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1.
The spin trap agent, 2,6-di-chloronitrosobenzene (DCNB), which is decomposed into a nitrogen monoxide and a chlorinated phenyl radical on slight warming, was known to act as a radical generator through hydrogen abstraction by the chlorinated phenyl radical from an adjacent molecule. An ESR spectrum was observed at room temperature from a poly(methyl methacrylate) (PMMA)-benzene solution after the addition of DCNB followed by a warming to ca 30°C. The radical concentration increased with time. The spectrum was assigned to the spin adducts of PMMA radicals generated and trapped by DCNB. Analyses of the spectra observed from normal PMMA and partially deuterated PMMA's indicated that the majority of the PMMA radicals were the chain-scission species and a minority were . It was concluded that the main-chain scissions in PMMA were caused by the radicals (D), which had been primarily produced by the chlorinated phenyl radicals. These ESR data are supported by the fact that a decrease in molecular weight of PMMA was observed after addition of DCNB, and further reinforced by the fact that a molecular weight estimated from the number of the scission radicals agreed fairly well with the measured molecular weight. Similar results were obtained when both tri-chlorinated nitrosobenzene and tetra-chlorinated nitrosobenzene were used instead of DCNB. 相似文献
2.
Mikio Ohno Keiichi Ohno Junkichi Sohma 《Journal of polymer science. Part A, Polymer chemistry》1987,25(5):1273-1284
Plasma-polymerized methyl methacrylate (PPMMA) film was produced by a radio-frequency glow discharge of methyl methacrylate (MMA) gas with argon. PPMMA deposited under a plasma of mild energy was separated into a soluble fraction (sol-PPMMA) and an insoluble matrix (insol-PPMMA), which is highly crosslinked, by solvent-extraction and filtration. The chemical structure of the sol-PPMMA was determined by pyrolysis/gas chromatography, IR spectroscopy, 1H-NMR, 13C-NMR, and elemental analysis techniques. On the other hand, the structure of the insol-PPMMA was examined with IR spectroscopy, 13C-NMR with CP/MAS method, and elemental analysis. The crosslinking mechanism in the plasma polymerization of MMA is discussed on the basis of product analyses of the sol-PPMMA and the insol-PPMMA. 相似文献
3.
The mechanism of uv (λ > 325 nm) photodegradation of polypropylene (PP) containing N,N,N′,N′-tetramethyl-p-phenylenediamine (T4MPD) has been investigated by means of ESR spectroscopy. The observed spectra after uv irradiation of both isotactic-PP (IPP) and stereoblock-PP (SPP) samples in vacuum at 77 K consisted principally of a broad singlet which was assigned to a T4MPD cation radical (T4MPD+·). On the other hand, the spectrum observed after irradiation of an atactic polypropylene (APP) sample at 77 K in vacuum was resolved into several components which decayed almost up to ca. 263 K to give rise to the broad singlet of T4MPD+·. One component was a sharp quartet which was assigned to a methyl radical, ·CH3·. The other component, a singlet, was attributed to a trapped electron, et?.By comparison of the ESR spectrum of deuterated T4MPD with that of the normal compound it was found that 60 ~ 70% of the methyl radicals arose from the added T4MPD due to β-scission, which also formed the N,N,N′-trimethyl-p-phenylenediamine radical, T3MPD·. The T3MPD· radical presumably captures an electron at lower temperatures to become a carbanion, T3MPD?, which releases the electron to reproduce the T3MPD· radical at elevated temperatures. This production of the radical T3MPD· due to the liberation of an electron provides an explanation for the observed increase in intensity of the decay curve in the temperature range from ? 168 K to 185 K. The remaining fraction, 30 ~ 40%, of the total methyl radicals was produced from the PP matrix by an energy transfer from the excited T4MPD1 to the PP matrix. The broad singlet which appeared in the temperature range near 195 K was attributed to an acyl radical ~CH2CH(CH3)CH2?O from the observed g-value. By photoillumination of this sample this broad singlet was converted reversibly into the quartet which was assigned to the radical ~CH2CH(CH2·)CH2CHO. 相似文献
4.
Identification of the radical species formed by γ-radiolysis of MTHF in the liquid phase was made by analysis of the ESR spectra observed from the spin-adducts of the radicals. A new secondary MTHF radical was found in addition to the tertiary radical. 相似文献
5.
ESR spectra were observed from amino radicals adsorbed on the pre-heat-treated zeolite sorbing ammonia molecules. The extra coupling with the sodium 23Na in the zeolite was observed in the spectrum from the amino-radicals. 相似文献
6.
Dr. Tatsuya Takimoto Prof. Hideaki Sasaki Prof. Hirohito Tsue Dr. Hiroki Takahashi Prof. Alexander D. MacKerell Jr. Ayumi Nakamura Katsuya Nakano Eori Okazaki Tatsuki Betsuyaku Ryosuke Tachibana Dr. Kazuhito Hioki Dr. Ozge Yoluk Dr. Sunhwan Jo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1648-1654
A simple approach to the synthesis of heterocyclophane consisting of two 4,4’-bithiazoles has been developed in mild conditions. The heterocyclophane with two short chains was conveniently prepared by Hantzsch thiazoles synthesis using the reaction of 3-tert-butoxycarbonyl-3-azapentanethiocarboxamide with 1,4-dibromobutane-2,3-dione in methanol under reflux for only 15 min. Amino groups at the linkers of this heterocyclophane can be functionalized to give acylated and carbamate derivatives. Their properties as protein kinase inhibitors were investigated, and one of the heterocyclophanes exhibited specific anti-activity for c-mesenchymal epithelial transition factor (IC50=603 nm ), among seven types of protein kinases investigated. The computational site identification by ligand competitive saturation method was used to determine why the one heterocyclophane exhibited strong anti-activity for c-mesenchymal epithelial transition factor. 相似文献
7.
Hirohito Ikeda Yukiko Sano Tomonori Matsubara Mitsunobu Kawahara Miho Yukawa Masao Fujisawa Eiji Yukawa Hatsumi Aki 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1135-1138
Propericiazine (PCZ) is an antipsychotic agent used for the treatment and the prevention of relapse of schizophrenia. We found that when an oral solution containing PCZ was mixed with a green tea drink, the residual content of PCZ was reduced by forming an insoluble complex between PCZ and tea polyphenol. In this study, the mechanism underlying the incompatibility of PCZ with green tea polyphenol (GTP) in the solution was clarified by isothermal titration microcalorimetry (ITC). Both solutions of 27.4 mM PCZ and 2.2 mM (?)-epigallocatechin gallate (EGCg), which is a main ingredient of GTP, were mixed and then PCZ in the filtrate was reduced to approximately 60 %. According to measurement at 298 K by ITC, PCZ formed an insoluble complex with EGCg at an associate constant (K) of 4.75 × 102 M?1 exothermically, ΔH = ?40.0 kJ mol?1. When (?)-epicatechin gallate (ECg) was used as the GTP, PCZ interacted with ECg with K and ΔH values of 3.74 × 102 M?1 and ?22.1 kJ mol?1, respectively. On the other hand, little heat of the reaction between PCZ and (?)-epigallocatechin or (?)-epicatechin was observed. The results indicated that the main reason for this incompatibility was the formation of an insoluble complex by PCZ and a gallate-type GTP such as EGCg and ECg in the aqueous solution. 相似文献
8.
Hiroyoshi Kamogawa Tsuyoshi Sakai Hirohito Sohma 《Journal of polymer science. Part A, Polymer chemistry》1988,26(5):1335-1341
Schiff base (SB) monomers of vinylbenzaldehyde with functional amines were prepared. Copolymers of SB monomers with N-vinyl-2-pyrrolidone soluble in aqueous solutions were obtained in most cases. However, p-aminobenzenesulfonamide monomer resulted in gel formation. Thus, the reaction of vinylbenzaldehyde copolymer with the sulfonamide was used instead of the copolymerization. The hydrolytic behaviors of SB monomers and copolymers to liberate respective amines were structure dependent and, for most copolymers, the rates were lower than those of the corresponding monomers. 相似文献
9.
Rational Design and Identification of a Non‐Peptidic Aggregation Inhibitor of Amyloid‐β Based on a Pharmacophore Motif Obtained from cyclo[‐Lys‐Leu‐Val‐Phe‐Phe‐] 下载免费PDF全文
Tadamasa Arai Takushi Araya Dr. Daisuke Sasaki Dr. Atsuhiko Taniguchi Dr. Takeshi Sato Dr. Youhei Sohma Prof. Motomu Kanai 《Angewandte Chemie (International ed. in English)》2014,53(31):8236-8239
Inhibition of pathogenic protein aggregation may be an important and straightforward therapeutic strategy for curing amyloid diseases. Small‐molecule aggregation inhibitors of Alzheimer’s amyloid‐β (Aβ) are extremely scarce, however, and are mainly restricted to dye‐ and polyphenol‐type compounds that lack drug‐likeness. Based on the structure‐activity relationship of cyclic Aβ16–20 (cyclo‐[KLVFF]), we identified unique pharmacophore motifs comprising side‐chains of Leu2, Val3, Phe4, and Phe5 residues without involvement of the backbone amide bonds to inhibit Aβ aggregation. This finding allowed us to design non‐peptidic, small‐molecule aggregation inhibitors that possess potent activity. These molecules are the first successful non‐peptidic, small‐molecule aggregation inhibitors of amyloids based on rational molecular design. 相似文献
10.
Serine‐Selective Aerobic Cleavage of Peptides and a Protein Using a Water‐Soluble Copper–Organoradical Conjugate 下载免费PDF全文
Yohei Seki Dr. Kana Tanabe Dr. Daisuke Sasaki Dr. Youhei Sohma Dr. Kounosuke Oisaki Prof. Dr. Motomu Kanai 《Angewandte Chemie (International ed. in English)》2014,53(25):6501-6505
The site‐specific cleavage of peptide bonds is an important chemical modification of biologically relevant macromolecules. The reaction is not only used for routine structural determination of peptides, but is also a potential artificial modulator of protein function. Realizing the substrate scope beyond the conventional chemical or enzymatic cleavage of peptide bonds is, however, a formidable challenge. Here we report a serine‐selective peptide‐cleavage protocol that proceeds at room temperature and near neutral pH value, through mild aerobic oxidation promoted by a water‐soluble copper–organoradical conjugate. The method is applicable to the site‐selective cleavage of polypeptides that possess various functional groups. Peptides comprising D ‐amino acids or sensitive disulfide pairs are competent substrates. The system is extendable to the site‐selective cleavage of a native protein, ubiquitin, which comprises more than 70 amino acid residues. 相似文献