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981.
Comparative study of urea and betaine solutions by dielectric spectroscopy: liquid structures of a protein denaturant and stabilizer 总被引:1,自引:0,他引:1
Hayashi Y Katsumoto Y Oshige I Omori S Yasuda A 《The journal of physical chemistry. B》2007,111(40):11858-11863
We performed dielectric spectroscopy measurements on aqueous solutions of glycine betaine (N,N,N-trimethylglycine), which is known to be a strong stabilizer of globular proteins, over a wide concentration range (3-62 wt %) and compared the results with our previously published data for aqueous solutions of urea, a representative protein denaturant. The hydration number of betaine (9), calculated on the basis of the reduction in the dielectric relaxation strength of bulk water with addition of betaine, is significantly larger than that of urea (2). Furthermore, the dielectric relaxation time increased with betaine concentration, while that remained nearly constant for the urea-water system over a wide concentration range. This difference between urea and betaine is probably related to their opposite effects on the protein stabilization. 相似文献
982.
[reaction: see text] A diastereoselective coupling of propargylic oxiranes with terminal alkynes has been developed with use of a palladium catalyst. The stereochemistries of the resulting 4-alkynyl-substituted 2,3-allenols have been altered depending on the palladium catalyst. An optically active anti-substituted allene was synthesized from the reaction of an enantiomerically enriched propargylic oxirane without loss of chirality. 相似文献
983.
Shindo M Yoshimura Y Hayashi M Soejima H Yoshikawa T Matsumoto K Shishido K 《Organic letters》2007,9(10):1963-1966
An efficient synthetic method for the preparation of multisubstituted furans, thiophenes, and pyrroles using ynolates was developed. This novel formal [4 + 1] annulation by C2-C3 and C3-C4 bond formations includes cycloaddition, cyclization, decarboxylation, and dehydration as key steps. 相似文献
984.
Addition of arylmagnesium bromides to aryl(alkyl)acetylenes proceeded in the presence of an iron catalyst and a N-heterocyclic carbene ligand to give high yields of the corresponding alkenylmagnesium reagents, which were transformed into tetrasubstituted alkenes by subsequent treatment with electrophiles. [reaction: see text] 相似文献
985.
A novel and efficient avenue for the preparation of dimeric vancomycins is described, and the dimers exhibited excellent antibacterial activities in the murine infection model. 相似文献
986.
987.
988.
989.
Yoshiya T Taniguchi A Sohma Y Fukao F Nakamura S Abe N Ito N Skwarczynski M Kimura T Hayashi Y Kiso Y 《Organic & biomolecular chemistry》2007,5(11):1720-1730
The O-acyl isopeptide method has recently received attention as an efficient synthetic method for peptides. Herein, forty kinds of "O-acyl isodipeptide unit" Boc-Ser/Thr(Fmoc-Xaa)-OH (1-40) were effectively synthesized in two-steps without epimerization. The O-acyl isodipeptide units are important building blocks to enable the routine use of the O-acyl isopeptide method. 相似文献
990.
A porphycene having four CF3 groups at the beta-pyrrolic positions affords a stable 20pi-conjugated form in the presence of a 2H+-2e- donor due to the high redox potential of the tetrapyrrole ring framework. No visible band in the UV-vis spectrum and the highly ruffled structure determined by X-ray crystallography support its nonaromatic character. The ethylene bridge moiety in the 20pi-conjugated framework displayed the olefinic reactivities. 相似文献