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101.
The three-dimensional structure of human cytochrome P450 3A4 was modeled based on crystallographic coordinates of four bacterial P450s: P450 BM-3, P450cam, P450terp, and P450eryF. The P450 3A4 sequence was aligned to those of the known proteins using a structure-based alignment of P450 BM-3, P450cam, P450terp, and P450eryF. The coordinates of the model were then calculated using a consensus strategy, and the final structure was optimized in the presence of water. The P450 3A4 model resembles P450 BM-3 the most, but the B helix is similar to that of P450eryF, which leads to an enlarged active site when compared with P450 BM-3, P450cam, and P450terp. The 3A4 residues equivalent to known substrate contact residues of the bacterial proteins and key residues of rat P450 2B1 are located in the active site or the substrate access channel. Docking of progesterone into the P450 3A4 model demonstrated that the substrate bound in a 6-orientation can interact with a number of active site residues, such as 114, 119, 301, 304, 305, 309, 370, 373, and 479, through hydrophobic interactions. The active site of the enzyme can also accommodate erythromycin, which, in addition to the residues listed for progesterone, also contacts residues 101, 104, 105, 214, 215, 217, 218, 374, and 478. The majority of 3A4 residues which interact with progesterone and/or erythromycin possess their equivalents in key residues of P450 2B enzymes, except for residues 297, 480 and 482, which do not contact either substrate in P450 3A4. The results from docking of progesterone and erythromycin into the enzyme model make it possible to pinpoint residues which may be important for 3A4 function and to target them for site-directed mutagenesis. 相似文献
102.
The nitrosyl-hemoglobin (HbNO) is the carrier of nitric oxide (NO) which is the important messenger molecule displaying multiple physiologic and pathophysiologic roles. However it is still not clear for the fate of HbNO molecules during the venous-arterial transit. In this letter, the HbNO transition in vitro was studied by using the electron paramagnetic resonance (EPR) spectra. It was found that HbNO molecules were stable when oxygen did not exist in the system but not stable in aerobic conditions. The absorption spectra further revealed that the methemoglobin (metHb) was the product of HbNO in aerobic environment, showing that the HbNO changed to metHb when there were enough oxygen molecules in the system. 相似文献
103.
Stereochemistry of 7-aryl-1,7,8,8a-tetrahydro-3(2H)-indolizinones was studied by1H and13C NMR. Complete assignment of1H NMR signals and analysis of1H-1H coupling constants were performed using the iterative PANIC program. Values of3
J
6,7,3
J
7,8endo, and4
J
5,7 allow one to unambiguously identify the correspondingexo- andendo-stereoisomers. For stereoisomers with exo-orientation of H(7), complete assignment of13C NMR signals was performed on the basis of analysis of the13C-1H coupling constants using two dimensional heteronuclear shift-correlating spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 591–593, March, 1996. 相似文献
104.
Structures with AIB2? and BaAl4?type Units. I The Compounds Sr4Pd5P5 and Sr2Pd3P3 Sr4Pd5P5 (Cmcm, a = 4.177(1) Å, b = 31.377(5) Å, c = 8.581(2) Å, Z = 4) und Sr2 Pd3P3(Pmmm, a = 4.199(1) Å, b = 4.212(1) Å, c = 34.227(4) Å, Z = 4) have been prepared by heating the elements. Both structures contain exclusively units characteristic for the AIB2? and BaAl4?type. The ratio between isolated P-atoms and P2?pairs is interpreted with an ionic splitting of the formulas. 相似文献
105.
N. V. Gorbulenko T. M. Tkachuk T. V. Shokol V. V. Semeniuchenko A. V. Turov V. P. Khilya 《Chemistry of Heterocyclic Compounds》2007,43(5):569-575
The interaction has been studied of a series of substituted 3-hetaryl-7-hydroxychromones with amino acids and formaldehyde
(reactants ratio 1: 1: 2 respectively). In the case of glycine and Het = 3-isoxazolyl the product of aminomethylation at position
8 of the chromone was obtained, and with other Het (including Het = 4-phenyl-1,2,4-triazol-3-yl) 2-[6-alkyl-3-hetaryl-4-oxo-9,10-dihydro-4H,8H-chromeno[8,7-e][1,3]-oxazin-9-yl]acetic
acids were formed. With β-alanine and Het = 4-phenyl-1,2,4-triazol-3-yl the corresponding β-substituted propionic acid was
synthesized, but proline did not participate in the reaction, leading to bis(6-ethyl-3-hetaryl-7-hydroxychromon-8-yl)methane.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 683–689, May, 2007. 相似文献
106.
von Niessen Wolfgang Cederbaum Lorenz S. Kraemer Wolfgang P. 《Theoretical chemistry accounts》1977,44(1):85-93
The vertical valence ionization potentials of cyclopropane, ethylene oxide and ethylene imine are calculated by a many-body Green's function method. For C3H6 the ordering of the ionization potentials is 2e(), 1e(), 2a1(), 1a2(), 1e(). The assignment of the 2a1 and the 1a2 ionization potentials which has been controversial is thus clarified. The ordering is in agreement with the result obtained via Koopmans' theorem. For ethylene oxide and ethylene imine Koopmans' theorem fails in predicting the correct order of ionic states. For C2H4O the ordering of the ionization potentials is 2b
1(), 4a
1, 1a
2(), 2b
2,3a
1, 1b
1(), 1b
2, 2a
1 and for C2H5N 6a, 5a, 3a, 2a, 4a, 3a, 1a, 2a. The agreement of the computed ionization potentials with the experimental values is very satisfactory. 相似文献
107.
G. A. Gazieva A. N. Kravchenko Yu. A. Strelenko O. V. Lebedev R. G. Gaziev V. M. Zhulin 《Chemistry of Heterocyclic Compounds》2003,39(6):784-789
Acid hydrolysis and acetylation of 6,8-dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-dioxides have been studied. 6,8-Dialkyl-3-thia-2,4,6,8-tetraazabicyclo[3,3,0]octan-7-one 3,3-dioxides disproportionate to 4,4'-sulfonyldiiminobis(1,3-dialkylimidazolidin-2-ones) and sulfamide when treated with acid at pH 1 or with acetyl chloride. The kinetics of the disproportionation have been studied. 相似文献
108.
Natural (+)-iridomyrmecin and its unnatural enantiomer (−)-iridomyrmecin were synthesized by intramolecular [3+2] dipolar
cycloaddition of silyl nitronates that had been generated from the nitro derivatives of (+)- and (−)-citronellenes, respectively.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1683–1687, September, 1997. 相似文献
109.
2,2-Dimethyl-3-(2-methyl-3-indolyl)cyclopropylacetic acid, its amide and esters, and the corresponding alcohol, viz., the product of ester reduction by LiAlH4, were synthesized. The chemoselectivity of N- and O-alkylation of these compounds was studied. Selective monoalkylation at the nitrogen atom of the heterocycle, O-alkylation to the side chain, or dialkylation at both nucleophilic sites can be carried out under conditions of phase-transfer catalysis. The N-acylation at the indole fragment of nitrile of this acid occurs only under the Vilsmeier—Haak formylation conditions. 相似文献
110.
Enol and keto tautomers of methyl 3-oxo pentanoate could be separated on a HP-5 capillary column. The chromatographic peaks
were identified by examining characteristic mass ions arose from the corresponding enol and keto molecular ions. The study
showed that the area percentage of enol tautomer is a function of temperature of the column. Treating the column as a reactor,
the energy of activation for the on-column tautomerization could be extracted (35.1 kJ mol−1) by monitoring the loss of the enol tautomer, because the reaction is found to obey pseudo first-order kinetics. The enthalpy
and the entropy changes (ΔH = −3.98 kJ mol−1, ΔS = −7.89 J K−1mol−1) for the enol-to-keto reaction in the stationary phase were also obtained. 相似文献