Salt Stress Proteins Identified by a Functional Approach in Yeast

We have performed functional genomics of salt stress by overexpression of gene libraries in yeast and selection for salt tolerance. Thirty halotolerance genes were isolated from yeast, Arabidopsis, and sugar beet. The results indicate that Na⁺ transport (uptake, efflux, and compartmentation), sulfate activation, RNA processing, and protein synthesis are crucial for salt tolerance.     

A study of the electrospray ionisation and ion-trap fragmentation of [M - H](-) ions of new 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazin-2-thiones

The electrospray ionisation (ESI) in negative mode of the pharmacologically significant 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazin-2-thiones, and their subsequent fragmentations using an ion-trap mass spectrometer, have been investigated. Experiments on sequential product ion fragmentations (MS(n)) were performed in order to elucidate the degradation pathways for these compounds. The data presented show that the fragmentation of the even-electron [M - H](-) ions could proceed through an internal nucleophilic substitution displacement. Decarboxylation and extrusion of carbon disulfide are other fragmentations observed.     

Ring-closing metathesis of chiral allylamines. Enantioselective synthesis of (2S,3R,4S)-3,4-dihydroxyproline

The ring-closing metathesis (RCM) of two types of unsaturated chiral allylamines III, easily available from enantiomerically enriched epoxy alcohols, has been studied. Fully protected allylamines IIIa [(1)R = CH(2)-(CH(2))(n)()-CH=CH(2); (2)R = Boc; (3)R = PMB] have been prepared from unsaturated epoxy alcohols, whereas bis-allylamines IIIb ((1)R = Ph, (2)R = allyl,(3)R = Boc or PMB) have been prepared from 2,3-epoxy-3-phenylpropanol. Both types have been subjected to RCM to provide either cyclic allylamine I or II. The synthetic potential of these intermediates has been demonstrated by the enantioselective synthesis of (2S,3R,4S)-3,4-dihydroxyproline.     

Capillary isoelectric focusing of erythropoietin glycoforms and its comparison with flat-bed isoelectric focusing and capillary zone electrophoresis

The influence of several operation conditions on separation of recombinant human erythropoietin glycoforms by capillary isoelectric focusing (cIEF) is explored. From this study it is deduced that in order to separate several glycoforms of erythropoietin, urea has to be added to sample, which should not be completely depleted of the excipients used in its formulation. On-line desalting does not provide separation enhancement for samples with high content of salt. Better resolution is obtained using a mixture of a broad and a narrow pH-range carrier ampholytes than with either one used separately. Under the experimental conditions, focusing voltages of 25 kV improve separation compared to lower and higher electric fields. Focusing times shorter than the time necessary for electric current to reach a minimum provide similar separations than longer focusing times at which a minimum value of the current has already been achieved. The optimized method allows the separation and quantitation in 12 min of at least seven bands containing glycoforms of recombinant erythropoietin with apparent isoelectric points in the range 3.78–4.69. Compared to flat-bed isoelectric focusing, cIEF provides better separation of bands of glycoforms in a shorter time, and allows quantitative determination. Capillary zone electrophoresis (CZE) gives rise to resolution of erythropoietin glycoforms similar to that obtained by cIEF. Although CZE requires a longer analysis time, its reproducibility in terms of peak area of glycoforms is better than in cIEF.     

Characterisation of pitch by HPLC

Summary A new high performance liquid chromatography method for the characterisation of toluene-soluble fractions of pitches has been developed. Although a chromatographic system typical of size exclusion chromatography was used, results indicate that, for these structurally complex samples, separation does not follow the usual discrimination by molecular size. A differentiation between several classes of polyaromatic hydrocarbons is achieved instead. Data are reported on the analysis of individual standard polyaromatic hydrocarbons, showing that four different elution ranges can be observed: three ofcata-condensed compounds (Cata1, Cata2 and Cata3) and one ofperi-condensed compounds (Peri). Results are reported proving the capacity of this high performance liquid chromatography method to distinguish between pitches of different origin and nature. It is also effective for the study of the chemical reactions occurring during heat treatment.     

Reactor power dependency of the neutron flux parameters fork 0-standardization

Using the facilities of the Triga Mark III reactor at the NNRI, Mexico and the HAV-1 multipurpose monitor, the reactor power dependency for thek ₀-standardization essential neutron flux parameters as: epithermal shape factor (), thermal to epithermal ratio (f) and neutron temperature (T _n ) were experimentally obtained. Evaluation of the obtained dependencies shows that it is unnecessary to analyze the possible introduction of correction factors in thek ₀-INAA experimental results. A single experimental procedure to determine throughf is suggested.     

A very sensitive flow system for the direct determination of copper in natural waters based on spectrophotometric detection

A very sensitive flow injection method with spectrophotometric detection has been developed for the on-line determination of copper in natural waters. The method exhibits a limit of detection three times lower than the most sensitive direct spectrophotometric method previously described and then allows the direct and simple in situ determination of copper in most natural waters.The method was based on the measurement of the absorbance of the coloured complex formed by copper with the chromogenic reagent di-2-pyridyl ketone benzoylhydrazone (dPKBH) in an alkaline medium. This complex presents stoichiometry 1:2 (Cu:dPKBH), and exhibits maximum absorbance at 370 nm. The manifold used was very simple, and consisted of two channels. The first one contained the sample while the second one contained the colorimetric reagent (3.3×10⁻⁴ M dPKBH in 10% ethanol), in a 1.6×10⁻² M phosphate buffer solution at pH 8. The performance of the system was optimised by using both univariate and modified simplex methodologies. When modified simplex was used, the best signal was obtained for a sample injection volume of 529 μl, a reaction coil length of 1.29 m, and a reagent flow rate of 4.8 ml min⁻¹. Under optimum conditions, the response was linear up to 3 mg l⁻¹ copper, the equation of the straight line being y=0.314x+5.2×10⁻⁴ (r²=0.998). The method allowed a sampling frequency of 40 samples per hour and exhibited a precision of 2.11% (as R.S.D., n=11). The limit of detection was 4.6 μg l⁻¹ (calculated as 3s_b/m, where s_b is the standard deviation of the y-intercept and m represents the slope of the straight line), and was therefore more sensitive than all the direct continuous methods reported previously.The method was successfully applied to the analysis of real water samples, with an average relative error of 5.32%.     

Determination of bisphenol A diglycidyl ether and its hydrolysis and chlorohydroxy derivatives by liquid chromatography-mass spectrometry

European Legislation establishes that the sum of the migration levels of bisphenol A diglycidyl ether (BADGE), its hydrolysis (BADGE.H2O and BADGE.2H2O) and chlorohydroxy (BADGE.HCl, BADGE.2HCl and BADGE.H2O.HCl) derivatives shall not exceed the limit of 1 mg/kg in foodstuffs or food simulants. A reversed-phase high-performance liquid chromatographic (RP-HPLC) method combined with mass spectrometry detection using atmospheric pressure chemical ionisation (APCI) is developed for the separation, quantification and identification of the interesting compounds. Quantification of the analytes was carried out in the single ion recording mode, once their characteristic masses were selected from their full spectra, by using an external calibration. The optimised method was suitable for the migration evaluation of these compounds in different samples.     

Admittance measurements of adsorption properties of 2,2′-bipyridine complexes: Part I. Cobalt(II) and nickel(II) complexes in aqueous solutions

The complex [Co bipy₃]²⁺ in aqueous perchlorate solution yields on the d.c. polarogramthree adsorption type pre-waves and a main reduction wave at ?1.2 V (SCE) corresponding to the reduction to monovalent complex. From admittance measurements and other results it can be concluded that two most positive pre-waves at ?0.2 V and ?0.5 V (SCE) are of non-faradaic nature being related to the adsorption of the complex with specifically adsorbed anions of the supporting electrolyte with the formation of a compact adsorbed layer of much lower interfacial capacity. The most negative pre-wave at ?0.9 V just preceding the main wave corresponds to the reduction of the adsorbed complex. The main wave at ?1.2 V is distorted by the adsorption of reaction products. Very similar and also strong adsorption-coupled interaction was found with divalent nickel trisbipyridine complex.     

Analytical aspects of capillary gas chromatography of lower fatty acids [up to C18]

The principal aspects influencing analytical capillary gas chromatography of fatty acids up to C18 have been evaluated. Selected fundamental problems of interlaboratory exchange of retention data were problems of defined temperature in commercial thermostated air baths, of capillary tubing, and of stationary phases. A modification of commercial thermostats has been proposed in order to secure a defined temperature for glass capillary columns. It has been found that retention data of fatty-acid methyl esters can be measured under standard conditions with the same accuracy as retention data of hydrocarbons on squalane. Metal capillary columns coated with Apiezon L were found to be unsuitable for the analysis of fatty-acid methyl esters when compared with the results of their quantitative analysis in packed Apiezon L and polar capillary columns. Possibilities of a nontraditional statistical evaluation of the results of measurements are suggested. A program in FORTRAN IV language is given for the calculation of Kovats' retention indices for fatty-acid methyl esters.