Expected and unexpected results from combined beta-hairpin design elements

A model beta-hairpin dodecapeptide [EFGWVpGKWTIK] was designed by including a favorable D-ProGly Type II' beta-turn sequence and a Trp-zip interaction, while also incorporating a beta-strand unfavorable glycine residue in the N-terminal strand. This peptide is highly folded and monomeric in aqueous solution as determined by combined analysis with circular dichroism and 1H NMR spectroscopy. A peptide representing the folded conformation of the model beta-hairpin [cyclic(EFGWVpGKWTIKpG)] and a linear peptide representing the unfolded conformation [EFGWVPGKWTIK] yield unexpected relative deviations between the CD and 1H NMR spectroscopic results that are attributed to variations in the packing interactions of the aromatic side chains. Mutational analysis of the model beta-hairpin indicates that the Trp-zip interaction favors folding and stability relative to an alternate hydrophobic cluster between Trp and Tyr residues [EFGYVpGKWTIK]. The significance of select diagonal interactions in the model beta-hairpin was tested by rearranging the cross-strand hydrophobic interactions to provide a folded peptide [EWFGIpGKTYWK] displaying evidence of an unusual backbone conformation at the hydrophobic cluster. This unusual conformation does not appear to be a result of the glycine residue in the beta-strand, as replacement with a serine results in a peptide [EWFSIpGKTYWK] with a similar and seemingly characteristic CD spectrum. However, an alternate arrangement of hydrophobic residues with a Trp-zip interaction in a similar position to the parent beta-hairpin [EGFWVpGKWITK] results in a folded beta-hairpin conformation. The differences between side chain packing of these peptides precludes meaningful thermodynamic analysis and illustrates the caution necessary when interpreting beta-hairpin folding thermodynamics that are driven, at least in part, by aromatic cross strand interactions.     

Development of fish gelatin-based artificial fish baits incorporating bioattractants from seafood processing waste

The study dealt with evolving an artificial fish bait by incorporating bioattractant concentrates derived from seafood processing wastes by enzymatic hydrolysis namely fish waste concentrate (FWC), squid waste concentrate (SWC), and shrimp processing concentrate (SPWC). They were characterized based on amino acid content and presence of different functional groups using FTIR. Among them, SWC was found to have the highest amino acid content of 60.85mg/100 mg followed by FWC (42.21mg/100 mg) and SPWC (24.82mg/100 mg). The developed artificial fish baits were subjected to protein leaching, solubility in seawater besides testing for acceptability by the red snapper. The study revealed that the bait incorporated with SWC at 3% level was found be the most ideal, with the protein leaching rate of 24.82 mg/g/h, solubility rate of 36.6 mg/g/h and the attractability score of 29/30. The amino acid leaching rate was 3.11 mg/h/100 mg and it was found to contain five amino acids such as glycine, proline, glutamic acid, alanine and serine. The study revealed that the hydrolyzed squid waste concentrate can be incorporated at 3% (w/w) with fish gelatin based biomatrix during gelation to prepare artificial bait.     

Effect of an external electric field on two-dimensional nucleation

Summary Two-dimensional nuclei of different possible shapes are considered in the presence of an external electric field which is applied either perpendicular or parallel to the nucleation surface. The additional driving force needed for the formation of a nucleus due to the electric field is found and used in the nucleation theory. The results show that the electric field can either stimulate or inhibit the nucleation process depending on the ratio of the dielectric constants and the orientation of the applied electric field with respect to the nucleation surface. The dependence of the two-dimensional nucleation rate on the intensity of electric field is also determined.

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Riassunto Si considerano nuclei bidimensionali di differenti forme possibili in presenza di un campo elettrico esterno che è applicato sia perpendicolare che parallelo alla superficie di nucleazione. Si trova e si usa nella teoria di nucleazione l’ulteriore forza guida necesaria per la formazione di un nucleo a causa del campo elettrico. I risultati mostrano che il campo elettrico può sia stimolare che inibire il processo di nucleazione che dipende dal rapporto delle costanti dielettriche e dell’orientamento del campo elettrico applicato rispetto alla superficie di nucleazione. Si determina anche la dipendenza del valore di nucleazione bindimensionale dall’intensità del campo elettrico.

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Резюме Рассматриваются двумерные ядра различных возможиых форм в присутствии внешнего электрического поля, которое либо перпендикулярно, либо параллельно поверхности вародышеобразования. Определяется и используется в теории зародяшеобразования дополнительная движущая сила, необходимая для образования ядра, всл⪟дствие действия электрического поля. Полученные результатя показяают, что электрическое поле может либо стимулировать, либо тормозить процесс зародышеобразования в зависимости от отношения диэлектричеких постоянных и от ориентации приложенного электричеслог поля отнонительно поверхности зародышеодразования. Такзе определяется зависимость скорости образвания двумерных ядер от интенсивности электрического поля.

     

Robust guaranteed cost control for discrete‐time systems via partially delay‐dependent controller with linear fractional uncertainties

In this article, a partially delay‐dependent controller is designed to analyze the guaranteed performance analysis of a class of uncertain discrete‐time systems with time‐varying delays. By constructing suitable Lyapunov–Krasovskii Functional (LKF), sufficient conditions are derived to ensure the system to be robustly stochastically stable in mean square sense by using Wirtinger‐based inequality and convex reciprocal lemma. The proper cost function is chosen to guarantee an adequate level of performance. The derived conditions are expressed in terms of linear matrix inequalities (LMIs) which can be easily solved by LMI Toolbox in MATLAB. Further, the advantage of employing the obtained results is illustrated via numerical examples. © 2016 Wiley Periodicals, Inc. Complexity 21: 113–122, 2016     

Hydrothermal synthesis of chalcopyrite CuInS2, CuInSe2 and CuInTe2 nanocubes and their characterization

CuInS₂, CuInSe₂ and CuInTe₂ nanocubes of chalcopyrite structure have been successfully synthesized by hydrothermal process using deionized water as solvent at 180 °C for 20 h. The crystallinity, compositional, morphological and optical properties of the synthesized samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), Raman and photoluminescence (PL) spectra analyses. The Raman spectra of the synthesized CuInS₂, CuInSe₂ and CuInTe₂ samples show the dominant A₁ modes at 293, 172 and 121 cm⁻¹ respectively. The possible chemical reaction and mechanism of nanocubes formation were discussed. The emission wavelength of as synthesized CuInS₂, CuInSe₂ and CuInTe₂ samples were blue shifted at 746 nm (1.66 eV), 863 nm (1.43 eV) and 859 nm (1.44 eV) respectively.     

Effect of N ion implantation on the optical properties of an organometallic complex—Zinc cadmium thiocyanate single crystal

A highly efficient non-linear optical organometallic compound zinc cadmium thiocyanate (ZCTC) single crystal was grown by solvent evaporation method. The as grown single crystals were implanted with 45 keV N⁵⁺ ions having energy at various fluencies of 1 × 10¹⁵, 5 × 10¹⁵, 1 × 10¹⁶ and 5 × 10¹⁶ ions/cm². The surface modification induced by the ion implantation was studied using scanning electron microscopy. The UV spectrum shows an increase in absorbance with the increase in the dosage of the ions implanted. There is a red shift in the cut off wavelength due to implantation which may be attributed to the lattice damage produced during implantation. From the Raman spectra, it is observed that there is no shift in the peak positions or any extra peaks due to implantation confirming that the nitrogen ions are not substituted into the lattice. The FWHM, area and intensity of the Raman peak corresponding to CN stretching vibration were calculated and the influence of ion implantation on these parameters was discussed. The effect of implantation on the PL spectra was analysed and discussed in detail. The change in refractive index of the sample due to implantation was reported.     

Characterization of electroplated ZnTe coatings

Zinc telluride (ZnTe) layers have been grown on conducting glass substrates using an electrochemical technique and characterized using cyclic voltammetry, X-ray diffractions, UV–vis-near infrared spectroscopy, and scanning electron microscopy (SEM). The reaction kinetics of binary film formation is also discussed. Cyclic voltammetry experiments were performed to elucidate the electrodic processes that occurred when potentials were applied and the optimum potential for electrodeposition were determined. X-ray diffraction studies revealed that the deposited films were polycrystalline in nature with zinc blende cubic structure. The various microstructural parameters were calculated using structural studies. The optical transmission and reflection spectrum were recorded and direct transition band gap energy is estimated about 2.26 eV by Tauc’s plot. The SEM pictures revealed that the nanoneedles protruding from nanorods with bunches of atoms agglomerate each other. The energy dispersive analysis by X-rays spectrum revealed the stoichiometry composition of ZnTe thin film at optimized preparative parameters.     

Synthesis and structural characterization of chiral dicationic imidazolophanes

Various chiral dicationic benzimidazolophanes were obtained from optically pure (S)-BINOL, benzimidazole and a suitable aryl alkyl dibromide.     

Effect of complexing agent (1,10-phenanthroline) on ADP and KDP crystals

1,10-Phenanthroline (Phen) as a new additive was added into the solutions of KH₂PO₄ (KDP) and NH₄H₂PO₄ (ADP) in a small amount (∼2.5·10⁻³ M L⁻¹). The crystals were grown from the aqueous solutions of pH ∼4.5 at constant temperature by solvent evaporation technique. It leads to an increase in metastable zone width and assists the bulk growth process. The growth rate of crystals in the presence of Phen decreases considerably with an increase in impurity concentration (∼2.5·10⁻² M L⁻¹). Not much variation is observed in FTIR and XRD of pure and doped ADP/KDP. It appears that the growth promoting effect (GPE) of Phen is caused by the adsorption of the organic additive on the prism faces of ADP/KDP crystals. Higher optical transmittance is observed in the presence of the dopant. Detailed microhardness studies of ADP crystals reveal the anisotropy in the hardness behaviour. Scanning electron microscope (SEM) photographs exhibit the effectiveness of the impurity in changing the surface morphology of ADP/KDP crystals. Contrary to expectations, Phen depresses the NLO efficiency of ADP/KDP, suggesting that the molecular alignments in the presence of Phen results in cancellation effects disturbing the non-linearity.