排序方式: 共有122条查询结果,搜索用时 15 毫秒
61.
Cemil Ibis Sibel Sahinler Ayla Şenol Yavuz Hatice Asar Funda Özkök Hakan Bahar 《Phosphorus, sulfur, and silicon and the related elements》2018,193(6):358-362
In this study, S-, S,S- and S,O-substituted novel nitrodiene compounds were synthesized. Cyclization products were formed when difunctional nucleophiles were used. The stereoisomerism of a heterocyclic nitrodiene is discussed with the help of XRD studies. The structures of all compounds were characterized by spectroscopic methods (FT-IR, 1H NMR, 13C NMR, 19F NMR, MS) and microanalysis. 相似文献
62.
A mixed experimental and theoretical study on chelidamate copper(II) complex with 4-methylpyrimidine
A new chelidamate complex, [Cu(chel)(H2O)2(mpd)] (chel = chelidamate; mpd = 4-methylpyrimidine), has been synthesized and characterized through a combination of single crystal X-ray analysis, electron paramagnetic resonance (EPR), ultraviolet-visible (UV-vis), and fourier transform infrared spectroscopy (FT-IR). The complex has six-coordinate distorted octahedral geometry around Cu(II). The theoretical vibrational frequencies and optimized geometric parameters (bond lengths and angles) have been calculated using Density Functional Theory (DFT)/B3LYP and Hartree Fock quantum chemical methods with 6-31G(d, p) basis set by Gaussian 09W software. The EPR spectrum of the compound showed that the paramagnetic center has rhombic symmetry. The EPR studies were carried out using the following unrestricted hybrid density functionals: B3LYP, CAM-B3LYP, HSEH1PBE, WB97XD, MPW1PW91, and BPV86. The UV–vis absorption spectra have been examined in different media and compared with the calculated one using TD-DFT method by applying the polarizable continuum model. Natural bond orbital property of complex has been performed by DFT/B3LYP with 6-31G (d, p) basis set. 相似文献
63.
Hatice Turgut Dr. Guillaume Delaittre 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1511-1521
The chemoselectivity of two thiol‐based modular ligations operating under mild conditions is assessed. For this purpose, a macromolecular scaffold possessing allyl and pentafluorophenyl groups in two distinct parts is employed, which enables facile characterization by NMR spectroscopy (1H and 19F) and size‐exclusion chromatography. By using appropriate triggers (introduction of a base or light irradiation), it is possible to direct thiols to an arbitrarily chosen part of the scaffold, without any change to the other part and with no involvement of protecting group chemistry. Dual functionalization experiments are achieved by applying these triggers consecutively with no consideration of the reaction sequence order, evidencing full bidirectionality. A set of one‐pot, purification‐free procedures that enable near‐quantitative to full dual functionalization in (very) short reaction times (17–180 min) is also presented. 相似文献
64.
Phase diagrams of multi‐wall carbon nanotube (MWNT)/nematic liquid crystal (E7) and buckminsterfullerene (C60‐I h)/nematic liquid crystal (E7) binary systems have been investigated by means of polarizing optical microscopy and differential scanning calorimetry. It was found that the isotropic–nematic phase transition temperature (T NI) of the liquid crystal component was enhanced by the incorporation of MWNT within a small composition gap. A chimney‐type phase diagram can be identified in the MWNT/E7 mixture over a narrow range of ~0.1–0.2% MWNT concentration. Upon substituting the nanotubes with isotropic fillers such as fullerene, the (C60‐I h)/E7 blend showed no discernible change of T NI in the same concentration range of the chimney of the MWNT/E7 mixture, suggesting a significant contribution of anisotropy (or the aspect ratio) of the nanotubes to the entropy of the system containing liquid crystal molecules. This enhanced T NI phenomenon may be attributed to anisotropic alignment of liquid crystal molecules along the carbon nanotube bundles. 相似文献
65.
Ersel Ozkazanc Sibel Zor Hatice Ozkazanc 《Journal of Macromolecular Science: Physics》2013,52(11):2122-2132
This study reports structural and thermal properties and temperature-dependent alternating current (AC) conductivity of polyaniline/selenium (PANI/Se) composites in emeraldine salt form prepared by a chemical polymerization method. Fourier transform infrared spectroscopy showed that the doping process significantly affected the N-H bond in PANI chain. The free energy change, which was calculated from the Langmuir adsorption isotherm, showed that Se was electrostatically adsorbed on PANI molecules. From the scanning electron microscopy images it was determined that morphological changes caused by the doping process on PANI surface could affect conductivity. Thermal analysis, which was performed with differential scanning calorimetry, showed that the addition of Se increased the degradation temperature of PANI. Depending on the doping level, significant increase was observed in the AC conductivity of PANI, approximately 11, 13, and 17 times for 300, 350, and 400 K temperatures respectively. 相似文献
66.
A new indole alkaloid, 7β-hydroxy-7H-mitraciliatine (1) and a new oxindole alkaloid, isospeciofoleine (2) together with nine known alkaloids were isolated from Mitragyna speciosa and characterized by NMR, CD, and MS spectroscopic data analyses. The 1H and 13C NMR spectroscopic data of isospeciofoline (3), isorotundifoline (4), paynantheine (5), and 3-isopaynantheine (6) were also reported for the first time. 相似文献
67.
Dr. Hatice Mutlu Dr. Jean‐François Lutz 《Angewandte Chemie (International ed. in English)》2014,53(48):13010-13019
The sequencing of biopolymers such as proteins and DNA is among the most significant scientific achievements of the 20th century. Indeed, modern chemical methods for sequence analysis allow reading and understanding the codes of life. Thus, sequencing methods currently play a major role in applications as diverse as genomics, gene therapy, biotechnology, and data storage. However, in terms of fundamental science, sequencing is not really a question of molecular biology but rather a more general topic in macromolecular chemistry. Broadly speaking, it can be defined as the analysis of comonomer sequences in copolymers. However, relatively different approaches have been used in the past to study monomer sequences in biological and manmade polymers. Yet, these “cultural” differences are slowly fading away with the recent development of synthetic sequence‐controlled polymers. In this context, the aim of this Minireview is to present an overview of the tools that are currently available for sequence analysis in macromolecular science. 相似文献
68.
Acrylamide based monomer, 2-methyl-N-[2-(phenylthio)phenyl]acrylamide (MPPA) was synthesized by reacting 2-(phenylthio) aniline with methacryloylchloride. The copolymerization of MPPA, with 2-(trimethylsyloxy)ethyl methacrylate(TSEM) was carried out with different monomer-to-monomer ratios in the feed. All the compounds were characterized by IR, Raman and 1H- and 13C-NMR techniques and SEM analysis. The elemental analysis of the copolymer composition led to the determination of reactivity ratios employing Fineman-Ross, Kelen-Tüdös and Extended Kelen-Tüdös linearization methods. These parameters were also estimated using a non-linear computational fitting procedure, known as reactivity ratio errors in variable model. The molecular weights and polydispersity index of polymers was determined by gel permeation chromatography. Thermal stability of the copolymers were found to increase with increasing mole fraction of MPPA from thermogravimetric analysis. The vibrational analysis of MPPA and poly(MPPA) were also performed to explain the vibrational spectra and to confirm the polymerization on the basis of a theoretical and experimental aproach. 相似文献
69.
Arif Sercan AHUTOLU Hatice DUMAN Steven Alex FRESE Sercan KARAV 《Turkish Journal of Chemistry》2020,44(6):1703
EndoBI-1 and EndoBI-2 are two endo- β-N- acetylglucosaminidase isoenzymes that cleave N-N’- diacetylchitobiosyl moieties found in various types of native N -glycans. These N -glycans are indigestible by human infants and adults due to the lack of responsible glycosyl hydrolases and they act as selective prebiotics for a probiotic microorganism, Bifidobacterium longum subsp . infantis , in the large intestine. The selectivity and the thermostability of EndoBI-1 and EndoBI-2 suggest that these enzymes may be useful for many scientific and industrial applications. In this study, the growing numbers of homologous sequences in different databases were exploited in a comparative approach to investigate structural properties of EndoBI-1 and EndoBI-2 enzymes. Moreover, the complete and partial homology models of these two enzymes were generated and evaluated. Selected models were used for docking studies of the plus subsite ligand of these enzymes for further understanding on the substrate selectivity of EndoBI enzymes. 相似文献
70.
This paper reports on the structural, thermal, and dielectric properties of polypyrrole/fullerene C60 nanocomposites synthesized by a interfacial polymerization method. Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-vis) analyses clearly indicated the existence of interactions between polypyrrole (PPy) and the fullerene C60 nanoparticles. Thermal analyses indicated that the extrapolated onset degradation temperature (Tdeg) of PPy increased with increasing doping level. Scanning electron microscopy (SEM) images showed that the fullerene C60 changed the morphology of PPy. Dielectric analyses showed a temperature dependent dielectric relaxation behavior. The relaxation time of the nanocomposites with high doping levels tended to increase with increasing temperature. This behavior of the polypyrrole/fullerene C60 nanocomposites indicated that they could be used as a high temperature ultrasonic transducer. 相似文献