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1.
P. Ghosh-Dastidar B.B. Goswami A. Das P. Das N.K. Gupta 《Biochemical and biophysical research communications》1981,99(3):946-953
Vaccinia viral core inhibits protein synthesis in reticulocyte lysates. In partial reactions using micrococcal nuclease treated reticulocyte lysates, the viral core inhibits Met-tRNAf binding to 40S ribosomes in response to physiological mRNAs such as globin mRNA, cowpea mosaic viral RNA, and brome mosaic viral RNA but not in response to a trinucleotide codon, AUG. The core has also no effect on Met-tRNAf binding to 40S ribosomes in a partial reaction using partially purified peptide chain initiation factors and AUG codon.The present observation of preferential inhibition by vaccinia viral core of Met-tRNAf·40S initiation complex formation with physiological mRNAs and not with an artificial mRNA such as AUG codon, suggests that the viral core inhibits some step(s) in peptide chain initiation involved in the recognition of structural feature(s) unique to physiological mRNAs. 相似文献
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Vasily Kurashov Michael Gorka Georgy E. Milanovsky T. Wade Johnson Dmitry A. Cherepanov Alexey Yu. Semenov John H. Golbeck 《BBA》2018,1859(12):1288-1301
This work aims to fully elucidate the effects of a trehalose glassy matrix on electron transfer reactions in cyanobacterial Photosystem I (PS I). Forward and backward electron transfer rates from A1A? and A1B? to FX, and charge recombination rates from A0?, A1B?, A1A?, FX?, and [FA/FB]? to P700+ were measured in P700–FA/FB complexes, P700–FX cores, and P700–A1 cores, both in liquid and in a trehalose glassy matrix at 11% humidity. By comparing CONTIN-resolved kinetic events over 6 orders of time in increasingly simplified versions of PS I at 480?nm, a wavelength that reports primarily A1A?/A1B? oxidation, and over 9 orders of time at 830?nm, a wavelength that reports P700+ reduction and A0? oxidation, assignments could be made for nearly all of the resolved kinetic phases. Trehalose-embedded PS I samples demonstrated partially arrested forward electron transfer. The fractions of complexes in which electron transfer did not proceed beyond A0, A1 and FX were 53%, 16% and 22%, respectively, with only 10% of electrons reaching the terminal FA/FB clusters. The ~10?μs and ~150?μs components in both liquid and trehalose-embedded PS I were assigned to recombination between A1B? and P700+ and between A1A? and P700+, respectively. The kinetics and amplitudes of these resolved kinetic phases in liquid and trehalose-embedded PS I samples could be well-fitted by a kinetic model that allowed us to calculate the asymmetrical contribution of the A1A? and A1B? quinones to the electrochromic signal at 480?nm. Possible reasons for these effects are discussed. 相似文献
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Reactions of [Pt2(μ-S)2(PPh3)4] with the diarylthallium(III) bromides Ar2TlBr [Ar = Ph and p-ClC6H4] in methanol gave good yields of the thallium(III) adducts [Pt2(μ-S)2(PPh3)4TlAr2]+, isolated as their salts. The corresponding selenide complex [Pt2(μ-Se)2(PPh3)4TlPh2]BPh4 was similarly synthesised from [Pt2(μ-Se)2(PPh3)4], Ph2TlBr and NaBPh4. The reaction of [Pt2(μ-S)2(PPh3)4] with PhTlBr2 gave [Pt2(μ-S)2(PPh3)4TlBrPh]+, while reaction with TlBr3 gave the dibromothallium(III) adduct [Pt2(μ-S)2(PPh3)4TlBr2]+[TlBr4]−. The latter complex is a rare example of a thallium(III) dihalide complex stabilised solely by sulfur donor ligands. X-ray crystal structure determinations on the complexes [Pt2(μ-S)2(PPh3)4TlPh2]BPh4, [Pt2(μ-S)2(PPh3)4TlBrPh]BPh4 and [Pt2(μ-S)2(PPh3)4TlBr2][TlBr4] reveal a greater interaction between the thallium(III) centre and the two sulfide ligands on stepwise replacement of Ph by Br, as indicated by shorter Tl-S and Pt?Tl distances, and an increasing S-Tl-S bond angle. Investigations of the ESI MS fragmentation behaviour of the thallium(III) complexes are reported. 相似文献
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Janet M. Arce Brian A. Naughton Gail A. Kolks Philip Liu Albert S. Gordon Sam J. Piliero 《Prostaglandins & other lipid mediators》1981,21(3):367-377
Prostaglandins A2, E1, E2, methylated E2s and F2α affected erythropoiesis and/or erythropoietin (Ep) production. This action is indicated in the exhypoxic, polycythemic mouse where radioiron incorporations into RBC increased after administration of these compounds. The kidney and liver have been indicated through previous studies, to actively participate in Ep production. By the removal of one of these active sites in a murine system treated with prostaglandins it is shown that a response is reflected in Ep levels. Interference of the action of prostaglandins (PG) is altered by the removal of one of these target sites of Ep production. The erythropoietic responses elicited by PGA2, E1, and perhaps the methylated PGE2s act through the liver whereas PGE2 may operate through a renal pathway for its response. PGF2α reveals no effect on erythropoietic activity and is no different than that observed for vehicle-treated controls. The prostaglandins tested appear to act primarily through the kidney or liver but the possibility exists that some yet undetermined organ site may also be involved. 相似文献
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Routes to the synthesis of the mixed sulfide-phenylthiolate complex [Pt2(μ-S)(μ-SPh)(PPh3)4]+ have been explored; reaction of [Pt2(μ-S)2(PPh3)4] with excess Ph2IBr proceeds readily to selectively produce this complex, which was structurally characterised as its PF6− salt. Reactions of [Pt2(μ-S)2(PPh3)4] with other potent arylating reagents (1-chloro-2,4-dinitrobenzene and 1,5-difluoro-2,4-dinitrobenzene) also produce the corresponding nitroaryl-thiolate complexes [Pt2(μ-S){μ-SC6H2(NO2)2X}(PPh3)4]+ (X = H, F). The complex [Pt2(μ-S)(μ-SPh)(PPh3)4]+ reacts with Me2SO4 to produce the mixed alkyl/aryl bis-thiolate complex [Pt2(μ-SMe)(μ-SPh)(PPh3)4]2+, but corresponding reactions with the nitroaryl-thiolate complexes are plagued by elimination of the nitroaryl group and formation of [Pt2(μ-SMe)2(PPh3)4]2+. [Pt2(μ-S)(μ-SPh)(PPh3)4]+ also reacts with Ph3PAuCl to give [Pt2(μ-SAuPPh3)(μ-SPh)(PPh3)4]2+. 相似文献
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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
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The rate of photosynthetic electron transport measured in the absence of ADP and Pi is stimulated by low levels of Hg2+ or Ag+ (50% stimulation ≈ 3 Hg2+ or 6 Ag+/100 chlorophyll) to a plateau equal to the transport rate under normal phosphorylating conditions (i.e. +ADP, +Pi). Chloroplasts pretreated in the light under energizing conditions with N-ethylmaleimide show a similar stimulation of non-phosphorylating electron transport. The stimulations of non-phosphorylating electron transport by Hg2+, Ag+ and N-ethylmaleimide are reversed by the CF1 inhibitor phlorizin, the CF0 inhibitor triphenyltin chloride, and can be further stimulated by uncouplers such as methylamine. The Hg2+ and N-ethylmaleimide stimulations, but not the Ag+ stimulation, are completely reversed by low levels of ADP (2 μM), ATP (2 μM), and Pi (400 μM). Ag+, which is a potent inhibitor of ATP synthesis, has little or no effect upon phosphorylating electron transport (+ADP, +Pi). Concomitant with the stimulations of non-phosphorylating electron transport by Hg2+, Ag+ and ADP + Pi, there is a decrease in the level of membrane energization (as measured by atebrin fluorescence quenching) which is reversed when the CF0 channel is blocked by triphenyltin. These results suggest that modification of critical CF1 sulfhydryl residues by Hg2+, Ag+ or N-ethylmaleimide leads to the loss of intra-enzyme coupling between the transmembrane protontransferring and the ATP synthesis activities of the CF0-CF1 ATP synthase complex. 相似文献
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The metalloligand [Pt2(μ-S)2(PPh3)4] reacts with Bi(S2CNEt2)3 or Bi(S2COEt)3 in methanol to produce the orange cationic adducts [Pt2(μ-S)2(PPh3)4Bi(S2CNEt2)2]+ and [Pt2(μ-S)2(PPh3)4Bi(S2COEt)2]+, respectively, isolated as their hexafluorophosphate salts. An X-ray structure determination on [Pt2(μ-S)2(PPh3)4Bi(S2CNEt2)2]PF6 reveals the presence of a six-coordinated bismuth centre with an approximately nido-pentagonal bipyramidal coordination geometry. Fragmentation pathways for both complexes have been probed using electrospray ionisation mass spectrometry; ions [Pt2(μ-S)2(PPh3)2Bi(S2CXEtn)2]+ (X = O, n = 1, X = N, n = 2) are formed by selective loss of two PPh3 ligands, and at higher cone voltages the species [(Ph3P)PtS2Bi]+ is observed. Ions formed by loss of CS2 are also observed for the xanthate but not the dithiocarbamate ions. 相似文献
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[Pt5(μ-CO)5(CO)L4] (L = PPh31, PPh2Bz 2, AsPh33, PEt34, PCy35) have been synthesized by reacting [Pt3(μ-CO)3(PR3)3] with H2O2 (1 and 2), by reduction of cis-[PtCl2(CO)(PEt3)] with Zn dust (4), and by the Zn reduction of [Pt3(μ-CO)3(PCy3)3] in the presence of [PtCl2(CH3CN)2] (5). Complex 5 has not been observed previously and has been characterized by X-ray crystallography. Oxidation of the phosphine ligands with H2O2 is a new way to synthesize 1 and 2. The first complete NMR characterization of these complexes has also been achieved, and showed that these pentanuclear cluster complexes exhibit similar stereochemistries in solution and in the solid state. The observed 1JPt-Pt values do not have any correlation with the corresponding bond lengths, again pointing out the irregular behaviour of such parameter in Pt complexes. 相似文献
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C3与C4植物的环境调控 总被引:9,自引:2,他引:9
环境条件决定着不同光合类型植物的地理分布范围和区域 ,一般来说 ,C4 植物分布于高温、强光的环境而 C3植物分布于阴凉、湿润的环境 ,且 C4 比 C3植物光合速率高。但环境条件影响着不同光合类型植物的光合潜能的发挥 ,C4 植物在高温、强光、干旱条件下所表现出来的优势在其它环境条件下未必就显现出来。环境条件甚至可以引起 C3、C4 光合途径间的相互转化 ,这使得目前几种鉴别植物光合类型的方法出现不一致的结果。因此 ,在判断植物的光合类型时 ,要注意多种手段的综合利用 ,同时注意植物所处环境条件的影响。 相似文献
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A new molecular loop composed of two quadruply bonded Mo2(DAniF)2 units (DAniF=N,N′-di-p-anisylformamidinate) linked by two chiral allene-1,3-dicarboxylate anions has been prepared from the reaction of [cis-Mo2(DAniF)2(MeCN)4](BF4)2 with the bis(tetraethylammonium) salt of allene-1,3-dicarboxylic acid. This compound, [cis-Mo2(DAniF)2]2(O2C-CHCCH-CO2)2 (1), has been characterized by X-ray crystallography and by 1H NMR and UV-Vis spectroscopy. The molecule possesses a center of inversion and hence is meso. There is only weak electronic coupling between the two Mo2 4+ units as revealed by electrochemical measurements. 相似文献
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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
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O -·2增强谷氨酸与其受体的结合力及EBSELEN的保护作用 总被引:1,自引:0,他引:1
用放射配体测定受体法研究了黄嘌呤(X)/黄嘌呤氧化酶(XO)体系产生的超氧阴离子自由基(O -·2)对[3H]DL-谷氨酸与大鼠大脑皮层突触膜谷氨酸受体结合的影响,结果表明O -·2明显增强谷氨酸与其受体的结合力,此作用能被2-苯基-1,2-苯并异硒唑-3(2H)酮(EBSELEN)(1 μmol/L)所抑制. 相似文献
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Reaction of [Pt2(μ-S)2(PPh3)4] with a number of transition metal-iodo complexes leads to the formation of the cationic iodo analogue [Pt2(μ-S)(μ-I)(PPh3)4]+, identified using electrospray ionisation mass spectrometry (ESI MS). Synthetic routes to this complex were developed, using the reaction of [Pt2(μ-S)2(PPh3)4] with either [PtI2(PPh3)2] or elemental iodine. The complex was characterised by NMR spectroscopy, ESI MS and an X-ray structure determination, which reveals the presence of a planar, disordered {Pt2SI}+ core. Monitoring the iodine reaction by ESI MS allows the identification of various iodine species, including the short-lived intermediate [Pt2(μ-S)2(PPh3)4I]+, which allows a mechanism for the reaction to be proposed. 相似文献