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171.
S. Sugai K. Kamashima S. Makino J. Noguchi 《Journal of Polymer Science.Polymer Physics》1966,4(2):183-198
Good yields of some crystalline γ-alkyl esters of L -glutamic acid were obtained by carrying out the esterfication with a small (20–50 mole-%) excess of alcohol in aqueous hydrochloric acid or 60–80% sulfuric acid followed by neutralization with an alkaline solution. This new method made it possible to synthesize various γ-alkyl L -glutamates, including those higher than ethyl, and consequently, various poly(γ-alkyl L -glutamates) such as methyl, ethyl, n-propyl, n-butyl, isobutyl, and isoamyl. The conformation of these poly-L -glutamates in the solid state was determined by the infrared absorption method. The molecular motions of the polymers of γ-methyl, -ethyl, -n-propyl, -n-butyl, and-isoamyl L -glutamates and poly(γ-methyl-D -glutamate) in the solid state were studied by NMR, and dielectric and mechanical measurements. At temperatures up to 400°K., the NMR spectra of poly(γ-methyl D -glutamate) can be explained only by rotational motion of the side chain. Also, from NMR results, rotational motion of C?O groups in the side chain of poly(γ-methyl D -glutamate) is expected near room temperature, and such a motion was examined by dielectric measurements. Rotation of C?O groups in the side chains of polymers of γ-methyl, γ-ethyl, γ-n-propyl, γ-n-butyl, and γ-isoamyl L -glutamate was also observed near room temperature by dielectric measurements in the frequency range from 102 to 106 cps. Activation energies obtained by dielectric and mechanical measurements were similar to those for the side chain motions of the corresponding esters of poly(methacrylic acid). Although it has been noted that the molecular motion of poly(γ-benzyl L -glutamate) in the solid state at room temperature may be related to the motion of its back bone, the molecular motion in these poly-L -glutamates at these temperatures can be explained only in terms of side-chain rotation. 相似文献
172.
Hirohara S Obata M Saito A Ogata S Ohtsuki C Higashida S Ogura S Okura I Sugai Y Mikata Y Tanihara M Yano S 《Photochemistry and photobiology》2004,80(2):301-308
Thirty-two glycoconjugated porphyrins were synthesized by a modification of Lindsey method in the presence of Zn(OAc)(2).2H(2)O as a template. The Zn(2+) ion template strategy improved the yield about three-fold in the case of meta-substituted tetraphenylporphyrins. In addition, free-base porphyrins were obtained almost quantitatively by demetalation with 4 M HCl. Sixteen deacetylated glycoconjugated porphyrins were tested as candidate photodynamic therapy (PDT) drugs using HeLa cells. Most of the deacetylated glycoconjugated porphyrins showed higher cellular uptake than tetraphenylporphyrin tetrasulfonic acid (TPPS), and 5,10,15,20-tetrakis[4-(beta-D-arabinopyranosyloxy)phenyl]porphyrin (p-5d) in particular showed 18.5-fold higher uptake than TPPS. The photocytotoxicity of 5,10,15,20-tetrakis[4-(beta-D-glucopyranosyloxy)phenyl]porphyrin (p-5a), p-5d and TPPS was examined with HeLa cells, using a light dose of 16 J/cm(2). These photosensitizers had no cytotoxicity in the dark, but their photocytotoxicity increased in the order of TPPS < p-5a < p-5d. These results suggest p-5d is a good candidate for a PDT drug. 相似文献
173.
A pair of copper(II) complexes 1 and 2 exhibit an enantiomeric chiral center at the oxygen atom that coordinates to the metal center. The configurations of the oxygen atom chirality and the chelate ring conformation are simply controlled by protected/free hydroxyl groups of the sugar moiety, yielding mirror image CD spectra. In this system, repulsive and attractive forces are used to regulate chirality on the copper-coordinated oxygen atom both in the solid state and in solution. 相似文献
174.
C.A. Cody R.C. Levitt Rampur S. Viswanath Philip J. Miller 《Journal of solid state chemistry》1978,26(3):281-291
The infrared and Raman spectra of alkali hydrogen selenites [(MHSeO3), where M = Li, Na, K, or Cs], selenous acid (H2Seo3), and their deuterated analogs have been recorded and interpreted. The internal mode frequencies observed in sodium hydrogen selenite, selenous acid, and sodium trihydrogen selenite are used to generate general valence force constants for HSeO?3 and H2SeO3 under the assumption of Cs geometry for each species. Calculations of observed deuterium frequency shifts are made to aid in the assignments of the various internal modes. A low-temperature proton-triggered phase transition is observed in CsHSeO3 and is confirmed in KHSeO3. A discussion of the effects of proton order and disorder upon the selenite frequencies is also presented. 相似文献
175.
4-Sulfenyl-2-carbamoyl-4-isoxazolin-3-ones (4) were designed on the basis of biological isosterism and prepared in four steps. Some of these compounds showed sufficient pre-emergent herbicidal activities against various kinds of weeds. Among the synthesized compounds, 2-(N-(4-chlorophenyl)-N-isopropylcarbamoyl)-4-ethylthio-5-methyl-4 -isoxazolin-3-one (4cd) exhibited the most promising activity. 相似文献
176.
alpha,beta-Differentiated 1,2-vicinal diamines have been efficiently synthesized by using new electrophilic imidazolination reaction of alkenes. The hydrolysis of imidazolines was performed by treatment with 6 M HCl in THF at 70 degrees C without epimerization. Eight examples were examined to give good to excellent yields (87-96%). 相似文献
177.
SPECTROPHOTOMETRIC IDENTITY OF THE ENERGY TRANSFER CHROMOPHORES IN RENILLA AND AEQUOREA GREEN-FLUORESCENT PROTEINS 总被引:1,自引:0,他引:1
William W. Ward Chris W. Cody Russell C. Hart Milton J. Cormier 《Photochemistry and photobiology》1980,31(6):611-615
Abstract— Spectral properties of guanidine-denaturated and pronase-digested green-fluorescent proteins (GFP) from two species of bioluminescent coelenterates have been investigated. Spectrophotometric titrations of Renilla and Aequorea GFP, following denaturation in 6 M guanidine HCl at elevated temperature, revealed identical absorption peaks in acid (383–384 nm) and in alkali (447–448 nm) and a single isosbestic point in the visible region at 405 nm. Both proteins exhibited a spectrophotometric pK. of 8.1 in guanidine -HCl. Pronase digestion of the heat-denaturated GFP's generated a methanol-soluble blue-fluorescent peptide with identical fluorescence emission spectra (λmax = 430 nm, uncorrected; φf1 = 0.003) for both coelenterate species. These data suggest that the large absorption differences between native Renilla and Aequorea GFP molecules result from unique protein environments imported to a common chromophore. 相似文献
178.
179.
Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH3 to CN under Extreme Conditions 下载免费PDF全文
Dr. Haiyan Zheng Dr. Kuo Li Dr. George D. Cody Dr. Christopher A. Tulk Dr. Xiao Dong Dr. Guoying Gao Jamie J. Molaison Dr. Zhenxian Liu Dr. Mikhail Feygenson Dr. Wenge Yang Dr. Ilia N. Ivanov Leonardo Basile Dr. Juan‐Carlos Idrobo Dr. Malcolm Guthrie Dr. Ho‐kwang Mao 《Angewandte Chemie (International ed. in English)》2016,55(39):12040-12044
Acetonitrile (CH3CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C?H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonstrated that C?H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH???N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp2 and sp3 bonded carbon. Finally, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C?H can be activated by high pressure, even at room temperature and without a catalyst. 相似文献
180.
The (13)C NMR shifts of 48 diazaphenanthrene-type alkaloids have been calculated at the B3LYP/6-311+G(2d,p) level of theory. The results support the structural reassignment of samoquasine A as 2. 相似文献