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1.
6-N-[3-3H]Trimethyl-dl-lysine was synthesized from 6-N-acetyl-l-lysine by the following chemical scheme: 6-N-acetyl-l-lysine → 2-keto-6-N-acetylcaproic acid → 2-[3-3H]keto-6-N-acetylcaproic acid → 2-[3-3H]keto-6-N-acetylcaproic acid oxime → 6-N-[3-3H]acetyl-dl-lysine → dl-[3-3H]lysine → 2-N-[3-3H]formyl-dl-lysine → 2-[3-3H]formyl-6-N-trimethyl-dl-lysine → 6-N-[3-3H]trimethyl-dl-lysine. Using a 70% ammonium sulfate fraction obtained from a high-speed rat kidney supernatant, the cosubstrate and cofactor requirements for 6-N-trimethyl-l-lysine hydroxylase activity as measured by tritium release from 6-N-[3-3H]trimethyl-dl-lysine were: α-ketoglutarate, ferrous ions, l-ascorbate, and oxygen, with added catalase showing a slight but distinct stimulatory effect. On incubation with the crude rat kidney preparation, the release of tritium from 6-N-[3-3H]trimethyl-dl-lysine was linear with both time of incubation and protein concentration. Hydroxylation of 6-N-trimethyl-l-lysine, as measured by tritium release from the labeled substrate, was examined in rat kidney, heart, liver, and skeletal muscle tissues, and found to be most active in the kidney.  相似文献   

2.
1. (Na+ +K+)-ATPase from rectal gland of Squlus acanthias contains 34 SH groups per mol (Mr 265000). 15 are located on the α subunit (Mr 106 000) and two on the β subunit (Mr 40 000). The β subunit also contains one disulphide bridge. 2. The reaction of (Na+ +K+)-ATPase with N-ethylmaleimide shows the existence of at least three classes of SH groups. Class I contains two SH groups on each α subunit and one on each β subunit. Reaction of these groups with N-methylmaleimide in the presence of 40% glycerol or sucrose does not alter the enzyme activity. Class II contains four SH groups on each α subunit, and the reaction of these groups with 0.1 mM N-ethylmaleimide in the presence of 150 mM K+ leads to an enzyme species with about 16% activity. The remaining enzyme activity can be completely abolished by reaction with 5–10 nM N-ethylmaleimide, indicating a third class of SH groups (Class III). This pattern of inactivation is different from that of the kidney enzyme, where only one class of SH groups essential to activity is observed. 3. It is also shown that N-ethylmaleimide and DTNB inactivate by reacting with the same Class II SH groups. 4. Spin-labelling of the (Na+ +K+)-ATPase with a maleimide derivative shows that Class II groups are mostly buried in the membrane, whereas Class I groups are more exposed. It is also shown that spin label bound to the Class I groups can monitor the difference between the Na+- and K+-forms of the enzyme.  相似文献   

3.
Substitution reaction of chloro η6-arene ruthenium N∩O-base complexes [(η6-arene)Ru(N∩O)Cl] [N∩O = pyrazine-2-carboxylic acid (pca-H), 8-hydroxyquinoline (hq-H); arene = p-iPrC6H4Me, N∩O = hq (1); arene = C6Me6, N∩O = hq (2)] with NaN3 yield the neutral arene ruthenium azido complexes of the general formula [(η6-arene)Ru(N∩O)N3] [N∩O = pca, arene = p-iPrC6H4Me (3), arene = C6Me6 (4); N∩O = hq, arene = p-iPrC6H4Me (5), arene = C6Me6 (6)]. These complexes undergo [3 + 2] dipolar cycloaddition reaction with activated alkynes dimethyl and diethyl acetylenedicarboxylates to yield the arene triazole complexes [(η6-arene)Ru(N∩O){N3C2(CO2R)2}] [N∩O = pca, R = Me, arene = p-iPrC6H4Me (7), C6Me6 (8); R = Et, arene = p-iPrC6H4Me (9), C6Me6 (10); N∩O = hq, R = Me, arene = p-iPrC6H4Me (11) C6Me6 (12); R = Et, arene = p-iPrC6H4Me (13), C6Me6 (14)]. On the bases of proton NMR study, in the above triazole complexes N(2) isomers are assigned with dimethylacetylenedicarboxylate whereas N(1) isomers with diethylacetylenedicarboxylate. All complexes have been characterized by IR and NMR spectroscopy as well as by elemental analysis. The molecular structures of the azido complexes [(η6-p-iPrC6H4Me)Ru(pca)N3] (3), [(η6-p-iPrC6H4Me)Ru(hq)N3] (5) and [(η6-C6Me6)Ru(hq)N3] (6) have been established by single crystal X-ray diffraction studies.  相似文献   

4.
H+-ATPase activity in plasma membranes isolated from Avena sativa root cells is inhibited by N-ethylmaleimide, a covalent modifier of protein sulfhydryl groups. The rate of inhibition is reduced by ADP, MgADP, and MgATP, but even at 40 millimolar ADP the enzyme is only partially protected against inactivation. When plasma membranes are treated wth N-[2-3H]ethylmaleimide and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis, prominent radioactive bands appear at Mr=100,000 and several other positions. However, only radioactivity in the Mr=100,000 protein is reduced by the presence of MgADP. These results provide independent evidence that the Mr=100,000 polypeptide which is observed in purified preparations of the enzyme is the catalytic subunit of the H+-ATPase. When tryptic peptides are produced from N-[2-3H]ethylmaleimide labeled Mr=100,000 protein and separated by reverse phase high performance liquid chromatography, two radioactive peaks are observed for which N-[2-3H]ethylmaleimide incorporation is reduced in the presence of MgADP.  相似文献   

5.
6.
Ribonucleoside triphosphate reductase from Lactobacillus leichmannii, after reduction by exposure to dithiothreitol, has been alkylated with N-ethylmaleimide. Under conditions where the unreduced enzyme does not incorporate N-ethylmaleimide residues, the reduced enzyme is rapidly alkylated to the extent of one N-ethylmaleimide per molecule of enzyme. Loss of enzyme activity parallels the incorporation of N-ethylmaleimide. The value of the second-order rate constant for the alkylation at 0 °C of the reduced enzyme is influenced by the presence of some of the effectors of the enzyme, e.g., dATP at 200 μm reduces this parameter from 0.61 to 0.33 mm?1 min?1. The addition of coenzyme B12 did not significantly affect the rate of alkylation of the reduced enzyme nor did it change the rate of alkylation of the dATP-reduced enzyme complex. Reduced enzyme, freed of dithiol, was shown to be unable to convert CTP stoichiometrically to dCTP when all of the usual enzyme assay components, except the dithiol, were present, nor did addition of CTP to the otherwise complete mixture decrease the level of N-ethylmaleimide-reactive thiol. However, the subsequent addition of dithiol was found to result in essentially complete reduction of CTP to dCTP. Hence, although reduction of the enzyme is probably required to generate an active form of the enzyme, the reduced enzyme does not appear to be capable of transferring its reducing equivalents stoichiometrically to the substrate to form dCTP from CTP. These results are discussed in terms of the mechanism of action of this enzyme.  相似文献   

7.
The kinetics of a Mn2+-requiring, NADP+-specific isocitrate dehydrogenase from Salmonella typhimurium have been examined by the measurement of initial velocity rates in the presence and absence of the reaction products. The binding of each of the cosubstrates, isocitrate, and NADP+, is not independent of the other, and the isocitrate-Mn2+ complex is the kinetically important substrate species. All of the reaction products, α-ketoglutarate, CO2, and NADPH are competitive with both cosubstrates and the mechanism appears to be of the rapid equilibrium random type. The enzyme has been purified to homogeneity and has an isoelectric point at pH 4.0–4.2, and an apparent molecular weight of 102,000.  相似文献   

8.
The cysteine-specific modifiers we reported previously, N-ethylmaleimide (NEM) and iodoacetanilide (IAA), have been applied to label cysteine residues of peptides in combination with electrospray ionization mass spectrometry (ESI-MS/MS), and their scope in proteomic studies was examined. Peptides modified with N-ethylmaleimide (NEM) or iodoacetanilide (IAA) showed significant enhancement in ionization efficiencies. These modifiers were also found to remain intact in tandem mass spectrometry. Both combinations of N-ethylmaleimide (NEM) and d5-N-ethylmaleimide (d5-NEM), and iodoacetanilide (IAA) and 13C6-iodoacetanilide (13C6-IAA) were also shown to be applicable to quantitative analysis of a peptide.  相似文献   

9.
It has been established that small molecule model complexes have been useful in studying more complex biological systems of metalloproteins. Because many metalloproteins have active sites that contain multiple histidine residues bound to a metal center, a series of imidazole-containing scorpionate ligands and the associated Co and Ni complexes have been developed to investigate the bonding parameters of histidine containing active sites. The tris(2-imidazolyl) carbinol (2-TIC, 6) and tris[2-(N-methylimidazolyl)] carbinol (2-MeTIC, 7) complexes of Ni2+ and Co2+, namely [Co(2-MeTIC)2]Cl2 (8), [Co(2-MeTIC)2](NO3)2 (9), [Ni(2-MeTIC)2]Cl2 (10), [Ni(2-MeTIC)2](NO3)2 (11), [Co(2-TIC)2](NO3)2 (12), and [Ni(2-TIC)2](NO3)2 (13), have been prepared from the reaction of the appropriate ligand and appropriate metal salt in polar solvent. These complexes have been characterized by single crystal X-ray diffraction, spectroscopic techniques, and magnetic susceptibility. In each solid-state structure the metal center in the cation coordinates to three N atoms from two ligands and adopts a pseudo-octahedral coordination geometry. The X-ray characterization of tris[2-(N-methylimidazolyl)] carbinol is also reported.  相似文献   

10.
These experiments examined the effects of N-ethylmaleimide on insullin- and oxidant-stimulated sugar transport in soleus muscle in terms of the Thiol-Redox model for insulin-stimulated adipocyte sugar transport (Czech, M.P. (1976) J. Cell. Physiol. 89, 661–668). Brief exposure (1 min) to N-ethylmaleimide (0.3?10 nM) inhibited the stimulatory effect of insulin (0.1 U/ml) on D-[U-14C]xylose uptake by rat soleus muscle. N-Ethylmaleimide also inhibited the stimulatory effects of H2O2 (5 mM), diamide (0.2 mM) and vitamin K-5 (0.05 mM). This effect of N-ethylmaleimide on insulin was paralleled by the inhibition of 125I-labelled insulin binding by the muscle. N-ethylmaleimide lowered muscle ATP; however, its effects on sugar transport and 125I-labelled insulin binding could be dissociated from its effect on ATP. Exposing muscles to insulin prior to N-ethylmaleimide did not abolish the inhibitory effect of sulphydryl blockae on insulin-stimulated sugar transport, but did reduce the effect of the inhibitor by 20–30%. Conversely, when muscles were first allowed to bind 125I-labelled insulin and then exposed to the inhibitor, there was no effect of N-ethylmaleimide on pre-bound insulin. Exposure to diamide or vitamin K-5 before N-ethylmaleimide (1 mM) attenuated the inhibitory effet of sulphydryl blockade but no protective effect was observed with H2O2. None of the oxidants protected against the inhibitory effect of 3 nM N-ethylmaleimide. It is concluded that there are two N-ethylmaleimide-sensitive sites involved in the activation of muscle sugar transport at the post-receptor level. One of these would appear to be similar to the Thiol-Redox site described in the adipocyte; the other site appears to be an essential sulphydryl group whose function does not involve oxidation to a disulphide.  相似文献   

11.
1. Modification of the Class II sulphydryl groups on the (Na+ + K+)-ATPase from rectal glands of Squalus acanthias with N-ethylmaleimide has been used to detect conformational changes in the protein. The rates of inactivation of the enzyme and the incorporation of N-ethylmaleimide depend on the ligands present in the incubation medium. With 150 mM K+ the rate of inactivation is largest (k1 = 1.73 mM?1 · min?1) and four SH groups per α-subunit are modified. The rate of inactivation in the presence of 150 mM Na+ is smaller (k1 = 1.08 mM?1 · min-1) but the incorporation of N-ethylmaleimide is the same as with K+. 2. ATP in micromolar concentrations protects the Class II groups in the presence of Na+ (k1 = 0.08 mM?1 · min?1 at saturating ATP) and the incorporation id drastically reduced. ATP in millimolar concentrations protects the Class II groups partially in the presence of K+ (k1 = 1.08 mM?1 · min?1) and three SH groups are labelled per α subunit. 3. The K+ -dependent phosphatase is inhibited in parallel to the (Na+ + K+)-ATPase under all conditions, and the ligand-dependent incorporation of N-ethylmaleimide was on the α-subunit only. 4. It is shown that the difference between the Na+ and K+ conformations sensed with N-ethylmaleimide depends on the pH of the incubation medium. At pH 6 there is a very small difference between the rates of inactivation in the presence of Na+ and K+, but at higher pH the difference increases. It is also shown that the rate of inactivation has a minimum at pH 6.9, which suggests that the conformation of the enzyme changes with pH. 5. Modification of the Class III groups with N-ethylmaleimide-whereby the enzyme activity is reduced from about 16% to zero-shows that these groups are also sensitive to conformational changes. As with the Class II groups, ATP in micromolar concentrations protects in the presence of Na+ relative to Na+ or K+ alone. ATP in millimolar concentrations with K+ present increases the rate of inactivation relative to K+ alone, in contrast to the effect on the Class II groups. 6. Modification of the Class II groups with a maleimide spin label shows a difference between Class II groups labelled in the presence of Na+ (or K+) and Class II groups labelled in the presence of K + ATP, in agreement with the difference in incorporation of N-ethylmaleimide. The spectra suggest that the SH group protected by ATP in the presence of K+ is buried in the protein. 7. The results suggest that at least four different conformations of the (Na+ + K+)-ATPase can be sensed with N-ethylmaleimide: (i) a Na+ form of the enzyme with ATP bound to a high-affinity site (E1-Na-ATP); (ii) a Na+ form without ATP bound (E1-Na); (iii) a K+ form without ATP bound (E2-K); and (iv) an enzyme form with ATP bound to a low-affinity site in the presence of K+, probably and E1-K-ATP form.  相似文献   

12.
Electrospray (ESI) mass spectra analysis of acetonitrile solutions of a series of neutral chloro dimers, pincer type, and monomeric palladacycles has enabled the detection of several of their derived ionic species. The monometallic cationic complexes Pd[κ1-C1-N1-S-C(CH3S-2-C6H4)C(Cl)CH2N(CH3)2]+ (1a) and [Pd[κ1-C1-N1-S-C(CH3S-2-C6H4)C(Cl)CH2N(CH3)2](CH3CN)]+ (1b) and the bimetallic cationic complex [κ1-C1-N1-S-C(CH3S-2-C6H4)C(Cl)CH2N(CH3)2]Pd-Cl-Pd[κ1-C1-N1-S-C(CH3S-2-C6H4)C(Cl)CH2N(CH3)2]+ (1c) were detected from an acetonitrile solution of the pincer palladacycles Pd[κ1-C1-N1-S-C(CH3S-2-C6H4)C(Cl)CH2N(CH3)2](Cl) 1. For the dimeric compounds {Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](μ-Cl)}2 (2, Y=H and 3, CF3), highly electronically unsaturated palladacycles [Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2]+ (2d, 3d) and their mono and di-acetonitrile adducts, namely, [Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](CH3CN)]+ (2e, 3e) and [Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](CH3CN)2]+ (2f and 3f) were detected together with the bimetallic complex [Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2]-Cl-Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N](CH3)2]+ (2a, 3a) and its acetonitrile adducts [κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](CH3CN)Pd-Cl-Pd[ κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2]+ (2b, 3b) and [κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](CH3CN)Pd-Cl-Pd[κ1-C, κ1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2(CH3CN)]+ (2c, 3c). The dimeric palladacycle {Pd[κ1-C1-N-C(CH3O-2-C6H4)C(Cl)CH2N(CH3)2](μ-Cl)}2 (4) is unique as it behaves as a pincer type compound with the OCH3 substituent acting as an intramolecular coordinating group which prevents acetonitrile full coordination, thus forming the cationic complexes [(C6H4(o-CH3O)CC(Cl)CH2N(CH3)2OCN)Pd]+ (4b), [(C6H4(o-CH3O)CC(Cl)CH2N(CH3)2- κOCN)Pd(CH3CN)]+ (4c) and [(C6H4 (o-MeO)CC(Cl)CH2N(CH3)2O, κCN)Pd-Cl-Pd(C6H4(o-CH3O)CC(Cl)CH2N(CH3)2OCN)]+ (4a). ESI-MS spectra analysis of acetonitrile solutions of the monomeric palladacycles Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](Cl)(Py) (5, Y=H and 6, Y=CF3) allows the detection of some of the same species observed in the spectra of the dimeric palladacycles, i.e., monometallic cationic 2d-3d, 2e-3e and {Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](Py)}+ (5a, 6a) and {Pd[κ1-C1-N-C(Y-2-C6H4)C(Cl)CH2N(CH3)2](CH3CN)(Py)}+ (5b, 6b) and the bimetallic 2a, 3a, 2b, 3b, 2c and 3c. In all cationic complexes detected by ESI-MS, the cyclometallated moiety was intact indicating the high stability of the four or six electron anionic chelate ligands. The anionic (chloride) or neutral (pyridine) ligands are, however, easily replaced by the acetonitrile solvent.  相似文献   

13.
The ligand hydrotris(1,4-dihydro-3-methyl-4-phenyl-5-thioxo-1,2,4-triazolyl)borato (TrPh,Me) was synthetized as natrium salt and the complexes [Zn(TrPh,Me)2] · 7.5H2O · 1.5CH3CN (2a), [Zn(TrPh,Me)2] · 8DMF (2b), [Co(TrPh,Me)2] · 8DMF (3a), [Ni(TrPh,Me)2] · H2O · 6DMSO (4a), [Bi(TrPh,Me)2]NO3 (5), have been isolated and structurally characterized by X-ray diffraction. In the zinc derivatives the ligand adopts different denticity and coordination modes, η2 and [S2] for 2a and η3 and [N3] for 2b, depending on the crystallization solvent, giving rise to tetrahedral and octahedral geometry, respectively. In the octahedral cobalt and nickel complexes the ligand is η3 and [N3] coordinated whereas in the bismuth complex the η3 and [S3] coordination is exhibited.  相似文献   

14.
Reaction of the trivalent uranium complex (C5Me5)2U(O-2,6-iPr2C6H3)(THF) (1) with copper(I) chloride affords the corresponding tetravalent mixed-ligand aryloxide-chloride complex (C5Me5)2U(O-2,6-iPr2C6H3)(Cl) (2). The oxidative functionalization protocol cannot be extended to the synthesis of (C5Me5)2U(O-tBu)(Cl) (3) since the corresponding trivalent precursor is not stable. Salt metathesis between (C5Me5)2UCl2 and KOtBu is the method of choice for the preparation of the tetravalent alkoxide-chloride derivative (C5Me5)2U(O-tBu)(Cl) (3). The X-ray crystal structures of (C5Me5)2U(O-2,6-iPr2C6H3)(Cl) (2) and (C5Me5)2U(O-tBu)(Cl) (3) are reported and represent the first structurally characterized uranium(IV) metallocene aryloxide-chloride and alkoxide-chloride complexes, respectively. Both complexes adopt a pseudo-tetrahedral geometry, with a chloride and aryloxide/alkoxide ligand occupying the plane bisecting the metallocene unit.  相似文献   

15.
The reactivity of Mo(PMe3)6 towards 6-membered heterocyclic aromatic nitrogen compounds, namely pyridine, pyrazine, pyrimidine and triazine, has been investigated as part of an effort to define the coordination chemistry of molybdenum relevant to hydrodenitrogenation. For example, Mo(PMe3)6 reacts with pyridine to yield initially (η2-N,C-pyridyl)Mo(PMe3)4H, an uncommon example of an η2-pyridyl-hydride complex. The formation of (η2-N,C-pyridyl)Mo(PMe3)4H is reversible and treatment with PMe3 regenerates Mo(PMe3)6 and pyridine. At elevated temperatures, (η2-N,C-pyridyl)Mo(PMe3)4H dissociates PMe3 and converts to the η6-pyridine complex (η6-pyridine)Mo(PMe3)3. Pyrazine, pyrimidine and 1,3,5-triazine likewise react with Mo(PMe3)6 to yield (η2-N,C-pyrazinyl)Mo(PMe3)4H, (η2-N,C-pyrimidinyl)Mo(PMe3)4H and (η2-N,C-triazinyl)Mo(PMe3)4H, respectively. At elevated temperatures (η2-N,C-pyrazinyl)Mo(PMe3)4H and (η2-N,C-pyrimidinyl)Mo(PMe3)4H dissociate PMe3 and convert to (η6-pyrazine)Mo(PMe3)3 and (η6-pyrimidine)Mo(PMe3)3 in which the heterocycle coordinates to molybdenum in an unprecedented η6-manner.  相似文献   

16.
The rate of photosynthetic electron transport measured in the absence of ADP and Pi is stimulated by low levels of Hg2+ or Ag+ (50% stimulation ≈ 3 Hg2+ or 6 Ag+/100 chlorophyll) to a plateau equal to the transport rate under normal phosphorylating conditions (i.e. +ADP, +Pi). Chloroplasts pretreated in the light under energizing conditions with N-ethylmaleimide show a similar stimulation of non-phosphorylating electron transport. The stimulations of non-phosphorylating electron transport by Hg2+, Ag+ and N-ethylmaleimide are reversed by the CF1 inhibitor phlorizin, the CF0 inhibitor triphenyltin chloride, and can be further stimulated by uncouplers such as methylamine. The Hg2+ and N-ethylmaleimide stimulations, but not the Ag+ stimulation, are completely reversed by low levels of ADP (2 μM), ATP (2 μM), and Pi (400 μM). Ag+, which is a potent inhibitor of ATP synthesis, has little or no effect upon phosphorylating electron transport (+ADP, +Pi). Concomitant with the stimulations of non-phosphorylating electron transport by Hg2+, Ag+ and ADP + Pi, there is a decrease in the level of membrane energization (as measured by atebrin fluorescence quenching) which is reversed when the CF0 channel is blocked by triphenyltin. These results suggest that modification of critical CF1 sulfhydryl residues by Hg2+, Ag+ or N-ethylmaleimide leads to the loss of intra-enzyme coupling between the transmembrane protontransferring and the ATP synthesis activities of the CF0-CF1 ATP synthase complex.  相似文献   

17.
18.
Metal-sulfur complex fragments, to which small molecules like N2, N2H2, N2H4, NH3, or CO can bind, are desirable model compounds concerning enzymatic N2 fixation.This paper reports on the effects of the phosphane co-ligand on formation and reactivity of [Ru(L)(PR3)(`N2Me2S2')] [`N2Me2S2'2−=1,2-ethanediamine-N,N-dimethyl-N,N-bis(2-benzenethiolate)(2−)] complexes with nitrogenase relevant ligands, especially N2, N2H4, NH3, and CO.Treatment of [Ru(NCCH3)4Cl2] with Li2`N2Me2S2', excessive LiOMe, bulky PPh3 or PCy3, respectively, led to the formation of two series of [Ru(L)(PR3)(`N2Me2S2')] complexes [for R=Ph: 1b, 1c (L=NCCH3), 6b (L=N2H4), 7b (L=N2), 8b1-3 (L=CO), 9b (L=NH3); for R=Cy: 1a (L=NCCH3), 6a (L=N2H4), 7a (L=N2), 8a (L=CO), 9a (L=NH3)]. While the use of PPh3 (θ=145°) yielded cis,trans and cis,cis isomers of [Ru(NCCH3)(PPh3)(`N2Me2S2')] (1b, 1c), no isomer formation was observed with the bulkier phosphane PCy3 (θ=170°). Sterically less demanding phosphanes (θ=118-132°) afforded bisphosphane complexes [Ru(PR3)2(`N2Me2S2')] [2d (R=Me), 2e (R=Et), 2f (R=nPr), and 2g (R=nBu)], which were practically inert and could only be converted in two cases and under drastic reaction conditions into the CO complexes [Ru(CO)(PR3)(`N2Me2S2')] [4e (R=Et), 4f (R=nPr)]. The chelating bidentate phosphane dppe (bisdiphenylphosphanoethane) yielded exclusively the mononuclear complex [Ru(dppe)(`N2Me2S2')] (3).  相似文献   

19.
J.L. Daniel  D.J. Hartshorne 《BBA》1974,347(2):151-159
Myosin reacted with N-ethylmaleimide in the presence of ADP lost its ability to be activated by actin. Subfragment 1 behaved similarly. About 2 moles of N-ethylmaleimide per mole of Subfragment 1 were required to eliminate actin activation of the Mg2+-ATPase activity. At the point at which actin activation was lost the K+-EDTA-ATPase activity was also lost, but the Ca2+-activated ATPase activity was increased. Kinetic measurements indicated that the labelling with N-ethylmaleimide in the presence of ADP reduced V (the ATPase activity at infinite actin concentration) but did not effect Kapp (which is related to the dissociation constant of the actin-Subfragment 1 complex). The Mg2+-activated activity of the reacted myosin alone remained unaltered and the ability to bind actin was retained. We propose that the N-ethylmaleimide labelling blocked the actin activation by preventing the accelerated release of hydrolysis products from the myosin.  相似文献   

20.
Haemophilus influenzae 6-phosphogluconate dehydrogenase (6-phospho-d-gluconate:NADP+ 2-oxidoreductase (decar☐ylating), EC 1.1.1.44) was purified 308-fold to electrophoretic homogeneity with a 16% recovery through a five-step procedure involving salt fractionation and hydrophobic and affinity chromatography. The purified enzyme was demonstrated to be a dimer of Mr 70 000, and to catalyze a sequential reaction process. The enzyme was NADP-specific and kinetic parameters for the oxidation of 6-phosphogluconate were determined for NADP and four structural analogs of NADP. Coenzyme-competitive inhibition by adenosine derivatives was significantly enhanced by the presence of a 2′-phosphoryl group consistent with the observed coenzyme specificity of the enzyme. The purified enzyme was effectively inhibited by 3-aminopyridine adenine dinucleotide phosphate, but at concentrations higher than that observed to inhibit growth of the organism. Rates of inactivation of the enzyme by N-ethylmaleimide were suggestive of sulfhydryl involvement in the reaction catalyzed.  相似文献   

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