An ionic liquid coating for determination of sildenafil and UK-103,320 in human serum by capillary zone electrophoresis-ion trap mass spectrometry

Ionic liquid (IL) was covalently bonded onto the silica capillary surface and the electroosmotic flow was reversed over a pH range of 3.5 to 7. Sildenafil (SL) and its metabolite UK-103,320 (UK) in human serum were detected by solid-phase extraction followed by capillary zone electrophoresis-mass spectrometry analysis. The running buffer contained 10 mM acetic acid adjusted to pH 4.5 with 1 M ammonia, and the separating voltage was set to -25 kV. The adsorption of the analytes onto the bare capillary wall was eliminated by the IL coating and the drugs were baseline-separated within 14 min with detection limits (S/N = 3) of 14 and 17 ng/mL for SL and UK, respectively. The method developed showed good intraday precision in terms of relative standard deviation (RSD) with respect to migration time (RSD 相似文献   

Preparation of α- or β-trifluoromethylated vinylstannanes and their cross-coupling reactions

α- or β-Trifluoromethylated vinylstannanes 1, 2a, 3 and 4 were prepared form 1,1-bis(phenylthio)-2,2,3,3,3-pentafluoropropylbenzene (5) via several steps. The cross-coupling arylation reactions of 1–4 with aryl iodides bearing a bromo, methoxy, methyl, nitro or trifluoromethyl group on para- or meta-position of benzene ring afforded the corresponding coupling products in good yields. Compounds 1, 2a and 4 underwent the acylation reaction with various types of acyl chlorides to give the corresponding trifluoromethylated enone derivatives in good yields. Reduction of trifluoromethylated enone derivatives with LiAlH₄, followed by Fridel-Craft’s type of cyclization with AlCl₃ provided trifluoromethylated indene derivatives in good yields.     

Proton exchange in type II isopentenyl diphosphate isomerase

[reaction: see text] Type II isopentenyl diphosphate:dimethylallyl diphosphate (IPP:DMAPP) isomerase from Synechocystis PCC 6803 catalyzes the interconversion of IPP and DMAPP. Upon incubation of the enzyme with IPP or DMAPP in 2H2O, one deuterium is incorporated into the C2 methylene of IPP, two deuteriums are incorporated at C4, and three deuteriums are incorporated into the (E)-methyl of DMAPP.     

A -dimensional extension of a lemma of Huneke's and formulas for the Hilbert coefficients

A -dimensional version is given of a -dimensional result due to C. Huneke. His result produced a formula relating the length to the difference , where is primary for the maximal ideal of a -dimensional Cohen-Macaulay local ring , is a minimal reduction of , , and is the Hilbert-Samuel polynomial of . We produce a formula that is valid for arbitrary dimension, and then use it to establish some formulas for the Hilbert coefficients of . We also include a characterization, in terms of the Hilbert coefficients of , of the condition .

     

Structured mesh generation with smoothness controls

In geometrically complex domains, the Ryskin and Leal (RL) orthogonal mesh generation system may cause mesh distortion and overlapping problems when using the ‘weak constraint’ method with specified boundary point distribution for all boundaries. To resolve these problems, an improved RL system with automatic smoothness control is proposed. In this improved RL system, the automatic smoothness control mechanism is based on five types of smoothness conditions and includes the self‐adjustment mechanism and the auto‐evaluation mechanism for an empirical parameter. The proposed system is illustrated using several test examples. Several applications to natural domains are also demonstrated. It is shown that the improved RL system is capable of resolving the above problems at little cost of orthogonality. Copyright © 2006 John Wiley & Sons, Ltd.