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71.
Summary. A series of Emivirine and GCA-186 analogues substituted at N-1 with indan-1-yloxymethyl (6a6c) and indan-2-yloxymethyl (6d6f) were synthesized by reaction of the corresponding bis(indanyloxy)methans with uracils having 5-ethyl or 5-isopropyl and 6-benzyl or 6-(3,5-dimethylbenzyl) substituents. A route to the corresponding N-1 substituted 4-hydroxybut-2-enyloxymethyl analogue was also devised. All newly synthesized compounds showed potent activity against wild-type HIV-1, the most active compound being 5-ethyl-1-(indan-1-yloxymethyl)-6-(3,5-dimethylbenzyl)uracil (6b), which was 50-fold more active than Emivirine.Present address: Chemistry Department, Faculty of Science, Tanta University, Tanta, EgyptA research center funded by The Danish National Research Foundation for studies on nucleic acid chemical biology  相似文献   
72.
(E)-beta-Trialkylstannyl-alpha,beta-unsaturated ketones are readily available from secondary propargylic alcohols via a two-step sequence involving highly regio- and stereoselective Pd(0)-catalyzed hydrostannation followed by mild oxidation (TPAP). The methodology has been applied to the synthesis of enantiomerically pure enone 12 which is a key intermediate for the total synthesis of zoanthamine, a structurally complex marine natural product.  相似文献   
73.
Non-enzymic glycation of human serum albumin (HSA) induces a change in its charge heterogeneity that may account for its particular renal clearance in patients with early diabetic nephropathy. A new high-performance liquid chromatographic analysis for the study of HSA heterogeneity is described based on a high content of formic acid in the mobile phase combined with a concave gradient of isopropanol. Under these conditions, native HSA was separated into three individual components (I, II and III). When glycated HSA was analysed, it was found that although the present method is not suitable for the separation of glycated from non-glycated HSA, it shows the effect of glycation in producing changes in HSA heterogeneity that are different from those reported on surface change. This finding suggests an additional factor (probably conformational changes) that is contributing to the heterogeneity of glycated HSA.  相似文献   
74.
Nielsen SC  Stürup S  Spliid H  Hansen EH 《Talanta》1999,49(5):27-1044
A rapid, robust, sensitive and selective time-based flow injection (FI) on-line solvent extraction system interfaced with electrothermal atomic absorption spectrometry (ETAAS) is described for analyzing ultra-trace amounts of Cr(VI). The sample is initially mixed on-line with isobutyl methyl ketone (IBMK). The Cr(VI) is complexed by reaction with ammonium pyrrolidine dithiocarbamate (APDC), and the non-charged Cr(VI)–PDC chelate formed is extracted into IBMK in a knotted reactor made from PTFE tubing. The organic extractant is separated from the aqueous phase by a gravity phase separator with a small conical cavity and delivered into a collector tube, from which 55 μl organic concentrate is subsequently introduced via an air flow into the graphite tube of the ETAAS instrument. The operations of the FI-system and the ETAAS detector are synchronously coupled. A significant advantage of the approach is that matrix constituents, such as high salt contents, effectively are eliminated. The extraction procedure was optimized by a simplex approach. A central composite design was subsequently employed to verify the estimated operational optimum. An 18-fold enhancement in sensitivity of Cr(VI) was achieved after preconcentration for 99 s at a sample flow rate of 5.5 ml min−1, as compared to direct introduction of 55 μl of sample, yielding a detection limit (3σ) of 3.3 ng l−1. The sampling frequency was 24.2 samples h−1. The proposed method was successfully evaluated by analyzing a NIST Cr(VI)-reference material, synthetic seawater and waste waters, and waste water samples from an incineration plant and a desulphurization plant, respectively.  相似文献   
75.
The aim of this prospective randomized study was to compare the clinical and cosmetic outcome of superficial basal cell carcinomas (BCC), using either laser or broadband halogen light, in photodynamic therapy with topical 5-aminolevulinic acid (ALA). A total of 83 patients with 245 superficial BCC were included in the study. Standard treatment involved 15 min of local pretreatment with 99% dimethylsulfoxide (DMSO) before topical application of 20% ALA with DMSO (2%) and ethylendiaminetetraacetic acid (2%) as cofactors for 3 h before light exposure with either laser or a broadband lamp (BL). A complete response was achieved in 95 lesions (86%) in the laser group and 110 lesions (82%) in the BL group 6 months after treatment. Of these, 80 lesions (84%) in the laser group and 101 lesions (92%) in the lamp group were independently evaluated to have an excellent or good cosmetic post-treatment score. No serious adverse events were reported. This study shows that there is no statistical significant difference in cure the rate (P = 0.49) and the cosmetic outcome (P = 0.075) with topical application of a modified ALA-cream between light exposure from a simple BL with continuous spectrum (570-740 nm) or from a red-light laser (monochromatic 630 nm). Cost and safety are further elements in favor of the BL in this setting.  相似文献   
76.
Abstract— The 248 nm laser flash photolysis of myoglobin in various redox states (oxy, met and ferryl) in neutral aqueous solution yielded hydrated electrons with concurrent changes in the visible absorption spectrum of the heme. The results could be ascribed to the photoionization of both the peptide and the heme group, in approximately equal yields. The ionization of met- and ferrylmyoglobin was biphotonic, but that of oxymyoglobin was a mixture of mono- and biphotonic processes. Using appropriate electron and radical scavengers, the changes in the heme absorption could be investigated at times ≥100 ns and were shown to be associated with a +1 increase of the formal oxidation state of the heme. Using this method, the formal iron(V) state of native myoglobin could be spectroscopically characterized for the first time. Its absorption, blue-shifted and less intense relative to the ferryl state, is reminiscent of that of the compound I of peroxidases, which contains a ferryl-oxo (iron[IV]) group and a porphyrin radical cation. On this basis, the same structure is proposed for the formal iron(V) state of native myoglobin. The transition from oxy- to metmyoglo-bin took -5 μs, which may reflect the kinetics of exchange of oxygen with water as ligand. The transitions from the met to the ferryl state, and from ferryl to iron(V) states were faster (∽250 ns), consistent with processes that involve proton or electron movements but no changes in the iron coordination state.  相似文献   
77.
A procedure has been developed using 242Pu as tracer for simultaneous determination of 237Np and 239,240Pu in environmental samples. The validity of the method has been demonstrated by ICPMS and a-spectroscopy for up to 10 gram soil and sediment, seawater up to 200 litres. The paper describes a suitable chemical procedure for Np and Pu including a quantitative pre-concentration of neptunium and plutonium, preparation of Np4+ and Pu4+, Np(NO3)6 2- and Pu(NO3)6 2-. The ratio of 237Np/242Pu (or 237Np/239Pu) before and after the procedure has been determined using 10 g soil (free from Np and Pu) R before/R after = 1.004±3.3% (S.D n = 20) and 1 litre seawater R before/R after = 1.019±1.9% (S.D., n = 12). Results from the intercomparison samples IAEA-135, IAEA-381 and from environmental samples are presented.  相似文献   
78.
Isolation of flavonoids from the aerial parts of Taverniera aegyptiaca Bioss. (Fabaceae) led to identification of one new flavonol glycoside, isorhamnetin-3-O-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranoside (1), along with eleven compounds, which previously have not been isolated from this plant quercetin-3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside] (2), isorhamnetin-3-O-α-l-arabinopyranoside (3), quercetin-3-O-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside (4), isorhamnetin-3-O-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside (7), isorhamnetin 3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside] (8), isorhamnetin 3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside] (9), kaempferol 3-O-α-l-rhamnopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside] (10), isorhamnetin (11), 4,4′-dihydroxy-2′-methoxychalcone (12), formononetin (13) and calycosin (15)] and some compounds already known from this plant [quercetin-3-O-robinobioside (5), isorhamnetin-3-O-robinobioside (6), afrormosin (14) and odoratin (16)].  相似文献   
79.
Single crystalline and polycrystalline -tin has been implanted at room temperature with 80-keV ions of radioactive119m Sn,119Sb, and119m Te. The radioactive nuclei decay to the Mössbauer level of119Sn. Mössbauer spectra of the emitted 24-keV radiation have been measured for different source temperatures by resonance counting techniques. Five individual lines in the spectra are characterized mainly by their isomer shifts and Debye temperatures. From these parameters the radiogenic119Sn atoms are concluded to be located in regular substitutional and interstitial lattice sites and in defect complexes. Simple models for the defects are proposed: A Sn-vacancy pair consists of Sn atoms on (nearly) substitutional sites with a dangling bond into an adjacent vacancy. In a complex oxygen-containing defect the Sn atoms have approximately a 5s 2 configuration withp-bonds to two nearest neighbour atoms. Sn atoms, having an atomic 5s 2 5p 2 configuration and large vibrational amplitudes, are concluded to be in non-bonding regular interstitial sites. For special implantation conditions minor fractions of SnO2 molecules are formed in the bulk. The interstitial119Sn and the119Sn-vacancy pairs are proposed to represent elementary point defects in -tin. Conclusions are also drawn concerning the lattice location and the defects created in the implantation process of the implanted parent isotopes.  相似文献   
80.
The infrared spectra of 1,5-hexadiyne (bipropargyl) and 1,5-hexadiyne-1,6-d2 as vapours, liquids, as solutes in various solvents and as crystalline solids at low temperatures and at high pressures have been recorded. Raman spectra were obtained for the liquids, including semiquantitative polarization measurements, and for the low temperature crystals.The data were interpreted in terms of two conformers, anti and gauche, in the vapour and liquid state and one, the anti, in the crystalline forms. A phase transition for 1,5-hexadiyne was observed at ca. 240 K. Both the high and low temperature crystals had molecules in the anti conformer.Interpretation of the spectra in terms of conformational equilibria was facilitated by a thorough vapour phase band contour analysis. With a few exceptions, all the vibrational fundamentals for both conformers were assigned and found to be in good agreement with results from normal coordinate calculations.  相似文献   
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