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1.
2 Deoxy D ribose (1) ,thesugarpartofDNA ,isoneofthemostimportantstartingmaterialnotonlyforthepreparationsofnucleosides ,nucleotides ,DNAandtheiranalogs,butalsoforthesynthesesofanumberofotherbio activecompounds .1Recentlyitsantipode 2 deoxy L ribose (2 )wasalsoattra…  相似文献   

2.
IntroductionSecondarybondingssuchashydrogenbondsandπ πinteractionsareimportantnon covalentintermolecularforces ,1whichcontributetoself assemblyprocesseswhenextendedstructuresareformedfromsimpleprecursors .Recentlymuchattentionhasbeenpaidtothehydrogenbond…  相似文献   

3.
IntroductionChiralityduetomethylbranchingisabundantamongseveralnaturallyoccuringsecondarymetabolites.Thisstructuralfeatureisparticularlypredominantamonginsectpheromones[1] ,manyofwhichareofeconomicsignificance .Asaconsequence ,aconsiderableefforthasbeenma…  相似文献   

4.
IntroductionHydrophobic lipophilicinteractions (HLI)playanimportantroleinchemicalandbiochemicalprocessessincewateristhecommonmediuminphysiologicalpro cesses.1 4 Somerecenteffortshavebeendedicatedtostudiesofhydrophobiceffectsonphotochemicalandpho tophysica…  相似文献   

5.
IntroductionPolyoxometalates (POMs)arealargeandrapidlygrowingclassofcompoundsthatgenerallyundergoaseriesofconsecutiveone ormulti electronreversibleredoxpro cesses.1 4 Thispropertymakesthemveryattractiveinelectrodemodification .SadakaneandSteckhan5havepre se…  相似文献   

6.
IntroductionThesupramolecularcomplexeformedbytheweakinteractions (electrostaticinteraction ,hydrogenbonds ,vanderWaalsforce ,short rangeexclusionforce ,etc .)ofmorethantwosortsofspeciesisanorganizingentitythatusuallypossessesspecialstructureandfunction .1Sup…  相似文献   

7.
IntroductionNitrogenasefromavarietyofN2-fixingorganismsiscomposedoftwo-componentprotein,MoFe-proteinandFe-protein.Fe-proteincontainsasingleFe4S4-cluster,whichhasthefunctionoftransferingelectronsfromdonortoMoFe-protein.MoFe-proteincontainsP-clusterpai…  相似文献   

8.
ChineseJournalofChemistryisaninternationaljournalpublishedinEnglishbytheChineseChemicalSocietywithitseditorialofficehostedbyShanghaiInstituteofOrganicChemistry , ChineseAcademyofSciences .ChineseJournalofChemistrypublishesoriginalresearchworkinallfield…  相似文献   

9.
ChineseJournalofChemistryisaninternationaljournalpublishedinEnglishbytheChineseChemicalSocietywithitseditorialofficehostedbyShanghaiInstituteofOrganicChemistry , ChineseAcademy ofSciences .ChineseJournalofChemistrypublishesoriginalre searchworkinallfie…  相似文献   

10.
ChineseJournalofChemistryisaninternationaljournalpublishedinEnglishbytheChineseChemicalSocietywithitseditorialofficehostedbyShanghaiInstituteofOrganicChemistry , ChineseAcademyofSciences .ChineseJournalofChemistrypublishesoriginalresearchworkinallfield…  相似文献   

11.
Conformation stabilities of intramolecular triple-helical DNAs (intra-tnplex DNAs: 5-d(TC)6-d(T)m-d(CT)6-d(C)n-d(AG)6-3',where m and n are chosen to be 4 and 3) have been examined by molecular mechanics.The four intra-triplexes (H-DNAs) are compared with the mtermolecular triplexes d(TC)6 * d ( AG)6 d(CT)6.The results revealed that loops do not significantly influence the mtratriplex conformations,loop conformations,however,depend partly on its length.Loop also makes strand Ⅱ of every intra-triplex DNA longer than that of the inter-triplex DNA.Most of residue sugar conformations of triple-helical DNAs are S-type,there aiso exist,however,N-type conformation and the conformations between S-type and N-type Possible models of the five triplex DNAs are presented.  相似文献   

12.
Tandem asymmetric double Michael addition/internal nucleophilic substitution of the novel chiral source, 5-(l-menthyloxy)-3-bromo-2(5H)-furanone with nucleophilic alcohol compounds has been investigated. The tandem asymmetric reaction can afford four new stereogenic centers with one reaction and give optically pure spiro-cyclopropane derivatives 5a--5d which are difficult to obtain by routine methods. The synthetic method for 5a--5d was studied in detail and the new compounds were identified on the basis of their analytical data and spectroscopic data, such as [α]~(20),IR,~1H NMR,~(13)C NMR, MS and elementary analysis. The absolute configuration of the sprio [5-l-menthyloxy-3-bromo butyrolactocyclopropane-3″, 3′(4′-methyloxy-5′-menthyloxybutyrolactone)] (5a) was established by X-ray crystallography. The work can provide important synthetic strategy in synthesis of some new optically active spiro-cyclopropane analogues and some biologically active molecules with complex structure.  相似文献   

13.
The thermal behaviour of binary mixtures between β-cyclodextrin (β-CD) and either carbamazepine polymorphic Form I (CBZ I), Form III (CBZ III) or dihydrate was investigated in order to assess possible interactions of CBZ solid phases with β-CD. Physical mixtures and kneaded binaries of β-CD and different CBZ crystal forms were studied by differential scanning calorimetry, thermogravimetric analysis and hot stage microscopy. The pattern of transition of CBZ Form III into Form I is strongly influenced by β-CD. The liquid-solid transition is practically absent when anhydrous CBZ/β-CD mixes are tested, as a consequence of an interaction between β-CD and liquid CBZ that hinders CBZ recrystallisation as Form I occurring after CBZ Form III melting. Water loss on heating of CBZ dihydrate in the presence of β-CD leads in all cases to the formation of CBZ Form I. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

14.
A new asymmetric oligobipyridine ligand, 1- (5’-methyl-2, 2’-bipyridin-5-y1)-2- (6’-methyl-2, 2’-bipyridin-6-yl)ethane (L), in which the bipyridine units are bridged by CH2CH2 at 5,6’-position has been synthesized. The ligand L reacts with Cu(I) and Cu(I1) ions giving double-stranded helical complexes [Cu 2 1 L2](C104)2.Et20 (1) and [Cu 2 II L2,(OH)(H20) ] [ClO4]3(2), respectively. Complexes 1 and 2 were characterized by X-ray diffraction analyses, ES-MS, ESR and cyclic voltammetry, etc. Differing from the oligobipyridine ligands bridged by CH2CH2 at 6,6’-or 5,5’-position, the ligand L not only forms a double-stranded helicate with Cu(1) ion, but also gives a double-stranded helicate with Cu(I1) ion. The results show that the linkage mode of the spacer group to the bipyridine units exerts a great impact on the formation of helix. Project supported by the National Natural Science Foundation of China (Grant NO. 29601003).  相似文献   

15.
三链DNA |dA10 2DT10的近红外付立叶拉曼光谱   总被引:1,自引:0,他引:1  
最近通过核磁共振、振动光谱和分子力学模拟研究表明,在溶液中三螺旋DNA的构象具有一定程度的复杂性和多样性.本文首次采用近红外付立叶拉曼光谱研究了三螺旋DNA dA10•2d10和相应的双螺旋DNA dA10•dT10在溶液中的构象.结果表明该三螺旋DNA同时存在C3’-内褶/反对称(A-型)和C2’-内褶/反对称(B-型)两种构象,而且在823cm-1处的较强谱带暗示还存在一种处于A和B构型之间的中间构型.对出现在1218cm-1和638cm-1处、归属于对糖环构象敏感的胸腺嘧啶残基的两个特征谱带进行分析,获得了除C2’-内褶构象外其它构型存在的证据.另外,双螺旋DNA的FT-Raman光谱表明该双螺旋DNA在溶液中以A-和B-两种构型共存.  相似文献   

16.
Conformational heterogeneity of the FAD cofactor in p-hydroxybenzoate hydroxylase (PHBH) was investigated with time-resolved polarized flavin fluorescence. For binary enzyme/substrate (analogue) complexes of wild-type PHBH and Tyr222 mutants, crystallographic studies have revealed two distinct flavin conformations; the ‘in’ conformation with the isoalloxazine ring located in the active site, and the ‘out’ conformation with the isoalloxazine ring disposed towards the protein surface. Fluorescence-lifetime analysis of these complexes revealed similar lifetime distributions for the ‘in’ and ‘out’ conformations. The reason for this is twofold. First, the active site of PHBH contains various potential fluorescence-quenching sites close to the flavin. Fluorescence analysis of uncomplexed PHBH Y222V and Y222A showed that Tyr222 is responsible for picosecond fluorescence quenching free enzyme. In addition, other potential quenching sites, including a tryptophan and two tyrosines involved in substrate binding, are located nearby. Since the shortest distance between these quenching sites and the isoalloxazine ring differs only little on average, these aromatic residues are likely to contribute to fluorescence quenching. Second, the effect of flavin conformation on the fluorescence lifetime distribution is blurred by binding of the aromatic substrates: saturation with aromatic substrates induces highly efficient fluorescence quenching. The flavin conformation is therefore only reflected in the small relative contributions of the longer lifetimes.  相似文献   

17.
The13C NMR spectra of chelate complexes of nucleosides with Mn(II) under fast-exchange conditions have been studied. It has been established that the state of the conformational equilibrium of the ribose ring within the framework of the two-sided exchange 2′-endo (S) ⇆ 3′-endo (N) can easily be evaluated from the broadening of the C-1′ and C-4′ signals. The results obtained by the broadening method agree well with those of methods used previously. All-Union Scientific-Research Institute of Applied Biochemistry, Olaine. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 678–680, September–October, 1980.  相似文献   

18.
The an­hydrous form, (I), of the title compound, (?)‐2‐(1,2,3,4,4a,7‐hexa­hydro‐4a,8‐di­methyl‐1,7‐dioxo‐2‐naphthyl)­propionic acid, C15H18O4, derived from a naturally occurring sesquiterpenoid, has two mol­ecules in the asymmetric unit, (I) and (I′), differing in the conformations of the saturated ring and the carboxyl group. The compound aggregates as carboxyl‐to‐ketone hydrogen‐bonding catemers [O?O = 2.776 (3) and 2.775 (3) Å]. Two crystallographically independent sets of single‐strand hydrogen‐bonding helices with opposite end‐to‐end orientation pass through the cell in the b direction, one consisting exclusively of mol­ecules of (I) and the other entirely of (I′). Three C—H?O=C close contacts are found in (I). The monohydrate, C15H18O4·H2O, (II), with two mol­ecules of (I) plus two water mol­ecules in its asymmetric unit, forms a complex three‐dimensional hydrogen‐bonding network including acid‐to‐water, water‐to‐acid, water‐to‐ketone, water‐to‐water and acid‐to‐acid hydrogen bonds, plus three C—H?O=C close contacts. In both (I) and (II), only the ketone remote from the acid is involved in hydrogen bonding.  相似文献   

19.
Interaction of metal complexes with nucleic acids is currently attracting wide attention due to their potential utility as drugs, regulators of gene expression and tools for molecular biology. Many metal complexes exhibit nucleolytic activity, the most important examples being Cu(II)-OP, Fe(H)-BLM, Fe(II)-EDTA, metalloporphyrins, Ru and Co complexes of 4,7-diphenyl-l,10-phenanthroline and more recently by Ni(II) complexes. Desferal, a well known siderophore and a highly effective drug in chelation therapy of iron overload diseases, forms a stable octahedral co-ordination Fe(III) complex Eerrioxamine B. We have been interested in the DNA damaging properties of metallodesferals and this paper describes the DNA cleaving ability of metallodesferals, metal-dependent base selectively in DNA scission reactions, mechanistic studies on DNA cleavage by CuDFO and targetting of DNA cutting by covalent MDFO conjugates. This paper reports the synthesis of Cu(II), Co (III) and Ni(II) complexes of a siderophore chelating drug desferal, the studies on cleavage of plasmid DNA, the sequence preference of cleavage reactions, and C1’ as the primary site of hydroxyl radical attack in the reactions. Oligonucleotides covalently linked with this molecular scissor can direct the cleavage of either single or double strand DNA’s, mediated by duplex or triple helix structures respectively. Such targetting of DNA cleavage reactions, mediated by oligonucleotide-Cu(II)/Co(III) desferal conjugates has demonstrated reasonable site specificity and efficiency  相似文献   

20.
The 11-undecanolide enthalpy of vaporization is obtained from the temperature dependence of the vapor pressure measured by transpiration. A conformational analysis of 8-octanolide (I), 11-undecanolide (II), and 13-tridecanolide (III) is performed. Quantum-chemical calculations are performed to study the moments of inertia, vibrational spectra, and most favorable conformations. The ideal gas thermodynamic properties of these compounds in the temperature range of 0-1500 K are determined. A procedure for the additive determination of polynomial coefficients for temperature-dependent properties is developed to assess the thermochemical data for lactones, lactides, and carboxylic hydroxyacids at 298.15–1000 K.  相似文献   

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