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41.
42.
 The analogy between H-bonded nucleobase pairs and their metalated analogues is extended to the hemiprotonated pair of 7,9-dimethylguanine (7,9-DimeG) and the Watson-Crick and reversed Watson-Crick pair between 7,9-dimethylguaninium (7,9-DimeGH+) and 1-methylcytosine (1-MeC). The crystal structure analyses of two model compounds, trans–[Pt(CH3NH2)2(7,9-DimeG-N1)2](NO3)2 (1) and trans–[Pt(NH3)2(1-MeC-N3)(7, 9-DimeG-N1)](PF6)2· 2.5 H2O (3a) are reported. Pt binding is through N1 of 7,9-DimeG and N3 of 1-MeC. In solution, 3a exists in a mixture with Watson-Crick and reversed Watson-Crick arrangements of the two bases, depending on solvent, concentration and anions. Received: 16 October 1996 / Accepted: 27 January 1997  相似文献   
43.
A large number ofPenicillium nalgiovense isolates from mould fermented sausages and the ex type culture were examined for characters of morphology, physiology and production of secondary metabolites. To separate biotypes within theP. nalgiovense species, the data obtained were evaluated using multivariate statistical methods. The macromorphological characters of the ex type culture and isolates from meat products appeared to be distinctive. The ex type culture is characterized by a brown reverse on both Czapek yeast extract and malt extract agar while the isolates from meat products have a yellow to orange reverse. Proteolytic and/or lipolytic activity was demonstrated by 75% of the examined cultures and all of them demonstrated ability to utilize lactate as sole carbon source. Growth on creatine sucrose agar was very inhibited and acid production was absent or very weak. TLC analysis showed production of three unknown secondary metabolites that constituted the characteristic profile. HPLC analysis showed production of only three known secondary metabolites; chrysogine (96%), nalgiolaxin and nalgiovensin (9%). The ex type culture produced nalgiolaxin and nalgiovensin but not chrysogine. The chemometric evaluation showed thatP. nalgiovense isolates from meat products from a homogenous species, which can not be divided into biotypes. The only indication of grouping, beside a separation of the ex type culture, was related to the conidium colour (white, turquoise or grey green). The examinedP. nalgiovense isolates showed some resemblance (morphologically and chemically) toP. chrysogenum.  相似文献   
44.
The strictly anaerobic homoacetogenic bacteria Acetobacterium woodii and Sporomusa sphaeroides differ with respect to their energy metabolism. Since growth as well as acetate and ATP formation of A. woodii is strictly dependent on Na+, but that of S. sphaeroides is not, the question arose whether these organisms also use different coupling ions for mechanical work, i.e. flagellar rotation. During growth on fructose in the presence of Na+ (50 mM), cells of A. woodii were vigorously motile, as judged by light microscopy. At low Na+ concentrations (0.3 mM), the growth rate decreased by only 15%, but the cells were completely non-motile. Addition of Na+ to such cultures restored motility instantaneously. Motility, as determined in swarm agar tubes, was strictly dependent on Na+; Li+, but not K+ partly substituted for Na+. Of the amilorides tested, phenamil proved to be a specific inhibitor of the flagellar motor of A. woodii. Growth and motility of S. sphaeroides was neither dependent on Na+ nor inhibited by amiloride derivatives. These results indicate that flagellar rotation is driven by ΔμNa + in A. woodii, but by ΔμH + in S. sphaeroides. Received: 30 May 1995 / Accepted: 31 August 1995  相似文献   
45.
A tonoplast protein of 31 kDa apparent molecular mass (TpP 31) was isolated from two-dimensional gels. Amino acid sequences were determined from LysC endoproteinase-peptide fragments. Using degenerate oligonucleotides, a corresponding cDNA clone of 1034 bp was isolated from a barley leaf cDNA library. It encodes for subunit E of the vacuolar H+-ATPase, the first one identified in plants so far. The open reading frame extends over 681 bp, encoding a gene product of 227 amino acids and a calculated molecular weight of 26 228 g mol?1. Northern and Western blot analysis indicates constitutive expression of subunit E in all plant organs with only small effects of salt stress. Localization of TpP 31 at the tonoplast was confirmed in fractions of purified vacuolar membrane obtained by free-flow electrophoresis. Immunoprecipitation of newly synthesized 35S-labelled membrane proteins with anti-TpP 31 gave two additional bands with apparent molecular masses of about 53 and 62 kDa. Gel filtration after mild solubilization showed co-purification of TpP 31 with the 55 kDa subunit of the H+-ATPase. Both results provide evidence beyond the sequence homology that TpP 31 is a structural component of the vacuolar H+-ATPase.  相似文献   
46.
The appearance rate of l- and d-phenylalanine in the venous blood of rat jejunal loops in vivo is increased up to 60% if the intraluminal solution is mixed more efficiently by the simultaneous perfusion of air. The effect decreases as the luminal concentration is increased to 100 mmol/1. Thus, the apparent Michaelis constants are by 50% lower in the case of the reduced unstirred layer (26 to 17 for l- and 9 to 6 mmol/1 for d-phenylalanine).The enhancement of the absorption and the reduction of the Michaelis constants can be attributed to the reduction of the effective unstirred layer thickness by about 400–500 μm.  相似文献   
47.
Elongation factor G (EF-G) is rapidly inactivated when irradiated at 253.7 nm. The inactivation follows first-order single-hit kinetics with a quantum efficiency of 3.15 × 10?5 μmol/μE. Inclusion of either GTP or GDP in the irradiation mixture does not alter the kinetics of inactivation, but does result in the covalent attachment of nucleotide to between 10 and 20% of the EF-G. This relatively low percentage of cross-linking is due to the rapid rate of photoinactivation as compared to the slower rate of covalent attachment. If EF-G is reacted before irradiation with N-ethylmaleimide, a modification known to block the nucleotide binding site [Rohrbach and Bodley (1976) J. Biol. Chem.251, 930], essentially no nucleotide can be photo-cross-linked to EF-G. Treatment of the photo-cross-linked GTP-EF-G with Raney nickel led to the liberation of the nucleotide moiety, indicating that the photo-cross-link to EF-G occurred through a sulfur atom. Although the formation of the EF-G nucleotide complex has been shown to be an obligatory first step in the formation of the EF-G nucleotide ribosome complex [Rohrbach and Bodley (1976) Biochemistry15, 4565], the covalent EF-G-nucleotide adduct cannot form a ternary complex with the ribosome. The presence of both nucleotide and ribosomes during irradiation drastically alters the kinetics of inactivation. The inactivation under these conditions follows multiple-hit kinetics with an initial period during which no EF-G activity is lost. Following this lag period, EF-G is inactivated at the same rate at which ribosomes lose their ability to bind EF-G. No nucleotide is cross-linked to EF-G or the ribosome under these conditions.  相似文献   
48.
Hairless male mice were given 2 mg Bleomycin i.p. on two successive days. At different time intervals from 1 to 10 days after the last Bleomycin injection, groups of animals were killed and water extracts of hemogenized skin were made. These extracts, supposed to contain the epidermal G1 and G2 chalones, were injected into female hairless mice, and their growth inhibitory potency determined by two methods. 5 mg of lyophilized crude skin extract were injected i.p. together with Colcemid, and the animals killed 4 hr later. The number of Colcemid-arrested mitoses was determined, and was considered to be a measure of the G2 inhibitor present in the skin extracts. 10 mg of the same extracts were injected i.p., and these animals also got 3H-TdR i.p. 12 hr later, and were killed after a subsequent 30 min. The epidermal LI was determined, and was considered to be a measure of the epidermal G1 factor in the skin extracts. The results obtained were compared to the effect of Bleomycin alone and to the effects of skin extracts from non-Bleomycin-treated animals. The results show that Bleomycin provoked slight alterations in the growth-inhibitory potency of the G1 chalone, whereas significant effects were seen in the G2 chalone, There was an increased amount of growth-inhibiting factors on days 2 and 3, and on days 8-10. The results are discussed and it is concluded that the most probable hypothesis is that Bleomycin, in addition to its known inhibition by accumulation of cells with high growth inhibitory potency. An initial, additional direct effect of Bleomycin on the chalone system cammot be excluded.  相似文献   
49.
Summary The release of substance P-like immunoreactive material (SPLI) from the vascularly perfused stomach of the rainbow trout, Oncorhynchus mykiss, was studied. In most cases, SPLI was detected in the collected vascular perfusate during experimental resting conditions. Distensions of the stomach, accomplished by a water-filled intragastric balloon, produced an initial rapid relaxation of the stomach, followed by a slow further relaxation and a stimulation of contractile activity. The amount of SPLI in the vascular perfusate was significantly elevated during the distension period. Tetrodotoxin had no effect on the response to distension or on the release of SPLI during distension, indicating release from tetrodotoxin-insensitive neurons or endocrine cells. The results suggest that a substance P-like peptide may be involved in the contractile response and/or in the maintenance of muscular tone during gastric distensions in the rainbow trout. Infusion of capsaicin had no effect on the release of SPLI. However, capsaicin caused an increase in vascular flow, an effect that could be repeated on a second infusion of capsaicin, indicating that the action may not be specific to sensory neurons.Abbreviations 5-HT 5-Hydroxytryptamine - RIA radioimmunoassay - SP substance P - SPLI substance P-like immunoreactive material - TTX tetrodotoxin  相似文献   
50.
Orcadian phase dependency in pharmacokinetics and hemodynamic effects on blood pressure and heart rate of different galenic formulations of nifedipine (immediate-release, sustained-release, and i.v. solution) were studied in healthy subjects or in hypertensive patients. Pharmacokinetics of immediate-release but not sustained-release and i.v. nifedipine were dependent on time of day: immediate-release nifedipine had higher Cmax (peak concentration) and shorter tmax (time-to-peak concentration) after morning than evening application, and bioavailibility in the evening was reduced by about 40%. Orcadian rhythm in estimated hepatic blood flow as determined by indocyanine green kinetics may contribute to these chronokinetics. A circadian time dependency was also found in nifedipine-induced effects on blood pressure and heart rate as monitored by 24-h ambulatory blood pressure measurements. In conclusion, the dose response relationship of oral nifedipine is influenced by the circadian organization of the cardiovascular system as well as by the galenic drug formulation.  相似文献   
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