On the utility of predictive chromatography to complement mass spectrometry based intact protein identification

The amino acid sequence determines the individual protein three-dimensional structure and its functioning in an organism. Therefore, “reading” a protein sequence and determining its changes due to mutations or post-translational modifications is one of the objectives of proteomic experiments. The commonly utilized approach is gradient high-performance liquid chromatography (HPLC) in combination with tandem mass spectrometry. While serving as a way to simplify the protein mixture, the liquid chromatography may be an additional analytical tool providing complementary information about the protein structure. Previous attempts to develop “predictive” HPLC for large biomacromolecules were limited by empirically derived equations based purely on the adsorption mechanisms of the retention and applicable to relatively small polypeptide molecules. A mechanism of the large biomacromolecule retention in reversed-phase gradient HPLC was described recently in thermodynamics terms by the analytical model of liquid chromatography at critical conditions (BioLCCC). In this work, we applied the BioLCCC model to predict retention of the intact proteins as well as their large proteolytic peptides separated under different HPLC conditions. The specific aim of these proof-of-principle studies was to demonstrate the feasibility of using “predictive” HPLC as a complementary tool to support the analysis of identified intact proteins in top-down, middle-down, and/or targeted selected reaction monitoring (SRM)-based proteomic experiments.     

Screening of biosorption bacteria tolerance towards copper and cadmium from oil sludge pond

Certain bacterial strains can be employed in the removal of heavy metals from the environment. The aim of this study was to screen potential bacteria that were tolerant towards Cu and Cd and instrumental neutron activation analysis (INAA) was used to determine the concentrations of heavy metals in the sludge samples. The sludge samples from oil refinery plant in Malaysia contained Cr, Cs, Cu, Eu, Fe, Hg, Mn, Sb, Sc, Th, U and Zn. Seven bacterial isolates were identified to be tolerant to 100 mg/kg of copper and cadmium.     

Kinetic aspects and swelling changes of magnesium and cerium titano-antimonates in aqueous and mixed solvents

Magnesium titano-antimonate (MgTi₅Sb₂O₁₆·12.5H₂O) and cerium titano-antimonate (Ce₂.₇Ti₅Sb₂O₁₉·15.0H₂O) were synthesized as new cation exchangers using the in situ precipitation technique. Physico-chemical investigations showed different behaviors for the obtained materials. The materials have significant stability at high acid concentration and temperature. The ion exchange capacity for Cs⁺ in the presence of different alcoholic solvents was found to increase and generally obey the order C₂H₅OH > CH₃OH > H₂O. Diffusion coefficients (D_i) and thermodynamic parameters of Cs⁺ exchange in both magnesium and cerium titano-antimonates in aqueous and alcoholic solutions were calculated. The swelling ratios of the materials were predicted by applying modified calculations at constant values of D_i. The results showed insignificant swelling behavior in the presence of organic solvents.     

One-pot synthesis,theoretical study and antimicrobial activity of 5,5′-(1,4-phenylenebis-(methanylylidene))Bis(3-Aryl(Alkyl)-2-thioxoimidazolidin-4-one) derivatives

A simple, facile, and convenient practical method for the one-pot synthesis of pharmaceutically interesting 5,5`-(1,4-phenylenebis-(methanylylidene))bis-thiohydantoins via a three-component condensation reaction of terephthalaldehyde, α-amino acids and isothiocyanates had been developed. The S-alkylated derivatives 6a and 6b were obtained by the alkylation of the bis-thiohydantoins 4a with methyl iodide and/or benzyl chloride in a basic media. The molecular structures of the synthesized compounds were confirmed by their elemental analyses and spectral data (IR, ¹H, ¹³C NMR and MS). The assignment of more stable Z- or E-isomers as the major form of 4a, 6a, and 8a was investigated by DFT calculations at B3LYP/6-31+G* level. Some of the prepared compounds were screened for their in-vitro antimicrobial activity. Compounds 4a, 6 b, 8 b and 8c exhibited low antibacterial activity against gram-positive bacteria Bacillus cereus. (5Z,5′Z)-5,5′-(1,4-Phenylenebis(methanylylidene))bis(3-benzyl-2-thioxoimidazolidin-4-one) (4b) exhibited good fungicidal activity against Fusarium oxysporum.     

A new method for the estimation of variance components directly from the sample covariance matrix

Statistical techniques for the estimation of variance components are usually associated with methodological and computational difficulties. In this paper a new computational method for the estimation of variance components directly from the sample covariance matrix is proposed. A comparison between this method and the maximum likelihood method for variance component estimation, based on their computational performance, is made. Cases for balanced and unbalanced simulated data assuming a two-way nixed model with correlated errors are considered, and a real-life application in animal breeding is presented.     

Fluorescence behaviour of 4-[5-(2-phenyloxazolyl)] benzenesulfonic acid and N-hexyl-4-[5-(2-phenyloxazolyl)] benzenesulfonamide in homogeneous micellar and microemulsion systems

The fluorescence and excitation spectra of 4-[5-(2-phenyloxazolyl)]benzenesulfonic acid (PPOS) and N-hexyl-4-[5-(2-phenyloxazolyl)] benzenesulfonamide (PPOSA) were investigated in homogeneous solutions of varying polarities (hexane, heptane, butanol and water) and in aqueous micellar systems of anionic surfactants (bis(2-ethylhexyl)sulfosuccinate, sodium salt (AOT), sodium dodecyl sulfate (SDS)) and cationic surfactants (benzyldimethylhexadecylammonium chloride (CDBA), hexadecyltrimethylammonium chloride (CTAB)). These compounds were also investigated in different oil-in-water (o/w) and water-in-oil (w/o) microemulsions of the system composed of SDS, n-butanol, cyclohexane and water. The results revealed that the two probes exhibit pronounced spectral changes in response to the changes in the polarity of the medium, and in hydrophobic—hydrophilic interactions. The spectral behaviour of PPOS and PPOSA in micellar systems indicates that these two probes are incorporated at the interface of the cationic micelles. In microemulsions, however, the probes exhibit different Stokes shifts compared with those found for homogeneous solutions, indicating different salvation processes of both the ground and the excited states.     

Decomposition of the t-butoxy radical: II. Studies over the temperature range 303—393 K

The near U-V photolysis of t-butyl nitrite has been studied over the temperature range 303–393 K. Under these conditions t-butyl nitrite was shown to be a very clean photochemical source of t-butoxy radicals. This allows a study of the decomposition of the t-butoxy radical to be made over this temperature range (3). (1) Extrapolation of the rate constants k₃ to high pressure and combination with our previous thermal data give the results:      

Instrumental neutron activation analysis of environmental samples using thek 0-standardization method

The use of thek ₀-standardization method in instrumental neutron activation analysis gives good accuracy and precision. The analysis time can be reduced drastically by employing software for thek ₀-standardization calculations. In this work samples were irradiated in a TRIGA reactor and the gamma spectrum was analysed by Sampo 90 and thek ₀-standardization by the KAYZERO/SOLCOI code (DSM Research). The efficiency measurement and the peak to total ratio at the reference and other geometries were measured and tested for their accuracy by analysing some reference materials. Reference materials such as SRM 1572 (Citrus leaves), SRM 1573 (Tomato leaves), SRM 1575 (Pine needles), IAEA Soil-7 (Soil) and SRM 1646 (Estuarine sediment) were analysed for the major, minor and trace element contents. The results were in good agreement with the certified or literature values. The recently released IAEA 140 (Sea plant homogenates) was also analysed for 28 elements.     

New colorimetric methods for the determination of trazodone HCl,famotidine, and diltiazem HCl in their pharmaceutical dosage forms

Two sensitive and simple spectrophotometric methods are developed for the determination of trazodone HCl, famotidine, and diltiazem HCl in pure and pharmaceutical preparations. The methods are based on the oxidation of the cited drugs with iron(III) in acidic medium. The liberated iron(II) reacts with 1,10-phenanthroline (method A) and the ferroin complex is colorimetrically measured at 510 nm against reagent blank. Method B is based on the reaction of the liberated Fe(II) with 2,2-bipyridyl to form a stable colored complex with lambda(max )at 520 nm. Optimization of the experimental conditions was described. Beer's law was obeyed in the concentration range of 1-5, 2-12, and 12-32 microg mL(-1) for trazodone, famotidine, and diltiazem with method A, and 1-10 and 8-16 microg mL(-1) for trazodone and famotidine with method B. The apparent molar absorptivity for method A is 1.06x10(5), 2.9x10(4), 1.2x10(4) and for method B is 9.4x10(4 )and 1.6x10(4), respectively. The suggested procedures could be used for the determination of trazodone, famotidine, and diltiazem, both in pure and dosage forms without interference from common excipients.