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1.
Nicewarner Peña SR Raina S Goodrich GP Fedoroff NV Keating CD 《Journal of the American Chemical Society》2002,124(25):7314-7323
We have investigated the impact of steric effects on the hybridization and enzymatic extension of oligonucleotides bound to 12-nm colloidal Au particles. In these experiments, a nanoparticle-bound 12-mer sequence is hybridized either to its solution phase 12-mer complement or to an 88-mer template sequence. The particle-bound oligonucleotide serves as a primer for enzymatic extension reactions, in which covalent incorporation of nucleotides to form the complement of the template is achieved by the action of DNA polymerase. Primers were attached via-C(6)H(12)SH, -C(12)H(24)SH, and -TTACAATC(6)H(12)SH linkers attached at the 5' end. Primer coverage on the nanoparticles was varied by dilution with (5')HSC(6)H(12)AAA AAA(3'). Hybridization efficiencies were determined as a function of linker length, primer coverage, complement length (12-mer vs 88-mer), and primer:complement concentration ratio. In all cases, hybridization for the 88-mer was less efficient than for the 12-mer. Low primer surface coverage, greater particle-primer separation, and higher primer:complement ratios led to optimal hybridization. Hybridization efficiencies as high as 98% and 75% were observed for the 12-mer and 88-mer, respectively. Enzymatic extension of particle-bound primers was observed under all conditions tested; however, the efficiency of the reaction was strongly affected by linker length and primer coverage. Extension of primers attached by the longest linker was as efficient as the solution-phase reaction. 相似文献
2.
Neutron activation, applied to silver and copper based coinage, leads to a measure of the mean concentrations of major and 12 trace elements, even if their distribution is heterogeneous. The drawbacks of this activation method applied to such a matrix are shielding effects and high radioactivity of major elements. Both effects were avoided by accurately calculating the correction coefficients and by choosing the optimal working conditions. Analytical results obtained lead to a better knowledge of the chronology and origin of Armorican protohistorical coinage. 相似文献
3.
J. C. Rouchaud M. Fedoroff G. Revel 《Journal of Radioanalytical and Nuclear Chemistry》1977,38(1-2):185-191
A new method of silicon determination in molybdenum by the30Si(n, γ)31Si was developed. All the problems occurring during this analysis: standardization, quantitative dissolution, silicon sorption
on vessels, reproducibility of β-counting...were carefully studied and new answers were brought to them. The chemical speratation
of silicon was performed with a column of anion exchange resin in HCl-HF-H2O2 solution and a column of alumina at pH 9. Accuracy and reproducibility were controlled on standard samples prepared by fusion
of inactive molybdenum and radioactive silicon in a plasma furnace. 相似文献
4.
Mme J. Blouri M. Fedoroff G. Revel 《Journal of Radioanalytical and Nuclear Chemistry》1973,17(1-2):185-194
Résumé Après une irradiation neutronique de 7 jours dans un flux de 3·1012 n·cm−2·sec−1, une trentaine d'éléments peuvent être dosés sans séparation chimique dans des échantillons d'aluminium de diverses provenances.
Les modalités de mesure et de calcul des radioactivités sont précisées et nous indiquons les limites de détection obtenues.
Elles sont comprises entre 5·10−2 et 5·10−6 μg/g selon les éléments recherchés. Pour certains d'entre eux (Fe, Zn, Zr) ces limites peuvent être améliorées par une séparation
chimique simple. 相似文献
5.
Various methods of radiochemical separation were tested for the determination of phosphorus in metals and alloys by neutron
activation analysis. Classical methods of separation revealed some defects when they were applied to this problem. Methods
using liquid extraction gave low yields and were not reproducible. Methods based on precipitation gave better results, but
were not selective enough in most of the cases. Retention on alumina was not possible without preliminary separations We studied
a new radiochemical separation based on the extraction of elemental phosphorus in the gaseous phase after reduction at high
temperature with carbon. Measurements with radioactive phosphorus showed that the extraction yield is better than 99%. 相似文献
6.
M. Fedoroff V. N. Samosyuk J. C. Rouchaud C. Loos-Neskovic 《Journal of Radioanalytical and Nuclear Chemistry》1987,112(2):395-402
Carbon and nitrogen were determined in iron, steel, and silicon by photon activation followed by chemical separation. Nitrogen was determined in the same types of samples by reactor neutron activation, chemical separation, and liquid scintillation counting. The comparison of two methods based on different radioactive elements is a way to control the accuracy of the determination. 相似文献
7.
S. Zouad C. Loos-Neskovic M. Fedoroff 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(2):337-349
The fixation mechanisms of strontium on polyantimonic acid (PAA) were studied in order to choose the best recovery conditions from nuclear wastes. This was performed through the determination of the composition and structure, the kinetics and capacity involving the use of different methods: radioactive tracers, X-ray diffraction, potentiometric measurements. The composition of PAA corresponds to H2Sb2O6·1.5H2O with a cubic pyrochlore type structure. A total exchange leading to SrSb2O6·nH2O is achieved in basic medium, while the capacity is lower in acid and neutral media. The kinetics can be divided into two stages: the first one may be due to a surface phenomenon and the second can be interpreted by a diffusion mechanism into the particle. These results were confirmed by potentiometric measurements. Owing to the rapidity of the first stage of fixation and to the high distribution coefficient, PAA offers a good alternative for column separation from dilute radioactive solutions. 相似文献
8.
J. C. Rouchaud L. Debove M. Fedoroff L. M. Mosulishvili V. Yu. Dundua N. E. Kharabadze N. I. Shonia E. Yu. Efremova N. V. Chikhladze 《Journal of Radioanalytical and Nuclear Chemistry》1987,113(1):209-215
An aluminium matrix and a phenolformaldehyde polymer were tested as base materials for multielement standards resistant to high neutron doses in activation analysis. Interlaboratory analyses showed that these standards can be certified for the concentrations of the majority of introduced elements. 相似文献
9.
A simplified calculation model of the recoil and irradiation enhanced diffusion which occur in neutron activation analysis
of metals is proposed. Under usual irradiation conditions, the recoil does not exceed 0.01 μm for n, γ reactions and 2 μm
for other reactions; the diffusion does not exceed 1 μm. Examples, in which deep impurity diffusion leading to important analytical
errors was put forward, are discussed through this calculation model. In most cases, the observed phenomena are not related
to diffusion but to other causes such as unefficient etching of the sample surface.
相似文献
10.
The problem of gamma ray spectrum analysis has been is studied. The difficulties encountered by different methods are explained. An empirical method which uses an experimental peak for the analysis of spectrum is developed. This method utilizes the simple algorithm of linear least squares and is able to analyze the multiplets. It gives more accurate results than other ones. It is well adapted for automatic treatment of gamma ray spectra by small computers. 相似文献