Influence of backbone length and synthetic mutations on orientation of neurotensin fragments adsorbed onto a colloidal silver surface: SERS studies

Neurotensin (NT) is a naturally occurring neurotransmitter that mediates the metabotropic seven‐transmembrane G protein‐coupled receptors, namely NTR1s, richly expressed on tumor surface. Therefore, mutated active molecular fragments of NT that possess selective antagonist or weak agonist properties and the high affinity to NTR1 have attracted considerable interest for use in thrombus, inflammation, and imaging/treatment of tumors. In this work, SERS spectra of three N‐terminal fragments of human NT (NT^1‐6, NT^1‐8, and NT^1‐11) and six specifically mutated C‐terminal fragments of human NT, including NT^8‐13, [Dab⁹]NT^8‐13, [Lys⁸,Lys⁹]NT^8‐13, [Lys⁸‐(®)‐Lys⁹]NT^8‐13, [Lys⁹,Trp¹¹,Glu¹²]NT^8‐13, and NT^9‐13, adsorbed onto nanometer‐sized colloidal silver particles in an aqueous solution at pH level of the solution 2 are presented. A comparison was made between the structures of the native and mutated fragments to determine how changes in peptide length and mutations of the structure influenced the NT adsorption properties. Based on the interpretation of the obtained data, we showed that all of the investigated NT fragments, excluding [Lys⁹,Trp¹¹,Glu¹²]NT^8‐13, tended to adsorb on the silver surface mainly through the L‐tyrosine residue and the carboxylate group. The Tyr ring lied more‐or‐less flat on the silver surface. The hydrogen atom from the phenol group dissociated upon binding. On the other hand, [Lys⁹,Trp¹¹,Glu¹²]NT^8‐13 bound to this substrate through the close to vertical co‐pyrrole ring of the indole ring (Trp¹¹) and –COO^‐ . Comparison of the presented data with those obtained earlier for NT allows to suggest that in the case of naturally occurring neurotensin, both Tyr residues together with the carboxylate group play crucial role in the binding to the nanometer‐sized colloidal silver particles. This geometry of binding forces the NT molecule to lay flat on the surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis, properties, and OFET characteristics of 5,5'-di(2-azulenyl)-2,2'-bithiophene (DAzBT) and 2,5-di(2-azulenyl)-thieno[3,2-b]thiophene (DAzTT)

Two azulene-based π-conjugated systems, 5,5'-di(2-azulenyl)-2,2'-bithiophene and 2,5-di(2-azulenyl)-thieno[3,2-b]thiophene, were constructed via Suzuki-Miyaura cross-coupling reactions. The crystal structures of both revealed an edge-to-face orientation in a well-defined herringbone packing. The molecules stood nearly perpendicular to the substrate in the film form, with features of an organic field-effect transistor at hole mobilities of up to 5.0 × 10(-2) cm(2) V(-1) s(-1).     

Efficient Nonlinear Optical Properties of Dyes Confined in Interlayer Nanospaces of Clay Minerals

Nonlinear optical (NLO) responses from organic dyes can be maximized when the dyes are aligned in appropriate manners in bulk materials. The use of restricted nanospaces provided by interlayer spacing of inorganic layered materials is a promising strategy for imposing suitable molecular alignments for NLO materials on dyes. The hybrid materials thus obtained exhibit salient NLO responses owing to the improved molecular orientation. In some cases, extension of the π‐electron system as a consequence of improved molecular planarity, obtained by the intercalation of a dye into the 2‐dimensional interlayer space of an inorganic layered material, is also observed as a factor that enhances NLO responses of chromophores at the molecular level. This review focuses on recent progress in the strategies for controlling the molecular orientation of NLO‐phores by employing clay minerals, which are one of the typical inorganic layered materials. In addition, development of a means for fabricating composites that satisfy the properties of an optical material, such as a sufficient size and thickness, a flat surface, and low light‐scattering characteristics is required to utilize the superior NLO properties observed for clay/dye hybrid materials for practical applications. A novel means for obtaining such a hybrid material is also outlined.     

Variable-precision dominance-based rough set approach and attribute reduction

In this paper, a variable-precision dominance-based rough set approach (VP-DRSA) is proposed together with several VP-DRSA-based approaches to attribute reduction. The properties of VP-DRSA are shown in comparison to previous dominance-based rough set approaches. An advantage of VP-DRSA over variable-consistency dominance-based rough set approach in decision rule induction is emphasized. Some relations among the VP-DRSA-based attribute reduction approaches are investigated.     

Comparative evaluation of bioactivity of crystalline trypsin for drying by Fourier-transformed infrared spectroscopy

The purpose of this study was to evaluate the enzymatic stability of colloidal trypsin powder during heating in a solid-state by using Fourier transform infrared (FT-IR) spectra with chemoinformatics and generalized two-dimensional (2D) correlation spectroscopy. Colloidal crystalline trypsin powders were heated using differential scanning calorimetry. The enzymatic activity of trypsin was assayed by the kinetic degradation method. Spectra of 10 calibration sample sets were recorded three times with a FT-IR spectrometer. The maximum intensity at 1634 cm⁻¹ of FT-IR spectra and enzymatic activity of trypsin decreased as the temperature increased. The FT-IR spectra of trypsin samples were analyzed by a principal component regression analysis (PCR). A plot of the calibration data obtained was made between the actual and predicted trypsin activity based on a two-component model with γ² = 0.962. On the other hand, a 2D method was applied to FT-IR spectra of heat-treated trypsin. The result was consistent with that of the chemoinformetrical method. The results for deactivation of colloidal trypsin powder by heat-treatment indicated that nano-structure of crystalline trypsin changed by heating reflecting that the β-sheet was mainly transformed, since the peak at 1634 cm⁻¹ decreased with dehydration. The FT-IR chemoinformetrical method allows for a solid-state quantitative analysis of the bioactivity of the bulk powder of trypsin during drying.     

Enhanced Raman Scattering by ZnO Superstructures: Synergistic Effect of Charge Transfer and Mie Resonances

A remarkable enhancement of Raman scattering is achieved by submicrometer‐sized spherical ZnO superstructures. The secondary superstructures of ZnO particles with a uniform diameter in the range of 220–490 nm was formed by aggregating ca. 13 nm primary single crystallites. By engineering the superstructure size to induce Mie resonances, leading to an electromagnetic contribution to the SERS enhancement. Meanwhile, a highly efficient charge‐transfer (CT) contribution derived from the primary structure of the ZnO nanocrystallites was able to enhance the SERS signals as well. The highest Raman enhancement factor of 10⁵ was achieved for a non‐resonant molecule by the synergistic effect of CT and Mie resonances. The Mie resonances scattered near‐field effect investigated in the present study provides not only an important guide for designing novel SERS‐active semiconductor substrates, but also a coherent framework for modelling the electromagnetic mechanism of SERS on semiconductors.     

Proton decay and flavor violating thresholds in SO(10) models

Discovery of neutrino mass has put the spotlight on the supersymmetric (SUSY) SO(10) model as a natural candidate for grand unification of forces and matter. However, the suppression of proton decay is a major problem in such SUSY grand unified models. In this Letter we show how to alleviate this problem by simple threshold effects which raise the colored Higgsino masses and the grand unification scale to greater than or similar to 10(17) GeV. There exist only four types of fields arising from different SO(10) representations which can generate this kind of threshold effect. Some of these fields also generate a sizable flavor violation in the quark sector compared to the lepton sector. The b-tau unification can work in these types of models even for intermediate values of tanbeta.     

End‐group characterization of homo‐ and copolyesters of cyclohexane‐1,4‐dimethanol

End groups after the thermal degradation of poly(ethylene terephthalate) (PET) and its cyclohexanedimethanol (CHDM) copolymer were characterized with ¹H NMR. Thermally degraded polymers were obtained by heat treatment at 290 °C. For the PET homopolymer, a vinyl end group appeared, which resulted from thermal cis‐β‐elimination. For the CHDM copolymer, in addition to a vinyl end group, methylcyclohexene and cyclovinylidene end groups originating from CHDM were formed. The assignment of the ¹H NMR spectrum was performed with information from ¹³C NMR and gas chromatography‐mass spectrometry. The total amounts of unsaturated species measured by NMR were compared with those estimated by bromination titration. There was good agreement between the values obtained by the two methods, indicating that all the major unsaturated species were accounted for. The mechanism of the formation of the unsaturated end groups was investigated. We suggest, on the basis of the NMR measurements, that the methylcyclohexene and cyclovinylidene groups originating from CHDM were formed by thermal cis‐β‐elimination as for the PET homopolymer. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 665–674, 2001