Precolumn isotope dilution analysis in nanoHPLC-ICPMS for absolute quantification of sulfur-containing peptides

A novel generic approach based on precolumn isotope dilution nanoHPLC-ICPMS analysis was developed for the accurate absolute quantification of sulfur-containing peptides. A 34S-labeled, species-unspecific sulfur spike (sulfate), noninteracting with analyte peptides under the optimized HPLC condition, was added directly to the chromatographic eluents. Thus a generic sulfur standard permanently present during analysis was used for peptide quantification. Interference-free detection of the 32S and 34S isotopes in ICPMS was achieved by eliminating O2+ ions in a collision cell using Xe gas at 130 microL min-1. The detection limit for sulfur was 45 microg L-1 which corresponded to 1-2 pmol of individual peptides. The method was validated by the analysis of a standard peptide solution showing high accuracy (recovery 103%) and good precision (RSD 2.1%). The combination of nanoHPLC-ICP IDMS with nanoHPLC-ESI MS/MS allowed the precise quantification and identification of sulfur-containing peptides in tryptic digests of human serum albumin and salt-induced yeast protein (SIP18) at the picomole level.     

Sensitive detection of selenoproteins in gel electrophoresis by high repetition rate femtosecond laser ablation-inductively coupled plasma mass spectrometry

A laser ablation-ICPMS method using an infrared (1030 nm), low-energy (39 microJ/pulse), high repetition rate (10 kHz), femtosecond laser was developed to improve the sensitivity of detection of heteroatom-containing proteins in 1D polyacrylamide gels. A 2-mm-wide lane was ablated by ultrafast (10 cm s(-1)) back-and-forth movement of a 20-microm laser beam parallel to the protein bands while the gel advanced perpendicularly. This procedure resulted in a considerable increase in detection sensitivity (>40-fold) compared to the nanosecond 266-nm laser ablation-ICPMS, mainly because of the much larger amount of ablated material introduced into the plasma on the time scale of the dwell time of the mass spectrometer. The method was applied to the specific detection in the gel of formate dehydrogenase expressed in Escherichia coli and of selenoproteins in Desulfococcus multivorans with detection limits at the low-femtomolar levels.     

Functional studies of synthetic gramicidin hybrid ion channels in CHO cells

The function of a gramicidin hybrid ion channel in living Chinese hamster ovary (CHO) cells was investigated by the patch clamp method. The synthetic ion channel 1 consists of two cyclohexyl ether amino acids that link two mini-gramicidin strands. With 1 at a concentration of 1.0 microM, an increase in the whole-cell membrane conductance was observed after 1.37 min. The conductance showed larger currents when Cs(+) was used as charge carrier than when Na(+) and K(+) were used. In single-channel recordings with Cs(+) as charge carrier, the substance showed comparable single-channel amplitudes in the membrane of living cells and artificial black lipid bilayers. In addition to functioning as a cation channel, compound 1 appeared to be a water channel. Exposure of the CHO cells to an extracellular hypoosmotic solution did not substantially change the cell volume. Extracellular hypoosmotic conditions in the presence of 1 increased the cell size to 146.5 % that of the control. Thus, the synthetic hybrid channel 1 can function as a cation channel with some Cs(+) specificity, and as a water channel in CHO cells.     

A Median-Unbiased Estimator of the AR(1) Coefficient

A proof is given that the median of the ratios of consecutive observations of a stationary first-order autoregressive process X_t = α X _{t −1} + Y_t with P ( Y_t ≥ 0) = P ( Y_t ≤ 0) = 1/2 and P ( X_t = 0) = 0 is a median-unbiased estimator of α.     

Low Temperature Endotherm in Multiblock Terpoly(ester‐b‐ether‐b‐amide) Thermoplastic Elastomers

The phenomenon of the occurrence of a middle‐temperature thermal effect in crystallizable multiblock thermoplastic elastomers, the so‐called annealing endotherm has not yet been univocally explained, hence, it was subjected to DSC analysis. The formation of this endotherm in response to the time and temperature of conditioning (stabilisation) of the sample has been followed. The investigations have been performed for a specific polymer system, poly(tetramethylene terephthalate)‐block‐poly(oxytetramethylene)‐block‐polylaurolactam‐(PBT‐b‐PTMO‐b‐PA12)‐_n. The specific property of this elastomer is the solubility or a partial solubility of one of the components (PBT block) in the two remaining ones being mutually insoluble. The occurrence of the two different amorphous phases (PBT and PA12) in this elastomer with glass transition temperatures T_g > 20°C is also possible. This specific system permits to observe an interesting phenomenon, since at the points determining the middle‐temperatures of the glass transition temperatures of the elastomer, the two small endotherms are shaping; after proper stabilisation they are approaching each other, and as a result of this process they would form one extreme. This extreme comprises the thermal effect of the dispersion of the mesomorphic aggregates being the intermediate form between the amorphous state and the crystalline state. The mesomorphic aggregates constitute the additional network points of the physical polymer network of the elastomer.     

Coat of Arctic Fox (Alopex lagopus L.) of Different Genetic Groups in Micro- and Macroscopic Studies and in DSC Investigations

The objective of this research project was to compare in different genetic groups of arctic foxes the composition of the coat, hair length, and thickness as well as the medulla of four hair types but, primarily, to investigate the hair of the two layers of the coat hair (the underhair and the overcoat) using, for this purpose, the differential scanning calorimetry (DSC) method. Generally speaking, Finnish foxes were characterized by the most favorable indices of these traits. Different proportions of genes exerted a different impact on the level of these traits.     

Catalyst-free synthesis, morphology evaluation and photocatalytic properties of pristine and calcinated titanate nanorods

Titanate nanorods with high photocatalytic activity was successfully synthesized through a simple catalyst-free hydrothermal method. The photocatalytic degradation of a model organic dye (Reactive Red 198) was accelerated by the calcination of the nanorods prior the reaction. The calcination of nanorods did not modify their morphology, however the crystallinity of the samples was significantly improved. Therefore, the quality of the samples is a key parameter determining their activity in the investigated photocatalytic process. The as-produced and annealed catalysts were characterized by high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Diffuse Reflectance (DR) UV-Vis and resonance Raman spectroscopy.     

Optimization of subtractive-transformative hybrid processes supported by the technological heredity concept

This paper presents the optimization procedure of a hybrid removal-forming type process based on the minimum energy consumption and demanded surface roughness which is supported by the analysis of transformation of the surface and sublayer properties termed as the technological heredity. The experimental investigation covers an alloy steel hardened to 35 HRC and 55 HRC which was initially turned using coated carbide and CBN tools and subsequently burnished to produce surfaces with Ra roughness parameter of about 0.15 μm. The modifications of the initial surface profiles, microstructure and microhardness of the sublayer were determined and relevant technological limits are selected.     

Unsaturated ester resins

Vinyl ester resins (VERs) are often described as a cross between unsaturated polyester resins and epoxy resins. VERs offer an upgrade to epoxy resins, and they tend to be selected when chemical and temperature resistance is required. This research was aimed at developing the synthesis of unsaturated ester resins (UERs), which are similar to VERs. UERs were synthesized by the addition of dihydrodicyclopentadienyl hydrogen maleate to the terminal epoxy groups in low‐molecular‐weight bisphenol A/epichlorohydrin epoxy resins. The effect of urethanization of UERs on the properties of the crosslinked polymer was also investigated. As crosslinking monomers, styrene and glycol dimethacrylates were used. The following properties of cured UERs were determined: the heat deflection temperature, alkali resistance, and the mechanical strength. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2627–2631, 2006     

Polymerization of chlorophenyl glycidyl ethers. VI

Summary Polymerization of p-chlorophenyl glycidyl ether initiated by potassium glycolates (ethylene, propylene and 2-methyl propylene glycolatea) in DMSO containing some 18-crown-6 ether or glycol was investigated. For the reaction system containing the propylene glycolate asymmetrically substituted with a methyl group, relatively high polymerization rates were obtained as compared with those found for the other systems studied, the resultant polymers also having higher molecular weights and comparatively low polydispersities. Aliphatic double bonds were found to be absent in the polymers synthesized, which would suggest that in the anionic polymerization process studied the growing chain is not transferred to the monomer.Dedicated to Prof. C.I. Simionescu on the occasion of the 60th anniversary of his birthday