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1.
2.
Dihydrotetrabenazine (DTBZ) derivatized from (+) Tetrabenazine (TBZ) has been used for imaging the expression of VMAT2 when labeled with 11C (t1/2 = 20.3 min) or 18F (t1/2 = 110 min) in neurodegenerative diseases or pancreatic beta-cell. Because 11C or 18F radiolabels are only available in the proximity of a biomedical cyclotron facility, here we report our work of derivatizing (+) and (−) DTBZ using a 64Cu-specific bifunctional chelator scaffold (64Cu: t1/2 = 12.7 h) for the preparation of long-lived VMAT2 targeted radiotracers, 64Cu-CB-TE2A-(+)-DTBZ and 64Cu-CB-TE2A-(−)-DTBZ. The specific VMAT2 binding affinity of 64Cu-CB-TE2A-(+)-DTBZ measured using rat brain homogenate or porcine islets was not compromised by our chemical modifications while that of its (−) counterpart remained low as in 11C or 18F labeled (±) DTBZ.  相似文献   
3.
Strictly anaerobic bacteria were enriched and isolated from freshwater sediment sources in the presence and absence of sulfate with sorbic acid as sole source of carbon and energy. Strain WoSo1, a Gram-negative vibrioid sulfate-reducing bacterium which was assigned to the species Desulfoarculus (formerly Desulfovibrio) baarsii oxidized sorbic acid completely to CO2 with concomitant stoichiometric reduction of sulfate to sulfide. This strain also oxidized a wide variety of fatty acids and other organic compounds. A Gram-negative rod-shaped fermenting bacterium, strain AmSo1, fermented sorbic acid stoichiometrically to about equal amounts of acetate and butyrate. At concentrations higher than 10 mM, sorbic acid fermentation led to the production of pentanone-2 and isopentanone-2 (3-methyl-2-butanone) as byproducts. Strain AmSo1 fermented also crotonate and 3-hydroxybutyrate to acetate and butyrate, and hexoses to acetate, ethanol, hydrogen, and formate. The guanine-plus-cytosine content of the DNA was 41.8±1.0 mol%. Sorbic acid at concentrations higher than 5 mM inhibited growth of this strain while strain WoSo1 tolerated sorbic acid up to 10 mM concentration.  相似文献   
4.
During chloroplast development in the primary leaves of Phaseolus vulgaris, the extractable activity of adenosine 5-phosphosulfate sulfotransferase increased ten-fold. When chloroplast development took place in air enriched with 3.5 l H2S·l-1 there was a decrease in adenosine 5-phosphosulfate sulfotransferase activity. Cyst(e)ine in concentrations up to 1 mM (in the external medium) did not affect the increase in adenosine 5-phosphosulfate sulfotransferase activity in intact plants. In plants with excised roots, 0.75 mM cyst(e)ine inhibited this increase. In green primary leaves, H2S or cyst(e)ine treatment resulted in a decrease of extractable adenosine 5-phosphosulfate sulfotransferase activity. In intact plants, this effect of cyst(e)ine was observed at a concentration of 1 mM, and in plants with excised roots, 0.25 mM had a comparable effect.In developing plants, the extractable activities of O-acetyl-L-serine sulfhydrylase (EC 4.2.99.9) and ribulosebisphosphate carboxylase (EC 4.1.1.39.) were not affected by H2S or cyst(e)ine.Abbreviations APS adenosine 5-phosphosulfate - APSSTase adenosine 5phosphosulfate sulfotransferase - BSA bovine serum albumin - DTE dithioerythritol - EDTA ethylenediaminetetra-acetic acid - OASSase O-acetyl-L-serine sulfhydrylase - PAPS adenosine 3-phosphate 5-phosphosulfate - POPOP 1,4 Di 2-(5-phenyloxazolyl)-benzene - PPO 2,5-diphenyloxazol - RubP ribulose-bisphosphate - RubPCase ribulosebiphosphate carboxylase This is no. 8 in the series Regulation of Sulfate Assimilation in Plants. The term cysteine is used when it is clear that cystine is not involved; cyst(e)ine is used for an undefined mixture of cysteine and cystine. The concentrations are expressed in all cases relative to cysteine  相似文献   
5.
Combination agents comprising two different pharmacophores with the same biological target have the potential to show additive or synergistic activity. Bis(thiosemicarbazonato)copper(II) complexes (e.g. 64Cu-ATSM) and nitroimidazoles (e.g. 18F-MISO) are classes of tracer used for the delineation of tumor hypoxia by positron emission tomography (PET). Three nitroimidazole-bis(thiosemicarbazonato)copper(II) conjugates were produced in order to investigate their potential as combination hypoxia imaging agents. Two were derived from the known bifunctional bis(thiosemicarbazone) H2ATSM/A and the third from the new precursor diacetyl-2-(4-N-methyl-3-thiosemicarbazone)-3-(4-N-ethylamino-3-thiosemicarbazone) - H2ATSM/en. Oxygen-dependent uptake studies were performed using the 64Cu radiolabelled complexes in EMT6 carcinoma cells. All the complexes displayed appreciable hypoxia selectivity, with the nitroimidazole conjugates displaying greater selectivity than a simple propyl derivative used as a control. Participation of the nitroimidazole group in the trapping mechanism is indicated by the increased hypoxic uptake of the 2- vs. the 4-substituted 64Cu-ATSM/A derivatives. The 2-nitroimidazole derivative of 64Cu-ATSM/en demonstrated superior hypoxia selectivity to 64Cu-ATSM over the range of oxygen concentrations tested. Biodistribution of the radiolabelled 2-nitroimidazole conjugates was carried out in EMT6 tumor-bearing mice. The complexes showed significantly different uptake trends in comparison to each other and previously studied Cu-ATSM derivatives. Uptake of the Cu-ATSM/en conjugate in non-target organs was considerably lower than for derivatives based on Cu-ATSM/A.  相似文献   
6.
The Mu phage virion contains tail-spike proteins beneath the baseplate, which it uses to adsorb to the outer membrane of Escherichia coli during the infection process. The tail spikes are composed of gene product 45 (gp45), which contains 197 amino acid residues. In this study, we purified and characterized both the full-length and the C-terminal domains of recombinant gp45 to identify the functional and structural domains. Limited proteolysis resulted in a Ser64-Gln197 sequence, which was composed of a stable C-terminal domain. Analytical ultracentrifugation of the recombinant C-terminal domain (gp45-C) indicated that the molecular weight of gp45-C was about 58 kDa and formed a trimeric protomer in solution. Coprecipitation experiments and a quartz crystal microbalance (QCM) demonstrated that gp45-C irreversibly binds to the E. coli membrane. These results indicate that gp45 shows behaviors similar to tail-spike proteins of other phages; however, gp45 did not show significant sequence homology with the other phage tail-spike structures that have been identified.  相似文献   
7.
8.
p64 is a protein identified as a chloride channel by biochemical purification from kidney microsomes. We expressed p64 in HeLa cells using a recombinant vaccinia virus/T7 RNA polymerase driven system. Total cell membranes were prepared from infected/transfected cells and fused to a planar lipid bilayer. A novel chloride channel activity was found in cells expressing p64 and not in control cells. The p64-associated activity shows strong anion over cation selectivity. Single channels show prominent outward rectification with single channel conductance at positive potentials of 42 pS. The chloride channel activity is activated by treatment of the membranes with alkaline phosphatase and inhibited by DNDS and by TS-TM calix(4)arene. Whole membrane anion permeability was determined by a chloride efflux assay, revealing that membranes from cells expressing p64 showed a small but highly significant increase in chloride permeability, consistent with expression of a novel chloride channel activity. Received: 17 November 1997/Revised: 9 February 1998  相似文献   
9.
Epigenetic modification can occur at a high frequency in crop plants and might generate phenotypic variation without changes in DNA sequences. DNA methylation is an important epigenetic modification that may contribute to environmentally-induced phenotypic variations by regulating gene expression. Rice Photoperiod-Thermo-Sensitive Genic Male Sterile (PTGMS) lines can transform from sterility to fertility under lower temperatures and short-day (SD) conditions during anther development. So far, little is known about the DNA methylation variation of PTGMS throughout the genome in rice. In this study, we investigated DNA cytosine methylation alterations in the young panicles of PTGMS line PA64S under two different conditions using methylation sensitive amplified polymorphism (MSAP) method. Compared with the DNA methylation level of PA64S under lower temperatures and SD conditions (fertility), higher methylation was observed in PA64S (sterility). The sequences of 25 differentially amplified fragments were successfully obtained and annotated. Three methylated fragments, which are homologous to D2, NAD7 and psaA, were confirmed by bisulfite sequencing and their expression levels were also evaluated by qPCR. Real time quantitative PCR analysis revealed that five of the six selected methylated genes were downregulated in PA64S (sterility). These results suggested that DNA methylation may be involved in the sterility–fertility transition of PA64S under two different environmental conditions.  相似文献   
10.
An artificial bean seed system was used to evaluate the effects of a cysteine proteinase inhibitor (E-64) and a serine proteinase inhibitor (Bowman-Birk inhibitor) on the developmental time and mortality of the common bean weevil, Acanthoscelides obtectus (Say). These inhibitors were incorporated into artificial bean seeds on which the insect fed. To better understand the mode of action of these inhibitors, free amino acids were also added to the seeds, alone and in combination with the inhibitors. E-64 was found to be highly effective in delaying development and increasing mortality of the insect. Both effects were directly related to the concentration of E-64. Bowman-Birk inhibitor had little effect on these parameters. Assays of gut proteolytic activity of insects reared on artificial seeds with various levels of E-64 demonstrated a direct relationship between E-64 concentration in the diet and reduction of gut proteolytic activity. Free amino acid supplementation to the diet did not prevent inhibition of gut proteolytic activity by E-64, but did reverse its effects on developmental time and mortality, strengthening the hypothesis that E-64 operates by inhibition of essential digestive proteinase activity.
Résumé Des grains artificiels de haricot ont été utilisés pour évaluer les effets sur la durée de développement et la mortalité d' Acanthoscelides obtectus. Say d'inhibiteurs de la protéinase de la cystéine (E-64) et de la protéinase de la sérine (l'inhibiteur de Bowman-Birk). Ces inhibiteurs avaient été incorporés dans les grains artificiels. Pour mieux comprendre leur voie d'action, des acides aminés libres étaient ajoutés à ces graines, seuls ou combinés aux inhibiteurs. E-64 a très efficacement retardé le développement et accru la mortalité; ces 2 effets étaient liés à sa concentration. L'inhibiteur de Bowman-Birk a eu peu d'effets sur ces paramètres. Des expériences sur l'activité protéolytique du tube digestif d'insectes élevés sur des graines artificielles avec différentes concentrations de E-64 ont montré une relation directe entre la concentration en E-64 et la réduction de l'activité protéolytique. L'addition d'acides aminés libres dans l'aliment n'a pas empêché l'inhibition de l'activité protéolytique par E-64, mais a inversé ses effets sur la durée de développement et la mortalité, renforçant l'hypothèse que E-64 agit en inhibant l'activité protéinase digestive essentielle.
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