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81.
Kiril A. Streletzky John T. McKenna Rami Mohieddine 《Journal of Polymer Science.Polymer Physics》2008,46(8):771-781
The structure and dynamics of crosslinked nanoparticles (microgels) made out of hydroxypropylcellulose (HPC) polymer chains were studied using dynamic light scattering spectroscopy. The microgel light scattering spectra were found to be highly nonexponential requiring a spectral time moment analysis in which the spectra were fit to a sum of stretched exponentials. Each term offers three parameters for analysis and represents a single spectral mode. At room temperature microgel spectra reveal three modes. Two faster modes are almost diffusive and correspond to apparent sizes of 25 and 450–650 nm. The slowest mode is independent of scattering angle and is reminiscent of the slow polymer mode observed in identical non‐crosslinked polymer solutions. When solution temperature is varied from 23 to 45°C and back, the microgel undergoes a reversible volume phase transition between 40 and 45°C. According to the time‐moment analysis, above the transition temperature two faster modes collapse into one with apparent hydrodynamic radius of 100–150 nm, while the slow mode remains largely unchanged. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 771–781, 2008 相似文献
82.
Mati Fridkin Eli Hazum Rami Kalir Miriam Rotman Yitschak Koch 《Applied biochemistry and biotechnology》1977,2(2):175-182
Luteinizing hormone-releasing hormone, pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2,2 was synthesized in a stepwise manner by two approaches: the use of insoluble polymeric active esters derived from (4-hydroxy-3-nitro)benzylated polystyrene and that of solubleN,N-dicyclohexylcarbodiimide. The overall yields of the syntheses were 40 and 7%, respectively. The efficiencies of the two synthetic routes, in which identical intermediate peptides were prepared, are compared. 相似文献
83.
Styrene–acrylonitrile (St–AN) copolymers of three compositions—27.4 mole-% (SA1); 38.5 mole-% (SA2); and 47.5 mole-% (SA3) acrylonitrile—and styrene–methyl methacrylate (St–MMA) copolymer (SM) of 46.5 mole-% methyl methacrylate were prepared by bulk polymerization at 60°C with benzoyl peroxide as the initiator, and were then fractionated. The molecular weights of unfractionated and fractionated samples were determined by light scattering in a number of solvents. The [η] versus M?w relations at 30°C were established for SA1, SA2, SM, and polystyrene (PSt) in ethyl acetate (EAc), dimethyl formamide (DMF), and γ-butyrolactone (γ-BL), and for SA3 in methyl ethyl ketone (MEK), DMF, and γ-BL. Second virial coefficients A2 and the Huggins constant were determined. From values of A2 and the exponent a of the Mark–Houwink relation it is seen that the solvent power for samples SA1, SA2, and PSt is in the order EAc < γ-BL < DMF, while for sample SA3 the solvent power is in the order MEK < γ-BL < DMF. The solvent power decreases with an increase in AN content. The solvent power of the three solvents used for SM copolymer sample is practically the same within experimental errors. From the a values it is concluded that in a given solvent the copolymer chains are more extended than the corresponding homopolymers. 相似文献
84.
Ismail Warad Maha Al-Ali Belkheir Hammouti Taibi Ben Hadda Rami Shareiah Mohamed Rzaigui 《Research on Chemical Intermediates》2013,39(6):2451-2461
A novel di-μ-chloro-bis[chloro(4,7-dimethyl-1,10-phenanthroline)cadmium(II)] dimer complex has been prepared by reacting CdCl2·2.5H2O with 4,7-dimethyl-1,10-phenanthroline (dmphen) ligand. The complex was characterized on the basis of elemental analysis, FAB-MS, IR, UV–visible, 1H, and 13C NMR spectroscopy, TG/DTA, and X-ray single-crystal diffraction studies. The Cd(II) ions in [CdCl2(C14H12N2)]2 are coordinated to three Cl atoms with the centrosymmetric dimer bridged through the Cl atoms and two N atoms in a slightly distorted square-pyramidal disposition. Several hydrogen bonds formed between the terminal Cl atoms and H-Me/H-Ph groups may stabilize the structure in the dimer form. 相似文献
85.
Rami Ayoub Jamal Jilani Qais Jarrar Raad Alani Chrismawan Ardianto Khang Wen Goh Dalia Ali Said Moshawih 《Molecules (Basel, Switzerland)》2022,27(9)
2-(4-Chlorophenyl)-5-benzoxazoleacetic acid (CBA) and its ester, methyl-2-(4-chloro-phenyl)-5-benzoxazoleacetate (MCBA), were synthesized, and their structures were confirmed by 1HNMR, IR, and mass spectrophotometry. The anti-psoriatic activities of CBA and MCBA were tested using an imiquimod (IMQ)-induced psoriatic mouse model, in which mice were treated both topically (1% w/w) and orally (125 mg/kg) for 14 days. The erythema intensity, thickness, and desquamation of psoriasis were scored by calculating the psoriasis area severity index (PASI). The study also included the determination of histopathological alterations in the skin tissues of treated mice. Topical and oral administration of CBA and MCBA led to a reduction in erythema intensity, thickness, and desquamation, which was demonstrated by a significant decrease in the PASI value. In addition, skin tissues of mice treated with CBA and MCBA showed less evidence of psoriatic alterations, such as hyperkeratosis, parakeratosis, scale crust, edema, psoriasiform, and hyperplasia. After administration of either topical or oral dosing, the anti-psoriatic effects were found to be stronger in MCBA-treated than in CBA-treated mice. These effects were comparable to those produced by Clobetasol propionate, the reference drug. This drug discovery could be translated into a potential new drug for future clinical use in psoriasis treatment. 相似文献
86.
M. Sc. Adrian Humboldt Dr. Fabian Rami M. Sc. Franka M. Topp M. Sc. Dejana Arnold Daniela Göhringer Dr. Pradeep S. Pallan Prof. Martin Egli Prof. Clemens Richert 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(15):e202319958
Nucleoside monophosphates (NMPs) are the subunits of RNA. They are incorporated into growing complementary strands when sequences are copied in enzyme-free reactions using organic leaving groups at the phosphates. Amino acids are rarely considered as leaving groups, but proline can act as a leaving group when N-linked to NMPs, so that prolinyl NMPs hydrolyze in aqueous buffer at 37 °C, with half-life times as short as 2.4 h, and they act as monomers in enzyme-free primer extension. Still, their level of reactivity is insufficient for practical purposes, requiring months for some extensions. Herein we report the synthesis of eight substituted prolinyl AMPs together with seven related compounds and the results of a study of their reactivity. A δ-carboxy prolinyl NMP was found to be converted with a half-life time of just 11 min in magnesium-free buffer, and a δ-isopropyl prolinyl NMP was shown to react sevenfold faster than its prolinyl counterpart in enzyme-free genetic copying of RNA. Our results indicate that both anchimeric and steric effects can be employed to increase the reactivity of aminoacidyl nucleotides, i.e. compounds that combine two fundamental classes of biomolecules in one functional entity. 相似文献
87.
Ali Bahadur Tehseen Ali Anjum Mah Roosh Shahid Iqbal Hamad Alrbyawi Muhammad Abdul Qayyum Zaheer Ahmad Murefah Mana Al-Anazy Eslam B. Elkaeed Rami Adel Pashameah Eman Alzahrani Abd-ElAziem Farouk 《Molecules (Basel, Switzerland)》2022,27(20)
Tungsten trioxide (WO3) is mainly studied as an electrochromic material and received attention due to N-type oxide-based semiconductors. The magnetic, structural, and optical behavior of pristine WO3 and gadolinium (Gd)-doped WO3 are being investigated using density functional theory. For exchange-correlation potential energy, generalized gradient approximation (GGA+U) is used in our calculations, where U is the Hubbard potential. The estimated bandgap of pure WO3 is 2.5 eV. After the doping of Gd, some states cross the Fermi level, and WO3 acts as a degenerate semiconductor with a 2 eV bandgap. Spin-polarized calculations show that the system is antiferromagnetic in its ground state. The WO3 material is a semiconductor, as there is a bandgap of 2.5 eV between the valence and conduction bands. The Gd-doped WO3’s band structure shows few states across the Fermi level, which means that the material is metal or semimetal. After the doping of Gd, WO3 becomes the degenerate semiconductor with a bandgap of 2 eV. The energy difference between ferromagnetic (FM) and antiferromagnetic (AFM) configurations is negative, so the Gd-doped WO3 system is AFM. The pure WO3 is nonmagnetic, where the magnetic moment in the system after doping Gd is 9.5599575 μB. 相似文献
88.
Haritha Meruvu Sri Rami Reddy Donthireddy 《Applied biochemistry and biotechnology》2014,172(1):196-205
The purpose of the research was to study the purification and partial characterization of antifungal alkaline chitinase from a newly isolated Citrobacter freundii haritD11. The enzyme was purified in a three-step procedure involving ammonium sulfate precipitation, dialysis, and Sephadex G-100 gel filtration chromatography. The enzyme was shown to have a relative high molecular weight of 64 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis and was purified 7.3-fold with a yield of 18.8 %. It was most active at 35 °C, pH 8.0, with colloid chitin as substrate and was very stable at alkaline pH contradicting the characteristic that most of the bacterial chitinases are active at acidic pH. Further, the purified chitinase exhibited remarkable antifungal activity against pathogenic fungi Aspergillus flavus MTCC 2798 and Aspergillus niger MTCC 9652 showing diametric inhibition zones of 27 mm and 21 mm, respectively. 相似文献
89.
The anionic polymerization and oligomerization of 4-vinyl pyridine by methanolic alkali metal methoxides in DMSO was studied. The molecular weights increased with increasing monomer concentration and decreased with increasing methanol concentration. This fact was utilized in the preparation of oligomers. Evidence is given that initiation is an acid-base reaction. Methanol leads not only to transfer but participates in solvation of the methoxide and growing carbanions affecting the rate of reaction. The rate of reaction decreases with increasing methanol concentration. 相似文献
90.