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1.
The determination of doxazosin by high-performance liquid chromatography with fluorescence detection is described. Propanolol was used as the internal standard. Plasma samples were treated with methanol to precipitate the proteins. Doxazosin was isolated with C18 reversed-phase extraction columns. The determination limit is 1 ng/ml of plasma, while the extraction columns can be reused frequently. The method is applied to clinical trial samples. 相似文献
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A micro-reactor system with continual spectrophotometric detection has been operated in Sequential Injection lab-on-valve (SI-LOV) mode and applied to enzyme kinetics and inhibition studies, using acetylcholinesterase (AChE) and angiotensin-converting enzyme (ACE) as model systems. With the advantages of automation, real-time kinetic measurement, and thorough mixing, the SI-LOV micro-reactor system allows for the monitoring of initial reaction rates and determination of reactant concentrations in the reaction mixture, both of which are essential for the determination of kinetic constants for enzymes and inhibitors. Enzyme, substrate, and inhibitor are precisely metered by the syringe pump and delivered to a stirred micro-reactor, followed by a reference scan that establishes the baseline for the following reaction rate measurement. Michaelis constants (Km) for AChE and ACE were determined to be 0.16 mM and 0.30 mM, respectively, which are consistent with literature values. The type of inhibition (competitive, uncompetitive, or mixed), the dissociation constants for the inhibitors, and the inhibitor dose-response curves were also determined. 相似文献
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Ohne Zusammenfassung 相似文献
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Chester M. Mikulski William Henry Louis L. Pytlewski Nicholas M. Karayannis 《Transition Metal Chemistry》1977,2(1):135-140
Summary Complexes (2 : 1) of diethyl benzoylphosphonate (debp) with 3d metal perchlorates were synthesized and characterized by means of i.r. and electronic spectral, magnetic susceptibility and conductance measurements. In new complexes of the types [M(debp)2(OClO3)(OH2)](ClO4) (M = Fe, Co, Zn) and [Fe(debp)2(OClO3)(OH2)](ClO4)2, both debp ligands function as bidentate chelating agents, coordinating through the P=O and C=O oxygens. In contrast, in the manganese(II) and nickel(II) complexes, which are of the [M(debp)2(OClO3)(OH2)2](ClO4) type, one debp acts as a bidentate chelating ligand, while the second debp is unidentate, coordinating only through the P=O oxygen. Hexacoordination in the new cationic complexes is completed by coordination of aqua and unidentate perchlorato ligands, which are in competition for sites in the inner coordination sphere of the central metal ion with the weak debp ligand. On the other hand, debp, owing to its bulkiness, and especially the presence of the benzoyl substituent, introduces sufficiently severe steric hindrance during coordination. As a result of this, the formation of [M(debp)3]n+ tris-chelate cationic complexes with the 3 d metal ions under study does not seem to be possible. 相似文献
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Glucose oxidase was bound to Sepharose, Sephadex, gelatin, and dextran, yielding immobilized soluble and insoluble derivatives of the enzyme. The soluble preparations possessed higher enzymic activity than the analogous insoluble ones. The reversible dissociation process of the bound enzyme into apoenzyme and flavin adenine dinucleotide (FAD) was studied with the soluble and insoluble glucose oxidase in relation to enzymic activity and conformational changes as measured by circular dichroism and fluorescence methods. Bound apoenzyme was found to be more stable than the apoenzyme obtained from the unmodified glucose oxidase. The binding constant of FAD in bound glucose oxidase (Kdiss≈10-8M) calculated from fluorescent studies was lower than that of FAD in the native enzyme (Kdiss10-10M). The circular dichroism measurements indicated that dextran-bound glucose oxidase has a conformation similar to that of the native enzyme. 相似文献
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Both enantiomers of imperanene, a platelet aggregation inhibitor, have been synthesized in 82-90% ee. The key step of establishing the chiral center was achieved through stereoselective alkylation with benzyl chloromethyl ether using Enders' RAMP/SAMP chiral auxiliary method. The natural product was determined to be the (S)-enantiomer through comparison of optical rotation data. Reaction: see text. 相似文献
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Application of the LCAO-MO-SCF- method to conjugated hydrocarbons leads with the effective nuclear Slater's charges, Zeff = Zeff = 3.25 to electronic transitions higher than experimental ones by about 50%.We show that in the case of all trans linear polyenes and fulvene, one may obtain satisfying results by the same method, without any reference to experience, by taking Zeff = 3.0 Zeff = 3.55. There the effective nuclear charges are near of these of the valence state of carbon V
41s2t1t2t32ptz:Zeff = 2.971 Zeff = 3.382 [10]. 相似文献
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