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101.
Puchkaev AV Wakagi T Ortiz de Montellano PR 《Journal of the American Chemical Society》2002,124(43):12682-12683
The cytochrome P450 superfamily of enzymes catalyzes a broad range of oxidative processes involved in the metabolism of fatty acids, biosynthesis of sterols, and elimination of drugs and xenobiotics. Application of the unique properties of P450 enzymes as fine biocatalysts in biotechnology is limited due to their thermal instability and the requirement for auxiliary electron-donor proteins and cofactors. CYP119, a thermophilic P450 enzyme from Sulfolobus solfataricus, was characterized some time ago, but no high-temperature redox partners have been available for it. Here we report reconstitution of CYP119 with a novel high-temperature electron-donor system consisting of a ferredoxin and 2-oxoacid:ferredoxin oxidoreductase from Sulfolobus tokodaii strain 7 that, unlike all other known P450 electron-donor partners, utilizes coenzyme-A and pyruvic acid rather than NADH or NADPH as the source of electrons. The oxidation of lauric acid by the reconstituted system increased 16-fold as the temperature increased from 25 to 70 degrees C and was functional for more than 30 min at the higher temperature. This first in vitro high-temperature P450 catalytic system is a key step in the development of practical high-temperature monooxygenase systems. 相似文献
102.
Maria J. Ortiz Antonia R. Agarrabeitia Gonzalo Duran-Sampedro Jorge Bañuelos Prieto Teresa Arbeloa Lopez Walter A. Massad Hernán A. Montejano Norman A. García Iñigo Lopez Arbeloa 《Tetrahedron》2012,68(4):1153-1162
A theoretical and experimental study on the iodination of BODIPY dyes with different degrees of substitution has been developed. Polyhalogenated BODIPYs synthesized in this work are the first examples of this type of dyes with more than two halogen atoms in the BODIPY core and they can be selectively functionalized. Surprisingly, the position in which halogen is attached has a marked effect in the photophysical properties and modulates the fluorescence capacity of the resulting BODIPY. These iodinated BODIPYs are efficient singlet oxygen generators. 相似文献
103.
Yahia Didane Rocio Ponce Ortiz Jian Zhang Keijyu Aosawa Toshinori Tanisawa Hecham Aboubakr Frédéric Fages Jörg Ackermann Noriyuki Yoshimoto Hugues Brisset Christine Videlot-Ackermann 《Tetrahedron》2012,68(24):4664-4671
Solution and solid-state properties of two new perfluoroalkyl end-substituted analogues of distyryl-bithiophene (CF3-DS2T and diCF3-DS2T) are presented. Vacuum deposited thin films were investigated by atomic force microscopy, X-ray diffraction, and implemented as active layers into organic thin film transistors. While physicochemical measurements in solution suggest a preferential hole injection and transport inside CF3-DS2T and diCF3-DS2T films, electrical measurements performed under high vacuum show that CF3-DS2T behaves as n-type semiconductor while no charge transport was measured in diCF3-DS2T. The results highlighted the importance of substituents on conjugated backbone and on the resulting fine ordering in solid state to control the charge transport. 相似文献
104.
Garcia Ruano JL Alemparte C Martin Castro AM Adams H Rodriguez Ramos JH 《The Journal of organic chemistry》2000,65(23):7938-7943
The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles. 相似文献
105.
The extraction of Al(III) and Zn(II) from an aqueous solution with two water-in-oil microemulsions, one containing di(2-ethylhexyl)phosphoric acid (DEHPA), was investigated to aid the understanding of the role of the extractant and the metal specific characteristics in the mechanism of microemulsion extraction. The extraction of Al with the DEHPA microemulsion increased by a factor of about 10 with respect to that in the conventional DEHPA system, whereas the extraction of Zn was lower than that in the single DEHPA system. Extraction with the DEHPA-free microemulsion was very low, showing that metal ion solubilization was not important in the mechanism of microemulsion extraction. It is proposed that the effect of the mixed microemulsion on the metal distribution coefficient is the result of the balance between a decrease in the complexation reaction yield due to the interaction between butanol and DEHPA, and the adsorption of the metal complex at the macro- and microinterfaces. The former leads to a decrease in Zn(II) extraction and the latter to Al(III) extraction synergism. Copyright 2000 Academic Press. 相似文献
106.
Oxidizing species in the mechanism of cytochrome P450 总被引:2,自引:0,他引:2
This review discusses the mechanisms of oxygen activation by cytochrome P450 enzymes, the possible catalytic roles of the various iron--oxygen species formed in the catalytic cycle, and progress in understanding the mechanisms of hydrocarbon hydroxylation, heteroatom oxidation, and olefin epoxidation. The focus of the review is on recent results, but earlier work is discussed as appropriate. The literature through to February 2002 is surveyed, and 175 referenced are cited. 相似文献
107.
de Ropp JS Sham S Asokan A Newmyer S Ortiz de Montellano PR La Mar GN 《Journal of the American Chemical Society》2002,124(37):11029-11037
The functional higher oxidation states of heme peroxidases have been proposed to be stabilized by the significant imidazolate character of the proximal His. This is induced by a "push-pull" combination effect produced by the proximal Asp that abstracts ("pulls") the axial His ring N(delta)H, along with the distal protonated His that contributes ("pushes") a strong hydrogen bond to the distal ligand. The molecular and electronic structure of the distal His mutant of cyanide-inhibited horseradish peroxidase, H42A-HRPCN, has been investigated by NMR. This complex is a valid model for the active site hydrogen-bonding network of HRP compound II. The (1)H and (15)N NMR spectral parameters characterize the relative roles of the distal His42 and proximal Asp247 in imparting imidazolate character to the axial His. 1D/2D spectra reveal a heme pocket molecular structure that is highly conserved in the mutant, except for residues in the immediate proximity of the mutation. This conserved structure, together with the observed dipolar shifts of numerous active site residue protons, allowed a quantitative determination of the orientation and anisotropies of the paramagnetic susceptibility tensor, both of which are only minimally perturbed relative to wild-type HRPCN. The quantitated dipolar shifts allowed the factoring of the hyperfine shifts to reveal that the significant changes in hyperfine shifts for the axial His and ligated (15)N-cyanide result primarily from changes in contact shifts that reflect an approximately one-third reduction in the axial His imidazolate character upon abolishing the distal hydrogen-bond to the ligated cyanide. Significant changes in side chain orientation were found for the distal Arg38, whose terminus reorients to partially fill the void left by the substituted His42 side chain. It is concluded that 1D/2D NMR can quantitate both molecular and electronic structural changes in cyanide-inhibited heme peroxidase and that, while both residues contribute, the proximal Asp247 is more important than the distal His42 in imparting imidazole character to the axial His 170. 相似文献
108.
The validation of an analytical procedure means the evaluation of some performance criteria such as accuracy, sensitivity, linear range, capability of detection, selectivity, calibration curve, etc. This implies the use of different statistical methodologies, some of them related with statistical regression techniques, which may be robust or not. The presence of outlier data has a significant effect on the determination of sensitivity, linear range or capability of detection amongst others, when these figures of merit are evaluated with non-robust methodologies.In this paper some of the robust methods used for calibration in analytical chemistry are reviewed: the Huber M-estimator; the Andrews, Tukey and Welsh GM-estimators; the fuzzy estimators; the constrained M-estimators, CM; the least trimmed squares, LTS. The paper also shows that the mathematical properties of the least median squares (LMS) regression can be of great interest in the detection of outlier data in chemical analysis. A comparative analysis is made of the results obtained by applying these regression methods to synthetic and real data. There is also a review of some applications where this robust regression works in a suitable and simple way that proves very useful to secure an objective detection of outliers. The use of a robust regression is recommended in ISO 5725-5. 相似文献
109.
110.