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1.
Fusarium tricinctum strain (KF 260) isolated from wheat in Poland, produced on maize cultures a compound (C 11H 14O5, MW 226) toxic to Artemia salina. The compound, identified by various spectroscopical tecniques as 5-hydroxy-4-methoxy-6,8a-dimethyl-6, 7-dihydro-2H, 8aH-pyrano/2, 3-b/pyran-2-one, was identical to chlamydosporol, a mycotoxin recentlydiscovered in cultures of F._ chlamydosporum isolated from rice. The compound showed inhibitory effect on human lymphocyte proliferation at concentration of 25 μg/mL. LD 50 on A. salina was 56 μg/mL. 相似文献
2.
To examine in more detail the mechanisms of cocklebur ( Xanthium pennsylvanicum Wallr.) seed germination and rice ( Oryza sativa L. cv. Sasanishiki) coleoptile elongation that were responsive to both C 2H 4 and CO 2, the effects of NBD (2,5-norbornadiene), a cyclic olefin known as a competitive inhibitor of C 2H 4, on those phenomena were tested under various conditions. NBD strongly inhibited germination of cocklebur seeds and their axial and cotyledonary growth. The NBD effects were significantly negated by endogenously evolved and exogenously applied CO 2 regardless of incubation temperature. Similarly, the inhibitory NBD effect was negated by C 2H 4 at 23°C, but at 33°C a low concentration (3 1/L) of C 2H 4 rather enhanced the inhibitory NBD effect. This phenomenon reflected the growth responses of the tip zone of axial tissues in cocklebur seeds to NBD and C 2H 4, in which both gases were antagonistic in regulating the axial growth at 23°C but additive in inhibiting it at 33°C. Maximal negation of these inhibitory NBD effects was brought about by simultaneous application of CO 2 and C 2H 4. Similarly, elongation of rice coleoptiles was suppressed by NBD, and when they were immature, its inhibitory action was counteracted by both C 2H 4 and CO 2, especially during simultaneous application. However, the inhibitory NBD effect was completely negated by C 2H 4 applied alone at concentrations above 500 1/L regardless of the physiological age of coleoptiles. These inhibitory NBD effects are additional evidence suggesting that C 2H 4 acts as a growth regulator in both cocklebur seed germination and rice coleoptile elongation. That NBD was capable of counteracting CO 2 action in some cases but was incapable of negating inhibitory C 2H 4 action, such as that observed in cocklebur seeds, suggests that NBD acts with some side effects besides being a competitive inhibitor of C 2H 4 actions. 相似文献
3.
Molecular orbital computations are performed on the different contributions to the variation of the chemical shifts of the non-exchangeable protons of the ribose ring in pyrimidine nucleosides as a function of the torsion angle X CN about the glycosyl bond. They show that the ring current effects are negligible, that the contribution of the atomic diamagnetic anisotropy is important for protons which come at very short distances to the anisotropic group (C 2 = 0 2) and that the polarization effect may have a determining influence on the sign of the variation of the chemical shift. The theoretical results are discussed in relation to the experimental findings on the differences between the chemical shifts of the ribose protons of pyrimidine nucleosides methylated at C 5 and C 6. 相似文献
4.
4-Hydroxyacids are products of ubiquitously occurring lipid peroxidation (C 9, C 6) or drugs of abuse (C 4, C 5). We investigated the catabolism of these compounds using a combination of metabolomics and mass isotopomer analysis. Livers were perfused with various concentrations of unlabeled and labeled saturated 4-hydroxyacids (C 4 to C 11) or 4-hydroxynonenal. All the compounds tested form a new class of acyl-CoA esters, 4-hydroxy-4-phosphoacyl-CoAs, characterized by liquid chromatography-tandem mass spectrometry, accurate mass spectrometry, and 31P-NMR. All 4-hydroxyacids with five or more carbons are metabolized by two new pathways. The first and major pathway, which involves 4-hydroxy-4-phosphoacyl-CoAs, leads in six steps to the isomerization of 4-hydroxyacyl-CoA to 3-hydroxyacyl-CoAs. The latter are intermediates of physiological β-oxidation. The second and minor pathway involves a sequence of β-oxidation, α-oxidation, and β-oxidation steps. In mice deficient in succinic semialdehyde dehydrogenase, high plasma concentrations of 4-hydroxybutyrate result in high concentrations of 4-hydroxy-4-phospho-butyryl-CoA in brain and liver. The high concentration of 4-hydroxy-4-phospho-butyryl-CoA may be related to the cerebral dysfunction of subjects ingesting 4-hydroxybutyrate and to the mental retardation of patients with 4-hydroxybutyric aciduria. Our data illustrate the potential of the combination of metabolomics and mass isotopomer analysis for pathway discovery. 相似文献
5.
Sertoli cells isolated from 17 day old rats were maintained in culture and incubated with [ 14C]-progesterone for 20 h. The cells and media were extracted with ether/chloroform and the extracts chromatographed two-dimensionally on TLC and the radioactive metabolites visualized by autoradiography. Nine of the metabolites (constituting about 88% of total metabolite radioactivity) were identified by relative mobilities of the compounds and their derivatives in TLC and GC systems and by recrystallizations with authentic steroids as the following: 20α-hydroxypregn-4-en-3-one, 3α-hydroxy-5α-pregnan-20-one, 5α-pregnane3α,20α-diol, 17β-hydroxy-5α-androstan-3-one, 5α-pregnane-3,20-dione, 17-hydroxypregn-4-ene-3,20-dione, testosterone, 5α-androstane-3α,17β-diol and androst-4-ene-3,17-dione. Over 71% of the metabolite radioactivity was due to 20α-hydroxypregn-4-en-3-one, the major metabolite. 5α-reduced pregnanes constituted about 12% and C 19 steroids comprised about 2.9% of the radioactivity of the metabolites. Calculation of relative steroidogenic enzyme activities from initial reaction rates suggested the following activities in μunits/mg Sertoli cell protein: 20α-hydroxysteroid oxidoreductase (20α-HS0; 7.71), 5α-reductase (4.77), 3α-HS0 (3.57), 17α-hydroxylase (0.93), 17β-HS0 (0.34) and C 17-C 20 lyase (0.34). The relatively high rate of steroidogenic enzyme activities in the Sertoli cells of young rats may indicate that Sertoli cells are less dependent on Leydig cell steroidogenesis than has been assumed. Since nearly all the metabolites of progesterone and testosterone are now identified, it is possible to construct a picture of Sertoli cell steroidogenic activity. 相似文献
6.
5′-Phosphoribosyl 5-amino-4-imidazole carboxamide was prepared by incubating 5-amino-4-imidazole carboxamide riboside and a phosphate compound with the bacteria characterized to phosphorylate at C 5′ via the phosphoryl transfer reaction. Aromatic phosphate compounds and 5′-nucleotides were able to act as the phosphate donor. This material was isolated chromatographically and its properties were studied. The other bacteria characterized to phosphorylate at C 3′ (or 2′) also phosphorylated a little probably at C 3′ (or 2′) of 5-amino-4-imidazole carboxamide riboside.The phosphoryl interconversion between nucleotides and nucleosides was studied to be carried out via the phosphoryl transfer reaction observed in bacteria. The phosphotransferase activity of Ps. trifolii mediated reversibly the phosphoryl transfer between 5′-nucleotides and nucleosides, and its optimal pH was at around 8.5, whereas that of Prot. mirabilis did transfer the phosphoryl radical from 2′- and 3′-nucleotide to nucleoside at its optimal pH, around 5.0.These donor- and product-isomer specificities of both bacteria were evident to be invariable, regardless of reaction pH and cultural conditions. These reactions, especially using the bacteria characterized to phosphorylate at C 5′ of nucleoside, were demonstrated to catalyze the phosphoryl interconversion between 5′-purine nucleotides and pyrimidine nucleosides or vice versa. 相似文献
7.
The pathogenic protozoan parasite Leishmania donovani is capable of both de novo pyrimidine biosynthesis and salvage of pyrimidines from the host milieu. Genetic analysis has authenticated L. donovani uracil phosphoribosyltransferase (LdUPRT), an enzyme not found in mammalian cells, as the focal enzyme of pyrimidine salvage because all exogenous pyrimidines that can satisfy the requirement of the parasite for pyrimidine nucleotides are funneled to uracil and then phosphoribosylated to UMP in the parasite by LdUPRT. To characterize this unique parasite enzyme, LdUPRT was expressed in Escherichia coli, and the recombinant enzyme was purified to homogeneity. Kinetic analysis revealed apparent Km values of 20 and 99 μ m for the natural substrates uracil and phosphoribosylpyrophosphate, respectively, as well as apparent Km values 6 and 7 μ m for the pyrimidine analogs 5-fluorouracil and 4-thiouracil, respectively. Size exclusion chromatography revealed the native LdUPRT to be tetrameric and retained partial structure and activity in high concentrations of urea. L. donovani mutants deficient in de novo pyrimidine biosynthesis, which require functional LdUPRT for growth, are hypersensitive to high concentrations of uracil, 5-fluorouracil, and 4-thiouracil in the growth medium. This hypersensitivity can be explained by the observation that LdUPRT is substrate-inhibited by uracil and 4-thiouracil, but 5-fluorouracil toxicity transpires via an alternative mechanism. This substrate inhibition of LdUPRT provides a protective mechanism for the parasite by facilitating purine and pyrimidine nucleotide pool balance and by sparing phosphoribosylpyrophosphate for consumption by the nutritionally indispensable purine salvage process. 相似文献
8.
Abstract At 23°C, both C 2H 4 and CO 2 stimulated the germination of freshly imbibed upper cocklebur ( Xanthium pennsylvanicum Wallr.) seeds, but C 2H 4, unlike CO 2, changed to an inhibitor of germination under some soaking conditions. However, when seeds were pre-soaked for more than several hours at 23 °C prior to treatment, C 2H 4 strongly inhibited their germination at 33 °C, the degree of inhibition increasing with the duration of pre-soaking. Maximum inhibition occurred at 1–3 cm 3 m ?3 C 2H 4 when seeds were pre-soaked for 1 week; further increases of C 2H 4 concentration and pre-soaking period decreased the inhibitory effect. C 2H 4 was synergistic with CO 2 when C 2H 4 promoted germination, whereas it was antagonistic when inhibitory. Such a transition of the C 2H 4 action occurred at ca. 27 °C. Also 1-andnocyclopropane-1-carboxylic acid, a C 2H 4 precursor, inhibited the germination of pre-soaked seeds at 33 °C, although it promoted the germination at 23 °C. When pre-soaked seeds were prepared for germination by chilling at 8 °C for 3 d, the inhibitory effect of C 2H 4 on the subsequent germination was manifested even at 23 °C. The reversal of the C 2H 4 action from promotion to inhibition in cocklebur seed germination is discussed in relation to the engagement of two respiratory pathways in the imbibed seeds. 相似文献
9.
A new natural product, 2( S),3( S)-3-hydroxy-4-methyleneglutamic acid (G3) has been isolated from seeds of Gleditsia caspica. The structure has been established by chemical and spectroscopic methods. Catalytic reduction of G3 yields 2( S),4( S)-4-methylglutamic acid and a new amino acid, 2( S),3( S),4( S)-3-hydroxy-4-methylglutamic acid. Ozonolysis of G3 followed by oxidation gives 2( S),3( R)-3-hydroxyaspartic acid. The S- (or l-) configurations at C 2 in G3 and in 2( S),3( S),4( S)-3-hydroxy-4-methyglutamic acid and the S-configurations at C 3 for G3 and 2( S),3( S),4( S)-3-hydroxy-4-methylglutamic acid and at C 4 for 2( S),3( S),4( S)-3-hydroxy-4-methylglutamic acid are inferred from the configurations at C 2 in 2( S),4( S)-4-methylglutamic acid and at C 2 and C 3 in 2( S),3( R)-3-hydroxyaspartic acid. The seeds also contain appreciable quantities of 2( S),3( S),4( R)-3-hydroxy-4-methylglutami c acid (G1) and 2( S),4( R)-4-methylglutamic acid. 相似文献
10.
Changes in the level of metabolites of the C 4 cycle and reductive pentose phosphate (RPP) pathway were measured simultaneously with induction of photosynthesis in maize ( Zea mays L.) to evaluate what may limit carbon assimilation during induction in a C 4 plant. After 20 minutes in the dark, there was an immediate rise in photosynthesis during the first 30 seconds of illumination, followed by a gradual rise approaching steady-state rate after 20 minutes of illumination. Among metabolites of the C4 cycle, there was a net increase in the level of C3 compounds (the sum of pyruvate, alanine, and phosphoenolpyruvate) during the first 30 seconds of illumination, while there was a net decrease in the level of C4 acids (malate plus aspartate). The total level of metabolites of the C4 cycle underwent a sharp increase during this period. At the same time, there was a sharp rise in the level of intermediates of the RPP pathway (ribulose-1,5-bis-phosphate, 3-phosphoglycerate, dihydroxyacetonephosphate, and fructose-1,6-bisphosphate) during the first minute of illumination. The net increase of carbon among intermediates of the C4 cycle and RPP pathway was far above that of carbon input from CO2 fixation, and the increase in intermediates of the RPP pathway could not be accounted for by decarboxylation of C4 acids, suggesting that an endogenous source of carbon supplies the cycles. After 3 minutes of illumination there was a gradual rise in the levels of intermediates of the C4 cycle and in the total level of metabolites measured in the RPP pathway. This rise in metabolite levels occurs as photosynthesis gradually increases and may be required for carbon assimilation to reach maximum rates in C4 plants. This latter stage of inductive autocatalysis through the RPP pathway may contribute to the final buildup of these intermediates. 相似文献
11.
The syntheses of three classes of C-3 perfluoroalkyl substituted steroids are described. They are the 3β-hydroxy-3α-perfluoroalkylandrost-4-en-17-ones ( 5a-c), 3-perfluoroalkylandrosta-3,5-dien-3-ones ( 8a-c) and 3β-hydroxy-3α-perfluoroalkylandrost-5-en-17-ones ( 12a-c). Addition of a series of perfluroalkylorganometallic reagents (R FLi; R F = C 2F 5, C 3F 7, or C 4F 9) to the 3 position of silylated testosterone 2b afforded Δ4 perfluoroalkyl carbinols 3. In Scheme 1, deprotection with HF and oxidation at the C-17 carbon with PCC produced Δ4 ketones 5. In Scheme 2 dehydration of 3 with 1,2-phenylenephosphorochloridite and iodine afforded Δ3,5 dienes 6 which were deprotected and oxidized as above to the C-17 ketones 8. In Scheme 3 isomerization of the double bond of 3 from the C-4 to the C-5 position using the allylic halogenation followed by treatment with lithium aluminum hydride led to the synthesis of the double bond isomer series 12. A new method for dehydration was developed. On average and within experimental error, 3β-hydroxy-3α-perfluoroalkylandrost-5-en-17 ones ( 12a-c) were better than the 3-perfluoroalkylandrosta-3,5-dien-17-ones ( 8a-c) and 3β-hydroxy-3α-perfluoroalkylandrost-4-en-17-ones ( 5a-c) at inhibiting glucose-6-phosphate dehydrogenase. 相似文献
12.
In this study we have profiled the free sterol content of cerebrospinal fluid by a combination of charge tagging and liquid chromatography-tandem mass spectrometry. Surprisingly, the most abundant cholesterol metabolites were found to be C 27 and C 24 intermediates of the bile acid biosynthetic pathways with structures corresponding to 7α-hydroxy-3-oxocholest-4-en-26-oic acid (7.170 ± 2.826 ng/ml, mean ± S.D., six subjects), 3β-hydroxycholest-5-en-26-oic acid (0.416 ± 0.193 ng/ml), 7α, x-dihydroxy-3-oxocholest-4-en-26-oic acid (1.330 ± 0.543 ng/ml), and 7α-hydroxy-3-oxochol-4-en-24-oic acid (0.172 ± 0.085 ng/ml), and the C 26 sterol 7α-hydroxy-26-norcholest-4-ene-3, x-dione (0.204 ± 0.083 ng/ml), where x is an oxygen atom either on the CD rings or more likely on the C-17 side chain. The ability of intermediates of the bile acid biosynthetic pathways to activate the liver X receptors (LXRs) and the farnesoid X receptor was also evaluated. The acidic cholesterol metabolites 3β-hydroxycholest-5-en-26-oic acid and 3β,7α-dihydroxycholest-5-en-26-oic acid were found to activate LXR in a luciferase assay, but the major metabolite identified in this study, i.e. 7α-hydroxy-3-oxocholest-4-en-26-oic acid, was not an LXR ligand. 7α-Hydroxy-3-oxocholest-4-en-26-oic acid is formed from 3β,7α-dihydroxycholest-5-en-26-oic acid in a reaction catalyzed by 3β-hydroxy-Δ 5-C 27-steroid dehydrogenase (HSD3B7), which may thus represent a deactivation pathway of LXR ligands in brain. Significantly, LXR activation has been found to reduce the symptoms of Alzheimer disease (Fan, J., Donkin, J., and Wellington C. (2009) Biofactors 35, 239–248); thus, cholesterol metabolites may play an important role in the etiology of Alzheimer disease. 相似文献
13.
Methyl 2,3,6-trideoxy-2- C-[2-hydroxy-1,1-(ethylenedithio)ethyl]-α-l-threo-hexopyranosid-4-ulo-2 2,4-pyranose ( 1) crystallizes in a rhombic space group P2 12 12 1 with four molecules in the elementary unit. The structure was refined to an R-value of 0.057. The aldopyranose ring adopts a 1C 4 conformation with an axial side-chain forming a hemiacetal ring to the keto group at C-4. Both six-membered rings connected in the 2,7-dioxabicyclo[3.3.1]nonane system differ only slightly from the 1C 4 chair conformation. The spirocyclic dithiolane ring adopts a nearly ideal envelope form with a deviation of C-21 from the plane S-1-C-7-S-2-C-22. The dihedral angle O-5-C-1 O-1-C-11 of 59.1° is an agreement with the exo-anomeric effect. 相似文献
14.
The reaction of 4-(chloroacetamido)pyrimidine (1) with ammonium thiocyanate gave 2-(pyrimidin-4-ylimino)thiazolidin-4-one (2) , which, when condensed with four substituted benzaldehyde analogues, gave the consequent 5-arylidine-2-(pyrimidin-4-ylimino)thiazolidin-4-ones 3a–d . In addition, the absorbance and fluorescence behaviours of pyrimidinylimino-thiazolidin-4-one hybrids 3a–d in various organic solvents were investigated. The emphasis was on studying UV absorption capacities and the effect of various structural components on photophysical qualities such as the 5-arylidene-2-(pyrimidin-4-ylimino)thiazolidin-4-ones and N, N-dimethylamino tail. The cytotoxic effect of four pyrimidinylimino-thiazolidin-4-one hybrids 3a–d on tumour cell lines (HepG2, HCT-116, PC3, MCF-7) and a normal cell line (WI38) is investigated in this work. The cytotoxicity was measured by comparing the half-maximal inhibitory concentration (IC 50) to the reference medication, 5-fluorouracil. The findings indicate that these hybrid compounds had varying cytotoxic effects on the cell lines examined; hybrids 3b and 3c demonstrated significant anticancer activity against MCF-7 with IC 50 values of 7.53 ± 0.43 and 9.17 ± 0.31 μM, respectively. The inhibitory efficacy of various synthesized hybrids on the epidermal growth factor receptor (EGFR) kinase was investigated. EGFR is a crucial target in cancer treatment because inhibiting it may reduce tumour development and proliferation. The IC 50 value was used to calculate the inhibitory activity, which is the concentration of inhibitor necessary to induce half-maximal inhibition of EGFR kinase activity. In addition, the predicted ADME results show that pyrimidinylimino-thiazolidin-4-one hybrids have good pharmacokinetic properties; hybrid 3d is more lipophilic than the other compounds. It has a medium molecular weight, a small number of hydrogen bond acceptors and donors, and a large number of aromatic heavy atoms. Moreover, molecular docking simulations revealed precise information on the interactions of pyrimidinylimino-thiazolidin-4-one hybrids 3a–d and 5-Fu with their respective protein targets. These interactions point to possible pathways for their biological activities and call for more testing to establish their effectiveness as bioactive molecules or therapeutic candidates. 相似文献
15.
The adduct 3-β-D-ribofuranosyl-3,7,8,9-tetrahydropyrimido[1,2-i]purin-8-ol ( 2), obtained from adenosine and epichlorohydrin, underwent ring fission at basic conditions. The initial ring-opening took place at C2 of the pyrimidine unit resulting in 2-(5-amino-1-β-D-ribofuranosyl-imidazol-4-yl)-1,4,5,6-tetrahydropyrimidin-5-ol ( 3). Also the tetrahydropyrimidine ring of 3 could be opened resulting in 5-amino-1-(β-D-ribofuranosyl)-imidazole-4-(N-3-amino-2-hydroxyl-propyl)-carboxamide ( 4). In hot acid conditions, 2 was both deglycosylated and ring-opened yielding 2-(5-amino-imidazol-4-yl)-1,4,5,6-tetrahydropyrimidin-5-ol ( 7) as the final product. When reacting 3 with CS 2 or HNO 2 ring-closure took place and 3-β-D-ribofuranosyl-3,4,7,8,9-pentahydropyrimido[1,2-i]purin-8-ol-5-thione ( 5), and 3-β-D-ribofuranosyl-imidazo[4,5-e]-3,7,8,9-tetrahydropyrimido[1,2-c][1,2,3]triazine-8-ol ( 6), respectively, were obtained. Also, the pyrimidine ring of the epichlorohydrin adduct with adenine, 10-imino-5,6-dihydro-4H,10H-pyrimido[1,2,3-cd]purin-5-ol ( 10), underwent ring fission and the product was identified as 3-hydroxy-1,2,3,4-tetrahydroimidazo[1,5-a]pyrimidine-8-carboximidamide ( 11). 相似文献
16.
Wax on leaves of Agropyron intermedium contains hydrocarbons (11%, C 27–C 33), esters (11%, C 32–C 60), free alcohols (180%, C 26) 25-oxohentriacontane-14,16-dione (17%), 10-oxohentriacontane-14,16-dione (5y%), 25-hydroxyhentriacontane-14,16-dione (12%) and 26-hydroxyhentriacontane-14,16-dione (2%). Wax on spikes contains additional components, C 25–C 33cis 9-alkenes (32% of hydrocarbons), and more β-diketones, 25-hydroxy (17%) and 26-hydroxy (3%) hentriacontane-14,16-diones, 10,25-dioxohentriacontane-14,16-dione (1%) and 4-hydroxy-25-oxo-(2%), 25-hydroxy-10-oxo-(1.3%) and 26-hydroxy-10-oxo-(0.7%) hentriacontane-14,16-diones; free alcohols were very minor components (1%, C 24–C 32). 相似文献
17.
The presence of small amounts of 3β-hydroxy-Δ 5-C 19- and C 21-steroid oxidoreductase in the microsomal fraction of rat liver is shown. NAD was the preferred cofactor. K m for the oxidation of dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one) into androstenedione (4-androstene-3,17-dione) was 3 × 10 −6 M. In similarity to the adrenal and gonadal 3β-hydroxy-Δ 5-C 19-steroid oxidoreductase, but in contrast to the hepatic 3β-hydroxy-Δ 5-C 27-steroid oxidoreductase involved in the biosynthesis of bile acids, the hepatic 3β-hydroxy-Δ 5-C 19-steroid oxidoreductase was inhibited by the 3β-hydroxy-Δ 5-steroid oxidoreductase inhibitor, 2α-cyano-4,4,17-trimethyl-17β-hydroxy-5-androsten-3-one, and the activity was greatly reduced with microsomes from immature rats. 相似文献
18.
The apicomplexan parasite Toxoplasma gondii does not possess complex I of the mitochondrial respiratory chain, but has two genes encoding rotenone-insensitive, non-proton pumping type-II NADH dehydrogenases (NDH2s). The absence of such “alternative” NADH dehydrogenases in the human host defines these enzymes as potential drug targets. TgNDH2-I and TgNDH2-II are constitutively expressed in tachyzoites and bradyzoites and are localized to the mitochondrion as shown by epitope tagging. Functional expression of TgNDH2-I in the yeast Yarrowia lipolytica as an internal enzyme, with the active site facing the mitochondrial matrix, permitted growth in the presence of the complex I inhibitor DQA. Bisubstrate kinetics of TgNDH2-I measured within Y. lipolytica mitochondrial membrane preparations were in accordance with a ping-pong mechanism. Using inhibition kinetics we demonstrate here that 1-hydroxy-2-alkyl-4(1)quinolones with long alkyl chains of C 12 (HDQ) and C 14 are high affinity inhibitors for TgNDH2-I, while compounds with shorter side chains (C 5 and C 6) displayed significantly higher IC 50 values. The efficiency of the various quinolone derivatives to inhibit TgNDH2-I enzyme activity mirrors their inhibitory potency in vivo, suggesting that a long acyl site chain is critical for the inhibitory potential of these compounds. 相似文献
19.
This paper describes the synthesis of compounds of Ni(II) with uracil, uridine and the nucleotides 5′UMP, 5′CMP, 5′GMP and 5′IMP, and their characterization, carried out by elemental analysis, by studying the infrared spectra, diffuse reflectance and conductivity measurement.In the complexes of NiURA (and NiURD) with acetate, direct coordination of the metal ion to the C 4O group of the pyrimidine ring is inferred from the changes observed on the infrared spectrum of the corresponding bands at vCO. The variations in frequency of the vCOO symmetric and asymmetric bands of the acetate group together with the conductivity and reflectance results seem to indicate the dimer structure of the compounds.In the compounds of NiURA (and NiURD) with ethylenediamine indirect bonding of Ni(II)to the pyrimidine ring is inferred, probably established through hydrogen bonds involving the C 4O groups in the base or nucleoside and the −NH 2 groups in the ethylenediamine.In the complexes of Ni-nucleotide, bonding seems to occur through the heterocyclic ring (C 4O for 5′UMP, N(3) for 5′CMP, N(7) for 5′GMP and 5′IMP) together with additional interactions through the phosphate group. 相似文献
20.
The activities of ribonucleases (RNase HS and RNase A), which hydrolyze ribonucleic acid at linkages attached to pyrimidine nucleotides were stimulated by polyamines, while the activities of ribonucleases (RNase T 1 and RNase M), which attack ribonucleic acid at linkages attached to purine nucleotides were not influenced by polyamines. In the presence of polyamines, the cleavage of C 5′-O-P linkages adjacent to cytosine nucleotide was stimulated, while the cleavage of C 5′-O-P linkages adjacent to uracil nucleotides was inhibited slightly. The effect of polyamines on the activities of ribonucleases occured through the binding of the polyamines to nucleic acid. 相似文献
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