Mass spectrometric analysis of integral membrane proteins at the subnanomolar level: application to recombinant photopigments.

Integral membrane proteins produced by eukaryotic expression systems are a subject of much current interest in biomedical investigation. Due to the low efficiency of their expression and the limited quantity of the expressed to the total amount of the membrane proteins, they have evaded mass spectrometric analysis. The methodology previously developed for mass spectrometric analysis of integral membrane proteins required proteins that were obtained relatively pure from their native membranes. The previously developed methodology has been modified and applied to the analysis of subnanomolar samples of rhodopsin. Bovine rhodopsin purified by affinity chromatography, from native membranes and from a eukaryotic expression system, was successfully analyzed, obtaining complete sequence coverage for the detection and localization of posttranslational modifications. The methodology presented here will enable mass spectrometric analysis of subnanomolar levels of photopigments or other integral membrane proteins either from their native membranes or as products of expression systems.     

Microstructure and environment dependence of 2H11/2 --> 4I15/2 upconversion emission in YVO4:Er3+, Yb3+ nanocrystals

Upconversion emission of different nanocrystalline YVO4:Er3+, Yb3+ synthesized by a hydrothermal process at low temperature was studied under 980 nm excitation where green [(2H11/2, 4S3/2) --> 4I15/2] and red (4F9/2 --> 4I15/2) emissions demonstrate sensitivity to the local environments of Er3+. Small particle size, high Yb3+ concentration, or high temperature favors the emission of the 2H11/2 --> 4I15/2 transition. Both XRD patterns and Raman spectra have confirmed that crystal lattice distortion of YVO4:Er3+, Yb3+ nanocrystals is more serious when the nanoparticle size is decreasing or Yb3+ concentration is increasing. This distortion is thought to play a key role in the observed spectral properties, which might lead to a new route to improve the monochromatic upconversion emission efficiency in these nanocrystals.     

Discrimination of neolacto-series gangliosides with alpha2-3- and alpha2-6-linked N-acetylneuraminic acid by nanoelectrospray ionization low-energy collision-induced dissociation tandem quadrupole TOF MS

A combined strategy of thin-layer chromatography immunostaining and negative ion nanoelectrospray low-energy CID mass spectrometry was established for the differentiation of isomeric alpha2-3 and alpha2-6 sialylated neolacto-series monosialogangliosides from human granulocytes. The gangliosides investigated differed in the ceramide moiety by substitution with C16:0 or C24:1 fatty acid and in their oligosaccharide chains due to nLc4 and nLc6 core structures. With respect to the type of sialylation, the homogeneity of the HPLC-purified ganglioside fractions was verified by use of specific anti-Neu5Acalpha2-3Galbeta1-4GlcNAc-R and anti-Neu5Acalpha2-6Galbeta1-4GlcNAc-R antibodies. A clear-cut series of fragment ions for both types of isomeric gangliosides, carrying alpha2-3- and alpha2-6-linked neuraminic acid, respectively, was obtained by low-energy CID. Additionally, a characteristic ring cleavage was detected exclusively in all species with Neu5Acalpha2-6Galbeta1-4GlcNAc terminus, regardless of ceramide fatty acid and oligosaccharide chain lengths. The diagnostic (0,2)X(4/6) ions, generated by ring cleavage of an alpha2-6-linked neuraminic acid are accompanied by a simultaneous decrease of the corresponding Y(4)/Y(6) ions. These results suggest the unequivocal discrimination of individual alpha2-3- and alpha2-6-sialylated neolacto-series monosialogangliosides by distinct fragmentation patterns in low-energy CID tandem MS.     

High-temperature mass spectrometric study of vaporization in nano- and microcrystalline Fe2O3-SnO2 and NiO-SnO2 oxide systems

Nano- and microcrystalline Fe₂O₃-SnO₂ and NiO-SnO₂ oxide systems have been studied by Knudsen cell mass spectrometry. The results demonstrate that the vaporization thermodynamics in these systems is independent of the particle size.     

Background analysis around Qββ for Ge double beta decay experiments, and statistics at low count rates

The background in the region of the Q-value for neutrinoless double beta decay of ⁷⁶Ge has been investigated by different methods: Simulation with GEANT 4 of the HEIDELBERG–MOSCOW experiment and analysis of other Ge double beta experiments. Statistical features of the analysis at very low count rates are discussed.     

Freeze-Dried Preparations of Ketoprofen and Heptakis- (2, 6-O-Dimethyl) -β-Cyclodextrin

ABSTRACT

The purpose of this study was to examine the inclusion formation in freeze-dried preparations of ketoprofen and heptakis-(2,6-0-dimethyl)-β-cyclodextrin. The products obtained were amorphous mixtures of the two components. X-ray diffractography, differential scanning calorimetry, ¹³C-CPMAS-NMR spectroscopy and thermofractography did not give any proof of an inclusion of ketoprofen in the cyclodextrin cavity.     

Experimental studies on the dynamic tensile behavior of Ti–6Al–2Sn–2Zr–3Mo–1Cr–2Nb–Si alloy with Widmanstatten microstructure at elevated temperatures

The tensile behavior of a newly developed Ti–6Al–2Sn–2Zr–3Mo–1Cr–2Nb–Si alloy, referred as TC21, is investigated at temperatures ranging from 298 to 1023 K and under constant strain rate loadings ranging from 0.001 to 1270 s⁻¹. The results show that temperature and strain rate have significant effects on the tensile behavior of the material. At low strain rates of 0.001 and 0.05 s⁻¹, a discontinuity is found in the yield stress–temperature curve. And the discontinuity temperature increases with increasing strain rate. The analysis of temperature and strain rate dependence of unstable strain indicates a high-velocity-ductility phenomenon at elevated temperatures. Scanning electron microscope (SEM) analysis shows that the material is broken in a mixture manner of ductile fracture and intergranular fracture under low strain rates at room temperature, while the fracture manner changes to totally ductile fracture under other testing conditions. The width and depth of ductile dimples increase with increasing temperature. No adiabatic shear band is found in the tensile deformation of the material.     

Impedance and modulus analysis of double perovskite Pb<Subscript>2</Subscript>BiVO<Subscript>6</Subscript>

The member of double perovskite family Pb₂BiVO₆ was synthesized by a moderate temperature (~700?°C) by solid-state route. The room temperature X-ray diffraction pattern of the sample confirms the formation of a single phase new compound. The scanning electron microscope image of the studied compound clearly shows the grains are uniformly distributed with minimal voids. Impedance, modulus and conductivity properties of the compound exhibits a strong correlation with the micro-structure and resistive properties of the material. The electrical transport properties of the material show the existence of non-exponential-type of conductivity relaxation in the material.     

Dynamic mechanical analysis and creep behaviour of β-PVDF films

In this work, tensile dynamic mechanical analysis (DMA) was used to characterise the solid-state rheological properties of a commercial β-polyvinylidene fluoride (PVDF) film in the two main directions (longitudinal and transversal to the stretch direction). The β-relaxation, assigned to the segmental motions within the amorphous phase, is observed at −25 °C. The _c-relaxation is observed above room temperature. This relaxation is the main responsible for the anelastic properties of the material and to the short-term creep behaviour. Longer-term creep tests along the longitudinal direction were also performed and the Eyring model was applied, in order to characterize the flow-process within the polymeric structure. The results suggest that long-term creep is mostly controlled by the deformation of amorphous tie-chains that connect adjacent crystalline lamellae.     

Mass Spectrometric Study of NF2, NF3, N2F2, and N2F4

Appearance potentia’s have been measured for selected ions from NF₂, NF₃, N₂F₂, and N₂F₄. Ionization-dissociation processes are identified and bond dissociation energies are calculated. In addition, the bond dissociation energy, D(F₂N–NF₂), has been directly measured to be 5.14±0.38 kj/mole (21.5± 1.6 kcal/mole). A summary is made of available thermochemical and mass spectrometric data for N–F compounds and some evidence is presented to support the designation of cis and trans structures for the N₂F₂ isomers.     

US backscatter and attenuation 30 to 50 MHz and MR T2 at 3 Tesla for differentiation of atherosclerotic artery constituents in vitro

This study compares quantitative characterization of atherosclerotic artery constituents by high resolution estimates of ultrasonic attenuation, ultrasonic attenuation-compensated backscatter, and magnetic resonance transverse relaxation time. Atherosclerotic human arteries were studied in vitro at 37°C. Backscattered radio frequency signals were acquired with a 50 MHz backscatter acoustic microscope. Ultrasonic parametric images were constructed from the integrated (30 to 50 MHz) backscatter and attenuation obtained using FFT methods with diffraction correction and a multinarrow-band attenuation algorithm. Parametric magnetic resonance images were constructed from calculated values of the transverse relaxation time T2 determined from an 8 echo-single-slice sequence at 3 Tesla. In a total of 54 regions of interest, average values of integrated attenuation, integrated backscatter compensated for the attenuation between the artery surface and the scattering volume, and the transverse relaxation time were correlated with local tissue composition as assessed by histology. Results show that ultrasound and magnetic resonance techniques offer complementary approaches for characterization of plaque composition     

Impedance spectroscopy analysis of double perovskite Ho<Subscript>2</Subscript>NiTiO<Subscript>6</Subscript>

The electrical properties of double perovskite Ho₂NiTiO₆ (HNT) are investigated by impedance spectroscopy in the temperature range 30–420 °C and frequency range 100 Hz to 1 MHz. The X-ray diffraction analysis reveals that the compound crystallizes in monoclinic phase. The imaginary part of impedance (Z″) as a function of frequency shows Debye type relaxation. The frequency dependence of Z″ peak is found to obey an Arrhenius law with an activation energy of 0.129 eV. Impedance data presented in the Nyquist plot (Z″ vs. Z′) are used to identify an equivalent circuit and to know the bulk and interface contributions. The complex impedance analysis of HNT exhibits the appearance of both the grain and grain-boundary contribution. The results of bulk ac conductivity as a function of temperature and frequency are presented. The activation energy (0.129 eV), calculated from the slope of log τ versus 10³/T plot, is found to be the nearly same as calculated (0.130 eV) from dc conductivity. The frequency dependent conductivity spectra obey the power law.     

Chemical changes and phase analysis of OPC pastes carbonated at different CO<Subscript>2</Subscript> concentrations

Chemical changes and phase analysis of OPC pastes exposed to accelerated carbonation using different concentrations of CO₂ (3%, 10% and 100%) have been undertaken and compared with those of natural carbonation (≅0.03%). ²⁹Si Magic Angle Spinning-Nuclear Magnetic Resonance (²⁹Si M.A.S-N.M.R), Thermogravimetric analyses (TG) and X-Ray Diffraction (XRD) have been used for characterisation. The carbonation of the samples has resulted in a progressive polymerisation of CSH that leads to formation of a Ca-modified silica gel and calcium carbonate. The carbonation of CSH and portlandite occurs simultaneously and the polymerisation of the CSH after carbonation increases with the increase in concentration of CO₂. When ≅0.03% and 3% CO₂ are used_, CSH gel with a lower Ca/Si than that of the uncarbonated sample, and quite similar for both samples remained. When carbonating at 10% and 100% of CO₂, the CSH gel completely disappears. For every condition, a polymerised Ca-modified silica gel is formed, as a result of the decalcification of the CSH. From these results it can be deduced that among the different concentrations of CO₂ tested, carbonation up to a 3% of CO₂, (that is to say, by a factor of 100) results in a microstructure much more similar to those corresponding to natural carbonation at ≅0.03% CO₂ than those at the 10% and 100% concentrations.     

Multiarray sensors with pattern recognition for the detection, classification, and differentiation of bacteria at subspecies and strain levels

This work describes the integration of a fully autonomous electrochemical biosensor with pattern recognition techniques for the detection and classification of bacteria at subspecies and strain level. The system provides a continuous, real-time monitoring of bacteria activity upon exposure to antibiotics. The system utilizes 96-well-type electrodes array (DOX-dissolved oxygen sensor) with principal component analysis (PCA) for rapid and routine classification of different classes of bacteria and related strains. A representative sample of a section of the bacteria kingdom has been analyzed and classified using the proposed DOX-PCA system, including the following: Corynebacterium glutamicum, Micrococcus luteus, Staphylococcus epidermidis, Yersinia ruckeri, Escherichia adecarboxylata, Comamonas acidovorans, Alcaligenes odorans, Bacillus globigii, and three strains of Escherichia coli (K12, SM10, ATCC 25922). The new classification scheme is based on the hypothesis that, under identical experimental conditions, various bacteria consume oxygen at different rates and are affected in different ways by selected antibiotics. Thus, the response of the individual electrode in the array is indirectly altered, compared to that of cells growing on medium, by the addition of the antibiotic. By using three different antibiotics in separate wells, a unique fingerprint can be created for a specific bacterium. With the proposed DOX-PCA system, classification of bacteria was achieved at subspecies and strain level in real time. This study represents a basic research tool that may allow researchers to rapidly detect, quantify, and classify bacteria type at subspecies and strain levels.     

Mass analysis of biological macromolecules at atmospheric pressure using nonresonant femtosecond laser vaporization and electrospray ionization

A nonresonant femtosecond laser pulse, with an intensity of 10(13) Wcm(-2), vaporizes proteins and biomolecules intact, regardless of molecular structure, size or electronic structure for subsequent electrospray ionization and transfer into a mass spectrometer. Rapid, direct analysis from dried sample, aqueous solution and cellular material is demonstrated at atmospheric pressure using laser electrospray mass spectrometry (LEMS). Measurements are presented for lysozyme (14.3 kDa), hemoglobin from human blood, ovalbumin (45 kDa) from hen egg white and phospholipids from hen egg yolk. Mass analysis of biological material is performed without dilution, extraction or sample preparation, other than placing the biological material onto the sample plate.