Comparative structural studies of psychrophilic and mesophilic protein homologues by molecular dynamics simulation

Comparative molecular dynamics simulations of psychrophilic type III antifreeze protein from the North-Atlantic ocean-pout Macrozoarces americanus and its corresponding mesophilic counterpart, the antifreeze-like domain of human sialic acid synthase, have been performed for 10 ns each at five different temperatures. Analyses of trajectories in terms of secondary structure content, solvent accessibility, intramolecular hydrogen bonds and protein–solvent interactions indicate distinct differences in these two proteins. The two proteins also follow dissimilar unfolding pathways. The overall flexibility calculated by the trace of the diagonalized covariance matrix displays similar flexibility of both the proteins near their growth temperatures. However at higher temperatures psychrophilic protein shows increased overall flexibility than its mesophilic counterpart. Principal component analysis also indicates that the essential subspaces explored by the simulations of two proteins at different temperatures are non-overlapping and they show significantly different directions of motion. However, there are significant overlaps within the trajectories and similar directions of motion of each protein especially at 298 K, 310 K and 373 K. Overall, the psychrophilic protein leads to increased conformational sampling of the phase space than its mesophilic counterpart.Our study may help in elucidating the molecular basis of thermostability of homologous proteins from two organisms living at different temperature conditions. Such an understanding is required for designing efficient proteins with characteristics for a particular application at desired working temperatures.     

A CMOS low noise amplifier based on common source technique for ISM band application

In this paper a 2.45 GHz narrowband low noise amplifier (LNA) for wireless communication system is enunciated. The proposed CMOS Low Noise amplifier has been verified through cadence spectre RF simulation in standard UMC 90 nm CMOS process. The proposed LNA is designed by cascoding of two transistors; that is the common source transistor drives a common gate transistor. To achieve better power gain along with low noise figure, cascoding of two transistor and source degeneration technique is used and for low power consumption, the MOS transistors are biased in subthreshold region. At 2.45 GHz frequency, it exhibits power gain 31.53 dB. The S11, S22 and S12 of the circuit is ?9.14, ?9.22 and ?38.03 dB respectively. The 1 dB compression point of the circuit is ?16.89 dBm and IIP3 is ?5.70 dBm. The noise figure is 2.34 dB, input/output match of ?9.14 dB/?9.22 dB and power consumption 8.5 mW at 1.2 V.     

Effect of the doses and nature of vegetable oil on carbon black/rubber interactions: Studies on castor oil and other vegetable oils

The effects of additives in various vegetable oils on the physical, mechanical, and adhesion properties of carbon black/rubber compounds were studied. Various doses of castor oil and some other oils such as paraffin oil, vegetable oil 1, and cashew nut shell liquid (CNSL) at a fixed dose (1 phr) were used. With an increase in the castor oil content, the modulus, tear strength, and tensile strength increased, whereas the hardness and adhesive strength exhibited little variation up to 1 phr. Beyond 1 phr castor oil, the modulus, tear strength, and hardness decreased, whereas the adhesive and tensile strengths increased up to 2.5–3 phr and then decreased. Therefore, castor oil seemed to behave as a coupling agent up to 1 phr and as a coupling agent and a plasticizer in the range of 1–3 phr; beyond that, the main role of castor oil was plasticization. When various oils at a fixed dose (1 phr) were compared, it was found that the vegetable oils exhibited enhanced properties in comparison with those of paraffin oil. In addition, both of the unsaturated oils (castor oil and vegetable oil 1) enhanced physical and mechanical properties in comparison with saturated paraffin oil. CNSL exhibited the best adhesion properties against mild steel and galvanized iron substrates. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1574–1578, 2003     

Mechanical properties of Nafion™ electrolyte membranes under hydrated conditions

Polymer electrolyte membrane fuel cells use a polymer membrane as the electrolyte to transport hydrogen ions from the anode to the cathode side. This paper reports a study of mechanical (stress-strain curves) and dynamic mechanical (temperature sweeps) properties of membranes made using Nafion™ under dry and hydrated conditions. Hydrating the membranes reduced the mechanical properties. Specifically there was significant change in the Young's modulus, yield strength, and transition temperatures of the different membranes tested. Presence of contaminant ions was studied through an ion exchange technique using selected ions (Na⁺, K⁺, Mg²⁺, Cu²⁺, Ni²⁺). Ion exchange in hydrated samples increased the stiffness of the material as well as the yield strength in order of increasing ionic radius. Transition onset temperatures observed on the mechanical damping of hydrated membranes also increased with the addition of ions.     

Resistance to Hardness of Water as an Analytical Parameter of Soap Quality

Resistance of soap to hardness of water as reflected by its ability to lather in hard water has been tried as as analytical parameter to assess the quality and hence effectiveness of the soap. The resistance of a soap to hardness of water can be considered to be the sum total effect of four factors: 1. Composition of the fat base, 2. solubility of the soap at the washing temperature, 3. polymorphism of soap crystals and 4. nature and proportions of additives in the soap. The method thus helps in assessing the quality of the soap with regard to these factors and in working out the economics of its use.     

Ion-solvent interactions in dimethylformamide + water mixtures

Standard Gibbs energies of transfer, ΔG°_t, of MCl (M = Li, Na, K, Rb and Cs) and K X (X = Br and I) have been determined by use of the double cells comprising M(Hg) and AgXAg electrodes in some aqueous mixtures of DMF at 25°C. These values were dissected into individual ion contributions using TATB reference electrolyte assumption, as obtained by measuring the solubility products of the salts viz. KPic, KBPh₄ and Ph₄AsPic. The observed increasingly positive magnitudes of ΔG°_t of the halide ions and the increased negative magnitudes of the cations including H⁺, reflect the well known anion-destabilization and the larger “basicity” and cationotropism of the aqueous mixtures of this co-solvent. And the observed distinctly flat regions of ΔG°_t curves of cations over an intermediate composition are attributable to strong intercomponent interactions. Comparison of the results with those in DMSO—water are ACN—water mixtures reveals that the solvating characteristics of DMF—water are somewhat similar to that of DMSO—water but different from that of ACN—water mixtures. Moreover, while the observed relative behaviour of Pic^? are found to be guided by the combined effects of dispersion interactions and anion destabilisation of these co-solvents, that of the large-sized tetraphenyl ion is, however, guided by the combined effects of dispersion interactions as well as the “cavity-forming” interactions as estimated in the light of scaled particle theory.     

Effect of different film preparation procedures on the thermal,morphological and mechanical properties of pure and calcite‐filled HDPE films

The effect of different film preparation procedures on the thermal, morphological and mechanical properties of high density polyethylene (HDPE) films have been studied using differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and ultimate tensile testing. Film preparation procedures included variation in cooling methods, including quenching, forces (fanning) and natural cooling and techniques such as extrusion followed by melt squeezing and compression molding. The heat of fusion (from DSC), the degree of crystallinity (from WAXRD) and the crystallite size (from WAXRD and AFM) were found to be highest for naturally cooled specimens, followed by fan‐cooled and quenched ones. AFM images of surface topology exhibit stacked lamellar morphology for forcefully cooled (fan‐cooled and quenched) samples and spherulitic ‘lozenges’ for naturally cooled ones. The Young's modulus and yield stress [from the universal testing machine (UTM)] were highest for naturally cooled samples, followed by fan‐cooled and quenched ones. Among the calcite‐filled composites, the ‘base film,’ which was prepared by extrusion followed by melt squeezing and natural cooling, exhibited the lowest heat of fusion and degree of crystallinity and a similar crystallite size relative to compression‐molded films. Lower yield stress, tensile strength and Young's modulus and higher elongation at break were observed for the base film in comparison to the naturally cooled composite film. The low degree of crystallinity and crystallite size in the ‘base film’ explain all of its mechanical and morphological properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1427–1434, 2004     

THERMODYNAMICS OF ALKANOLAMINE+WATER SYSTEM

Design of gas treating processes requires knowledge of the vapor-liquid equilibrium behavior of the (acid gas + aqueous alkanolamine) system. The present study is focused on thermodynamics and associated nonideal behavior of binary MEA + H₂O, DEA + H₂O, and MDEA + H₂O systems, which is required to predict the vapor-liquid equilibrium of acid gases such as CO₂ and H₂S over aqueous alkanolamine solutions. Determination of binary interaction parameters and analytical prediction of infinite dilution activity coefficient, heats of solution at infinite dilution, the excess Gibbs free energy, and excess enthalpy for nonideal alkanolamine-water systems are the objectives of this study.     

Utilizing time-linkage property in DOPs: An information sharing based Artificial Bee Colony algorithm for tracking multiple optima in uncertain environments

An information sharing artificial bee colony (ABC) algorithm has been proposed for locating and tracking multiple peaks in non-stationary environments. The niching method has been adapted by hybridizing two techniques. A modified variant of the fitness sharing has been used for detecting multiple peaks simultaneously and a speciation based technique is employed to keep the better individuals of the previous generation. The base algorithm used here is a modified variant of ABC that helps to synchronize the employer and onlooker forager swarms by synergizing the local information. The main crux of our algorithm is its independency of the problem dependent control parameters, like niche radius, and the absence of any hard-partitioning technique that leads to high computational burden. Our framework aims at bringing about a simple, robust approach that can be applied to a variety of dynamic functional landscapes. Experimental investigations are undertaken on standard benchmarks focussing on the competitive performance of our algorithm in contrast to the existing state-of-the-art to highlight the significance of our work.     

Efficient dispersion in a modified two-phase non-Newtonian downflow bubble column

A comprehensive study of dispersion of gas-non-Newtonian fluid has been made in a modified downflow bubble column. Distribution of gas holdup in axial location has been anticipated from hydrostatic force balance. The experimental gas holdup data in such modified bubble column have been analyzed by slip velocity and drift-flux models. A correlation in terms of various physical, geometric and operating parameters of the present system has also been developed to analyze the gas holdup.