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201.
Transition metal complexes that reversibly bind to DNA have been studied for almost 30 years. In the last few years a variety of new systems have been developed, employing a range of metal ions and ligand architectures. In many cases, high affinity binding and specific selectivities have been observed. These complexes display properties that make them attractive as probes of DNA structure and function, suggesting that they may find a r?le as prototypical tools for a spectrum of applications, from basic molecular biology to medicine. This review presents an overview of some of the structures and properties of such complexes. 相似文献
202.
Synthesis and Properties of Di-molybdenum-μ-nitrido-heptachloride, Mo2NCl7 Mo2NCl7 was prepared by the reaction of molybdenum pentachloride with the bromide of Millon's base, [Hg2N]Br, in boiling CCl4. It forms a moisture sensitive, dark green crystal powder, the magnetic moment at 20°C (μeff = 0.95 B.M.) being strongly reduced. With acetonitrile the μ-nitrido complex Mo2NCl7 · 3CH3CN is formed, with phosphoryl chloride the donor acceptor complex Mo2NCl7 · 2POCl3, respectively. Partial oxidation of the latter complex with chlorine leads to very unstable Mo2NCl8 · 2POCl3, from which (PPh4)3[Mo3NCl10] can be obtained by the reaction with PPh4Cl. For the complex (PPh4)3[Mo2NCl10] is also found a reduced paramagnetism of μeff = 1.47 B.M. at 20°C. All complexes are characterized by i.r. spectroscopy. 相似文献
203.
Cabrerizo FM Petroselli G Lorente C Capparelli AL Thomas AH Braun AM Oliveros E 《Photochemistry and photobiology》2005,81(5):1234-1240
Pterins are heterocyclic compounds with important biological functions, and most of them may exist in two acid-base forms in the pH range between 3 and 13 in aqueous solution. In this work, the photophysical properties of acid and basic forms of six compounds of the pterin family (6-hydroxymethylpterin [HPT], 6-methylpterin [MPT], 6,7-dimethylpterin [DPT], rhamnopterin [RPT], N-methylfolic acid [MFA], and pteroic acid [PA]) have been studied. The effects of the chemical nature of the substituents at position 6 of the pterin moiety and the effects of the pH on the absorption and emission properties are analyzed. The fluorescence characteristics (spectra, quantum yields, lifetimes) of these compounds have been investigated using the single-photon-counting technique. Results obtained for pterin derivatives containing small substituents with 1 carbon atom (HPT, MPT, DPT) and short hydrocarbon chain (4 carbon atoms) (RPT) are different from those found for pterin derivatives containing a p-aminobenzoic acid (PABA) moiety in the substituent (MFA and PA). Fluorescence quantum yields (Phi(F)) of the first group of compounds are relatively high (>/=0.4), whereas MFA and PA exhibit very small Phi(F) values (=0.01). 相似文献
204.
Thorsten Oldag Thomas Aussieker Hans‐Lothar Keller Christian Preitschaft Arno Pfitzner 《无机化学与普通化学杂志》2005,631(4):677-682
Solvothermal Synthesis and Crystal Structure Determination of AgBiI4 and Ag3BiI6 AgBiI4 and Ag3BiI6 were synthesized by solvothermal reaction from AgI and BiI3 in diluted HI‐solution (20 %) at a temperature of 160 °C. The greyish‐black crystals grow as octahedra (AgBiI4) or hexagonal/trigonal platelets (Ag3BiI6). AgBiI4 crystallizes in space group Fd3¯m with a = 1222.3(1) pm (300 K) and Z = 8 whereas Ag3BiI6 shows the space group R3¯m with a = 435.37(6) pm, c = 2081.0(4) pm (300 K) and Z = 1. Both crystal structures show stacking sequence abcabc… of hexagonal layers containing Iodine. Bismuth and silver are sharing octahedral sites with different mass ratio in both structures. The part of silver which could be localized varies with temperature. This behaviour indicates mobility of silver within the crystal structure. The ionic conductivity of AgBiI4 is explored. AgBiI4 and Ag3BiI6 show close structural relationship, with AgBiI4 as a variant with a higher degree of order. 相似文献
205.
Brieler FJ Grundmann P Fröba M Chen L Klar PJ Heimbrodt W Krug von Nidda HA Kurz T Loidl A 《Journal of the American Chemical Society》2004,126(3):797-807
Arrays of highly ordered Zn(1-x)MnxS quantum wires with x ranging from 0.01 to 0.3 and with lateral dimensions of 3, 6, and 9 nm were synthesized within mesoporous SiO2 host structures of the MCM-41 and SBA-15 type. The hexagonal symmetry of these arrays (space group p6m) and the high degree of order was confirmed by X-ray diffraction and transmission electron microscopy (TEM) studies. Physisorption measurements show the progressive filling of the pores of the SiO2 host structures, while TEM and Raman studies reveal the wire-like character of the incorporated Zn(1-x)MnxS nanostructures. X-ray absorption near-edge structure, extended X-ray absorption fine structure, photoluminescence excitation (PLE), and electron paramagnetic resonance studies confirm the good crystalline quality of the incorporated Zn(1-x)MnxS guest species and, in particular, that the Mn2+ ions are randomly distributed and are situated on tetrahedrally coordinated cation sites of the Zn(1-x)MnxS wires for all x up to 0.3. The amount of Mn2+ ions loosely bound to the surface of the Zn(1-x)MnxS nanowires is less than 4% of the total Mn content even for the 3 nm nanostructures up to the highest Mn content of x = 0.3. The effects of the reduction of the lateral dimensions on electronic properties of the diluted magnetic semiconductor were studied by PLE spectroscopy. Due to the quantum confinement of the excitons in the wires an increase of the direct band gap with decreasing particle size is observed. 相似文献
206.
Guido Kickelbick Dieter Rutzinger Thomas Gallauner 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1157-1164
Summary. Hexadentate ligands were formed by the reaction of primary dimethylaminoethyl- or methoxyethylamines with formaldehyde. The
resulting N, N′, N″-functionalized hexahydro-1,3,5-triazines contain pending amino or ether functionalities which are able to coordinate to
metals in addition to the ring nitrogen atoms. Both ligands were reacted with CuBr, and novel tricopper clusters were isolated
and characterized by X-ray structure analysis. In these compounds a ring nitrogen atom, the pending amino or ether functionality,
and two bridging bromine atoms coordinate each of the copper atoms.
Received January 22, 2002; accepted (revised) March 22, 2002 相似文献
207.
Thomas Verdier 《Journal of solid state chemistry》2005,178(11):3243-3250
Nanocrystalline ZnFe2O4 spinel powders are synthesized by high-energy ball milling, starting from a powder mixture of hematite (α-Fe2O3) and zincite (ZnO). The millings are performed under air using hardened steel vials and balls. X-ray diffraction and Mössbauer spectrometry are used to characterize the powders. A spinel phase begins to appear after 3 h of milling and the synthesis is achieved after 9 h. Phase transformation is accompanied by a contamination due to iron coming from the milling tools. A redox reaction is also observed between Fe(III) and metallic iron during milling, leading to a spinel phase containing some Fe(II). The mechanism for the appearance of this phase is studied: ZnO seems to have a non-negligeable influence on the synthesis, by creating an intermediate wüstite-type phase solid solution with FeO. 相似文献
208.
The effect of the superposition of electroosmotic flow and pressureinduced hydrodynamic counterflow on efficiency has been investigated for different capillary electrophoretic systems. Results are shown for 50 and 75 μm internal diameter capillaries at several voltage and counterpressure levels. Hydrodynamic counterflows were successfully applied in electrokinetic chromatography in order to delay the entry of a UV-active pseudostationary phase, tetraphenyl porphyrintetrasulfonate, into the detection zone allowing the separation of neutral nitroaromatics. The separations are based on the weak charge-transfer interactions between the porphyrin and the analytes. 相似文献
209.
Cooper SM Laosripaiboon W Rahman AS Hothersall J El-Sayed AK Winfield C Crosby J Cox RJ Simpson TJ Thomas CM 《Chemistry & biology》2005,12(7):825-833
Mupirocin, a polyketide-derived antibiotic from Pseudomonas fluorescens NCIMB10586, is a mixture of pseudomonic acids (PA) that target isoleucyl-tRNA synthase. The mup gene cluster encodes both type I polyketide synthases and monofunctional enzymes that should play a role during the conversion of the product of the polyketide synthase into the active antibiotic (tailoring). By in-frame deletion analysis of selected tailoring open-reading frames we show that mupQ, mupS, mupT, and mupW are essential for mupirocin production, whereas mupO, mupU, mupV, and macpE are essential for production of PA-A but not PA-B. Therefore, PA-B is not simply produced by hydroxylation of PA-A but is either a precursor of PA-A or a shunt product. In the mupW mutant, a new metabolite lacking the tetrahydropyran ring is produced, implicating mupW in oxidation of the 16-methyl group. 相似文献
210.
We describe a versatile, efficient method for the preparation of ether analogues of (S,S)-lysobisphosphatidic acid (LBPA) and its enantiomer from (S)-solketal. Phosphorylation of a protected sn-2-O-octadecenyl glyceryl ether with 2-cyanoethyl bis-N,N-diisopropylamino phosphine and subsequent deprotection generated the bisether LBPA analogues. By simply changing the sequence of deprotection steps, we obtained the (R,R)- and (S,S)-enantiomers of 2,2'-bisether LBPA. An ELISA assay with anti-LBPA monoclonal antibodies showed that the bisether LBPAs were recognized with the same affinity as the natural 2,2'-bisoleolyl LBPA. [reaction: see text] 相似文献