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371.
Orth ES Medeiros M Bortolotto T Terenzi H Kirby AJ Nome F 《The Journal of organic chemistry》2011,76(24):10345-10348
We report a detailed kinetic and mechanistic study of the reaction of a widely used therapeutic agent, deferoxamine (DFO), which contains three nucleophilic hydroxamate groups, with the model phosphate diester bis-2,4-dinitrophenylphosphate BDNPP. We clarify the mechanism by detecting important phosphorylated intermediates in the model reaction and show that the mechanism can be extended to the reaction with DNA. The effectiveness of DFO in cleaving DNA was examined over a range of pH in the absence and presence of a biologically available metal (Zn(2+)). The results inform and complement ongoing studies involving DFO, which can act as a powerful nucleophile toward DNA and other targets susceptible to nucleophilic attack. 相似文献
372.
Orth ES Wanderlind EH Medeiros M Oliveira PS Vaz BG Eberlin MN Kirby AJ Nome F 《The Journal of organic chemistry》2011,76(19):8003-8008
The phosphorylation of imidazole by two activated phosphate diesters and a triester gives phosphorylimidazole derivatives that are stable enough in aqueous solution to be observed and identified by ESI-MS/MS and NMR. Half-lives ranging from hours to days (in the case of the monoethyl ester) show that it is possible to design molecules with variable half-lives with potential to be used for biological intervention experiments as possible inhibitors of biosignaling processes or as haptens for the generation of antibodies. 相似文献
373.
374.
Theoretical study of the importance of the spectator groups on the hydrolysis of phosphate triesters
The spontaneous hydrolysis of a series of five triaryl and two dialkyl aryl phosphate triesters, previously studied experimentally, is examined theoretically using two different hybrid density functional methods, B3LYP and M06; two basic sets, 6-31+G(d) and 6-311++G(d,p); and the Gaussian 09 program. The B3LYP/6-31+G(d) methodology combined excellent accuracy with minor computational cost. The calculations show excellent quantitative agreement with experiment, which is best in the presence of three discrete water molecules. The results support a two-step mechanism involving a pentacovalent addition intermediate, with a lifetime of tenths of a millisecond. The rate-determining formation of this intermediate involves general base catalysis, defined by concerted proton transfers in a six-membered cyclic activated complex (TS1), which involves two hydrogen-bonded water molecules supporting a well-developed H(2)O···P bond (mean % evolution 77.83 ± 0.97). The third water molecule is hydrogen-bonded to P═O and subsequently involved in product formation via TS2. The effects on reactivity of all the groups attached to phosphorus in TS1 are examined in detail: the two non-leaving groups in particular are found to play an important role, accounting for the substantial difference in reactivity between triaryl and dialkyl aryl phosphate triesters. 相似文献
375.
We prove that Schanuel's conjecture for the reals is equivalentto a uniform version of itself. 2000 Mathematics Subject Classification11J81, 11U09, 03C64. 相似文献
376.
Pectin is an integral component of plant cell walls. It is believed to form an interconnected network structure independent
of the cellulose–xyloglucan network structure. Pectin gels are often used as a model for the pectin network structure within
the plant cell wall. The middle lamella pectin can be extracted with chelating agents and is believed to be associated through
cooperative binding of calcium ions in the so-called egg-box junction zones. Although a great deal is known about the nature
of the junction zones in pectin gels, less is known about the long-range structure within calcium-set gels. Two plausible
alternative models for long-range order in these gels are a pseudo rubber-like structure and a fibrous network structure.
Atomic force microscopy studies of calcium-induced gel precursors, and fragments released from gels, suggest that association
leads to a branched fibrous structure within the gels. Enzymatic de-esterification of high methoxy pectin in the presence
of calcium ions can induce gelation of the pectin. Thus pectin gel networks may provide a model for a self-assembled network
structure within the middle lamella region of the plant cell wall. 相似文献