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71.
72.
A model is presented for the potential distribution across a charged membrane. The membrane-fixed charges are assumed to be distributed through a surface layer of non-zero thickness on the membrane. We treat the surface layer as a different phase from the surrounding solution phase. The potential arises from the membrane-fixed charges and from different solubilities of positive and negative electrolyte ions in the two phases. Equations are presented for the potential distribution, which involve the partition coefficients of electrolyte ions and the relative permittivity of the surface layer. 相似文献
73.
Single nucleotide polymorphisms (SNPs) of cancer repression gene p53 were analyzed electrochemically with ferrocenyl naphthalene diimide (1) as a hybridization indicator. The SNPs studied were the transition to A from G in the codon for amino acid at positions 175, 248 or 273 and the transversion to C from G in the codon for the amino acid at position 72. Thus, 20-meric oligonucleotides carrying the SNP site were used both as a sample and a probe with the latter immobilized on an electrode. Even one base difference on the p53 gene resulted in a significant difference in the current response of 1 and the magnitude of the response correlated with the amount of the DNA hybrid on the electrode. Moreover, when PCR products of exon 4, on which the P72/R72 SNP resides, of the p53 gene were analyzed by this method, the heterozygote and homozygotes were discriminated with modest precision. 相似文献
74.
A new chiral oxazaborolidine catalyst was prepared in situ from 3, 5-bis(trifluoromethyl)phenylboron dichloride and N-(p-toluenesulfonyl)-(S)-tryptophan. This catalyst is much more active than Corey's original catalyst for the Mukaiyama aldol reaction of aldehydes with silyl enol ethers. The observed syn selectivities and re-face attack of silyl enol ethers on carbonyl carbon of aldehydes imply that the extended-transition state model is applicable. 相似文献
75.
Qiang Xu Prof. Dr. Nobuko Tsumori Prof. Dr. Ling Jiang Masanobu Kondo Ryuichi Arakawa Prof. Dr. 《化学:亚洲杂志》2007,2(5):599-608
Carbonyldinitrosyltris(fluorosulfato)tungstate(II) and ‐molybdate‐(II) anions, [fac‐M(CO)(NO)2(SO3F)3]? (M=W, Mo), which are novel weakly coordinating anions that contain a metal carbonyl/nitrosyl moiety, have been generated in fluorosulfonic acid and completely characterized by multinuclear NMR, IR, and Raman spectroscopy as well as ESI mass spectrometry. ESI MS measurements performed for the first time on a superacidic solution system unambiguously reveal the formation of the monoanionic, mononuclear W and Mo complexes formulated as [M(CO)(NO)2(SO3F)3]? (M=W, Mo). Multinuclear NMR spectroscopic studies at natural abundance and 13C and 15N enrichment clearly indicate the presence of one CO ligand, two equivalent NO ligands, and two types of nonequivalent SO3F? groups in a 2:1 ratio. The IR and Raman spectra reveal that the two equivalent NO ligands have a cis conformation, thus indicating a fac structure. Density functional calculations at the B3LYP level of theory predict that these anions have a singlet ground state (1A′) with a Cs symmetry along with C–O and N–O vibrational frequencies that are in agreement with the experimental observations. Mulliken population analysis shows that the monovalent negative charge is dispersed on the bulky sphere, the surface of which is covered by all the negatively charged O and F atoms with charge densities much lower than SO3F?, suggesting that [fac‐M(CO)(NO)2(SO3F)3]? (M=W, Mo) are weakly nucleophilic and poorly coordinating anions. 相似文献
76.
Hideo Kondo Kouki Matsubara Hideo Nagashima 《Journal of the American Chemical Society》2002,124(4):534-535
Coordinatively unsaturated diruthenium complexes, [(eta5-C5Me5)Ru(mu2-iPrNC(Me)=NiPr)Ru(eta5-C5Me5)]+, of which crystallography revealed structures bearing a bridging amidinate ligand perpendicular to the Ru-Ru axis, were synthesized by anion exchange of [(eta5-C3Me5(Ru(mu2-iPrNC(Me)=NiPr)Ru(eta5-C5Me5)]+ Br- by weakly coordinating anions. Variable-temperature NMR showed rapid motion of the bridging amidinate ligand. The coordinatively unsaturated nature of the cationic complexes provides their high reactivity toward a series of two electron donor ligands. Oxidative addition of molecular hydrogen occurred to give [(eta5-C5Me5)Ru(mu2-iPrNC(Me)=NiPr)(mu-H)Ru(eta5-C5Me5)(H)]+, which was isolated and characterized. 相似文献
77.
Fukuyama T Yamaura R Higashibeppu Y Okamura T Ryu I Kondo T Mitsudo TA 《Organic letters》2005,7(26):5781-5783
[reaction: see text] Catalytic [2 + 2 + 1 + 1] cocyclization reaction of an alkyne, an alkene, and two molecules of carbon monoxide, leading to functionalized hydroquinones, was studied. Using [Cp*RuCl2]2 as a catalyst, we found that a variety of electron-deficient alkenes, such as alpha,beta-unsaturated ketones, esters, amides, and nitriles, can be employed as an alkene coupling partner to give the corresponding hydroquinones. 相似文献
78.
79.
Incubation of diosgenone (1, 25D-spirost-4-en-3-one) with Verticillium theobromae (Turconi) Mason et Hughes (CBS) afforded 20α-hydroxypregn-4<ne-3,16-dione (3) and 3α,11β,20α-trihydroxy-5α-pregnan-16-one (4). The same transformation products were also obtained by the use of Stachylidium bicolor Link (IFO 6647). Isolation and identification processes of the products are discussed. 相似文献
80.
Yoshiyuki Tanaka Makoto Arakawa Yohei Yamaguchi Chieko Hori Masahiro Ueno Takeyuki Tanaka Tatsushi Imahori Yoshinori Kondo 《化学:亚洲杂志》2006,1(4):581-585
A metal‐free acetylide was observed by using NMR spectroscopy. Metal‐free acetylides are closely related to reactive intermediates (carbanions) in solution; therefore, they have been regarded as unobservable species. However, we generated this highly reactive and unstable species through the deprotonation of phenylacetylene by using the strong nonmetallic phosphazene base tBu‐P4. In the presence of tBu‐P4, the J coupling between the ethynyl carbon and hydrogen nuclei (1JC,H) of phenylacetylene disappeared; this indicates the deprotonation of the alkyne terminal. Furthermore, a large low‐field shift (approximately 90 ppm) of the alkyne carbon resonance was observed. We concluded that we have observed a metal‐free carbanion with a formal charge on an sp‐hybridized carbon atom for the first time. 相似文献