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1.
We provide a comprehensive study of single- (ss) and double-strand (ds) oligonucleotides with either 25 or 10 bases or base pairs (bp) immobilized on polycrystalline and single-crystal Au(111) surfaces. The study is based on X-ray photoelectron spectroscopy, cyclic and differential pulse voltammetry, interfacial capacitance data, and electrochemical scanning tunnelling microscopy (in situ STM). The sequences used were the 25-bp sequence from the BRCA1 gene (25-mer), while the 10-bp oligonucleotides contained solely linear adenine and thymine sequences. The oligonucleotides were modified by the dimethoxytrityl group (DMT) via a disulfide group [DMT-S-S-ss25-mer and DMT-S-S-ds(AT)10], a pure disulfide group (A10-S-S-T10), or a thiol group [HS-ss25-mer and HS-ds-(AT)10], all via a hexamethylene linker. The overall pattern suggests strategies for controlled adsorption of DNA-based molecules and recognition of complementary strands or other molecules.  相似文献   
2.
Explorative data analysis of two-dimensional electrophoresis gels   总被引:1,自引:0,他引:1  
Methods for classification of two-dimensional (2-DE) electrophoresis gels based on multivariate data analysis are demonstrated. Two-dimensional gels of ten wheat varieties are analyzed and it is demonstrated how to classify the wheat varieties in two qualities and a method for initial screening of gels is presented. First, an approach is demonstrated in which no prior knowledge of the separated proteins is used. Alignment of the gels followed by a simple transformation of data makes it possible to analyze the gels in an automated explorative manner by principal component analysis, to determine if the gels should be further analyzed. A more detailed approach is done by analyzing spot volume lists by principal components analysis and partial least square regression. The use of spot volume data offers a mean to investigate the spot pattern and link the classified protein patterns to distinct spots on the gels for further investigation. The explorative approach in analysis of 2-D gels makes it possible, in a fast and convenient way, to screen many gels in order to determine the protein patterns that form clusters and could be selected for further examination.  相似文献   
3.
The isotopic exchange of CO adsorbed on Pt(111) was studied using polarization modulation IR reflection absorption spectroscopy (PM-IRRAS) and temperature programmed desorption. It was found that the rate constants for the exchange reaction are much higher than would be expected from previous investigations of CO adsorbed on Pt nanoparticles. The adsorption of CO on Pt(111) under elevated pressures of CO and H(2) was also studied using PM-IRRAS. It was seen that CO pressures above 1 mbar lead to a shift in the absorption peak arising from CO adsorbed on a bridge site from 1850 to 1875 cm(-1). Exposing the CO-covered Pt(111) surface to 1000 mbar H(2) did not lead to any significant desorption of CO at room temperature, whereas at 363 K H(2) exposure did lead to a significant desorption of CO, due to the increased chemical potential of H(2). In a mixture of CO and H(2) with partial pressures of 0.01 mbar and 1000 mbar, respectively, no significant effect of H(2) on the PM-IRRAS spectrum was seen at temperatures below 423 K.  相似文献   
4.
A number of nucleophilic ring openings of 3-substituted pyridinium salts have been reinvestigated and summarized. The structure of the resulting stable glutaconaldehyde derivatives was investigated in detail by 1H NMR. It has been concluded that in general nucleophilic pyridinium ring openings are highly regiospecific. In each case investigated to date a single product was isolated, as a result of attack by the nucleophile at only one of the pyridine α-positions. With the OH ion as the only nucleophile, attack occurs at the pyridine C-2, while larger nucleophiles such as amines and carbanions attack at the pyridine C-6. This was found to be the case for a variety of 3-substituted pyridines such as 3-methyl, 3-methoxy-, 3-cyano-, 3 chloro-pyridine.  相似文献   
5.
In this work, different extracts from the microalga Spirulina platensis are obtained using pressurized liquid extraction (PLE) and four different solvents (hexane, light petroleum, ethanol and water). Different extraction temperatures (115 and 170 degrees C) were tested using extraction times ranging from 9 to 15 min. The antioxidant activity of the different extracts is determined by means of an in vitro assay using a free radical method. Moreover, a new and fast method is developed using micellar electrokinetic chromatography with diode array detection (MEKC-DAD) to provide a preliminary analysis on the composition of the extracts. This combined application (i.e., in vitro assays plus MEKC-DAD) allowed the fast characterization of the extracts based on their antioxidant activity and the UV-vis spectra of the different compounds found in the extracts. To our knowledge, this work shows for the first time the great possibilities of the combined use of PLE-in vitro assay-MEKC-DAD to investigate natural sources of antioxidants.  相似文献   
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A systematic study of Hg2+ and CH3Hg+ (MeHg+) speciation using hyphenated techniques, was performed for high-performance liquid chromatography coupled to on-line UV irradiation and cold-vapour atomic fluorescence spectroscopy (HPLC-UV-CV-AFS). First, a comparative study of the behaviour of three mobile phase compositions (using tetrabutylammonium bromide (TBAB), L-cysteine and ammonium pyrrolidinedithiocarbamate (APDC)) is presented. The separation and detection system was optimised by considering factors that modify fluorescence signal and the separation such as, the addition of different percentages of an organic modifier (methanol (MeOH) and acetonitrile (ACN)) to the mobile phase, the type of reducing agent used (SnCl2 and NaBH4) and the potential memory effects of the material of which the injection system is made (stainless steel, PEEK). The mobile phase selected for its sensitivity was a mixture 80?:?20 MeOH?:?0.0015?mol?l–1 APDC and 0.01?mol?l–1 NH4CH3COO (pH 5.5). The detection and quantification limits were close to 1.5 and 5?µg?l?1 for both species (as Hg), respectively. Recoveries obtained using fortified water samples of distinct origin (soft mineral, tap, river, seawater, and wastewater), ranged from 90 to 115% for concentrations about 2 and 20 times over quantification limits. Good repeatability was obtained (about 5%) independently of the concentrations, with reproducibility values about 20% at low concentrations and 5–10% at higher concentrations. Our proposed method proved to be straightforward for use by environmental laboratories for routine Hg2+ and MeHg+ determinations in polluted water samples.  相似文献   
9.
Abstract

Tetrathiafulvalene S-oxide (TTF-ox) was first detected by mass spectrometry in samples of Tetrathiafulvalene (TTF) which had been exposed to oxygen. Pure TTF-ox was prepared by peracid oxidation of TTF and isolated as a relativly stable solid. Physical data will be presented.  相似文献   
10.
The use of a carbazolyl-connected di-gold(I) metallotweezer for the encapsulation of several electron-poor organic substrates, and a planar Au(III) complex containing a CNC pincer ligand, is described. The binding affinity of the receptor depends on the electron-deficient character of the planar guest, with larger association constants found for the more electron-poor guests. The X-ray diffraction molecular structures of two host:guest adducts show that the host approaches its arms in order to facilitate the optimum interaction with the surface of the planar guests, in a clear example of an guest-induced fit conformational arrangement. The electrochemical studies of the encapsulation of N,N’-dimethyl-naphthalenetetracarboxy diimide (NTCDI) show that the redox active guest is released from the receptor upon one electron reduction, thus constituting an example of redox-switchable binding.  相似文献   
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