Generation of a high-quality partially coherent dark hollow beam with a multimode fiber

We report the experimental generation of a high-quality partially coherent dark hollow beam (DHB) by coupling a partially coherent beam into a multimode fiber (MMF) with a suitable incidence angle. The interference experiment of the generated partially coherent DHB passing through double slits is demonstrated. It is found that the coupling efficiency of the MMF, the quality, and the coherence of the generated partially coherent DHB are closely controlled by the coherence of the input beam. (c) 2008 Optical Society of America.

Matrix-assisted laser desorption/ionization mass spectrometry using porous silicon and silica gel as matrix

Porous silicon powder and silica gel particles have been applied as inorganic matrices for the analysis of small molecules in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOFMS). In contrast to conventional MALDI-TOFMS, the signal interference of low-molecular analytes by the matrix has been eliminated. Almost no fragmentations of the analytes were observed. Effects of various factors, such as the particle and pore size, the suspending solution, and sample preparation procedures, on the intensity of mass spectra have been investigated. The pore structure of the inorganic matrix and penetration of the analytes into the pores must be optimized for effective desorption and ionization of the analytes. Matrices (DHB and HCCA) were covalently bound to silica gel for improvement of spectrum intensity. Copyright (C) 2001 John Wiley & Sons, Ltd.

基质辅助激光解吸电离飞行时间质谱表征细胞色素C

A matrix-assisted laser desorption ionization time-of-flight mass spectrometry(MALDI-TOF—MS) technique was used for analysis of moleculear weight of cytochrome C.The effects of three kinds of matrix,such as 2,5-dihydroxybenzoic acid(DHB),a-cyano-4-hydroxycinnamic acid(a-CHC) and sinapinic acid(SA),were used to compared and a suitable a-CHC was found.Experimental data showed that this method was properable to analysis of the congeneric biochemical samples.

Investigation of a series of synthetic cationic porphyrins using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to study a series of synthetic cationic porphyrins as the perchlorate and bromide salts. This work presents the analytical results for the porphyrins obtained using 2,5-dihydroxybenzoic acid (DHB) and 1,8,9-anthratriol as matrices. The selective use of matrix affects ion formation from these porphyrins. By using DHB as the matrix, we not only observed [M - nCIO(4)](+) (n = 1-4) ions, but also obtained [2M - nCIO(4)](+) (n = 2-7) ions from the synthetic cationic porphyrins. The space volume of the side chains (R groups) and the nature of the anions (Br- or CIO4-) affected the relative importance of monomeric and dimeric ions of the porphyrin. The possible mechanisms of desorption and ionization of these cationic porphyrins were also considered in this study. MALDI-TOFMS proved to be a very useful method for obtaining structural information on these synthetic cationic porphyrins. Copyright (C) 1999 John Whey & Sons, Ltd.

Matrixassisted laser desorption/ionization mass spectral study of saccharides

Matrixassisted laser desorption/ionization (MALDI) mass spectra of saccharides with three common matrixes were studied here. It is shown that Na+ and K+ play important roles in the determination of oligasaccharide molecule weight and the molecular weights (MW) of glucans(dextran) with MW more than 10 000 is determined successfully with the help of column chromatography, By comparing the effects of three matrixes in saccharide analysis and comparing positive-ion and negative-ion matrixassisted laser desorption/ionization mass spectra of oligo- and polysaccharides, the most suitable matrix for saccharide analysis, 2,5-dihydroxylbezonic acid (DHB), is selected and the ion formation processes of saccharides under matrix-assisted laser adsorption/ionization condition are clarified.