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1.
Analysis of the Role of Recombination and Repair in Mutagenesis of ESCHERICHIA COLI by Uv Irradiation 总被引:14,自引:0,他引:14
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Multiple mutant strains have been tested for their mimicry of the UV-mutagenesis deficiency of a recA single mutant. Revertants to histidine prototrophy and clear plaque mutants of lambda were scored to determine capacity for UV-mutagenesis. Nearly normal capacity was shown by a uvr+ recB- recF - strain, which shows almost no recA-dependent recombination, by uvr- recB+ recF - strains, which show almost no recA-dependent repair and by a uvrA- recB- recF- strain, which shows neither recA-dependent recombination nor repair. Since the uvr mutants can be assumed to show additionally no excision repair, these results may mean that UV-mutagenesis occurs during processes other than recombination and repair. Alternative hypotheses are discussed. The slight difference in mutagenic capacity was traced to the recF single mutation, which blocks the production of unmixed bursts of clear-plaque lambda mutants. Since this accounts for only about 10% of the mutations leading to clear-plaque mutants, it is suggested that there is more than one UV-mutagenic process. 相似文献
2.
Lethal and mutagenic effects of nitrous acid and UV radiation onMycobacterium phlei were studied Three auxotrophic strains of the PA strain ofMycobacterium phlei were obtained: ala-, his-, and gly- (ser-) INHr Bods of the his- strain grown in liquid media are longer to filamentous as compared with cells of the prototrophic PA strain grown in the
same media, whereas cells of the gly- (ser-) INHr mutant are shorter to coccobacillary. Cells of the ala- strain are characterized by their various length from normal to coccobacillary. The auxotrophic strains obtained differ from
each other by a frequency of spontaneous reversions to prototrophy. The his- strain is the most stable, a frequency of spontaneous reversions to prototrophy being 10-9. The gly- (ser-) INHr strain reverts spontaneously to prototrophy with a frequency of 10-8 to 10-7. The ala- strain spontaneously reverting with a frequency of 10-5 is the most labile. The auxotrophic mutants obtained do not differ from the original prototrophic strain in the other properties
studied.
A change in a frequency of INH and STM-resistant mutants was also studied. It was found that under the influence of UV radiation
a frequency of INH-resistant mutants increases 43 to 80 fold as compared with a frequency of spontaneous mutations, this latter
being about 2.6 × 10-6. No substantial increase in a frequency of STM-resistant mutants was found using UV irradiation under the given experimental
conditions; their spontaneous frequency equals to 9.0 × 10-9 to 2.0 X 10-8. 相似文献
3.
《Phytochemistry》1986,25(5):1205-1207
A new flavanol glycoside has been isolated from stems of Erythroxylum novogranatense and its structure has been elucidated on the basis of MS and 1H NMR spectroscopy and hydrolytic studies as (+)-catechin 3-O-α-L-rhamnopyranoside. On a similar basis of chemical and spectroscopic evidence, the presence of ombuin 3-O-rutinoside has been established. Furthermore, the occurrence of procyanidin biflavanoids has been demonstrated by the characterization of B1 and B3 as the first representatives of B-type proanthocyanidins in the genus Erythroxylum. 相似文献
4.
Synechococcus strain GL24 is a unicellular cyanobacterium that was isolated from Fayetteville Green Lake, New York, a meromictic lake which has high Ca2+ and SO42- concentrations. Epicellular mineralization of Synechococcus cells in the lake is the mechanism by which extensive calcitic bioherms (or microbial reefs) have been formed on the lake's shore and a marl sediment has been built on the lake bottom. Previous studies have shown that calcium carbonate (calcite) formation on the Synechococcus surface is dependent upon an alkaline pH, which is produced in the cellular microenvironment by the cells as their activity increases with seasonal warming of the lake water. At the circumneutral pH of bulk lake water, calcium sulfate (gypsum) is formed. In this study, we show that Synechococcus mediates a similar sulfate-to-carbonate transformation when Sr2+ is the major divalent cation present, forming celestite and strontianite. In experimental systems to which equimolar amounts of Ca2+ and Sr2+, Ca2+ or Sr2+ and Mg2+, or all three ions together were added to artificial lake water, Ca2+ and Sr2+ were incorporated equally into mineral formation to form CaSr(CO3)2. No Mg2+ -containing carbonates were formed when either or both of the other two ions were present. Mineral formation takes place on a hexagonally arranged proteinaceous template (an S-layer) which forms the outermost surface of the Synechococcus cell. Our results provide evidence that the S-layer exhibits selectivity with respect to the ions bound and subsequently incorporated into carbonate minerals and that celestite and strontianite, previously thought to be purely evaporitic minerals, can be biogenically formed. 相似文献
5.
Cytoplasmic Inheritance of a Cell Surface Antigen in the Mouse 总被引:4,自引:1,他引:3
Mta is a cell surface antigen of the mouse and serves as a target for specific T killer lymphocytes. Using a killer cell assay, the antigen has been found in 72 strains of laboratory mice and, with one exception, in all tested samples of mice caught in the wild or bred from such, including Mus molossinus, Mus castaneus and Mus spretus. Five strains of rats, non-inbred NMRI mice, most substrains of NZB mice and the closely related strain NZO are negative for Mta. In reciprocal F1 crosses between several Mta+ and two Mta- strains, the antigen is maternally transmitted; that is, Mta+ females bear only positive offspring, whereas Mta- females bear only negative offspring, regardless of the genotype of the male. Since 34 foster-nursed mice had the Mta type of their genetic mothers, the factor that determines expression of Mta must be transmitted before birth and not via the milk. The cytoplasmic genes of Mta+ strains have been combined with the chromosomal genes of Mta- strains, and vice versa, by repeated backcrossing. All progeny retained the Mta type of their maternal lines. Thus, the Mta type is determined solely by maternal inheritance and is not influenced by chromosomal genes. We found no evidence of incompatibility between the cytoplasmic factors and nuclear genes of Mta- and Mta + strains. 相似文献
6.
Effect of Mg doping in Sr2SiO4:Eu2+ nanophosphors for blue and white emission at near‐UV excitation
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Nanophosphors of (Sr0.98‐xMgxEu0.02)2SiO4 (x = 0, 0.18, 0.38, 0.58 and 0.78) were prepared through low temperature solution combustion method and their luminescence properties were studied. The emission peak for Eu2+ ?doped Sr2SiO4 nanophosphor is observed at ~490 nm and ~553 nm corresponding to two Sr2+ sites Sr(I) and Sr(II) respectively for 395 nm excitation. However the addition of Mg2+ dopant in Sr2SiO4 leads to suppression of ~553 nm emission peak due to absence of energy levels of Sr (II) sites which results in a single broad emission at ~460 nm. It was shown that the emission peak blue shifted with increase in Mg concentration which may be attributed to change in crystal field environment around Sr(I) sites. Therefore, the (Mg0.78Sr0.20Eu0.02)2SiO4 nanophosphor can be used for blue emission and the Sr2SiO4:Eu0.042+ for green–yellow emission at 395 nm excitations. The Commission International de L'Eclairage (CIE) chromaticity coordinates for mixed powders of (Mg0.78Sr0.20Eu0.02)2SiO4 and Sr2SiO4:Eu0.042+ (in a 1:1 ratio) fall in the white region demonstrating the possible use of the mixture in white light generation using near‐UV excitation source. 相似文献
7.
Anil Boda Sk. Musharaf Ali Madhav R. K. Shenoi Hanmanth Rao Sandip K. Ghosh 《Journal of molecular modeling》2011,17(5):1091-1108
Crown ether architectures were explored for the inclusion of Cs+ and Sr2+ ions within nano-cavity of macrocyclic crown ethers using density functional theory (DFT) modeling. The modeling was undertaken
to gain insight into the mechanism of the complexation of Cs+ and Sr2+ ion with this ligand experimentally. The selectivity of Cs+ and Sr2+ ions for a particular size of crown ether has been explained based on the fitting and binding interaction of the guest ions
in the narrow cavity of crown ethers. Although, Di-Benzo-18-Crown-6 (DB18C6) and Di-Benzo-21-Crown-7 (DB21C7) provide suitable
host architecture for Sr2+ and Cs+ ions respectively as the ion size match with the cavity of the host, but consideration of binding interaction along with
the cavity matching both DB18C6 and DB21C7 prefers Sr2+ ion. The calculated values of binding enthalpy of Cs metal ion with the crown ethers were found to be in good agreement with
the experimental results. The gas phase binding enthalpy for Sr2+ ion with crown ether was higher than Cs metal ion. The ion exchange reaction between Sr and Cs always favors the selection
of Sr metal ion both in the gas and in micro-solvated systems. The gas phase selectivity remains unchanged in micro-solvated
phase. We have demonstrated the effect of micro-solvation on the binding interaction between the metal ions (Cs+ and Sr2+) and the macrocyclic crown ethers by considering micro-solvated metal ions up to eight water molecules directly attached
to the metal ion and also by considering two water molecules attached to metal-ion-crown ether complexes. A metal ion exchange
reaction involving the replacement of strontium ion in metal ion-crown ether complexes with cesium ion contained within a
metal ion-water cluster serves as the basis for modeling binding preferences in solution. The calculated O-H stretching frequency
of H2O molecule in micro-solvated metal ion-crown complexes is more red-shifted in comparison to hydrated metal ions. The calculated
IR spectra can be compared with an experimental spectrum to determine the presence of micro-solvated metal ion–crown ether
complexes in extractant phase. 相似文献
8.
Qianwei Li Laszlo Csetenyi Graeme Iain Paton Geoffrey Michael Gadd 《Environmental microbiology》2015,17(8):3082-3097
The urease‐positive fungi Pestalotiopsis sp. and Myrothecium gramineum, isolated from calcareous soil, were examined for their properties of CaCO3 and SrCO3 biomineralization. After incubation in media amended with urea and CaCl2 and/or SrCl2, calcite (CaCO3), strontianite (SrCO3), vaterite in different forms [CaCO3, (CaxSr1?x)CO3] and olekminskite [Sr(Sr,Ca)(CO3)2] were precipitated, and fungal ‘footprints’ were observed on mineral surfaces. The amorphous precipitate mediated by Pestalotiopsis sp. grown with urea and equivalent concentrations of CaCl2 and SrCl2 was identified as hydrated Ca and Sr carbonates by Fourier transform infrared spectroscopy. Liquid media experiments showed M. gramineum possessed the highest Sr2+ removal ability, and ~ 49% of supplied Sr2+ was removed from solution when grown in media amended with urea and 50 mM SrCl2. Furthermore, this organism could also precipitate 56% of the available Ca2+ and 28% of the Sr2+ in the form of CaCO3, SrCO3 and (CaxSr1?x)CO3 when incubated in urea‐amended media and equivalent CaCl2 and SrCl2 concentrations. This is the first report of biomineralization of olekminskite and coprecipitation of Sr into vaterite mediated by fungi. These findings suggest that urease‐positive fungi could play an important role in the environmental fate, bioremediation or biorecovery of Sr or other metals and radionuclides that form insoluble carbonates. 相似文献
9.
《Journal of Molecular Catalysis .B, Enzymatic》2000,8(1-3):85-94
A new PQQ model compound [dimethyl 7-(1,4,7,10-tetraoxa-13-azacyclopentadec-13-yl)carbonyl-4,5-dihydro-4,5-dioxo-1H-pyrrolo[2,3-f]quinoline-2,9-dicarboxylate, 1], in which a 1-aza-15-crown-5 group is attached through an amide linkage at the 7-position, has been synthesized in order to develop an efficient model system of calcium-containing quinoprotein alcohol dehydrogenases. It has been found that Ca2+ binds to the quinone most strongly among the alkaline earth metal ions examined (Ca2++>Sr2++≫Ba2++≫Mg2+) and the binding constant (KM) for Ca2+ is as large as 2.1×105 M−1. Formation of the C-5 hemiacetal derivatives with ethanol is also investigated spectrophotometrically to show that the alcohol-addition to the quinone is enhanced in the presence of the metal ions. In this case, Ca2+ and Sr2+ show a similar efficiency that is several times larger than that of Ba2+. Addition of a strong base such as DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) into a MeCN solution containing the metal ion complex of 1 and ethanol leads to redox reactions to give the Ca2+ complex of 1H2 (quinol form) and acetaldehyde. Kinetic studies on the redox reactions have been performed to gain insight into the mechanism of the alcohol-oxidation reaction catalyzed by the metal complexes of coenzyme PQQ. 相似文献
10.
L5178Y mouse lymphoblastic leukemia cells are auxotrophic for l-asparagine (ASN) and have been widely used as a model system for studies on l-asparagine independence, were treated with known chemical mutagens to investigate the molecular basis of this mutation. Mutagens which primarily induce base pair substitutions—ethyl methanesullfonate (EMS) and N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)—as well as those which induce frame-shift mutations (the acridine half-mustards ICR-372 and ICR-191) each increased the frequency of ASN+ cells in treated cultures to at least ten times the usual background frequency of 1 to 2 ASN+ cells per 106 cells. The effectiveness of both classes of mutagens indicates that the change to asparagine prototrophy might occur by a mechanism other than, or in addition to, reversion of a specific base pair, point mutation. The mutability of this easily assayed nutritional genetic marker in a cell line that can be grown either in vitro or in vivo may provide a useful system for assay of other agents of unknown mutagenic potential. 相似文献
11.
H Washio 《The Journal of general physiology》1972,59(2):121-134
Electrical properties of locust leg muscle fibers were studied by means of intracellular electrodes. In most fibers, a depolarizing current pulse initiated a local response. A delayed decrease in membrane resistance appeared with more than about 10 mv depolarization. In some fibers a regenerative response also was found. Membrane constants were measured, applying the short cable model. The value of the space constant λ was 1.6 mm and the calculated value of Rm was about 1750 ohm cm2. Action potentials could be elicited when the bathing fluid contained more than 2–5 mM Ba or Sr. Similar responses were seen with 2 mM Ca in the presence of tetraethylammonium (TEA). The overshoot of these action potentials increased with increasing [Ca++]o, [Sr++]o, or [Ba++]o, the increment for a 10-fold increase being about 29 mv for Ca and Sr and between 40 and 50 mv for Ba. These action potentials were inhibited by Mn ions but were not affected by tetrodotoxin or procaine. In solutions containing Ba or Sr, action potentials generated were suppressed by addition of Ca. The removal of Na ions did not change the configuration of the action potential. The results suggest that an increase in permeability to Ca, Ba, or Sr ions makes a major contribution to the initiation of action potentials in this tissue. 相似文献
12.
Although strontium (Sr2+) is found in soils, sediments and surface waters, there is limited evidence about its biosorption. In this study, a surface water strain being highly tolerant to Sr2+ was isolated and identified as Micrococcus luteus Sr02 by using 16S rRNA sequencing. Biosorption behavior and mechanisms of Sr2+ by M. luteus Sr02 were investigated through batch experiments, zeta potential measurements, Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that M. luteus Sr02 have potential to sorb Sr2+ and can be used efficiently for the removal of Sr2+ from aqueous solutions. 相似文献
13.
Sol–gel preparation and luminescent properties of red‐emitting phosphor Sr‐Ba‐Mo‐W‐O‐(Eu3+,Sm3+)
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Two series of red‐emitting phosphors Sr‐Ba‐Mo‐W‐O:Eu,Sm and Sr‐Ba‐Mo‐W‐O:Eu have been synthesized by a sol–gel method. The effects of the chemical composition, concentrations of Sm3+ and Eu3+, the Sr2+/Ba2+ ratio, and the W6+/Mo6+ ratio on the luminescent properties were investigated. The as‐prepared phosphors were characterized by X‐ray diffraction and Raman spectra. Results showed that single phases of the two series were prepared. The compositions of Sr0.6Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10 had the strongest luminescent intensity. The excitation spectra of Sm3+, Eu3+ co‐doped phosphors were broader and the strongest peak moved to 404 nm when compared with that of Eu3+ single‐doped phosphors. The luminescent intensity of the Sr0.6Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 at 618 nm were 2.8 times greater than that of Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10. The luminescent intensity of Sr0.6Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10 at 150 °C decreased to 56.8% and 50.3% of the initial value at room temperature, respectively. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
14.
Balter V 《Oecologia》2004,139(1):83-88
In biological systems, strontium (Sr) and barium (Ba) are two non-essential elements, in comparison to calcium (Ca) which is essential. The Sr/Ca and Ba/Ca ratios tend to decrease in biochemical pathways which include Ca as an essential element, and these processes are termed biopurification of Ca. The quantitative pathway of the biopurification of Ca in relation to Sr and Ba between two biological reservoirs (R n and Rn -1) is measured with an observed ratio (OR) expressed by the (Sr/Ca) Rn /(Sr/Ca) Rn-1 and (Ba/Ca) Rn /(Ba/Ca) Rn-1 ratios. For a mammalian organism, during the whole biopurification of Ca starting with the diet to the ultimate reservoir of Ca which is the bone, the mean values for ORSr and ORBa are 0.25 and 0.2, respectively. In this study, published Sr/Ca and Ba/Ca ratios are used for three sets of soils, plants, and bones of herbivorous and carnivorous mammals, each comprising a trophic chain, to illustrate the biopurification of Ca at the level of trophic chains. Calculated ORSr and ORBa of herbivore bones in relation to plants and of bones of carnivores in relation to bones of herbivores give ORSr=0.30±0.08 and ORBa=0.16±0.08, thus suggesting that trophic chains reflect the Sr/Ca and Ba/Ca fluxes that are prevalent at the level of a mammalian organism. The slopes of the three regression equations of log(Sr/Ca) vs. log(Ba/Ca) are similar, indicating that the process of biopurification of Ca with respect to Sr and Ba is due to biological processes and is independent of the geological settings. Modifications of the logarithmic expression of the Sr/Ca and Ba/Ca relationship allow a new formula of the biopurification process to be deduced, leading to the general equation ORBa=ORSr1.79±0.33,where the allometric coefficient is the mean of the slopes of the three regression equations. Some recent examples are used to illustrate this new analysis of predator-prey relations between mammals. This opens up new possibilities for the utilization of Ba/Ca and Sr/Ca in addition to stable isotope ratios (13C and 15N) for the determination of the relative contribution of different food sources to an animals diet. 相似文献
15.
The conformation in solution of derivatives of methyl hexopyranosides has been studied by n.m.r. The esters of methyl 2,3-O-isopropylidene-α-D-manno- and -talopyranosides as well as their 4-deoxy-4-C-methyl analog having a manno configuration exist mainly in a flattened (4,0F) chair conformation (4C1). The presence in the talo epimer of the 4-deoxy-4-C-methyl analog of the bulky methyl group on the endo side of the bicyclic system results in a skew form (3S1). The methyl 4-deoxy-2,3-O-isopropylidene-4-C-methylene-α-D-lyxo-hexopyranosides monosubstituted at C-4′ adopt, in solution, a conformation close to 3S1, whichever their configuration (cis or trans) at the double bond, as indicated by their allylic coupling constants. 相似文献
16.
Cotransformation and Targeted Gene Inactivation in the Maize Anthracnose Fungus, Glomerella graminicola 总被引:1,自引:1,他引:0
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Cotransformation of Glomerella graminicola was achieved with the G. graminicola genes TUB1R1 (encoding a β-tubulin which confers resistance to the fungicide benomyl) and PYR1 (encoding orotate phosphoribosyl transferase, which confers pyrimidine prototrophy). The cotransformation frequency was about 30% when selection was for pyrimidine prototrophy (Pyr+) and 87% when selection was for benomyl-resistant (Bmlr) transformants. Southern blots confirmed that both transforming DNAs had integrated into the genomes of transformants which were expressing both Pyr+ and Bmlr phenotypes. A plasmid, p23, which contained a truncated 500-bp segment representing the central region of the PYR1 gene was constructed. The plasmid was introduced with pCG7, containing TUB1R1, into G. graminicola M1.001 (Pyr+ Bmls), and Bmlr transformants were selected. The Bmlr transformants were screened on medium which did not contain uridine in order to identify Pyr- mutants created by integration of p23 at the PYR1 locus. None of the primary transformants were Pyr-, but 0.2% of uninucleate conidia collected from the pooled primary transformants gave rise to Pyr- auxotrophs. Southern blots representing two of these Pyr- mutants confirmed that they had the expected homologous integration of p23 at the PYR1 locus. This suggested that integration resulted in production of two nonfunctional copies of the gene, one lacking the 5′ sequences and the other lacking the 3′ sequences. This study demonstrates the feasibility of using cotransformation to perform targeted gene disruptions in G. graminicola. 相似文献
17.
The plasmid pULB113 has been transferred to the facultative methylotrophs, Methylobacterium AM1 and Methylobacterium extorquens and to the obligate methanotroph Methylosinus trichosporium OB3b. Subsequent transfer from the methanotroph to the facultative methylotrophs and from the methanotroph and the facultative methylotrophs to Escherichia coli K-12 strains has been observed. In crosses from M. extorquens to restriction-deficient recombination-impaired E. coli strains, restoration of phenotype to auxotrophs was demonstrated and R-primes isolated from these recipients could transform auxotrophic strains to prototrophy. 相似文献
18.
A method of selective suppression of absorption of radioactive strontium from ingested food material is described which allows calcium to be available to the body. In the present study the effects of administering calcium alginate were determined. Studies on the relative binding of Ca and Sr by calcium alginate in vivo are also important to the investigation of calcium-strontium exchange.Samples of calcium alginate were obtained commercially or prepared from sodium salts and the binding properties with Ca45 and Sr89 were tested in vivo. There was a free exchange of radioactive calcium as well as of strontium with bound inactive calcium. The amount of Ca45 retained in the gut by calcium alginate is proportionally less than Sr89, so that the ratio Sr89/Ca45 in the bone is consistently and significantly lower in treated rats. Calcium alginate acts differently from other calcium salts, although in a manner similar to sodium alginate. 相似文献
19.
Gypsogenin (L1; 3-hydroxy-23-oxoolean-12-en-28-oic acid), a natural saponin, was isolated from the boiling water extract of Gypsophila arrostii roots. In addition, the derivatives gypsogenin thiosemicarbazone (L2; 23-[(aminocarbonothioyl)hydrazono]-3-hydroxolean-12-en-28-oic acid) and gypsogenin thiosemicarbazone glyoxime (L3H2; (3β)-3-hydroxy-23-[({[(1Z,2E)-N-hydroxy-2-(hydroxyimino)ethanimidoyl]amino}carbonothioyl)hydrazono] olean-12-en-28-oic acid) as well as the Cu(II) and Co(II) complexes of L3H2 were prepared. The structures were established on NMR analysis (1H, 13C NMR, HMBC, HMQC, and NOESY), FT-IR and completed by analysis of LC/MS. Furthermore, the antiproliferative effects of the Co(II) and Cu(II) complexes of the gypsogenin derivatives were assayed in human promyelocytic leukemia (HL 60) cells. These complexes were found to be potent anticancer agents with concentrations that inhibited 50% of proliferation (IpC50) between 5 μM and 40 μM. Cell death was distinguished by HO/PI double staining. The Co(II) complex of L3H2 has shown approximately %50 apoptotic effect at 10 μM concentration. Paclitaxel has been used as positive control. 相似文献
20.
Yuki Kato Tadao Shibamoto Shoichi Yamamoto Tadashi Watanabe Naoko Ishida Miwa Sugiura Fabrice Rappaport Alain Boussac 《BBA》2012,1817(11):1998-2004
Ca2+ and Cl? ions are essential elements for the oxygen evolution activity of photosystem II (PSII). It has been demonstrated that these ions can be exchanged with Sr2+ and Br?, respectively, and that these ion exchanges modify the kinetics of some electron transfer reactions at the Mn4Ca cluster level (Ishida et al., J. Biol. Chem. 283 (2008) 13330–13340). It has been proposed from thermoluminescence experiments that the kinetic effects arise, at least in part, from a decrease in the free energy level of the Mn4Ca cluster in the S3 state though some changes on the acceptor side were also observed. Therefore, in the present work, by using thin-layer cell spectroelectrochemistry, the effects of the Ca2+/Sr2+ and Cl?/Br? exchanges on the redox potential of the primary quinone electron acceptor QA, Em(QA/QA?), were investigated. Since the previous studies on the Ca2+/Sr2+ and Cl?/Br? exchanges were performed in PsbA3-containing PSII purified from the thermophilic cyanobacterium Thermosynechococcus elongatus, we first investigated the influences of the PsbA1/PsbA3 exchange on Em(QA/QA?). Here we show that i) the Em(QA/QA?) was up-shifted by ca. + 38 mV in PsbA3-PSII when compared to PsbA1-PSII and ii) the Ca2+/Sr2+ exchange up-shifted the Em(QA/QA?) by ca. + 27 mV, whereas the Cl?/Br? exchange hardly influenced Em(QA/QA?). On the basis of the results of Em(QA/QA?) together with previous thermoluminescence measurements, the ion-exchange effects on the energetics in PSII are discussed. 相似文献