摘要:

In a previous paper we have shown that it was possible to quantify protein solutions at very weak concentrations directly by UV-visible spectroscopy. Nevertheless the protein quantification could not be possible if there is any trace of interferents left in the solution. So it is necessary to eliminate all the interferents to make the measure at 190 and/or 277 nm possible. We have developped a method based on the use of Microcon membranes and centrifugation. Interferents could be eliminated from protein solutions after four centrifugations at 13000 g during 5 min. This procedure allowed the recovering of proteins, with 80 to 99 % yield, and thus making microquantification possible.

ISSN:0038-7010    

DOI:10.1080/00387019808002744

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A microdetermination method at ng mL−1level for beryllium by solid-phase spectrophotometry was been developed. Chrome Azurol S was used as chromogenic reagent to form a blue complex which was easily and strongly sorbed and concentrated on a dextran-type anion-exchange resin. The resin-phase absorbances at 594- and 800 nm were measured directly. Beryllium could be determined over the 1.5 - 15.0 ng mL−1range with a RSD of 2.7 % by using 100 mL of sample solution. The detection limit was 0.21 ng mL−1. By using only 10 mL of sample solution, the calibration graph was linear over the concentration range 10–85 ng mL−1, the RSD being 1.2 %. The method was applied to the determination of beryllium in underground and mining waste water samples and in beryl mineral.

ISSN:0038-7010    

DOI:10.1080/00387019808002745

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The solution structures of nine pyrophthalone-type substances are determined by14N /15N-NMR-spectroscopy. Mostly depending on the conditions (solvent, solubility, chemical nature of the compound), both isotopes can be used complementary to obtain reliable data. Additionally, for some compounds15N solid state NMR data are available and demonstrate the structural identity in solution and the solid state.

ISSN:0038-7010    

DOI:10.1080/00387019808002746

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The IR-spectra of Pd (II) complexes with 2-aminopyridine, obtained both in sulphuric acid and alkaline solution are studied in the region 1700- 1400 cm−1. The structural conclusions are based on comparison with the IR- and UV-spectra of the free ligand and aminopyridinium sulphate, as well as of trans-dichloro-di-2-aminopyridine-palladium and deuterated at the amino group analogues of the investigated compounds.

ISSN:0038-7010    

DOI:10.1080/00387019808002747

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The X-band EPR spectra of Cu+doped into cadmium formate dihydrate single crystal was studied at 113 °K. The powder spectrum of the same material was studied over the temperature range from 113 to 300 °K The observed values of thegandAhyperfine coupling constants and linewidths were found to be temperature dependent.

ISSN:0038-7010    

DOI:10.1080/00387019808002748

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We have developed a non-thermal laser ablation model which may reduce thermal damage to neighboring structures. Based on this model, the three critical parameters for a well controlled non-thermal microsurgery are (1) the laser wavelength with its photon energy matching closely the bond dissociation energy, (2) the energy fluence must be above threshold to avoid thermal process due to non-radiative relaxation from the excited electronic states to vibrational, (3) ultra short laser pulses (few fs) to completely eliminate thermal and direct biomolecular reactions. In this model the UV laser photon dissociates the molecular bonds which leads to the splitting of longer polymer chains into small fragments. The excess energy if any may appear as kinetic energy in the polymer-fragments. The extreme rapidity of the bond breaking process reduces heat conduction. The model establishes a relationship between ablation depth per pulse, the absorption coefficient, the incident laser energy fluence, and the threshold energy fluence. The ablation depths per pulse were calculated for the polymers Polymethyl methacrylate (PMMA) and polyimide for various commercially available UV lasers. It has been found that the minimum ablations depth occurs at 193 nm for both PMMA and polyimide. This assures a well defined incision with minimal thermal damage to the surrounding structures at this wavelength. There exists a definite threshold energy fluence for non-thermal ablation for any given biomolecule and below the threshold the non-radiative relaxation process may cause thermal ablation. New ultra fast lasers (few femtoseconds) (fs) will completely eliminate thermal diffusion as well as direct biomolecular reactions.

ISSN:0038-7010    

DOI:10.1080/00387019808002749

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A complete assignment of the signals in the1H and13C NMR spectra and the stereostructural analysis of the compounds prepacifenol epoxide and the new dehydroxyprepacifenol epoxide are presented. These compounds were extracted from the marine molluscAplysia dactylomelaand represent the first occurrence of chamigrenes found in Brazilian waters. The NMR analyses are supported by NOE difference and COSY experiments and also by gradient selected HMBC, HSQC-TOCSY and HSQC-DE.1H spectra simulations were done for the final fitting of the chemical shifts and coupling constants.

ISSN:0038-7010    

DOI:10.1080/00387019808002750

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The17O NMR spectra for a series of saturated diols were investigated. From these studies both hydroxyl induced substituent chemical shift (SCS) effects of hydroxyl oxygen17O NMR chemical shifts were determined. In addition, linear correlations between the17O chemical shift of the hydroxyl oxygen (ROH) and the13C chemical shift for the methyl group in the corresponding hydrocarbon (RCH3) were obtained.

ISSN:0038-7010    

DOI:10.1080/00387019808002751

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The differential cross sections for coherent scattering of 59.5 keV γ-rays by Mo and Sn were measured using a high-purity germanium detector. The results were compared with predictions of form factor theories and S-matrix calculations.

ISSN:0038-7010    

DOI:10.1080/00387019808002752

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A series of rare earth (Gd, Eu, Tb) complexes with different substituent group carboxylic acids (ortho-hydroxylbenzioc acid, ortho-aminobenzoic acid and ortho- methoxy benzoic acid) and 1,10-phenanthroline were synthesized. The spectroscopic studies of the photophysical properties such as luminescence properties, energy match and intramolecular energy transfer were carried out. The lowest triplet state energies of ligands and the intramolecular energy transfer efficiencies were determined with the measurement of low phosphorescence spectra and lifetimes of Gd complexes.

ISSN:0038-7010    

DOI:10.1080/00387019808002753

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor