共查询到20条相似文献,搜索用时 31 毫秒
1.
Je-Nie Phue Sang Jun Lee Jeanne B. Kaufman Alejandro Negrete Joseph Shiloach 《Biotechnology letters》2010,32(12):1897-1903
Individual deletions of acs and aceA genes in E. coli B (BL21) showed little difference in the metabolite accumulation patterns but deletion of the ackA gene alone or together with pta showed acetic acid gradually accumulated to 3.1 and 1.7 g/l, respectively, with a minimal extended lag in bacterial growth
and a higher pyruvate formation. Single poxB deletion in E. coli B (BL21) or additional poxB deletion in the ackA-pta mutants did not change the acetate accumulation pattern. When the acetate production genes (ackA-pta-poxB) were deleted in E. coli B (BL21) acetate still accumulated. This may be an indication that perhaps acetate is not only a by-product of carbon metabolism;
it is possible that acetate plays also a role in other cellular metabolite pathways. It is likely that there are alternative
acetate production pathways. 相似文献
2.
Yuqiang Sun Xianlong Zhang Yichun Nie Xiaoping Guo 《Plant Cell, Tissue and Organ Culture》2005,83(3):303-310
Fertile somatic hybrids were obtained via symmetric electrofusion of protoplasts from two combinations of tetraploid cotton (G. hirsutum cv. Coker 201, AD genome) and diploid wild cottons G. bickii (G genome) and G. stockii (E genome), respectively. Observation by morphological, flow cytometric analysis, chromosome counting and RAPD analysis of the tested hybrids of Coker 201 + G. bickii and Coker 201 + G. stockii confirmed the regenerated plants as hybrid status. Cytological investigation of the metaphase root-tip cells revealed there were 78 chromosomes in the hybrids. Flow cytometric analysis showed the tested plants had a relative DNA contents close to the total DNA contents of the two parents. RAPD analysis revealed the hybrids contained specific genomic fragments from both fusion partners, further confirmed their hybridity. The morphology of the hybrids was intermediate between the two fusion partners. The hybrid plants were successfully transferred to the soil, and they bloomed and set bolls. It is sure that the new hexaploids developed by cell fusion would contribute to cotton breeding through backcrossing with the elite genotypes of G. hirsutum. 相似文献
3.
Georg Rüppell 《Journal of Ornithology》1975,116(2):168-180
Zusammenfassung Die Sturztauchmanöver vom Meerespelikan (Pelecanus occidentalis) und vom Blaufußtölpel (Sula nebouxii) werden beschrieben und miteinander verglichen. Der Tölpel erreicht durch eine widerstandsarme Eintauchhaltung erheblich größere Tauchtiefen als der Pelikan. Seine Flügelkonstruktion erlaubt es ihm darüber hinaus, weite Nahrungssuchflüge über dem Meer durchzuführen. Der Tölpel erscheint durch seine Flugfähigkeit der besser an die Verhältnisse des Meeres angepaßte Vogel zu sein. Ein Zusammenhang zwischen Fluganpassung und geographischer Verbreitung wird diskutiert.
Diving-manoeuvres of the Brown Pelican(Pelecanus occidentalis) and the Bluefooted-Booby(Sula nebouxii)
Summary The booby dives deeper because his body-posture produces only few drag while plunging into the water. His wing-construction is good for long distance flight over the ocean. The booby seems to be better adapted to the conditions of live at sea by his flight-cabability as the pelican. A connection between flight-adaptations and geographical distribution is discussed.相似文献
4.
Shi-Han Zhang Ling-Lin Cai Yun Liu Yao Shi Wei Li 《Applied microbiology and biotechnology》2009,82(3):557-563
The biological reduction of Fe(III) ethylenediaminetetraacetic acid (EDTA) is a key step for NO removal in a chemical absorption–biological
reduction integrated process. Since typical flue gas contain oxygen, NO2
− and NO3
− would be present in the absorption solution after NO absorption. In this paper, the interaction of NO2
−, NO3
−, and Fe(III)EDTA reduction was investigated. The experimental results indicate that the Fe(III)EDTA reduction rate decrease
with the increase of NO2
− or NO3
− addition. In the presence of 10 mM NO2
− or NO3
−, the average reduction rate of Fe(III)EDTA during the first 6-h reaction was 0.076 and 0.17 mM h−1, respectively, compared with 1.07 mM h−1 in the absence of NO2
− and NO3
−. Fe(III)EDTA and either NO2
− or NO3
− reduction occurred simultaneously. Interestingly, the reduction rate of NO2
− or NO3
− was enhanced in presence of Fe(III)EDTA. The inhibition patterns observed during the effect of NO2
− and NO3
− on the Fe(III)EDTA reduction experiments suggest that Escherichia coli can utilize NO2
−, NO3
−, and Fe(III)EDTA as terminal electron acceptors. 相似文献
5.
Chaoqiang Jiang Qingsong Zheng Zhaopu Liu Wenjun Xu Ling Liu Gengmao Zhao Xiaohua Long 《Trees - Structure and Function》2012,26(3):685-694
Salinity is a major abiotic stress factor limiting plant growth and productivity. One possible method to enhance plant salt-resistance
is to compartmentalize sodium ions away from the cytosol. In the present work, a vacuolar Na+/H+ antiporter gene AtNHX1 from Arabidopsis thaliana, was transferred into Populus × euramericana ‘Neva’ by Agrobacterium tumefaciens in order to enhance poplar salt-resistance. The results showed that the transgenic poplar were more resistant to NaCl than
the wild-type (WT) in greenhouse condition. Compared with the WT, plant growth and photosynthetic capacity of the transgenic
plants were enhanced, and the transgenic plants accumulated more Na+ and K+ in roots and leaves under the same NaCl condition, whereas malondialdehyde and relative electrical conductivity were lower.
All of these properties of the transgenic poplar were likely to be a consequence of the overexpression of AtNHX1 caused Na+ sequestration in the vacuoles and improved K+ absorption, thus reducing their toxic effects. These results indicated overexpression of the AtNHX1 enhanced salt-resistance of poplar, and AtNHX1 played an important role in the compartmentation of Na+ into the vacuoles. Therefore, this study provides an effective way for improving salt resistance in trees. 相似文献
6.
Summary pKM101, a plasmid R factor of the N compatibility group increases methylmethane sulfonate mutagenesis and diminishes UV-killing in recA
+
lex
+ and recA
+
lex
– strains, but not in recA
–
lex
+ strains. The induction of a reclex dependent colicin is not present in lex
– strains carrying the pKM101 factor. These facts indicate that pKM101 acts through an error-prone DNA repair system, which is recA
+ dependent, but not lex
+ dependent.This paper is published on the occasion of Dr. C. Callerio's seventy-fifth birthday 相似文献
7.
The Escherichia coli chaperone DnaK is vital for many cellular functions, including ribosome biogenesis at high temperature. Thus, the dnaK756-ts (λ
R
) mutant, at the non-permissive temperature, is inhibited at a late stage of ribosome assembly, yielding 21S, 32S and 45S
precursor particles. This defect, unlike the λ resistance and thermosensitivity phenotypes, is not complemented by lysogenisation
with a transducing phage λ
dnaK
+
bearing the wild-type dnaK gene. However this dominant phenotype becomes recessive when dnaK
+
is expressed from a medium-copy-number plasmid. On the other hand, an excess of DnaK causes an unexpected dominant-lethal
effect of the dnaK756 allele near non-permissive temperatures. This interplay between the dnaK
+
and dnaK756 alleles supports the idea of that DnaK oligomers form in the cell.
Received: 28 April 1998 / Accepted: 24 July 1998 相似文献
8.
Kazuhiro Kawabata 《Inorganica chimica acta》2005,358(6):2082-2088
[Ir(η5-C5Me5)(C8H4S8)] (1) [ = 2-{(4,5-ethylenedithio)-1,3-dithiole-2-ylidene}-1,3-dithiole-4,5-dithionate(2−)] was reacted with iodine in dichloromethane to afford one-electron- and two-electron-oxidized species [IrI(η5-C5Me5)(C8H4S8)] (2), [IrI(η5-C5Me5)(C8H4S8)](I3) (3) and [IrI(η5-C5Me5)(C8H4S8)](I5) (4). The oxidized species exhibit electrical conductivities of (1.1-5.0) × 10−6 S cm−1 measured for compacted pellets at room temperature. The X-ray crystal structures of the two-electron-oxidized complexes 3 and 4 revealed the Ir-I bonds for both of them and the presence of for 3 and ions for 4 as the counter anions. They have many S-S and S-I non-bonding contacts to form two-dimensional molecular interaction sheets in the solid state. 相似文献
9.
Ethanol-hypersensitive strains (ets mutants), unable to grow on media containing 6% ethanol, were isolated from a sample of mutagenized Schizosaccharomyces pombe wild-type cells. Genetic analysis of these ets strains demonstrated that the ets phenotype is associated with mutations in a large set of genes, including cell division cycle (cdc) genes, largely non-overlapping with the set represented by the temperature conditional method; accordingly, we isolated some ets non-ts cdc
– mutants, which may identify novel essential genes required for regulation of the S. pombe cell cycle. Conversely, seven well characterized ts cdc
– mutants were tested for their ethanol sensitivity; among them, cdc1–7 and cdc13–117 exhibited a tight ets phenotype. Ethanol sensitivity was also tested in strains bearing different alleles of the cdc2 gene, and we found that some of them were ets, but others were non-ets; thus, ethanol hypersensitivity is an allele-specific phenotype. Based on the single base changes found in each particular allele of the cdc2 gene, it is shown that a single amino acid substitution in the p34cdc2 gene product can produce this ets phenotype, and that ethanol hypersensitivity is probably due to the influence of this alcohol on the secondary and/or tertiary structure of the target protein. Ethanol-dependent (etd) mutants were also identified as mutants that can only be propagated on ethanol-containing media. This novel type of conditional phenotype also covers many unrelated genes. One of these etd mutants, etd1-1, was further characterized because of the lethal cdc
– phenotype of the mutant cells under restrictive conditions (absence of ethanol). The isolation of extragenic suppressors of etd1-1, and the complementation cloning of a DNA fragment encompassing the etd1
+ wild-type gene (or an extragenic multicopy suppressor) demonstrate that current genetic techniques may be applied to mutants isolated by using ethanol as a selective agent. 相似文献
10.
Brooks Low 《Molecular & general genetics : MGG》1973,122(2):119-130
Summary The recombinant forming ability of recB
– or recC
– strains of E. coli K12 is almost totally recovered in merozygotes which are heterozygous for a genetic locus denoted rac which is located five minutes clockwise from trp on the genetic map. This transient recovery phenomenon only occurs when the donor strain is rac
+ (wild type) and the recipient strain is rac
-. The recombinants derived from such crosses all have the normal phenotype characteristic of recB
– (or recC
–) strains, and they are almost always rac
-. The results imply that the rac
+ locus (or loci) is zygotically expressed and excised from the chromosome in a manner which is analogous to the zygotic induction of a prophage. 相似文献
11.
Summary Nonsense codon suppressing lysogens of E. coli have been made using 80 psu
3
+
-A2 and 80 psu
oc
+
-A2, heat-sensitive amber and ochre suppressing derivatives, respectively, of bacteriophage 80. The various lysogens selected differ in strength of suppression as well as in heat sensitivity of suppressor function. Heat-resistant derivatives, some still carrying the A2 mutation, can be selected from the heat sensitive parents. Mapping expreiments indicate that the 80 derivatives integrate at the tyrTV locus, which contains two copies of tRNA
1
Tyr
. The origin of the various suppressor phenotypes appears to be related to the great variety of distinctive recombination events possible either between the incoming tRNA
1
Tyr
gene and the host copies, or among the three copies of this gene in the lysogens. 相似文献
12.
长江三角洲地区雨水中NH4+-N/NO3--N和δ15NH4+值的变化 总被引:4,自引:0,他引:4
2003年6月至2005年7月,利用自行设计的雨水收集器对位于长江三角洲地区的常熟、南京和杭州3个观测点进行了全年性雨水观测,分析了雨水中NH4+-N/NO3--N和铵态氮自然丰度(δ15NH4+)值的变化.结果表明:研究区3个观测点雨水中NH4+-N/NO3--N和δ15NH4+值均呈相似的季节性变化规律,两者的规律性变化在以田间农事耕作为主的常熟观测点尤其明显,而位于市区的南京观测点和位于城乡结合部的杭州观测点的规律性次之;雨水中NH4+-N/NO3--N的峰值出现在6月下旬到8月上旬,然后逐渐下降,冬季降到最低;雨水中δ15NH4+值在6月下旬到8月中旬为负值,在8月下旬到11月中下旬为正值,12月至翌年3月又变为负值,5至6月中旬又转变为正值.雨水中NH4+-N/NO3--N和δ15NH4+值的季节变化与不同作物生育期间氮肥的施用、当地气候的季节性变化以及其他NH3释放源的NH3挥发有关(人和动物排泄物、氮污染水体及有机氮源中的氨挥发),其对大气湿沉降中NH4+的来源、形态组成及陆地不同NH3排放源的强度具有明显的指示意义. 相似文献
13.
14.
G.Christian Friesinger Oswald Oelz Brian J. Sweetman Alan S. Nies Joann L. Data 《Prostaglandins & other lipid mediators》1978,15(6):969-981
Prostaglandin (PG) D2 was biosynthesized by rabbit renal papillae incubates in vitro. Quantification of the renal prostaglandins by gas chromatography-mass spectroscopy demonstrated that the concentration of PGD2 generated by renal papillae was
to
the amount of PGE2 or about 1 μg/g tissue/30 min. Infusion of the sodium salt of PGD2 into the renal artery of the dog produced a dose related increase in renal blood flow and urine flow, free water clearance, sodium excretion and potassium excretion without changes in systemic hemodynamics. At low doses PGD2 increased renal blood flow to all cortical zones. Higher concentrations of PGD2 produced a shift in the intrarenal distribution of blood flow toward the juxtamedullary nephrons. 相似文献
15.
The improved methods for the preparation of valency hybrid hemoglobins, (α3+β2+)2 and (α2+β3+)2 were presented. The (α3+β2+)2 valency hybrid was separated from the solutions of partially reduced methemoglobin with ascorbic acid, by using CM 32 column chromatography. The (α2+β3+)2 valency hybrid was also isolated from hemoglobin solutions, which were partially oxidized with ferricyanide, by chromatography on CM 32 column. These valency hybrid hemoglobins were found to be single on isoelectric focusing electrophoresis. Present procedures are very simple and are suitable for the bulk preparation of (α3+β2+)2 and (α2+β3+)2 valency hybrids. 相似文献
16.
On the interrelations of the Na+-and Cl?-influxes in the pulmonate freshwater snailLymnaea stagnalis 总被引:1,自引:1,他引:0
N. D. de With R. C. van der Schors 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1982,148(1):131-135
Summary In the freshwater snailLymnaea stagnalis the influxes of Na+ and Cl– were studied at different external concentrations of these ions. The characteristies of the Na+- and Cl–-influxes are similar with respect to saturation kinetics,K
m (0.1 mM) and activation by low-salt adaptation. In short-term experiments the Na+- and Cl–-influxes are independent. Because of the counter-ions (H+ and HCO
3
–
) involved, this indicates a potential acid-base regulatory capacity. Low-salt adaptation, due to either Na+-or Cl–-depletion, activates both the Na+- and the Cl–-influx. It is suggested that under both conditions the number of active integumental pumps, involved in Na+- as well as in Cl–-uptake, is increased. 相似文献
17.
Cu(C6H9N3O2)2Cl2对小麦的生态毒理效应 总被引:1,自引:0,他引:1
以冬小麦为实验材料,比较研究了(1)不同浓度配合物对小麦生长的影响;(2)相同浓度的CuC l2、配体C6H9N3O2和配合物Cu(C6H9N3O2)2C l2对冬小麦种子萌发、苗期生长及其保护酶活性的影响。结果表明:与对照相比,(1)不同浓度新配合物对小麦生长具有不同程度的抑制作用,随着浓度的增高抑制作用逐渐增大;(2)CuC l2、配合物Cu(C6H9N3O2)2C l2对小麦种子总淀粉酶活性、蛋白酶活性、萌发率、生长势、根长、株高、总生物量均具有显著的抑制作用,配合物Cu(C6H9N3O2)2C l2的抑制作用小于CuC l2,而配体C6H9N3O2对上述生物学参数具有促进作用;(3)CuC l2、配合物Cu(C6H9N3O2)2C l2处理引起膜脂过氧化,显著的提高了幼苗的M DA浓度,导致SOD、POD、CAT活性降低,CuC l2的抑制作用大于配合物Cu(C6H9N3O2)2C l2,而配体C6H9N3O2处理对SOD、POD、CAT活性的提高有促进作用。上述结果说明C6H9N3O2对CuC l2生理胁迫具有保护作用,结合态的Cu2 (配合物Cu(C6H9N3O2)2C l2)的毒性显著的降低。在此基础上探讨了配合物抑制小麦生长发育的生物学机制。 相似文献
18.
The potentials of a series of one-electron oxidation and reduction reactions have been determined for manganese group half-sandwich complexes of the tricarbadecaboranyl ligand PhC3B7H9 and the penta-organo fullerene ligand C60Bn2PhH2 (Bn = benzyl). The anodic processes were studied in CH2Cl2 and the cathodic processes were studied in both CH2Cl2 and THF, the supporting electrolyte being [NBu4][B(C6F5)4]. The manganese complex Mn(CO)2(PMe3)(PhC3B7H9) (1) is a member of a three-electron transfer series which includes oxidation to 1+ (0.51 V versus ferrocene) and successive reductions to 1− (−1.66 V) and 12− (−1.77 V). Both the oxidation and reduction of the closely-related complex Mn(CO)2(PPh3)(PhC3B7H9) (2) are chemically irreversible under slow-scan cyclic voltammetry conditions. The rhenium complex Re(CO)2(PPh3)(PhC3B7H9) (3) oxidizes (E1/2 = 0.82 V versus ferrocene) to a radical cation which, unlike its cyclopentadienyl analogue, shows no evidence of dimerization. Oxidation of the fullerene-based complex Re(CO)3(C60Bn2PhH2) is more facile than that of its cyclopentadienyl analogue, in contrast to previous findings in this class of metal-fullerene derivatives. An electrochemical ligand factor, EL, of 0.63 is calculated for the PhC3B7H9 ligand in manganese group half-sandwich complexes. 相似文献
19.
A method for measuring the gas temperature in an oxygen plasma by spectroscopy of the electronic transition from the O2(b
1Σ
g
+
, v = 0) metastable state of molecular oxygen into the O2(X
3Σ
g
−
, v = 0) ground state is considered in detail. The method is verified experimentally for the plasma of dc glow discharge in pure
oxygen. It is shown that the gas temperature can be determined by analyzing high-resolution spectra of the P branch of this transition, no matter whether its fine structure (P
P and P
Q branches) is resolved or masked, provided that the rotational structure of the spectrum is resolved. The feasibility of the
method proposed in 1999 by P. Maco and P. Veis for determining the gas temperature from the ratio between the intensity maxima
of the R and P branches of the O2(b
1Σ
g
+
, v = 0) → O2(X
3Σ
g
−
, v = 0) transition in a poorly resolved spectrum was studied experimentally. It is shown that, in order to use this method,
it is necessary to know the spectrograph instrumental function. The effect of the spatial inhomogeneity of the temperature
and concentration of O2(b
1Σ
g
+
) molecules on the accuracy of integral (over the plasma volume) measurements of the gas temperature is investigated using
spatially resolved spectroscopy of the O2(b
1Σ
g
+
, v = 0) → O2(X
3Σ
g
−
, v = 0) transition. It is shown that precise measurements of the temperature require that the optical measurement system be
thoroughly adjusted in order for the temperature and concentration of the emitting particles to vary insignificantly over
the optically selected volume.
Original Russian Text ? S.M. Zyryanov, D.V. Lopaev, 2007, published in Fizika Plazmy, 2007, Vol. 33, No. 6, pp. 563–574. 相似文献
20.
The reduction of ethanolic solutions of niobium pentachloride with zinc, followed by treatment with aqueous acids serves as a versatile entry into the aqueous solution chemistry of niobium. From the zinc-reduced solution, the major intermediate, Nb4(μ2-O)2(μ2-OC2H5)4Cl4(OC2H5)4(HOC2H5)4, was isolated and the crystal structure determined by X-ray crystallography. The complex crystallizes in the orthorhombic space group Pccn, with Z=4, a=21.0105(9), b=11.0387(5), c=19.1389(8), V=4438.9(3) Å3, Mr=1090.19,R1=0.0327 and wR2=0.0876. The structure revealed a centrosymmetric tetrameric Nb(IV) complex, consisting of a pair of edge-sharing bi-octahedral Nb2(μ2-OC2H5)4Cl2(OC2H5)2(HOC2H5)2 units that are joined by two axial oxo ligands. The Nb-Nb distance of 2.7458(3) Å is consistent with a single metal-metal bond. 相似文献