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1.
Methanetrisphosphonic acids provide a branch point for synthetic nucleotide analogues which can be exploited either to generate novel tripodal nucleotides or to incorporate additional negative charge into linear analogues relative to the parent nucleotide, as exemplified in the picture for ATP and diadenosine tetraphosphate (Ap4A). These compounds show valuable discriminatory behavior as competitive inhibitors for the tumor suppressor protein Fhit and a second ApnA pyrophosphohydrolase. X=H, Cl, F.  相似文献   

2.
4‐Methyl‐2‐((trimethylsilyl)amino)pyridine (ApTMSH) was synthesized via a salt metathesis reaction. Lithiation of ApTMSH with n‐BuLi afforded the transmetallation agent [(ApTMS)2Li2(OEt2)2] ( 1 ) which was structurally characterized. Reaction of 1 with AgCl and [AuCl(tht)] (tht = tetrahydrothiophene) at low temperatures in THF yielded homoleptic aminopyridinates of the heavier group 11 metals, namely [(ApTMS)6Ag6] ( 2 ) and [(ApTMS)4Au4] ( 3a and b ) after work‐up in hexane. All compounds were characterized by X‐ray crystal structure analysis. The quality of the structure determination of 3a allows establishing the connectivity only. The lithium complex 1 shows the expected structure from analogous compounds. The hexameric silver compound shows a new structural motif for silver aminopyridinates. The six‐membered ring of silver atoms has a chair conformation. Compounds 3a and b are the first homoleptic gold aminopyridinates and exhibit a rhombic arrangement of the four gold atoms.  相似文献   

3.
The enzymatic cleavage of a scissile P O bond can be blocked by recourse to phosphonate analogues of biological phosphate esters. α-Fluorophosphonates have an enhanced electronegativity at the bridging carbon, which, in many cases, makes them superior to simple methylene phosphonates for the study of enzyme reactions. Thus, the β,γ-difluoro-methylene analogue of ATP is a good substrate for the interferon-induced (2→5)An synthetase, which converts it into a (2→5)A4 species having a 5′-β,γ-difluoromethylenetriphosphate. This binds strongly to RNase L but does not activate it. The unsymmetrical Ap4Aases from Artemia and Lupin are strongly inhibited by P1,P4-dithiophosphate analogues of diadenosyl-5′,5‴-P1,P4-tetraphosphate although nonregiospecific cleavage of certain P2,P3-methylene analogues can be observed. Some of these analogues are remarkably effective inhibitors of platelet aggregation and are effective inhibitors in vivo of arterial blood-clotting in rabbits. Separation of all diastereoisomers of P1,P4-dithiophosphate analogues of Ap4A is achieved cleanly using reverse-phase hplc chromatography and this provides direct access to β,γ-CHF-bridged analogues of ATP with resolved stereochemistry at the CHF center. Lastly, growing cells of Dictyostelium discoideum not only tolerate a range of substituted methylene bisphosphonates in their growth medium but actually incorporate them into nucleotide analogues of ATP and Ap4A.  相似文献   

4.
5.
A detailed investigation on resorcinol as the Belousov–Zhabotinsky (BZ) oscillator in manganese(II) ion catalyzed reaction system with inorganic bromate (oxidant) and acetone (cosubstrate) was carried out in aqueous sulfuric acid medium (1.3 M). The aforesaid reagents were mixed with various concentrations to evolve the effective concentrations at which the reaction system exhibited better oscillations. The various oscillatory parameters such as time period (tp), induction period (tin), frequency (v), amplitude (A), and number of oscillations (n) were derived, and the dependence of concentration of the reacting species on these oscillatory parameters was interpreted on the basis of the Field–Koros–Noyes mechanism. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 650–657, 2009  相似文献   

6.
A new heme–thiolate peroxidase catalyzes the hydroxylation of n‐alkanes at the terminal position—a challenging reaction in organic chemistry—with H2O2 as the only cosubstrate. Besides the primary product, 1‐dodecanol, the conversion of dodecane yielded dodecanoic, 12‐hydroxydodecanoic, and 1,12‐dodecanedioic acids, as identified by GC–MS. Dodecanal could be detected only in trace amounts, and 1,12‐dodecanediol was not observed, thus suggesting that dodecanoic acid is the branch point between mono‐ and diterminal hydroxylation. Simultaneously, oxygenation was observed at other hydrocarbon chain positions (preferentially C2 and C11). Similar results were observed in reactions of tetradecane. The pattern of products formed, together with data on the incorporation of 18O from the cosubstrate H218O2, demonstrate that the enzyme acts as a peroxygenase that is able to catalyze a cascade of mono‐ and diterminal oxidation reactions of long‐chain n‐alkanes to give carboxylic acids.  相似文献   

7.
In this work we consider the equilibrium state of a multicomponent system in which chemical reactions occur, and its sensitivity to the change of any of the thermodynamic parameters influencing the equilibrium. A general expression is obtained for the sensitivity coefficientn i/Y, wheren i is the equilibrium amount of theith chemical species in the system, andY is a thermodynamic parameter such as temperature, pressure, initial amount of a species, chemical potential of a species, etc. We demonstrate that the sensitivity coefficients are linear combinations of contributions originating from certain special reactions, called response reactions, which are defined in the paper.  相似文献   

8.
Sensitive and rapid detection of multiple analytes and the collection of components from complex samples are important in fields ranging from bioassays/chemical assays, clinical diagnosis, to environmental monitoring. A convenient strategy for creating magnetically encoded luminescent CdTe@SiO2@n Fe3O4 composite nanoparticles, by using a layer‐by‐layer self‐assembly approach based on electrostatic interactions, is described. Silica‐coated CdTe quantum dots (CdTe@SiO2) serve as core templates for the deposition of alternating layers of Fe3O4 magnetic nanoparticles and poly(dimethyldiallyl ammonium chloride), to construct CdTe@SiO2@n Fe3O4 (n=1, 2, 3, …?) composite nanoparticles with a defined number (n) of Fe3O4 layers. Composite nanoparticles were characterized by zeta‐potential analysis, fluorescence spectroscopy, vibrating sample magnetometry, and transmission electron microscopy, which showed that the CdTe@SiO2@n Fe3O4 composite nanoparticles exhibited excellent luminescence properties coupled with well‐defined magnetic responses. To demonstrate the utility of these magnetically encoded nanoparticles for near‐simultaneous detection and separation of multiple components from complex samples, three different fluorescently labeled IgG proteins, as model targets, were identified and collected from a mixture by using the CdTe@SiO2@n Fe3O4 nanoparticles.  相似文献   

9.
We report efficient, one-flask procedures for the synthesis of a family of 14 analogs of AZTp4A and Ap4A containing BH3, S, or Se, along with two bisphosphonate analogs of Ap4A. These compounds should slow unwanted enzymatic hydrolysis and have the potential to create unique binding interactions in biochemical and structural studies of the excision reaction responsible for resistance of HIV-1 to AZT, as well as assist in drug design.  相似文献   

10.
Summary Theoretical calculation of95Mo-NMR chemical shifts for [MoO4–n S n ]2– (n=0–4) compounds is reported here for the first time on the basis of Fenske-Hall method and Sum-Over-State (SOS) perturbation theory. A systematic decrease in shielding of95Mo nuclei with increase of number of sulfur in [MoO4–n S n ]2–, which is observed experimentally, can be reasonably explained by our calculation. A good linear relationship between chemical shifts of calculation and experiment is obtained. The electronic structure and bonding in these compounds are also discussed.Supported by Nature Science Foundation of China  相似文献   

11.
Linear and nonlinear halogen dependencies of the 13C magnetic shielding constants of CH4−nIn, CH4−nBrn, CCl4−nIn, and CBr4−nIn were fairly reproduced by the ab initio generalized unrestricted Hartree–Fock (GUHF)/finite perturbation (FP) method including spin‐orbit (SO) interaction and spin‐free relativistic (SFR) terms. As seen from the experimental trends, the calculated 13C chemical shifts in CCl4−nIn and CBr4−nIn depend linearly on n=0–4, while those in CH4−nIn and CH4−nBrn depend nonlinearly. We found that both the linear and nonlinear dependencies are due to the relativistic effects, and especially due to the Fermi–Contact (FC) term originating from the SO interaction. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 528–536, 2001  相似文献   

12.
Treatment of 6,7-dimethyl-2,3-diphenylquinoxaline with sodium in tetrahydrofuran formed a monomeric dianion. The chemical behavior of this dianion was investigated by a variety of reagents. As the result, alkylation reactions gave 1,2-dihydro derivatives, while acylation reactions occured at 1,4-positions. Annulation of the pyrazine ring system was accomplished by treating the dianion with oligomethylene dichlorides, Cl(CH2) n Cl, n = 2–4.  相似文献   

13.
This paper presents the synthesis, physico‐chemical and biological properties of four new coordination compounds with mixed ligands: acrylate ion (acr) and benzimidazole/benzimidazole derivatives with the general formula [Co(L) 2 (acr) 2 nH 2 O [ (1) L: benzimidazole (HBzIm), n: 0.5; (2) L: 2‐methylbenzimidazole (2‐MeBzIm), n: 0.5; (3) L: 5‐methylbenzimidazole (5‐MeBzIm), n: 0; (4) L: 5,6‐dimethylbenzimidazole (5,6‐Me2BzIm), n: 0]. Their chemical formulae were achieved correlating the chemical analysis with mass spectrometry data, the ligands coordination modes were assigned by Fourier transform‐infrared measurements, and the trigonal bipyramidal geometry of cobalt ion in complexes was assigned by data correlation of UV–Vis‐NIR spectra and magnetic moments measurements. Single‐crystal X‐ray diffraction reveals a mononuclear structure with a pentacoordinated cobalt (II) ion, connected to two acrylato coordinated in different modes and two unidentate 5,6‐dimethylbenzimidazole ligands for compound (4) . The biological tests were performed against several microbial strains, the cytotoxicity was evaluated on HCT8 cellular lines and the cell cycle analysis was performed on HT29 cellular lines. Microbiological assays indicated that Co (II) complexes present a very good to good activity against Candida albicans 1760, Enterococcus faecium E5, Bacillus subtilis ATCC 6683 and Escherichia coli ATCC 25922. Predictive pharmacokinetic (ADME), toxicity and drug‐likeness profiles were evaluated for Co (II) complexes. Our results highlight that Co (II) complexes depicted in the present study are suitable to be used as efficient pharmacological agents.  相似文献   

14.
Abstract

A general method for synthesis of 3-phosphorylated phosphatidylinositols is described.

Phosphatidylinositol (PI) and phosphatidylinositol phosphates (PIPn), such as PI-4-P, PI-4,5-P2 undergo receptor-mediated cleavage by phosphatidylinositol-specific phospholipase C, and are precursors of second messengers important in diverse cellular signaling pathways. In contrast, the 3-phosphorylated phosphatidylinositols, such as PI-3-P (1), PI-3,4-P2 (2) and PI-3,4,5-P3 (3), which are formed in response to signals of growth factors, are resistant to hydrolysis by this enzyme, and their cellular function is only beginning to emerge [1,2]. These compounds are formed in minute quantities, and therefore have to be synthesized for many practical applications.  相似文献   

15.
16.
The possible geometrical structures and relative stability of silicon–sulfur clusters (SiS2) (n=1–6) are explored by means of density functional theory (DFT) quantum chemical calculations. We also compare DFT with second‐order Møller–Plesset (MP2) and Hartree–Fock (HF) methods. The effects of polarization functions, diffuse functions, and electron correlation are included in MP2 and B3LYP quantum chemical calculations, and B3LYP is effective in larger cluster structure optimization, so we can conclude that the DFT approach is useful in establishing trends. The electronic structures and vibrational spectra of the most stable geometrical structures of (SiS2)n are analyzed by B3LYP. As a result, the regularity of the (SiS2)n cluster growing is obtained, and the calculation may predict the formation mechanism of the (SiS2)n cluster. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 81: 280–290, 2001  相似文献   

17.
The syntheses of fluorinated vinyl ethers (H2C?CHOCH2CH2CnF2n+1, n = 6 or 8) and their copolymerizations with bis(4‐vinyloxybutyl) isophthalate are reported. The fluorinated monomers were prepared by the transetherification of ethyl vinyl ether and fluorinated alcohols in a 75% yield. Added in low concentrations (0.1–3.0 wt %) to formulations containing bis(4‐vinyloxybutyl) isophthalate, they did not affect the kinetics of the cationic photopolymerization. The cured films were transparent and showed interesting properties in terms of wettability, hardness, cross‐cut adhesion, and chemical inertness. The fluoromonomers increased the hydrophobicity of the film surface, whereas the adhesion on various substrates such as glass and wood was unchanged. An increase in the methyl ethyl ketone resistance was also observed. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2890–2897, 2003  相似文献   

18.
Abstract

For pure sodium polyphosphates, Na n + 2P n O3n + 1, exhibiting 3 through 6 phosphorus atoms per molecule, the 31P chemical shift of the middle group phosphorus atoms as measured in aqueous solution (0.1 M in P) at pH 7 was seen to increase with increasing magnesium ion concentration until there was one Mg atom per polyphosphate molecule, after which the chemical shift decreased. Finally the rate of decrease diminishes and precipitation occurs. For the longer-chain phosphates, Na n + 2P n O3n + 1 with n = 8, 9, 10, or an average of 100, as well as for the ring phosphates, Na n P n O3n for n ranging from 3 through 10, an increase in magnesium concentration simply leads to a decrease in chemical shift which diminishes at the higher concentrations. These data lend additional support to the concept that polymerized phosphate anions in solution exist in preferred conformations which depend on the nature of the counteraction.  相似文献   

19.
Ternary clusters (NH3)·(H2SO4)·(H2O)n have been widely studied. However, the structures and binding energies of relatively larger cluster (n > 6) remain unclear, which hinders the study of other interesting properties. Ternary clusters of (NH3)·(H2SO4)·(H2O)n, n = 0-14, were investigated using MD simulations and quantum chemical calculations. For n = 1, a proton was transferred from H2SO4 to NH3. For n = 10, both protons of H2SO4 were transferred to NH3 and H2O, respectively. The NH4+ and HSO4 formed a contact ion-pair [NH4+-HSO4] for n = 1-6 and a solvent separated ion-pair [NH4+-H2O-HSO4] for n = 7-9. Therefore, we observed two obvious transitions from neutral to single protonation (from H2SO4 to NH3) to double protonation (from H2SO4 to NH3 and H2O) with increasing n. In general, the structures with single protonation and solvated ion-pair were higher in entropy than those with double protonation and contact ion-pair of single protonation and were thus preferred at higher temperature. As a result, the inversion between single and double protonated clusters was postponed until n = 12 according to the average binding Gibbs free energy at the normal condition. These results can serve as a good start point for studies of the other properties of these clusters and as a model for the solvation of the [H2SO4-NH3] complex in bulk water.  相似文献   

20.
The experimental approaches to estimation of comparative electronegativity and chemical hardness of organometallic groups have been proposed. Qualitative data on the electronegativity of L nM groups were obtained from 19F NMR study of model systems 4‐FC6H4QMLn (Q = CC, N(R), O, C(O)O, S), (4‐FC6H4)3 SnML n and (4‐FC6H4)3SnQML n (Q = O, S), containing a great variety of different organometallic groups containing transition or heavy main‐group metals. The data on chemical hardness of L nM groups were obtained from NMR study of distribution of different L nM groups between hard and soft anions. The following basic results have been obtained. (1) The relative electronegativity and chemical hardness of L nM groups can change in parallel or not with the electronegativity and hardness of the central metal atom. (2) The substituents in Ar can substantially modify electronegativity and hardness of Ar nM groups; the influence of Ar groups has an inductive nature; the increase in electron‐donating ability of aryl ligands enhances the hardness of Ar nM cations. (3) The relative electronegativity and hardness of L nM groups in L nMX are invariant and do not depend on X.  相似文献   

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