The synthesis and properties of a perylenediamide diol linker and several DNA hairpins possessing this linker are described. The diol linker absorbs and fluoresces strongly in the visible. Hairpins having poly(dA)-poly(dT) stems have fluorescence quantum yields and decay times similar to those of the linker, indicating that hole injection does not occur from the singlet excited linker into the base pair domain. Fluorescence quenching by dG or dZ bases is observed when these bases are located near the linker. The strong distance dependence of fluorescence quenching is consistent with a superexchange mechanism for electron transfer. Failure to observe formation of the linker anion radical by means of femtosecond time resolved absorption spectroscopy is attributed to fast charge recombination. The properties and behavior of the perylene linker and its hairpins are compared to those of other arenedicarboxamide linkers. 相似文献
Summary TheN-methyl-2-[1-(2-pyridinyl-1-oxide)ethylidene]hydrazinecarbothioamide, HLO4M, has been used to prepare a series of CoIII, NiII and CuII complexes. Species with two deprotonated LO4M ligands, one LO4M and one HLO4M ligand, two HLO4M ligands and one HLO4M ligand with two small anionic ligands have been isolated. The deprotonated LO4M bonds as a tridentate ligandvia theN-oxide oxygen, the imine nitrogen (N1 and the sulphur while the HLO4M ligand coordinates primarily as a bidentate ligandvia only the first two atoms listed above. I.r., electronic, mass and e.s.r. spectra have been used to determine the nature of these complexes. One of the more striking differences between these compounds and those prepared with other thiosemicarbazones of 2-acetylpyridine and 2-acetylpyridineN-oxide is that tetrahedral yellow [Ni(HL)X2] rather than planar brown [NiLX] (X=Cl or Br) solids have been isolated with this ligand. Other differences in the nature of the coordination spheres of the various metal ions occur with this particular ligand when compared to previously studied thiosemicarbazone complexes.NATO Fellow, on leave from Medical Faculty, Istanbul University. 相似文献
Reaction of the carbonyl Ru3(CO)12 with water leads to the formation of polynuclear hydrides α-H4Ru4(CO)12, α-H2Ru4(CO)13; the corresponding reaction with Os3(CO)12 yields the complexes (H)(OH)Os3(CO)10, H2Os4(CO)13, H4Os4(CO)12, H2Os5(CO)16, H2Os5(CO)15, H2Os6(CO)18 and H2Os7(CO)19C. 相似文献
Bisdemethylaaptamine (6), a proposed biosynthetic precursor of the aaptamines has been isolated from an Aaptos sp. marine sponge harvested off the Indonesian coast, and its identity confirmed by comparison of its spectral data with that of synthetic material. Bisdemethylaaptamine-9-O-sulfate (7) was also isolated from the same source. This is the first report of a sulfated aaptamine. 相似文献
Treatment of H2Os3(CO)10 with cyclonona-l,2-diene produced HOs3(CO)9C9H13 and Os2(CO)6(C9H4)2. Single crystal X ray analysis has shown that the latter is not isostructural with Fe2(CO)6(C9H14)2. 相似文献
The ionic conductivity of polycrystalline pellets of Li2MgSn3O8 with ramsdellite-type structure was measured by complex impedance technique. The conductivity is 1.2 × 10?8 (Ω cm)?1 at 300°C and 2.3 × 10?4 (Ω cm)?1 at 450°C. The results are discussed in relation to structural properties. 相似文献
Drug particulate interactions in pressurized metered dose inhalers (pMDI) may lead to a decrease in aerosolization efficiency and subsequent efficacy in patient treatment. The interactions between salbutamol sulfate (commonly used in Ventolin pMDIs) and a series of pMDI canister materials were investigated using the atomic force microscope (AFM) colloid probe technique. Approximately 4000 individual force-distance curves were determined for a drug probe and three surfaces (10 x 10 mum areas) in situ, in a model propellant. The area under each force-distance curve was integrated to obtain separation energy values. Median separation energy values followed the rank order borosilicate glass > aluminum > PTFE, suggesting PTFE to be the most suitable canister coating. 相似文献
High resolution separation of several dyes and related intermediates, as well as other compounds employed in the dye-manufacturing and dye-using industries, has been achieved using capillary zone electrophoresis (CZE).
The analysis of anionic dyes and some non-coloured anionic intermediates has been achieved using 10 mM Na2B4O7−40 mM sodium dodecyl sulphate (SDS) buffer; high-resolution separations of water soluble anionic, neutral and cationic intermediates were also achieved using this micellar buffer. Micellar electrokinetic capillary chromatography (MECC) has also been developed for the analysis of aqueous insoluble, electrically neutral compounds by incorporating a co-solvent, acetonitrile, into a micellar buffer. In addition, MECC has been used successfully for following all the major steps involved in the synthesis of a disperse dye. 相似文献
Recently developed carbon transverse relaxation dispersion experiments (Skrynnikov, N. R.; et al. J. Am. Chem. Soc. 2001, 123, 4556-4566) were applied to the study of millisecond to microsecond time scale motions in a cavity mutant of T4 lysozyme (L99A) using methyl groups as probes of dynamics. Protein expressed in E. coli cells with (13)CH(3)-pyruvate as the sole carbon source contained high levels of (13)C enrichment at a total of 80 Val gamma, Leu delta, Ile gamma (2), Ala beta, and Met epsilon methyl positions with little extraneous incorporation. Data for 72 methyl groups were available for analysis. Dispersion profiles with large amplitudes were measured for many of these residues and were well fit to a two-state exchange model. The interconversion rates and populations of the states, obtained from fitting relaxation dispersion profiles of each individual probe, were remarkably homogeneous and data for nearly all methyl groups in the protein could be collectively fit to a single cooperative conformational transition. The present study demonstrates the general applicability of methyl relaxation dispersion measurements for the investigation of millisecond time scale protein motions at a large number of side-chain positions. Potential artifacts associated with the experiments are described and methods to minimize their effects presented. These experiments should be particularly well suited for probing dynamics in high molecular weight systems due to the favorable NMR spectroscopic properties of methyl groups. 相似文献