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851.
Tamara A. Vaganova Vladimir I. Rodionov Georgij E. Sal’nikov Evgenij V. Malykhin 《Journal of fluorine chemistry》2008,129(4):253-260
Monoamination of octafluoronaphthalene by liquid ammonia affords 2-aminoheptafluoronaphthalene mainly (isolated yield 85-90%). Diamination of octafluoronaphthalene or amination of 2-aminoheptafluoronaphthalene affords a mixture of isomeric 1,6-, 1,7-, 2,6-, and 2,7-diaminohexafluoronaphthalenes with considerable prevalence of the 2,7-isomer (∼70%), thus being the first example of the predominant substitution at position 7 in 2-substituted polyfluoronaphthalenes. The 2,7/2,6 ratio of 2-X-heptafluoronaphthalene (X = −NH, NH2 and NHAc) amination diminishes with the decrease of electron-donating effect of the substituent; 2,7-diaminohexafluoronaphthalene forms in the reactions of 2-aminoheptafluoronaphthalene or octafluoronaphthalene with excess of NaNH2 in liquid ammonia and 2,6-diaminohexafluoronaphthalene—in the reaction of 2-acetylamidoheptafluoronaphthalene with liquid ammonia followed by acetylamido group hydrolysis. The method of the selective preparation of these diamines based on the reversible transformation of amino group and a convenient technique of their high purity isolation by complexation with crown ether have been elaborated. 相似文献
852.
853.
854.
Vladimir Varlamov 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2008,59(3):381-399
Fractional integrals and derivatives of Airy functions (Riesz potentials) are considered. For half integrals D
−1/2
Ai(x) and D
−1/2
Gi(x) explicit representations are found in terms of the products of Airy functions. Here Ai(x) and Gi(x) are the Airy function of the first kind and the Scorer function, respectively. Based on that representations are obtained
for all semi-integer derivatives of Ai(x) and Gi(x). Applications to Korteweg–de Vries type equations are provided.
相似文献
855.
856.
We solve a special case of the single-robot cyclic scheduling problem with a fixed robot operation sequence and time window constraints on processing times. It generalizes the known single-part fixed-sequence problems into the one to cover a processing network with multiple part types and setup time requirements between the processing steps for different parts at the shared stations. The objective is to minimize the cycle time. We prove that this problem is equivalent to the parametric critical path problem, and propose a strongly polynomial time solution algorithm which uses a new labeling procedure to identify all feasible parameter values. The proposed algorithm is based on an extension to the known Bellman–Ford algorithm. 相似文献
857.
858.
Elena V. Schmalhausen Vladimir I. Muronetz Natalya K. Nagradova 《Applied biochemistry and biotechnology》2000,88(1-3):211-220
D-Glyceraldehyde-3-phosphate dehydrogenase (GAPDH, EC 1.2.1.12) catalyzes the oxidative phosphorylation of its substrate in
a two-step reaction. Asa result of the first, oxidativestep, the covalent intermediate where in 3-phosphoglyceroyl moiety
is bound to Cys149 of the active center is subjected to nucleophilic attack by inorganic phosphate, but remains resistant
to hydrolytic decomposition. This ensures tight coupling of oxidation with phosphorylation in glycolysis. In this article,
we present the experimental evidence for the conversion of GAPDH into a form capable of performing the reaction in the absence
of inorganic phosphate. The structural basis for this conversion is the oxidation of a cysteine residue (probably Cys 153)
into a sulfenic acid derivative under mild conditions to affect the integrity of the essential Cys 149. As a result, an intram
olecular transfer of 3-phosphoglyceroyl group from the active center Cys 149 to Cys 153 becomes possible with subsequent hydrolysis
of the sulfenyl carboxylate intermediate. 相似文献
859.
Konstantin A. Kozhanov Michael P. Bubnov Nina N. Vavilina Larisa Yu. Efremova Georgy K. Fukin Vladimir K. Cherkasov Gleb A. Abakumov 《Polyhedron》2009,28(13):2555-2558
Structural study of dialkyl (PCP)-pincer o-semiquinonato nickel complexes indicated sloped relative positions of bi- and tri-dentate ligands. It became bright confirmation of propositions made on the base of their EPR spectra followed by molecular modelling. 相似文献
860.
Kateryna O. Znovjyak Olesia V. Moroz Vladimir A. Ovchynnikov Tatyana Yu. Sliva Svitlana V. Shishkina Vladimir M. Amirkhanov 《Polyhedron》2009,28(17):3731-3738
Coordination compounds with general formula [Ln(L1)3phen], where Ln = Nd, Eu, Er, Yb, HL1 = N,N′-dipyrrolidine-N′′-trichloracetylphosphortriamide, phen = 1,10-phenanthroline; [Ln(L1)3bpm], where Ln = La, Nd, Eu, Gd, Er, Y, bpm = 2,2′-bipyrimidine and [{Ln(L2)3}2(μ-bpm)], where Ln = La, Nd, Eu, Gd, Er, Y, HL2 = dimethyl-N-trichloracetylamidophosphate have been synthesized and characterized by means of IR and UV–Vis spectroscopy. Crystal structures of [Nd(L1)3phen] (1), [Nd(L1)3bpm] (2) and [{Nd(L2)3}2(μ-bpm)] (3) have been determined. It was found, that in the deprotonated form the phosphoryl ligands (L1)? and (L2)? are coordinated to the neodymium atoms in a bidentate manner via the oxygen atoms of the phosphoryl and the carbonyl groups with formation of six-membered metallocycles. In the case of compounds 1 and 2 the 1,10-phenanthroline (or 2,2′-bipyrimidine) molecules are coordinated to the metals in a bidentate manner via the nitrogen atoms. In contrast 2,2′-bipyrimidine acts in the bidentate-bridge mode forming binuclear complex 3. Variable-temperature magnetic susceptibility measurements of 3 and [{Gd(L2)3}2(μ-bpm)] (4) reveal a weak antiferromagnetic interaction between the two magnetic centres, whereas in the case of [{Eu(L2)3}2(μ-bpm)] (5) the presence of spin–orbit coupling leads to a deviation from the Curie and Curie–Weiss laws. 相似文献