共查询到20条相似文献,搜索用时 15 毫秒
1.
The positive ion electrospray mass spectrometry (ESI-MS) of trans-[Ru(NO)Cl)(dpaH)2]Cl2 (dpaH=2,2′-dipyridylamine), obtained from the carrier solvent of H2O–CH3OH (50:50), revealed 1+ ions of the formulas [RuII(NO+)Cl(dpaH)(dpa)]+ (m/z=508), [RuIIICl(dpaH)(dpa−)]+ (m/z=478), [RuII(NO+)(dpa)2]+ (m/z=472), [RuIII(dpa)2]+ (m/z=442), originating from proton dissociation from the parent [RuII(NO+)Cl(dpaH)2]2+ ion with subsequent loss of NO (17.4% of dissociative events) or loss of HCl (82.6% of dissociative events). Further loss of NO from the m/z=472 fragment yields the m/z=442 fragment. Thus, ionization of the NH moiety of dpaH is a significant factor in controlling the net ionic charge in the gas phase, and allowing preferential dissociation of HCl in the fragmentation processes. With NaCl added, an ion pair, {Na[RuII(NO)Cl(dpa)2]}+ (m/z=530; 532), is detectable. All these positive mass peaks that contain Ru carry a signature ‘handprint’ of adjacent m/z peaks due to the isotopic distribution of 104Ru, 102Ru, 101Ru, 99Ru, 98Ru and 96Ru mass centered around 101Ru for each fragment, and have been matched to the theoretical isotopic distribution for each set of peaks centered on the main isotope peak. When the starting complex is allowed to undergo aquation for two weeks in H2O, loss of the axial Cl− is shown by the approximately 77% attenuation of the [RuII(NO+)Cl(dpaH)(dpa)]+ ion, being replaced by the [RuII(NO+)(H2O)(dpa)2]+ (m/z=490) as the most abundant high-mass species. Loss of H2O is observed to form [RuII(NO+)(dpa)2]+ (m/z=472). No positive ion mass spectral peaks were observed for RuCl3(NO)(H2O)2, ‘caged NO’. Negative ions were observed by proton dissociation forming [RuII(NO)Cl3(H2O)(OH)]− in the ionization chamber, detecting the parent 1− ion at m/z=274, followed by the loss of NO as the main dissociative pathway that produces [RuIIICl3(H2O)(OH)]− (m/z=244). This species undergoes reductive elimination of a chlorine atom, forming [RuIICl2(H2O)(OH)]− (m/z=208). The ease of the NO dissociation is increased for the negative ions, which should be more able to stabilize a RuIII product upon NO loss. 相似文献
2.
Lawrence K. House Jacqueline Ramí rez Mark J. Ratain 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1998,720(1-2):245-250
A sensitive assay was developed for the quantitation of 5-fluorouracil (5-FU) and uracil using liquid–liquid extraction (LLE) and HPLC with UV detection. Analyses were performed with four μBondapak C18 columns connected in series using 20 mM acetic acid with 1% ACN as mobile phase. The calibration curves were linear across the range of 26–1000 ng ml−1 (0.21–7.8 μM) for 5-FU and 1.0–14.0 μg ml−1 (0.01–110 μM) for uracil. This assay has been implemented to determine the plasma concentrations for pharmacokinetic studies for 5-FU and uracil in conjunction with clinical trials. 相似文献
3.
Vasdev N LaRonde FJ Woodgett JR Garcia A Rubie EA Meyer JH Houle S Wilson AA 《Bioorganic & medicinal chemistry》2008,16(9):5277-5284
Protein kinase A (PKA) is an important signal transduction target for drug development because it influences critical cellular processes implicated in neuropsychiatric illnesses such as major depressive disorder. The goal of the present study was to develop the first imaging agent for measuring the levels of PKA with positron emission tomography (PET). By rational derivatization of 5-isoquinoline sulfonamides, it was found that the introduction of a methyl group to the sulphonamidic nitrogen on the known PKA inhibitors N-(2-aminoethyl)isoquinoline-5-sulfonamide (H-9, 1) and N-(2-(4-bromocinnamylamino)ethyl)isoquinoline-5-sulfonamide (H-89, 2), (yielding N-(2-aminoethyl)-N-methyl-isoquinoline-5-sulfonamide (4) and N-(2-(4-bromocinnamylamino)ethyl)-N-methyl-isoquinoline-5-sulfonamide (5), respectively) does not appreciably reduce in vitro potency toward PKA. We have facilitated the synthesis of 4 by reacting isoquinoline-5-sulfonyl chloride with N-methylethylenediamine (20% yield). Several techniques were used to thoroughly characterize 4 including multi (1H, 13C and 15N) NMR spectroscopy and X-ray crystallography. Compound 4 and 1-(4-bromophenyl)-1-propen-3-yl bromide were reacted to produce 5 in 16% yield. Compound 2 was reacted with [11C]CH3I to prepare N-(2-(4-bromocinnamylamino) ethyl)-N-[11C]methyl-isoquinoline-5-sulfonamide ([11C]5), with a decay-corrected radiochemical yield of 32%, based on [11C]CO2. [11C]5 was produced with >98% radiochemical purity and 1130 mCi/μmol specific activity after 40 min (end of synthesis). Conscious rats were administered [11C] 5 and sacrificed at 5, 15, 30 and 60 min after injection. Radioactivity from all excised brain regions was <0.2%ID/g at all time points. The modest brain penetration of [11C]5 may limit its use for studying PKA in the central nervous system. 相似文献
4.
Lone Jrgensen Nils Brünner Mogens Spang-Thomsen Mattie R. James Robert Clarke Per Dombernowsky Birgit Svenstrup 《The Journal of steroid biochemistry and molecular biology》1997,63(4-6):275-281
Androgen and estrogen metabolism was investigated in the hormone-dependent human breast cancer cell line MCF-7 and its two hormone-resistant sublines MCF-7/LCC1 and MCF-7/LCC2. Using the product isolation method, the activity of aromatase, 5-reductase, 3/β-hydroxysteroid oxidoreductase and 17β-hydroxysteroid oxidoreductase were investigated isolating the following steroids: estriol (E3), estradiol (E2), estrone (E1), 3/β-androstanediol (A-diol), testosterone (T), dihydrotestosterone (DHT), androsterone (AND), androstenedion (4-AD) and androstanedione (A-dion). For all experiments, cells were preincubated with cortisol and subsequently incubated with [14C]T or [14C]4-AD as the substrate in medium without phenol red and with serum charcoal stripped of steroids. The results showed no aromatase activity in any of the cell lines under the experimental conditions used, and preincubation with cortisol had no effect on the enzyme activity. With [14C]T as the substrate, the metabolized level of DHT was very similar in the three cell lines, though MCF-7/LCC1 and MCF-7/LCC2 utilized the substrate to a much lesser extent. The amount of DHT and 4-AD produced were comparable in the two hormone-resistant cell lines, while the amount of 4-AD was significantly higher in MCF-7 cells. No differences in enzyme activity were found in the three cell lines when [14C]4-AD was used as the substrate. This study showed an altered androgen metabolism in the MCF-7/LCC1 and MCF-7/LCC2 sublines compared to the parent MCF-7. However, since treatment with DHT and T inhibited cell growth equally well in all three tumor cell lines, it is unlikely that the found differences in steroid metabolism was involved in the acquisition of the endocrine resistance of the two MCF-7 sublines. 相似文献
5.
Toshiaki Yonemura Kimi Shibuya Ken-ichi Okamoto Tomoharu Ama Hiroshi Kawaguchi Takaji Yasui 《Inorganica chimica acta》1997,260(2):m1127-128
Cobalt(III) complexes with a thiolate or thioether ligand, t-[Co(mp)(tren)]+ (2), t-[Co(mtp)(tren)]2+ (1Me) and t-[Co(mta)(tren)]2+ (2Me), (mp = 3-mercaptopropionate, MA = 3-(methylthio)propionate and MTA = 2-(methylthio)acetate) have been prepared in aqueous solutions. The crystal structures of 1, 2, 1Me and 2Me were determined by X-ray diffraction methods. The crystal data are as follows, t-[Co(mp)(tren)]ClO4 (1CIO4): monoclinic, P21/n, A = 10.877(8), B = 11.570(4), c = 12.173(7) Å, β = 92.20(5)°, V = 1531(1) Å3, Z = 4 and R = 0.060; t-[Co(ma)(tren)]Cl·3H2O (2Cl·3H2O): monoclinic, P21/n, a = 7.7688(8), B = 27.128(2), C = 7.858(1) Å, β = 100.63(1)°, V = 1627.7(3) Å3, Z = 4 and R = 0.066; (+)465CD-t-[Co(mtp)(tren)](ClO4)2 ((+)465CD-1Me(ClO4)2): orthorhombic, P212121, A = 10.6610(7), B = 11.746(1), C = 15.555(1) Å, V = 1947.9(3) Å3, Z = 4 and R = 0.068; (+)465CD-t-[Co(mta)(tren)](ClO4)2 ((+)465CD-2Me(ClO4)2): orthorhombic, P212121, a = 10.564(1), B = 11.375(1), C = 15.434(2) Å, V = 1854.7(4) Å3, Z = 4 and R = 0.047. All central Co(III) atoms have approximately octahedral geometry, coordinated by four N, one O, and one S atoms. All of the complexes are only isomer, of which the sulfur atom in the didentate-O,S ligands are located at the trans position to the tertiary amine nitrogen atom of tren. 1 and 1Me contain six-membered chelate ring, and 2 and 2Me do five-membered chelate ring in the didentate ligand. The chirality of the asymmetric sulfur donor atom in (+)465CD-1Me is the S configuration and that in (+)465CD-2Me is the R one. The 1H NMR, 13C NMR and electronic absorption spectral behaviors and electrochemical properties of the present complexes are discussed in relation to their stereochemistries. 相似文献
6.
Alexander N. Grechkin Nina V. Kuchtina Tatiana E. Gafarova Rustem A. Kuramshin 《Plant science》1990,70(2):175-180
The oxidation of [1-14C]linoleate in isolated microsomes from pea leaves was found to be stimulated by NADPH addition. The formation of one of the main metabolites, 12-hydroxy-9(Z)-dodecenoic acid is particularly NADPH-dependent. The predominant products in the absence of NADPH were hydroperoxides and in the presence of NADPH, 12-hydroxy-9(Z)-dodecenoic acid. Exogenous [1-14C]-13-hydroperoxy-9(Z), 11(E)-octadecadieoic acid and [1-14C]-12-oxo-9(Z)-dodecenoic acidwere the efficient precursors of 12-hydroxy9(Z)-dodecenoic acid. It was concluded that 12-hydroxy-9(Z)-dodecenoic acid is formed by NADPH-dependent enzymatic reduction of 12oxo-9(Z)-dodecenoic acid. The observed inhibition of linoleate oxidation in isolated microsomes by CO and metryapone suggests the involvement of cytochrome P-450 in the reaction. The relative contribution of lipoxygenase and monooxygenase activity to linoleate oxidation in microsomes is discussed. 相似文献
7.
Wenresti G. Gallardo Atsushi Hagiwara Yuichi Tomita Terry W. Snell 《Journal of experimental marine biology and ecology》1999,240(2):599-191
Growth hormone (GH, 0.0025 and 0.025 I.U. ml−1) and γ-aminobutyric acid (GABA, 50 μg ml−1) enhance rotifer population growth in batch cultures. In order to further understand the mechanism of their actions, we conducted experiments culturing isolated females at low food and high free ammonia levels. At an optimum food level of 7×106 Nannochloropsis oculata cells ml−1 or at low free ammonia level of 2.4 μg ml−1, the F1 offspring of rotifers treated with GH at 0.0025 I.U. ml−1 had significantly higher population growth rate (r) and net reproduction rate (Ro), and shorter generation time than untreated rotifers. At a lower food level of 7×105 cells ml−1 or at high free ammonia level of 3.1 μg ml−1, rotifers treated with GABA at 50 μg ml−1 had significantly higher r and Ro, and shorter generation time. These results indicate that GABA is effective in enhancing rotifer reproduction when rotifers are cultured under stress whereas GH enhances rotifer reproduction when culture conditions are optimal. Significant effects were also observed in F1 and F2 generations which were not treated with hormones. These data may be useful for treating rotifer mass cultures to mitigate the effects of stress caused by high population densities. 相似文献
8.
Vesamicol [2-(4-phenylpiperidino)cyclohexanol, formerly AH5183] at a concentration of 10 μM reduced by 16–20% the amount of vesicle-bound ACh in intact pieces of Torpedo electric organ (isolated prisms). When [14C]acetate was applied to prisms in the presence of 10 μM vesamicol, vesicular translocation of newly synthesized [14C]ACh was inhibited by 40%. During short trains of field shocks given at 10 Hz to the tissue, vesamicol inhibited by 93% the release of [14C]ACh, but left the release of prestored ACh unaltered. In spite of these alterations, 10 μM vesamicol did not impair nerve-electroplaque transmission, even after prolonged electrical stimulation and during a recovery period. It is concluded that in the Torpedo electric organ the actions of vesamicol on ACh metabolism have apparently little or no effect on the efficiency of synaptic transmission. 相似文献
9.
Irina V. Pisareva Igot T. Chizhevsky Pavel V. Petrovskii Eugenii V. Vorontzov Vladimir I. Bregadze Fedor M. Dolgushin Aleksandr I. Yanovsky 《Inorganica chimica acta》1998,280(1-2):233-237
The first η2-olefinic monocarbon metallacarbone closo-2-(Ph3P)-1-N,2-[μ-(η2-CH2CH=Ch2)]-1-N-(σ-CH2CH=CH2)-2,1- RhCB10H10 has been prepared by the reaction of the dimeric anion {[Ph3PRhB10H10CNH2]2-μ-H}−[PPN]+ with allyl bromide and characterized by a combination of spectroscopic methods and a single-crystal X-ray diffraction study. The variable temperature 1H and 13C NMR studies revealed the fluxional behavior of the η2-olefinic complex in CD2Cl2 solution which is associated with the allyl side-chain exchange process. 相似文献
10.
L. Galzigna M. Bianchi A. Bertazzon A. Barthez G. Quadro M. A. Coletti-Previero 《Journal of neurochemistry》1984,42(6):1762-1766
Abstract: N -Pivaloyl-leucyl–γ-aminobutyric acid (PLG) is a synthetic dipeptide with a partition coefficient of 1.67 in an ethyl acetate/water system that partially inhibits the synaptosomal uptake and activates the release of [U- 14 C]-γ-aminobutyric acid ([U-14 C]GABA). The displacement of GAB A from crude synaptic membranes by PLG occurs with an IC50 of 10−5 M . The compound has the capacity to cross the blood-brain barrier and increase central GABA levels. Its ED50 on cardiazol-induced convulsions is 60-65 mg/kg. PLG is resistant to hydrolysis by chymotrypsin and partially inhibits the proteolytic activity of trypsin. 相似文献
11.
A. P. Tulloch 《Chemistry and physics of lipids》1982,30(4):325-335
[2S-2-2H]- and [2R-2-2H]hexadecanoic acids were synthesized in overall yields of 59–67%. Methyl(2R)-2-hydroxyhexadecanoate, from the acid produced by Hansenula sydowiorum, was converted to the p-toluenesulphonate, reduced to trideutero alcohol with lithium aluminium deuteride and oxidized to [2S-2-2H]hexadecanoic acid. Methyl (2S)-2-chlorohexadecanoate, which was a by-product of tosylation and was also prepared by chlorinatioon of the hydroxy ester with thionyl chloride, on reduction and oxidation as before gave [2R-2-2H]-hexadecanoic acid. Intermediates were fully characterized, isotopic purity was 97% and optical purity was maintained throughout the syntheses. Attempts to reduce the tosyl or chloro groups, only, with sodium borodeuteride gave low yields probably due to preferential reduction of the ester group; 1,2-epoxyhexadecane was obtained from the tosylate and 2-chlorohexadecan-1-ol from the chloro ester. 相似文献
12.
Lutz Weber Cornelia D ge GÜ Nter Haufe Rolf Hommel Hans-Peter Kleber 《Biocatalysis and Biotransformation》1992,5(4):267-272
Biotransformation of [1-13C] labelled hexadecane, hexadecanol and hexadecanoic acid have been investigated using the yeast Torulopsis apicola. The yeast produces a microcrystalline mixture of two glycolipids, the lipophilic moiety of which consists of ω- or (ω-l)-hydroxylated hexadecanoic acid. Biosynthesis of these glycolipids takes place via hydroxylation of hexadecane, oxidation to hexadecanoic acid and ω or (ω-l)-hydroxylation of hexadecanoic acid. Feeding the cell cultures with a mixture of hexadecane and [1-13C] labelled hexadecane derivatives one observes 13C enrichment ratios which indicate that neither of the biohydroxylation or oxidation steps are rate limiting in the formation of the glycolipids, furthermore, two different monooxygenase systems appear to be involved in hydroxylation of hexadecane and hexadecanoic acid. 相似文献
13.
Coldham NG Howells LC Santi A Montesissa C Langlais C King LJ Macpherson DD Sauer MJ 《The Journal of steroid biochemistry and molecular biology》1999,70(4-6):169-184
Biotransformation of the phytoestrogen [14C]genistein was investigated in male and female rats by application of narrow-bore radio-HPLC-MSn (LCQ, Finnigan) to determine intermediates in metabolism. Urine contained five metabolites, Gm1–Gm5, 24 h after dosing by gavage with [14C]genistein (4 mg kg−1). Structural analysis following ESI revealed molecular ions [M+H]+ of m/z 447, 449, 273, and 271 for metabolites Gm2, Gm3, Gm5 and genistein, respectively and an [M–H]− of m/z 349 for Gm4. Metabolite structure was deduced by evaluation of product ion spectra derived from unlabelled and [14C]-labelled ions and sensitivity to treatment with β-glucuronidase. These studies indicated identity of metabolites with genistein glucuronide (Gm2), dihydrogenistein glucuronide (Gm3), genistein sulphate (Gm4) and dihydrogenistein (Gm5). Detection of the β-glucuronidase resistant major metabolite Gm1 by ESI was poor and so was analysed by negative ion APCI; this revealed a deprotonated molecular ion of m/z 165 which had chromatographic and mass spectral properties consistent with authentic 4-hydroxyphenyl-2-propionic acid, a novel metabolite of genistein. In vitro metabolism studies with anaerobic caecal cultures derived from male and female rats revealed metabolism of genistein to Gm1 via Gm5 and an additional metabolite (Gm6) which was identified from product ion spectra as 6′-hydroxy-O-desmethylangolensin. Biotransformation of genistein by both isolated hepatocytes and precision-cut liver slices was limited to glucuronidation of parent compound. Commonality of genistein metabolites found in rats with those reported in man suggest similar pathways of biotransformation, primarily involving gut micro-flora. 相似文献
14.
R.Douglas Carter Robert E. Hardy Hollye K. Lannom Kilian Dill Bernard Ferrari AndrA. Pavia 《International journal of biological macromolecules》1984,6(6):348-352
13C nuclear magnetic resonance spectroscopy (13C n.m.r.) was used to determine the pH titration parameters for the N-terminal N,N-[13C]dimethylamino and N,N-[13C]monomethylamino groups of glycophorins AM and AN, and some 28 related glycoproteins, glycopeptides and peptides. The results show that glycosylation of the Ser and Thr residues at positions 2, 3 and 4 of the glycophorins have a pronounced effect on the titration parameters. Substitution of amino acids 4 and 5 in the glycophorin sequence appears to minimally affect our titration parameters. Internal hydrogen-bonding involving the N-terminal Ser residue may explain some of the unusual pH titration results observed for glycophorin AM. 相似文献
15.
H.R. Anderson I. Fairweather D.R. Bamford W.I. Montgomery 《International journal for parasitology》1993,23(8):1053-1062
The effect of the deacetylated (amine) metabolite of diamphenethide (DAMD, 10 μg ml−1) on the uptake and incorporation by adult Fasciola hepatica of radioactively labelled precursors of DNA, RNA and protein synthesis ([3H]thymidine, [3H]uridine and [3H] leucine, respectively) was measured by liquid scintillation counting. Comparison was made between the effects of DAMD and those of specific inhibitors of DNA, RNA and protein synthesis, namely, 5-fluorouracil, cordycepin and cycloheximide, respectively. DAMD caused a significant decrease in the overall uptake and incorporation of [3H]uridine by F. hepatica, decreased the incorporation of [3H] leucine and also caused a significant decrease in the overall protein content of the flukes. The effect of DAMD was similar to that of cycloheximide (1 × 10−3M), a potent inhibitor of protein synthesis, which also caused a significant decrease in the incorporation of [3H] leucine by the fluke and a decrease in the overall protein content of the fluke. Cordycepin (100 μg ml−1) caused a significant decrease in the protein content of the fluke, but had no effect on the uptake or incorporation of [3H]uridine. 5-Fluorouracil (1 × 10−4
) did not affect the uptake or incorporation of [3H]thymidine, nor did it decrease the protein content of the fluke. The results indicate that DAMD inhibits protein synthesis by F. hepatica, possibly by inhibiting RNA synthesis. The results are also consistent with previous morphological investigations involving DAMD. 相似文献
16.
Protein phosphorylation in vitro was investigated in guard cells from Vicia faba. A number of proteins with apparent molecular masses of 72, 67, 57, 52, 49, 44, 37, and 26 kDa were phosphorylated when guard-cell extract was incubated with [γ-32P]ATP under Ca2+-free conditions. In the presence of Ca2+ at 1 μM, several proteins with apparent molecular masses of 125, 83, 41, 31, and 25 kDa were newly phosphorylated. These Ca2+-dependent protein phosphorylations were suppressed by (8R*,9S*,11S*)-(−)-9-hydroxy-9-methoxycarbonyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1H,8H,11H-2,7b,11a- triazadibenzo[a,g]cycloocta[cde]trinden-1-one (K-252a), a wide-range inhibitor of protein kinases, suggesting that the protein phosphorylations were mediated by protein kinases. Several proteins were phosphorylated in vitro in mesophyll extract from Vicia. In contrast to guard cells, there was no detectable Ca2+-dependent protein phosphorylation in mesophyll cells. 1-(5-Indonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-7), an inhibitor of myosin light chain kinase (MLCK), and an antagonist of calmodulin (CaM), N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), inhibited Ca2+-dependent phosphorylation of 41- and 25-kDa proteins in guard cells. Fractionation experiments revealed that the Ca2+-dependent phosphorylated proteins with molecular masses of 41 and 25 kDa were present in the mitochondria, and the 125- and 31-kDa proteins in the cytosol. These results suggest that Ca2+-dependent protein phosphorylation occurs markedly in guard cells, and that Ca2+-dependent phosphorylation of 41- and 25-kDa proteins may be catalyzed by MLCK or MLCK-like protein kinase in guard cells. 相似文献
17.
Sarah J. Young John P. Hart Antony A. Dowman David C. Cowell 《Biosensors & bioelectronics》2001,16(9-12):887-894
Previous research has shown that lactate dehydrogenase (LDH) was competitively inhibited by pentachlorophenol (PCP) and a modified assay produced a detection limit of 1 μM (270 μg l−1). This work used spectrophotometric rate-determination but in order to move towards biosensor development the selected detection method was electrochemical. The linkage of LDH to lactate oxidase (LOD) provided the electroactive species, hydrogen peroxide. This could be monitored using a screen-printed carbon electrode (SPCE) incorporating the mediator, cobalt phthalocyanine, at a potential of +300 mV (vs. Ag/AgCl). A linked LDH/LOD system was optimised with respect to inhibition by PCP. It was found that the SPCE support material, PVC, acted to reduce inhibition, possibly by combining with PCP. A cellulose acetate membrane removed this effect. Inhibition of the system was greatest at enzyme activities of 5 U ml−1 LDH and 0.8 U ml−1 LOD in reactions containing 246 μM pyruvate and 7.5 μM NADPH. PCP detection limits were an EC10 of 800 nM (213 μg l−1) and a minimum inhibition detectable (MID) limit of 650 nM (173 μg l−1). The inclusion of a third enzyme, glucose dehydrogenase (GDH), provided cofactor recycling to enable low concentrations of NADPH to be incorporated within the assay. NADPH was reduced from 7.5 to 2 μM. PCP detection limits were obtained for an assay containing 5 U ml−1 LDH, 0.8 U ml−1 LOD and 0.1 U ml−1 GDH with 246 μM pyruvate, 400 mM glucose and 2 μM NADPH. The EC10 limit was 150 nM (39.9 μg l−1) and the MID was 100 nM (26.6 μg l−1). The design of the inhibition assays discussed has significance as a model for other enzymes and moves forward the possibility of an electrochemical biosensor array for pollution monitoring. 相似文献
18.
Yukiko Shimizu Carol Yarborough Yoshio Osawa 《The Journal of steroid biochemistry and molecular biology》1993,44(4-6):651-656
In order to better understand the function of aromatase, we carried out kinetic analyses to asses the ability of natural estrogens, estrone (E1), estradiol (E2), 16-OHE1, and estriol (E3), to inhibit aromatization. Human placental microsomes (50 μg protein) were incubated for 5 min at 37°C with [1β-3H]testosterone (1.24 × 103 dpm 3H/ng, 35–150 nM) or [1β-3H,4-14C]androstenedione (3.05 × 103 dpm 3H/ng, 3H/14C = 19.3, 7–65 nM) as substrate in the presence of NADPH, with and without natural estrogens as putative inhibitors. Aromatase activity was assessed by tritium released to water from the 1β-position of the substrates. Natural estrogens showed competitive product inhibition against androgen aromatization. The Ki of E1, E2, 16-OHE1, and E3 for testosterone aromatization was 1.5, 2.2, 95, and 162 μM, respectively, where the Km of aromatase was 61.8 ± 2.0 nM (n = 5) for testosterone. The Ki of E1, E2, 16-OHE1, and E3 for androstenedione aromatization was 10.6, 5.5, 252, and 1182 μM, respectively, where the Km of aromatase was 35.4 ± 4.1 nM (n = 4) for androstenedione. These results show that estrogens inhibit the process of andrigen aromatization and indicate that natural estrogens regulate their own synthesis by the product inhibition mechanism in vivo. Since natural estrogens bind to the active site of human placental aromatase P-450 complex as competitive inhibitors, natural estrogens might be further metabolized by aromatase. This suggests that human placental estrogen 2-hydroxylase activity is catalyzed by the active site of aromatase cytochrome P-450 and also agrees with the fact that the level of catecholestrogens in maternal plasma increases during pregnancy. The relative affinities and concentration of androgens and estrogens would control estrogen and catecholestrogen biosynthesis by aromatase. 相似文献
19.
Jeffrey P. Flemming Mark C. Pilon Oleg Ya. Borbulevitch Mikhail Yu. Antipin Vladimir V. Grushin 《Inorganica chimica acta》1998,280(1-2):87-98
Single crystal X-ray diffraction studies of trans-[(Ph3P)2Pd(Ph)X] (X = F (1), Cl (2), Br (3), and I (4) were carried out. The four structures split in two isostructural and isomorphous groups, namely orthorhombic for 1 and 2 (space group Pbca, Z = 8) and triclinic for 3 and 4 (space group P-1, Z = 2). According to the Pd---C bond length, the trans influence of X within these pairs follows the trend Cl>F and 1>Br. However, the trans influence of Cl is slightly stronger than that of Br. Both structural and 13C NMR studies revealed that electron-donating effects of (Ph3P)2PdX increase along the series X=I
− for the Pd centre in [(Ph3P)2Pd(Ph)]− were studied by 31P NMR in rigorously anhydrous CH2Cl2 solutions, and equilibrium constants and ΔG values were obtained for all possible combinations. The sequence F− > Cl− > Br− > I− is characteristic of halide preference for the Pd complexes. Dissolving 1 and PPN Cl in dry CH2Cl2 resulted in the release of ‘naked’ F− which fluorinated the solvent smoothly to give a mixture of CH2ClF and CH2F2 in high yield. When chloroform was used instead of CH2Cl2, dichlorocarbene was generated slowly, forming the corresponding cyclopropane in the presence of styrene. All observations were rationalized successfully in terms of the filled/filled effect and push/pull interactions. 相似文献
− for the Pd centre in [(Ph3P)2Pd(Ph)]− were studied by 31P NMR in rigorously anhydrous CH2Cl2 solutions, and equilibrium constants and ΔG values were obtained for all possible combinations. The sequence F− > Cl− > Br− > I− is characteristic of halide preference for the Pd complexes. Dissolving 1 and PPN Cl in dry CH2Cl2 resulted in the release of ‘naked’ F− which fluorinated the solvent smoothly to give a mixture of CH2ClF and CH2F2 in high yield. When chloroform was used instead of CH2Cl2, dichlorocarbene was generated slowly, forming the corresponding cyclopropane in the presence of styrene. All observations were rationalized successfully in terms of the filled/filled effect and push/pull interactions. 相似文献
20.
Qi Song Marco L. Gomez-Barrios Elise L. Hopper Martin A. Hjortso Nikolaus H. Fischer 《Phytochemistry》1995,40(6):1659-1665
Biosynthetic studies of the guaianolide-type sesquiterpene lactones 11βH,13-dihydrolactucin-8-O-acetate and 8-desoxylactucin were performed in Agrobacterium rhizogenes—transformed hairy root cultures of blue-flowered lettuce, Lactuca floridana. The 13C NMR spectra of the two guaianolides labelled by incorporation of [1-13C], [2-13C], [1,2-13C2]acetate and [2-13C]mevalolactone showed patterns of enrichment consistent with a previously proposed biogenetic pathway for guaianolide-type sesquiterpene lactones via the acetate-mevalonate-germacradiene route. 相似文献