Screening and sequencing of glycated proteins by neutral loss scan LC/MS/MS method

Nonenzymatic protein glycation is caused by a Schiff's base reaction between the aldehyde groups of reducing sugars and the primary amines of proteins. A reversed-phase liquid chromatography method followed by a neutral loss scan mass spectrometric method was developed for the screening of glycation in proteins. The neutral loss scan was based on a unique sugar moiety neutral loss (-162 Da) that we observed in the fragmentation spectra of glycated peptides on Q-Tof type mass spectrometers. The collision energy was optimized for this neutral loss using a glycated synthetic peptide, and 20 eV was found to be the optimum collision energy. The neutral loss scan experiment was composed of two segments. In the first segment, the glycated peptides were identified based on the signature neutral loss of 162 Da when the collision energy was elevated to 20 eV. In the second segment, the glycated peptides were selected as the parent ions and fragmented at higher collision energy to break the peptide bonds. The fragmentation spectra of the selected glycated peptides revealed both the amino acid sequences and the sites of glycation. This neutral loss scan method was used to study the glycation in human serum albumin (HSA). The glycation sites in HSA were identified based on the retention time shift of glycated peptides, the mass accuracy from the MS scan, the signature neutral loss, and MS/MS information. Using this method, we were able to identify that 31 lysine residues were partially glycated from the glycated HSA sample, which has a total of 59 lysine residues.     

Controlled drug release characteristics and enhanced antibacterial effect of graphene nanosheets containing gentamicin sulfate

A novel methanol derived graphene (MDG) and gentamicin sulfate nanohybrid was prepared, and the loading and release behaviour of gentamicin on MDG is investigated. An efficient drug loading of 2.57 mg mg(-1) was obtained at pH 7. By applying release kinetic models, the mechanism of release of the drug from the MDG matrix was found to be following the Korsmeyer-Peppas model. However, the diffusional release exponent (n) value lies below 0.5 demonstrating that the mechanism controlling the drug release is the Fickian diffusion.     

Low‐Energy Ion‐Scattering Spectroscopy of Modified Silicate Glasses

Low‐Energy Ion‐Scattering (LEIS) spectroscopy is a technique with a unique sensitivity to the elemental composition of the top atomic layer of a solid surface. LEIS measurements of ternary silicate glasses modified with Na₂O, Cs₂O, CaO, and BaO show that the compositions of the as‐cast (melt) surface and the in‐vacuum fracture surface often differ. While the as‐cast surface is usually depleted of alkali ions (Na⁺ or Cs⁺) compared to the nominal (batch) glass composition, there is often strong accumulation of the same mobile cations on the fresh fracture surface. Depth profiles obtained by sputter etching reveal elemental concentration gradients normal to the glass surface. The final concentrations often fail to reach the nominal glass composition, suggesting the likely presence of preferential sputtering effects and thereby the distortion of the measured concentration gradient. At present, the lack of reliable standards and preferential sputtering effects in the LEIS of multicomponent glasses limit somewhat the absolute chemical composition and structural information that can be obtained with this otherwise unique and powerful method of surface analysis.     

ISOTHERMAL FATIGUE BEHAVIOR OF SIGMA/T1METAL 21S LAMINATES,PART I: EXPERIMENTAL RESULTS

Experimental results are reported on the effect of static and cyclic loading (at 0.1 and 0.001 Hz) on the inelastic response of and damage development in (0)4, (0190), and (0/ ±45/90), SiC/Ti (Sigma/Timetal 21S) laminates, and the Timetal 21S matrix, at 650^°C and 21^°C. At the elevated temperature, viscoplastic deformation of the matrix can be observed even at relatively low applied stresses. At both temperatures, reduction of unloading elastic moduli of the laminates, which indicates onset of damage by interface decohesion, also starts after hailing to relatively low stresses. The cyclic loading rate has a significant effect on the number of cycles to failure, but not on the endurance limit of the (0/90), and (0/ ±45/90), laminates loaded by constant-amplitude tension at 650^°C. In the (0)₄ laminate, higher endurance limits were detected at 0.1 Hz than at 0.001 Hz However, regardless of loading rate and layup, the total strain at failure under both static and cyclic loading at 650^°C was measured at 1 ±0.1%. The experimental results are interpreted by micromecha-nical models in Part II [1].     

A computational analysis of the impact of mass transport and shear on three-dimensional stem cell cultures in perfused micro-bioreactors

In this study, Computational Fluid Dynamics(CFD) is used to investigate and compare the impact of bioreactor parameters(such as its geometry, medium flow-rate, scaffold configuration) on the local transport phenomena and, hence, their impact on human mesenchymal stem cell(hM SC) expansion. The geometric characteristics of the TissueFlex174;(Zyoxel Limited, Oxford, UK) microbioreactor were considered to set up a virtual bioreactor containing alginate(in both slab and bead configuration) scaffolds. The bioreactor and scaffolds were seeded with cells that were modelled as glucose consuming entities. The widely used glucose medium, Dulbecco's Modified Eagle Medium(DMEM), supplied at two inlet flow rates of 25 and 100 μl·h~(-1), was modelled as the fluid phase inside the bioreactors. The investigation, based on applying dimensional analysis to this problem, as well as on detailed three-dimensional transient CFD results, revealed that the default bioreactor design and boundary conditions led to internal and external glucose transport, as well as shear stresses, that are conducive to h MSC growth and expansion. Furthermore, results indicated that the ‘top-inout' design(as opposed to its symmetric counterpart) led to higher shear stress for the same media inlet rate(25 μl·h~(-1)), a feature that can be easily exploited to induce shear-dependent differentiation. These findings further confirm the suitability of CFD as a robust design tool.     

Toward perfect antireflection coatings: numerical investigation

A perfect antireflection (AR) coating would remove completely the reflection from an interface between two media for all wavelengths, polarizations, and angles of incidence. The degree to which this can be achieved is investigated numerically. It is shown that wideband solutions can be found provided that layers can be deposited with refractive indices that are close to that of the low-index medium. Thus realistic solutions exist for interfaces between two solid media. Narrow-band high-angle AR solutions are also possible for polarized light and for unpolarized light in the vicinity of certain reststrahlen bands.     

Crack interaction study in piezoelectric materials under thermo-electro-mechanical loading environment

Multiple voids and cracks were generated during material processing techniques, which interact with each other and affects the service performance of piezoelectric components. This work aims to study the behavior of piezoelectric components in presence of multiple cracks under thermo-electro-mechanical loading environment. Extended finite element method has been implemented to model geometrical discontinuities with crack interaction phenomenon. In this work, thermo-electro- mechanical problem has been decoupled into thermal and electro-elastic problems. Temperature distribution has been obtained by solving heat conduction equation and then used as an input to the electro-elastic problem. In post processing phase, interaction integral method and generalized Stroh formalism were used to predict the stress intensity factors. The methodology has been implemented with in-house developed MATLAB code. Set of cases for crack interaction studies were presented using the proposed approach.

     

A sustainable multi-parametric sensors network topology for river water quality monitoring

Wireless Networks - The deterioration of water quality due to natural and man-made hazards has affected the life on the Earth. Hence, water quality needs to be monitored regularly. The traditional...