Detection of tyrosine phosphorylated peptides by precursor ion scanning quadrupole TOF mass spectrometry in positive ion mode

Phosphorylation is a common form of protein modification. To understand its biological role, the site of phosphorylation has to be determined. Generally, only limited amounts of phosphorylated proteins are present in a cell, thus demanding highly sensitive procedures for phosphorylation site determination. Here, a novel method is introduced which enables the localization of tyrosine phosphorylation in gel-separated proteins in the femtomol range. The method utilizes the immonium ion of phosphotyrosine at m/z 216.043 for positive ion mode precursor ion scanning combined with the recently introduced Q2-pulsing function on quadrupole TOF mass spectrometers. The high resolving power of the quadrupole TOF instrument enables the selective detection of phosphotyrosine immonium ions without interference from other peptide fragments of the same nominal mass. Performing precursor ion scans in the positive ion mode facilitates sequencing, because there is a no need for polarity switching or changing pH of the spraying solvent. Similar limits of detection were obtained in this approach when compared to triple-quadrupole mass spectrometers but with significantly better selectivity, owing to the high accuracy of the fragment ion selection. Synthetic phosphopeptides could be detected at 1 fmol/microL, and 100 fmol of a tyrosine phosphorylated protein in gel was sufficient for the detection of the phosphorylated peptide in the unseparated digestion mixture and for unambiguous phosphorylation site determination. The new method can be applied to unknown protein samples, because the identification and localization of the modification is performed on the same sample.     

Influence of Boundary Conditions on the Dynamic Characteristics of Squeeze Films in MEMS Devices

Micromechanical structures that have squeeze-film damping as the dominant energy dissipation mechanism are of interest in this paper. For such structures with narrow air gap, the Reynolds equation is used for calculating squeeze-film damping, which is generally solved with trivial pressure boundary conditions on the side walls. This procedure, however, fails to give satisfactory results for structures under two important conditions: 1) for an air gap thickness comparable to the lateral dimensions of the microstructure and 2) for nontrivial pressure boundary conditions such as fully open boundaries on an extended substrate or partially blocked boundaries that provide side clearance to the fluid flow. Several formulas exist to account for simple boundary conditions. In practice, however, there are many micromechanical structures such as torsional microelectromechanical system (MEMS) structures that have nontrivial boundary conditions arising from partially blocked boundaries. Such boundaries usually have clearance parameters that can vary due to fabrication. These parameters, however, can also be used as design parameters if we understand their role on the dynamics of the structure. We take a MEMS torsion mirror as an example device that has large air gap and partially blocked boundaries due to static frames. We actuate the device and experimentally determine the quality factor Q from the response measurements. Next, we model the same structure in ANSYS and carry out computational fluid dynamics analysis to evaluate the stiffness constant K, the damping constant D, and the quality factor Q due to the squeeze film. We compare the computational results with experimental results and show that without taking care of the partially blocked boundaries properly in the computational model, we get unacceptably large errors.     

Diamond like carbon coatings deposited by microwave plasma CVD: XPS and ellipsometric studies

Diamond-like carbon (DLC) films were deposited by microwave assisted chemical vapour deposition system using d.c. bias voltage ranging from −100 V to −300 V. These films were characterized by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry techniques for estimating sp ³/sp ² ratio. The sp ³/sp ² ratio obtained by XPS is found to have an opposite trend to that obtained by spectroscopic ellipsometry. These results are explained using sub-plantation picture of DLC growth. Our results clearly indicate that the film is composed of two different layers, having entirely different properties in terms of void percentage and sp ³/sp ² ratio. The upper layer is relatively thinner as compared to the bottom layer.     

Tracking-based baseline restoration circuit for acquisition of bio signals

Most bio signal waveforms have a baseline that may drift over a large range compared to the excursion of the signal component. A circuit is developed, based on the amplitude tracking technique, for fast estimation and removal of the baseline drift, for effective use of the input dynamic range of the signal acquisition setup     

Changes in the glaciers of Chandra–Bhaga basin,Himachal Himalaya,India, between 1980 and 2010 measured using remote sensing

This study reports the glacier changes of Chandra–Bhaga basin, northwest Himalaya, India, from 1980 to 2010. Satellite remote-sensing data from the Landsat Multispectral Scanner (MSS) and Thematic Mapper (TM), the Linear Imaging Self Scanning Sensor (LISS) and Advanced Wide Field Sensor (AWiFS) of the Indian Remote Sensing (IRS) series, and the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) were used to study the changes in glacier parameters such as glacier area, length, snout elevation, and the impact of glacier topographical parameters (glacier slope, aspect, and altitude range) on the glacier changes. It was found that the total glaciated area had shrunk to 368.2 km² in 2010 from 377.6 km² in 1980, a loss of 2.5%. The average position of glacier terminuses retreated by 465.5 ± 169.1 m from 1980 to 2010 with an average rate of 15.5 ± 5.6 m year^?1. The decadal scale analysis showed that the average rate of retreat had increased the most in the recent decade. A moraine-dammed lake located in the study region was found to have expanded in area from (0.65 ± 0.01) km² in 1980 to (1.26 ± 0.03) km² in 2010. Glaciers with steep slope and less altitude range have lost more area than the glaciers having gentle slope and greater altitude range.     

Harnessing the sun for an evergreen revolution: a study of solar-powered irrigation in Bihar,India

In 2012, the government of Bihar revived 34 non-functioning public tubewells using solar panels. The performance of 16 of these wells over 12 months was tracked and analyzed using data from tubewell operators and 240 farmers. Access to affordable irrigation from solar pumps led to a 9–10% increase in productivity of rice and wheat. Furthermore, in a severe drought, farmers could grow paddy in the entire area irrigated by solar pumps, when nearly 40% of other land was left fallow. Solar pumps can help increase crop productivity, reduce the cost of irrigation, and make agriculture more resilient to climate change.     

Moisture adsorption behaviour of esterified rubber wood (Hevea brasiliensis)

Hevea brasiliensis ) esterified with acetic anhydride, maleic anhydride and phthalic anhydride was studied for moisture adsorption behaviour. FTIR spectroscopic technique was used to analyse the chemical changes in the wood through the correspondent reactions. Spectra indicated increasing intensity of the C=O and C-O stretching bands, and reduction in O-H stretching vibrations that reflects formation of less hygroscopic ester bonds with hydroxyl groups of cell wall polymers. Moisture adsorption isotherms show low equilibrium moisture content in esterified wood at all relative humidity values as compared to a control. The adsorption data was analysed by applying Hailwood-Horrobin theory which separated the adsorbed water into hydrated water and dissolved water corresponding to mono-layer and multi-layer adsorption. Curve for M_h and M_s were similar in pattern for esterified wood and control with different magnitude. Low M_h and M_s in esterified wood indicate reduction in moisture adsorption sites. Inaccessible fraction of wood for water vapour was increased by 43%, 32% and 26% in acetic, maleic and phthalic anhydride treated wood, respectively, compared to the control. Acetic anhydride treatment was found most effective in reducing hygroscopicity of wood.

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Hevea brasiliensis ) wurde verestert mit Anhydriden der Maleins?ure, Essigs?ure und Phtals?ure. Das Adsorptionsverhalten bei verschiedenen Feuchten wurde mit FTIR-Methoden untersucht, um die entsprechenden chemischen Abl?ufe zu erfassen. Intensivere C=O, und -C-O- Streckschwingungen sowie reduzierte OH-Schwingungen reflektieren die neu gebildeten, weniger hygroskopischen Esterbindungen. Bei allen modifizierten Proben ergaben sich niedrigere Gleichgewichtsfeuchten. Die Adsorptions-Isothermen wurden mit Hilfe der Hailwood-Horrobin Theorie analysiert, um adsorbiertes (M_h) und gel?stes (M_s) Wasser zu unterscheiden. Der Kurvenverlauf für M_h und M_s für modifiziertes und unbehandeltes Holz war qualitativ ?hnlich, und unterschied sich nur quantitativ. Geringe Werte für M_h und M_s zeigen eine Verringerung der m?glichen Adsorptionsstellen an. Der nicht zug?ngliche Anteil des Holzes, bezogen auf Kontrollproben, verringerte sich auf 43% (Acetanhydrid), 32% (Maleins?ureanhydrid) und 26% (Phthals?ureanhydrid). Acetanhydrid erwies sich als das effektivste Mittel, um die Hygroskopizit?t zu erniedrigen.

     

Crystallization, microstructure development and dielectric behaviour of glass ceramics in the system [SrO · TiO2]-[2SiO2 · B2O3]-La2O3

Various glasses in the system (65 – x)[SrO · TiO₂]-(35)[2SiO₂ · B₂2O₃]-(x)La₂O₃, where x = 1,5,10 (wt%) were prepared by melting in alumina crucible (1375–1575 K). Heat treatment schedules were selected from DTA plots of respective glasses. X-ray diffraction studies of glass ceramic samples containing different concentrations of La₂O₃ revealed the formation of Sr₂B₂O₅, Sr₃Ti₂O₇ and TiO₂ (rutile) phases. The addition of La₂O₃ results in the development of well formed, elongated crystallites of different phases. Results of the dielectric behaviour demonstrate higher values of dielectric constant for some of the glass ceramic samples. This can be ascribed to the relaxation polarization at the crystal-glass interface due to conductivity differences between crystalline and glassy phases.