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1.
Wen Guo Xu Yuan Chun Zhang Shi Xiang Lu Rui Chun Zhang 《Journal of molecular modeling》2009,15(11):1329-1336
The equilibrium geometries, total energies, and vibrational frequencies of anions X2Y2
− (X = C, Si, Ge and Y = N, P, As) are theoretically investigated with density functional theory (DFT) method. Our calculation
shows that for C2N2
− species, the D
2h
isomer is the most stable four-membered structure, and for other species the C
2v
isomer in which two X atoms are contrapuntal is the most stable structure at the B3LYP/6-311 +G* level. Wiberg bond index (WBI) and negative nucleus-independent chemical shift (NICS) value indicate the existence of delocalization
in stable X2Y2
− structures. A detailed molecular orbital (MO) analysis further reveals that stable isomers of these species have strongly
aromatic character, which strengthens the structural stability and makes them closely connected with the concept of aromaticity. 相似文献
2.
《Carbohydrate research》1998,310(4):229-238
Eight positional isomers of 61,6m-di-O-α-d-mannopyranosyl-cyclomaltooctaose (γCD) (m=2–5) and 6-O-α-(n-O-α-d-mannopyranosyl)-d-mannopyranosyl-γCD (n=2, 3, 4, and 6) in a mixture of products from γCD and d-mannose by condensation reaction of α-mannosidase from jack bean were isolated by HPLC. The structures of four isomers of 6-O-α-(n-O-α-d-mannopyranosyl)-d-mannopyranosyl-γCD were elucidated by NMR spectroscopy. On the other hand, four positional isomers of 61,6m-di-O-α-d-mannopyranosyl-γCD were determined by LC–MS analysis of degree of polymerization of the branched oligosaccharides produced by enzymatic degradation with bacterial saccharifying α-amylase (BSA), and combination of BSA and glucoamylase. Similarly cyclomaltodextrin glucanotransferase also digested these isomers. 相似文献
3.
The structure and stability of neutral polyoxometalate cages (Mo2O6)m (m=1-13) have been computed systematically. These neutral cages can be viewed topologically as polyhedra containing triangles (f3) and squares (f4). The relative stability of these polyhedra is associated with the location and separation of the f3. The initial stable isomers were preselected by the number of shared triangle edges (N33), and the predicted stability was validated further at the GGA-PW91/DND level of density function theory with the fine quality of mesh size. For large clusters, the square neighbor signature (P4444), which is similar to the hexagon neighbor rule for fullerene, becomes more applicable. The calculated disproportionation energies indicate that Mo6O18 (O(h), Lindqvist), Mo12O36 (O(h), alpha Keggin), Mo18O54 (D(3h), Wells-Dawson) and Mo24O72 (O(h)) cages have enhanced stability. [structure in text]. Mo6O18 (O(h)), Mo12O36 (O(h)), Mo18O54 (D(3h)) and Mo(24)O72 (O(h)) are the most stable neutral polyoxometalate cages on the basis of the structural and energetic criteria. They can therefore be considered as the inorganic fullerenes. 相似文献
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6.
Shu-Jing Li Yao Qi Jing-Jing Zhao Ya Li Xiao-Yan Liu Xian-Hua Chen Ping Xu 《The Journal of biological chemistry》2013,288(13):8898-8909
The serine/arginine-rich (SR) proteins are one type of major actors in regulation of pre-mRNA splicing. Their functions are closely related to the intracellular spatial organization. The RS domain and phosphorylation status of SR proteins are two critical factors in determining the subcellular distribution. Mammalian Transformer-2β (Tra2β) protein, a member of SR proteins, is known to play multiple important roles in development and diseases. In the present study, we characterized the subcellular and subnuclear localization of Tra2β protein and its related mechanisms. The results demonstrated that in the brain the nuclear and cytoplasmic localization of Tra2β were correlated with its phosphorylation status. Using deletional mutation analysis, we showed that the nuclear localization of Tra2β was determined by multiple nuclear localization signals (NLSs) in the RS domains. The point-mutation analysis disclosed that phosphorylation of serine residues in the NLSs inhibited the function of NLS in directing Tra2β to the nucleus. In addition, we identified at least two nuclear speckle localization signals within the RS1 domain, but not in the RS2 domain. The nuclear speckle localization signals determined the localization of RS1 domain-contained proteins to the nuclear speckle. The function of the signals did not depend on the presence of serine residues. The results provide new insight into the mechanisms by which the subcellular and subnuclear localization of Tra2β proteins are regulated. 相似文献
7.
Reaction of the ligand N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine (mpppa) with equimolar amounts of [Cu(H2O)6][ClO4]2 or CuCl2 · 2H2O in MeCN afforded mononuclear copper(II) complexes [Cu(mpppa)][ClO4]2 (1) and [Cu(mpppa)Cl2] (2). Crystal structure analysis reveals CuN3O (two pyridyl, an aliphatic amine, and an amide oxygen) coordination in 1 and CuN3Cl2 (two pyridyl, an aliphatic amine, and two chlorides) coordination in 2. Crystal packing diagram of 1 reveals that one of the perchlorate counteranions provides weak coordination to copper(II) centers and in turn the copper(II) centers assume pseudo-six-coordination, generating 1D chain. Notably, one of the copper(II)-coordinated chloride ions in 2 participates in an intramolecular N–H?Cl interaction. Intermolecular C–H?Cl interactions in the solid state generate helical structure. Spectroscopic (IR, UV–Vis, and EPR) and redox properties of the two complexes have been investigated and compared. 相似文献
8.
Takayuki Oritani Kyohei Yamashita 《Bioscience, biotechnology, and biochemistry》2013,77(10):1965-1971
By microorganisms or esterase they produce, (±)-1 and 2-decalyl acetates were asymmetrically hydrolyzed to (?)-1-(R)-trans,cis-1-decalol (IIa), (+)-1-(S)-cis,cis-1-decalol (IIIb), (+)-1-(R)-cis,trans-1-decalol (IVa) and (+)-1-(S)-trans,trans-2-decalol (VIIb), (?)-cis,cis-2-decalol (IXb) with the acetates of their antipodes, whereas the axial acetates of (±)-decalols were scarecely hydrolyzed. 相似文献
9.
L. A. Pershina O. M. Numerova L. I. Belova E. P. Devyatkina T. S. Rakovtseva V. K. Shumny 《Russian Journal of Genetics》2004,40(5):510-514
The fertility characteristics expressed during morphogenesis in first-generation self-pollinated backcrossed progenies (BC1) obtained from amphiploid barley–wheat hybrids [Hordeum geniculatum All. (2n= 28) ×Triticum aestivum L. (2n= 42)] (2n = 70) backcrossed with common wheat were studied. It was found that, in the case of self-pollination of BC1 plants, karyotype stabilization leads to the formation of alloplasmic euploid (2n = 42), telocentric substitution (2n = 40 + 2t), and telocentric addition (2n = 42 + t), (2n = 42 + 2t) plant forms, which may serve as the sources of the respective alloplasmic lines of common wheat. That the expression of fertility characters in BC1F8plants was shown to depend on growth conditions. The main mechanism of hybrid incompatibility of BC1F1–BC1F8plants was expressed as grass-clump dwarfism. 相似文献
10.
Lee B Kwak JH Huang SW Jang JY Lim S Kwak YS Lee K Kim HS Han SB Hong JT Lee H Song S Seo SY Jung JK 《Bioorganic & medicinal chemistry》2012,20(9):2860-2868
A series of novel 4-O-methylhonokiol analogs were synthesized in light of revealing structure-activity relationship for inhibitory effect of COX-2 enzyme. The key strategy of the molecular design was oriented towards modification of the potential metabolic soft spots (e.g., phenol and olefin) or by altering the polar surface area via incorporating heterocycles such as isoxazole and triazole. Most of all exhibited the inhibitory effects on COX-2 and PGF(1) production but not macrophage NO production. Especially, aryl carbamates 10 and 11 exhibited more potent inhibitory activity against COX-2 and PGF(1) production. 相似文献
11.
The physicochemical and biological properties of the new branched cyclomaltooligosaccharides (cyclodextrins; CDs), 2-O-α-D-galactosyl-cyclomaltohexaose (2-O-α-D-galactosyl-α-cyclodextrin, 2-Gal-αCD) and 2-O-α-D-galactosyl-cyclomaltoheptaose (2-O-α-D-galactosyl-β-cyclodextrin, 2-Gal-βCD), were investigated. The formation of inclusion complexes of 2-Gal-CDs with various kinds of guest compounds (clofibrate, cholesterol, cholecalciferol, digitoxin, digitoxigenin, and prostaglandin A(1)) was examined by a solubility method, and the results were compared with those of non-branched CDs and other 6-O-glycosyl-CDs such as 6-O-α-D-galactosyl-CDs, 6-O-α-D-glucosyl-CDs, and 6-O-α-maltosyl-CDs. The inclusion abilities of 2-Gal-αCD for clofibrate and prostaglandin A(1), and 2-Gal-βCD for clofibrate, cholecalciferol, cholesterol, and digitoxigenin were markedly weaker than those of non-branched CD and other 6-O-glycosyl-CDs in each series, probably because of a steric hindrance caused by the α-(1→2)-galactoside linkage. The hemolytic activities of 2-Gal-CDs on human erythrocytes were the lowest among each CD series, and the compounds showed negligible cytotoxicity towards Caco-2 cells up to at least 100mM. 相似文献
12.
G. Andrei R. Snoeck J. Balzarini E. De Clercq 《Nucleosides, nucleotides & nucleic acids》2013,32(3-5):559-562
Abstract Combinations of high concentrations of AZT with BVDU, acyclovir (ACV) or ganciclovir (GCV) show antagonism against TK+ HSV-1, but not TK+ VZV strains, in cell cultures. When BVDU and AZT were used in combination against TK? HSV-1, TK? HSV-2 and TK? VZV strains, a pronounced inhibition of viral replication was observed. This potentiating effect was not seen if AZT was combined with ACV or GCV. 相似文献
13.
The structure and conformational stability of vinyl selenonyl fluoride, chloride and bromide CH2=CH–SeO2X (X is F, Cl and Br) were investigated using density functional B3LYP/6-311+G** and ab initio MP2/6-311+G** calculations. From the calculations the molecules were predicted to exist only in the non-planar gauche
conformation with the vinyl C=C group almost eclipsing one of the selenonyl Se=O bonds as a result of conjugation between the two moieties. Single-minimum potential scans were calculated at the DFT level for the molecules. The vibrational frequencies were computed using B3LYP/6-311+G**. Normal coordinate calculations were then carried out and potential energy distributions were calculated for the three molecules in the
gauche conformation.Figure Potential function for the asymmetric torsion in vinyl selenonyl fluoride (dotted line), chloride (dashed line) and bromide (solid line) as determined at the DFT-B3LYP/6-311+G** level 相似文献
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15.
Yasuhiro Yamada Tomio Emori Shinichi Kinoshita Hirosuke Okada 《Bioscience, biotechnology, and biochemistry》2013,77(3):649-652
(±)-Azetidine-2-carboxylic acid and 3-substituted-2-pyrrolidinones were synthesized from 2-pyrrolidinone via 3-bromo-2-methoxy-1-pyrroline (IIIa). The bromide (IIIa) was obtained by the bromination of 2-methoxy-l-pyrroline using NBS. 相似文献
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17.
《Bioscience, biotechnology, and biochemistry》2013,77(11):1807-1809
(±)-Homosarkomycin (2) and (±)-rosaprostol (3) were synthesized from (±)-methyl 2-oxo-bicyclo[3.1.0]hexane-1-carboxylate (1) by using the nucleophilic ring opening reaction on the double-activated cyclopropane ring as the key step. 相似文献
18.
Yasuhiro Yamada Kota Hatano Masanao Matsui 《Bioscience, biotechnology, and biochemistry》2013,77(10):1536-1540
(±)-Lamprolobine, the (+)-enatiomer of which was isolated from the leaves of Lamprolobium fruticosum, and (±)-epilamprolobine were synthesized from δ-valerolactam. 相似文献
19.
Yuichi Yoshimura Hiroshi Satoh Shinji Sakata Noriyuki Ashida Shuichi Miyazaki Akira Matsud 《Nucleosides, nucleotides & nucleic acids》2013,32(3-5):427-429
Abstract 2′-C-Cyanomethyl-2′-deoxy-arabinosylcytosine 3 and 2′-C-azidomethyl-2′-deoxy-arabinosylcytosine 4 were synthesized from uridine. The antineoplastic activities of these compounds were evaluated. 相似文献
20.
Two dinuclear iron(III) complexes with tetradentate N-donor ligand 1,4-di(2′-pyridyl)aminophthalazine (PAP), [Fe2(μ-OMe)2(PAP)Cl4] (2) and [Fe2(μ-OMe)2(PAP)(OAc)4] (3) were prepared and characterized. Single crystal X-ray molecular structure of [Fe2(μ-OMe)2(PAP)Cl4] · 2MeOH have been elucidated. The six-coordinate iron atoms are in distorted octahedral environment bridged by the oxygen atoms of two methoxy groups and the PAP ligand. The Mössbauer spectra of both complexes show one quadrupole doublet and the isomer shift and quadrupole splitting values indicate the presence of octahedral high-spin FeIII ions. Complex 2 showed catalytic activity for alkane oxidation with hydrogen peroxide. 相似文献