the monsoonal precipitation mechanism. Seventeen field stations of the Chinese Network of Isotopes in Prec...     

Specific degradation of photosystem II D1 protein by a protease （Air3815） in heterocysts of the cyanobacterium Anabaena sp. PCC7120

Some filamentous cyanobacteria form heterocysts under conditions lacking combined nitrogen for nitrogen fixation.Photosystem II is removed from heterocyst during the process of cell differentiation.Here,we demonstrate that Alr3815 is a protease that is capable of degrading D1 protein of photosystem II.Strain-322,which lacks alr3815,is impaired in nitrogen fixation in air because some oxygen evolving activity is retained in its heterocysts.Our results also suggest that calcium may play a regulatory role in D1 degradation during heterocyst differentiation.     

Expression of thymosin-β4, RACK1 and HMGB in adult amphioxus:implication for the evolutionary conservation of organ related functional molecules

Vertebrate thymosin-β4, RACK1 and HMGB are important molecules functioning in embryonic development and adult life. Here we report the expression patterns of amphioxus thymosin-β4, RACK1 and HMGB genes in tissues of adult amphioxus as revealed by RT-PCR and in situ hybridization. These three genes are all strongly expressed in the central nervous system and ovary, but differently expressed in other tissues including gut, testis, wheel organ, gill and endostyle.