Ferrocenylphosphine-imine ligands for Pd-catalyzed asymmetric allylic alkylation

Ferrocenylphosphine-imine ligands 6 derived front (R,S)-PPFNH2-R 5 and a variety of benzaldehydes were applied in the Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenylprop-2-en-1-yl acetate 7a or pivalate 7b with dimethyl malonate. The substituent effects on the catalytic reaction were investigated, and 96% e.e. with 99% yield was achieved when the m-nitro substituted ligand 6k was used. (C) 2002 Elsevier Science Ltd. All rights reserved.

Modification of a poly(methyl methacrylate) injection-molded microchip and its use for high performance analysis of DNA

Inexpensive and permanently modified poly(methyl methacrylate)(PMMA) microchips were fabricated by an injection-molding process. A novel sealing method for plastic microchips at room temperature was introduced. Run-to-run and chip-to-chip reproducibility was good, with relative standard deviation values between 1-3% for the run-to-run and less than 2.1% for the chip-to-chip comparisons. Acrylonitrile-butadiene-styrene (ABS) was used as an additive in PMMA substrates. The proportions of PMMA and ABS were optimized. ABS may be considered as a modifier, which obviously improved some characteristics of the microchip, such as the hydrophilicity and the electro-osmotic flow (EOF). The detection limit of Rhodamine 6G dye for the modified microchip on the home-made microchip analyzer showed a dramatic 100-fold improvement over that for the unmodified PMMA chip. A detection limit of the order of 10(-20) mole has been achieved for each injected phiX-174/HaeIII DNA fragment with the baseline separation between 271 and 281 bp, and fast separation of 11 DNA restriction fragments within 180 seconds. Analysis of a PCR product from the tobacco ACT gene was performed on the modified microchip as an application example.

Human plasma proteome analysis by multidimensional chromatography prefractionation and linear ion trap mass spectrometry identification

A resurgence of interest in the human plasma proteome has occurred in recent years because it holds great promise of revolution in disease diagnosis and therapeutic monitoring. As one of the most powerful separation techniques, multidimensional liquid chromatography has attracted extensive attention, but most published works have focused on the fractionation of tryptic peptides. In this study, proteins from human plasma were prefractionated by online sequential strong cation exchange chromatography and reversed-phase chromatography. The resulting 30 samples were individually digested by trypsin, and analyzed by capillary reversed-phase liquid chromatography coupled with linear ion trap mass spectrometry. After meeting stringent criteria, a total of 1292 distinct proteins were successfully identified in our work, among which, some proteins known to be present in serum in < 10 ng/mL were detected. Compared with other works in published literatures, this analysis offered a more full-scale list of the plasma proteome. Considering our strategy allows high throughput of protein identification in serum, the prefractionation of proteins before MS analysis is a simple and effective method to facilitate human plasma proteome research.

Mini-electrochemical detector for microchip electrophoresis

This paper presents the development of a mini-electrochemical detector for microchip electrophoresis. The small size (3.6 x 5.0 cm(2), W x L) of the detector is compatible with the dimension of the microchip. The use of universal serial bus (USB) ports facilitates installation and use of the detector, miniaturizes the detector, and makes it ideal for lab-on-a-chip applications. A fixed 10 M Omega feedback resistance was chosen to convert current of the working electrode to voltage with second gain of 1, 2, 4, 8, 16, 32, 64 and 128 for small signal detection instead of adopting selectable feedback resistance. Special attention has been paid to the power support circuitry and printed circuit board (PCB) design in order to obtain good performance in such a miniature size. The working electrode potential could be varied over a range of +/-2.5 V with a resolution of 0.01 mV. The detection current ranges from -0.3 x 10(-7) A to 2.5 x 10(-7) A and the noise is lower than 1 pA. The analytical performance of the new system was demonstrated by the detection of epinephrine using an integrated PDMS/glass microchip with detection limit of 2.1 mu M (S/N = 3).

High resolution time-of-flight spectrometer for crossed molecular beam study of elementary chemical reactions

In this article, we describe an apparatus in our laboratory for investigating elementary chemical reactions using the high resolution time-of-flight Rydberg tagging method. In this apparatus, we have adopted a rotating source design so that collision energy can be changed for crossed beam studies of chemical reactions. Preliminary results on the HI photodissociation and the F atom reaction with H-2 are reported here. These results suggest that the experimental apparatus is potentially a powerful tool for investigating state-to-state dynamics of elementary chemical reactions. (c) 2005 American Institute of Physics.