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991.
Sergei Kh. Degtyarev Olga A. Belichenko Natalya A. Lebedeva Vladimir S. Dedkov Murat A. Abdurashitov 《Nucleic acids research》2000,28(11):e56
The recognition sequence and cleavage positions of a new restriction endonuclease BtrI isolated from Bacillus stearothermophilus SE-U62 have been determined. BtrI belongs to a rare type IIQ of restriction endonucleases, which recognise non-palindromic nucleotide sequences and cleave DNA symmetrically within them. 相似文献
992.
Lectins LI and LII, localized on the surface of the nitrogen-fixing soil bacterium Bacillus polymyxa 1460, were shown to possess proteolytic activity. A relationship was found between the proteolytic and hemagglutinating activities
of the lectins. Blocking of hemagglutinating activity with specific carbohydrate haptens led to significant changes in the
enzyme activity of both lectins. When lectin activity was blocked with glucuronic acid and fructose-1,6-diphosphate, the proteolytic
activity of both LI and LII declined, whereas incubation with d-galactosamine and d-glucosamine promoted increases in the
proteolytic activity of LII. This study proposes that the molecules of the B. polymyxa lectins may have two centers on their surfaces: one responsible for lectin activity and the other for proteolytic activity.
Received: 27 March 2000 / Accepted: 26 April 2000 相似文献
993.
Vujanovic Vladimir; St-Arnaud Marc; Barabe Denis; Thibeault Genevieve 《Annals of botany》2000,86(1):79-86
This study reports the ability of Fusarium to induce orchidseed colouration and germination. The in vitro bioassay germinationtest, using a Fusarium isolate from the protocorm of Cypripediumreginae, was compared with standard chemical procedures of triphenyltetrazolium chloride (TTC) and acid fuchsin (AC) for testingseed viability. With Cypripedium reginae, Cypripedium parviflorumand Platanthera grandiflora, the efficiency of the bioassaywas similar to that of the TTC and AC procedures. However, thebioassay was more appropriate for estimating embryo viabilityafter a prolonged seed pretreatment (more than 2 h) in 10% sodiumhypochlorite, a surface sterilant often used to enhance germinationof terrestrial species. We also obtained in vitro Cypripediumreginae seed germination induction and protocorm formation bythe same Fusarium isolate. This is the first confirmation ofBernard's early reports that orchid fusaria could stimulateseed germination (Bernard N. 1990.Révue Généralede Botanique12 : 108120). However, the importance ofthe non-mycorrhizal Fusarium fungus in promoting germinationseems to be relatively minor compared to that of specificRhizoctoniaorchid mycorrhizas. Our results are discussed in light of thecurrent North American strategy on orchid conservation methodswhich proposes the use of symbiotic germination.Copyright 2000Annals of Botany Company Orchid, Cypripedium, Platanthera, seed, Fusarium, bioassay, staining, viability, germination, protocorm, mycorrhiza 相似文献
994.
Nikolaos Ioannidis Gert Schansker Vladimir V. Barynin Vasili Petrouleas 《Journal of biological inorganic chemistry》2000,5(3):354-363
Thermus thermophilus catalase. Flash fluorescence studies indicate that the S3 state of the OEC in the presence of ca. 0.6 mM NO is reduced to the S1 with an apparent halftime of ca. 0.4 s at about 18 °C, compared with a biphasic decay, with approximate halftimes of 28 s
for S3 to S2 and 140 s for S2 to S1 in the absence of NO. Under similar conditions the S2 state is reduced by NO to the S1 state with an approximate halftime of 2 s. These results extend a recent study indicating a slow reduction of the S1 state at −30°C, via the S0 and S−1 states, to a Mn(II)-Mn(III) state resembling the corresponding state in catalase. The reductive mode of action of NO is repeated
with the di-Mn cluster of catalase: the Mn(III)-Mn(III) redox state is reduced to the Mn(II)-Mn(II) state via the intermediate
Mn(II)-Mn(III) state. The kinetics of this reduction suggest a decreasing reduction potential with decreasing oxidation state,
similar to what is observed with the active states of the OEC. What is unique about the OEC is the rapid interaction of NO
with the S3 state of the OEC, which is compatible with a metalloradical character of this state.
Received: 16 June 1999 / Accepted: 28 February 2000 相似文献
995.
Hula NM 《Ukrainski? biokhimicheski? zhurnal》2000,72(4-5):21-25
The review deals with the scientific activity of the Department of Biochemistry of Lipids of the Palladin Biochemistry Institute of the National Academy of Sciences of Ukraine. The estimation of the functional role of some major lipids and of the minor lipid components, namely, N-acylethanolamines (NAE), is the main problem of the scientific investigations of the Department. The role of some lipids in the pathogenesis of diseases accompanied by the oxidative stress was also studied. The Department was the first to find and identify NAE in neuroblastoma C1300 N18 cells. It was shown that NAE with long saturated acyl chains inhibited veratridine-activated fast sodium channels. NAE also activated uterine plasma membrane smooth muscle Ca2+, Mg(2+)-ATPase, and inhibited Fe(2+)-induced free radical oxidation in mitochondria. The results of these investigations served as a basis for development of pharmacological substances with membrane protective properties. It was shown that, at different diseases accompanied by the oxidative stress, a significant change in the lipid composition of cell membranes occurred. Sometimes these changes were adaptive in character, which favored the cell viability adaptation to pathological conditions. The new level of regulation of adaptive reactions can be accompanied by the development of additive injuries of cell viability, which may be caused by the altered level of biologically active cell lipid components. Based on the results of these investigations, the preparation intended for treatment of male infertility was developed. The pharmacological substances intended for treatment of morphine abuse and acute ischemia of myocardium were created. 相似文献
996.
Frol'kis VV Artamonov MV Zhukov OD Klimashevs'kiĭ VM Marhitych VM Hula NM 《Ukrainski? biokhimicheski? zhurnal》2000,72(1):56-63
The heart contractility and changes of lipid composition of isolated rat heart (n = 26) under total ischemia and ischemia-reperfusion was studied. The effect of N-stearoyl-ethanolamine under these conditions was investigated. N-stearoyl-ethanolamine leads to remodelling of fatty acyl chain composition of myocardial phospholipids: to drastic fall of polyunsaturated fatty acyl chains (18:2w6, 20:3w6, 20:4w6, 22:5w3, 22:5w6, 22:6w3 and 22:6w6) and enhancement of 18:0. This can be caused by N-stearoyl-ethanolamine-induced suppression of polyunsaturated fatty acids synthesis. Naturally occurring minor lipids--N-acyl phosphatidylethanolamine and its derivative N-acylethanolamine were detected in isolated rat heart under ischemia-reperfusion. It is notable that approximately 12% of total N-acylethanolamines were composed by anandamide. Treatment of N-acyl phosphatidylethanolamine by phospholipase D with subsequent fatty acyl chain analysis demonstrates that fatty acid composition of both N-acyl chains of N-acyl phosphatidylethanolamine and free N-acylethanolamine are similar and their main fatty acyl chains are 16:0, 18:0 and 20:4w6. It was shown that exogenous N-stearoyl-ethanolamine did not alter the levels of endogenous N-acyl phosphatidylethanolamine and N-acylethanolamine, but caused the decrease of lyso-phosphatidylcholine and phosphatidylglycerol levels. The rate of heart contractility and heart relaxation was found to increase during the early period of reperfusion. N-stearoyl-ethanolamine prevents this alteration and exerts a negative inotropic effect. It is concluded that membrane protective properties of N-stearoyl-ethanolamine at least partly depend on its ability to inhibit decrease amount of arachidonic and docosahexaenoic acids, to modulate the fatty acyl chains of cardiac phospholipids and to decrease the level of lyso-phosphatidylcholine. 相似文献
997.
998.
Yan G. Zorbas Kirill P. Charapakin Vassil J. Kakurin Nikolai K. Kuznetsov Maxim A. Federov Vladimir K. Popov 《Biological trace element research》1999,69(2):81-98
The aim of this study was to assess the effect of a daily intake of copper supplements on negative copper balance during prolonged
exposure to hypokinesia (decreased number of kilometers per day). During hypokinesia (HK), negative copper balance is shown
by increased, not by decreased, serum copper concentration, as it happens in other situations.
Studies were done during a 30-d prehypokinetic period and a 364-d hypokinetic period. Forty male trained volunteers aged 22–26
yr with a peak oxygen uptake of 66.4 mL/min/kg and with an average of 13.7 km/d running distance were chosen as subjects.
They were equally divided into four groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic
subjects (UHKS), supplemented hypokinetic subjects (SHKS), and supplemented ambulatory control subjects (SACS). The SACS and
SHKS groups took 0.09 mg copper carbonate/kg body weight daily. The SHKS and UHKS groups were maintained under an average
running distance of 1.7 km/d, whereas the SACS and UACS groups did not experience any modifications in their normal training
routines.
During the 30-d prehypokinetic period and the 346-d hypokinetic period, urinary excretion of copper, calcium, and magnesium
and serum concentrations of copper, calcium, and magnesium were measured. Copper loss in feces and copper balance was also
determined. In both UHKS and SHKS groups, urinary excretion of copper, calcium, and magnesium and concentrations of copper,
magnesium, and calcium in serum increased significantly when compared with the SACS and UACS groups. Loss of copper in feces
was also increased significantly in the SHKS and UHKS groups when compared with the UACS and SACS groups. Throughout the study,
the copper balance was negative in the SHKS and UHKS groups, whereas in the SACS and UACS groups, the copper balance was positive.
It was concluded that a daily intake of copper supplements cannot be used to prevent copper deficiency shown by increased
copper concentration. Copper supplements also failed to prevent negative copper balance and copper losses in feces and urine
in endurancetrained subjects during prolonged exposure to HK. 相似文献
999.
1000.
Computer models can be combined with laboratory experiments for the efficient determination of (i) peptides that bind MHC molecules and (ii) T-cell epitopes. For maximum benefit, the use of computer models must be treated as experiments analogous to standard laboratory procedures. This requires the definition of standards and experimental protocols for model application. We describe the requirements for validation and assessment of computer models. The utility of combining accurate predictions with a limited number of laboratory experiments is illustrated by practical examples. These include the identification of T-cell epitopes from IDDM-, melanoma- and malaria-related antigens by combining computational and conventional laboratory assays. The success rate in determining antigenic peptides, each in the context of a specific HLA molecule, ranged from 27 to 71%, while the natural prevalence of MHC-binding peptides is 0.1–5%. 相似文献