Browsing by Author "Weng, MF"

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Affinity capture using vancomycin-bound magnetic nanoparticles for the MALDI-MS analysis of bacteria
(2005-03-15)
Lin, YS
;
Tsai, PJ
;
Weng, MF
;
Chen, YC
;
應用化學系
Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) provides a straightforward means to differentiate microorganism species based on mass spectral fingerprinting. The pathogen cell concentration in an infected sample, however, is generally lower than that capable of being detected directly by MALDI-MS. Furthermore, the presence of proteins or metabolites in biological fluids always causes unavoidable interference for the identification of microorganism species. Vancomycin, which binds to D-Ala-D-Ala moieties on the cell walls of Gram-positive bacteria and, therefore, inhibits peptidoglycan synthesis, is one of the most potent antibiotics. Thus, we have employed vancomycin-modified magnetic nanoparticles as affinity probes to selectively trap Gram-positive pathogens from sample solutions; i.e., these bacteria can be isolated from sample solutions by applying a magnetic field. The isolated cells could then be characterized by MALDI-MS. This approach effectively reduces the interference of protein and metabolite signals in the mass spectra of Gram-positive bacteria because vancomycin has such high specificity for the D-Ala-D-Ala units of the cell walls. The lowest cell concentration we detected for both Staphylococcus saprophyticus and Staphylococcus aureus in a urine sample (3 mL) was similar to 7 x 10(4) cfu/mL.
Using sol-gel/crown ether hybrid materials as desalting substrates for matrix-assisted laser desorption/ionization analysis of oligonucleotides
(2004)
Weng, MF
;
Chen, YC
;
應用化學系
;
Department of Applied Chemistry
This study demonstrates the feasibility of using sol-gel/crown ether hybrid materials as sample substrates that reduce the intensity of the signals of sodium ion adducts of oligonucleotides during matrix-assisted laser desorption/ionization (MALDI) analysis. 2-Hydroxymethyl[15]crown-5 and 2-hydroxymethyl[18]crown-6 were added as dopants during the sol-gel process to generate desalting substrates for MALDI sample deposition. The results demonstrate that the sol-gel/crown ether hybrid materials effectively suppress the formation of sodiated oligonucleotides during MALDI analysis. The largest detectable molecular size for an oligonucleotide was a 100-mer, and the detection limit for an oligonucleotide 36-mer was ca. 20 fmol. Copyright (C) 2004 John Wiley Sons, Ltd.