Performance analysis of electrically coupled SRR bowtie antenna for wireless broadband communications

Wireless Networks - This paper presents a broadband Bowtie antenna with metamaterial periodical structure for broadband wireless systems and emerging 5G communication frequency band. The modified...     

Structural interpretation of site-directed mutagenesis and specificity of the catalytic subunit of protein kinase CK2 using comparative modelling

The catalytic subunit of protein kinase casein kinase 2 (CK2),which has specificity for both ATP and GTP, shows significantamino acid sequence similarity to the cyclin-dependent kinase2 (CDK2). We constructed site-directed mutants of CK2 and useda three-dimensional model to investigate the basis for the dualspecificity. Introduction of Phe and Gly at positions 50 and51, in order to restore the pattern of the glycine-rich motif,did not seriously affect the specificity for ATP or GTP. Weshow that the dual specificity probably originates from theloop situated around the position His115 to Asp120 (HVNNTD).The insertion of a residue in this loop in CK2 subunits, comparedwith CDK2 and other kinases, might orient the backbone to interactwith the base A and G; this insertion is conserved in all knownCK2. The mutant N118, the design of which was based on the modelling,showed reduced affinity for GTP as predicted from the model.Other mutants were intended to probe the integrity of the catalyticloop, alter the polarity of a buried residue and explore theimportance of the carboxy terminus. Introduction of Arg to replaceAsn189, which is mapped on the activation loop, results in amutant with decreased k_cat, possibly as a result of disruptionof the interaction between this residue and basic residues inthe vicinity. Truncation at position 331 eliminates the last60 residues of the subunit and this mutant has a reduced catalyticefficiency compared with the wild-type. Catalytic efficiencyis restored in the truncation mutant by the replacement of apotentially buried Glu at position 252 by Lys, probably owingto a higher stability resulting from the formation of a saltbridge between Lys252 and Asp208.     

Synthesis,molecular docking and antibacterial evaluation of 2-(4-(4-aminophenylsulfonyl)phenylamino)-3-(thiophen-2-ylthio)naphthalene-1,4-dione derivatives

A new series of 2-(4-(4-aminophenylsulfonyl)phenylamino)-3-(thiophen-2-ylthio)naphthalene-1,4-dione derivatives (3a-3n) were synthesized and characterized by spectral techniques. To understand the interaction of binding sites with bacterial protein receptor, the docking study was performed by the GLIDE program and compound N-(4-(4-(1,4-dioxo-3-(thiophen-2-ylthio)-1,4-dihydronaphthalen-2-ylamino)phenylsulfonyl)phenyl)-3-methylbenzamide (3b) exhibited good glide and E model scores of ?5.89 and ?94.90, respectively. Moreover among all the molecules studied including the standards used, namely Sparfloxacin (4.8 μg/mL) and Norfloxacin (no inhibition observed) for their antibacterial property, compound N-(4-(4-(1,4-dioxo-3-(thiophen-2-ylthio)-1,4-dihydronaphthalen-2-ylamino)phenylsulfonyl)phenyl)-4-nitrobenzamide (3e) exhibited the lowest minimum inhibitory concentration (MIC) value of 1.3 μg/mL against Proteus vulgaris.     

Mutagenesis, biochemical characterization and X-ray structural analysis of point mutants of bovine chymosin

Chymosin B point mutants, A115T and G243D (chymosin A), were expressed in Escherichia coli and Trichoderma reesei respectively, characterized biochemically, crystallized and studied by X-ray analysis at 2.3 and 2.8 angstroms resolutions respectively. The three-dimensional structures showed that the mutations gave rise to local conformational changes only when compared with that of chymosin B. Kinetic analysis of the A115T mutant with a six residue synthetic peptide revealed a reduction in Km with respect to the wild type, possibly caused by the small local changes in the vicinity of S1 and S3. Although, kinetic analyses of the G243D mutant using the short substrate showed reduced catalytic activity, use of a 15 residue substrate based on residues 98- 112 of kappa-casein, the natural substrate, revealed an increase in the kcat compared with chymosin B, probably a consequence of the charge introduced that may interact with the substrate between P4 and P8.      

Crystal structure and characterization of a novel organic optical crystal: 2-Aminopyridinium trichloroacetate

2-Aminopyridinium trichloroacetate, a novel organic optical material has been synthesized and crystals were grown from aqueous solution employing the technique of controlled evaporation. 2-Aminopyridinium trichloroacetate crystallizes in monoclinic system with space group P2₁/c and the lattice parameters are a = 8.598(5) Å, b = 11.336(2) Å, c = 11.023(2) Å, β = 102.83(1)° and volume = 1047.5(3) Å³. High-resolution X-ray diffraction measurements were performed to analyze the structural perfection of the grown crystals. Thermal analysis shows a sharp endothermic peak at 124 °C due to melting reaction of 2-aminopyridinium trichloroacetate. UV-vis-NIR studies reveal that 2-aminopyridinium trichloroacetate has UV cutoff wavelength at 354 nm. Dielectric studies show that dielectric constant and dielectric loss decreases with increasing frequency and finally it becomes almost a constant at higher frequencies for all temperatures. The negative nonlinear optical parameters of 2-aminopyridinium trichloroacetate were derived by the Z-scan technique.     

Free and bound triacontanol in tea leaves

A direct gas chromatographic method of identification and determination of 1-triacontanol, a plant growth substance, in tea leaves is reported. Treatment of the tea leaves with calcium oxide releases more triacontanol, showing that the compound occurs also in a bound form in tea leaves.