A CE−MALDI Interface Based on the Use of Prestructured Sample Supports

Abstract

We have developed an off-line coupling of capillary electrophoresis (CE) to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS) based on CE fraction collection onto prestructured MALDI sample supports. Analyte carryover and detection sensitivity were investigated using a standard peptide mixture. Low femtomole amounts were detected, and no noticeable carryover was discovered. The performance of the method was evaluated with a mixture of tryptic digests of proteins from a human fetal brain cDNA expression library. The total number of identified peptides was increased from 47 to 211 when the CE-MALDI interface was used compared to direct MALDI-MS analysis. Sequence coverage with CE-MALDI was in the 25-60% range for the different proteins, corresponding to an increase of 1.3-4.9 times relative to that obtained with MALDI-MS of the crude mixture. Fractionation of sample components also facilitated protein identification by MALDI postsource decay analysis. Our initial results suggest this CE-MALDI interface can be used for the analysis of complex peptide mixtures isolated from biological tissues.

Recent Developments in Capillary Electrophoresis–Mass Spectrometry of Proteins and Peptides

“…[67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83] Only these two configurations are covered in this review, although, brief descriptions of the other three are given in the succeeding paragraphs.…”

“…68 Johnson et al 69 reported on the identification of more peptides from a mixture of tryptic digests by CE-MALDI, compared to direct MALDI analysis.…”

“…Moreover, since the actual amount of the sample consumed in MALDI is much lower than what is required for analysis, a sample can be reanalyzed further, or recovered, for other experiments. 69 To minimize sample handling and potential losses, strategies for the on-line coupling of CE with MALDI have also been developed. These include the use of a continuous flow (CF) through a capillary to transport the matrix and the analyte to the tip of the sample probe, 106 a pneumatic nebulizer to spray the solution containing the matrix and the analyte into the mass spectrometer, 107 and a moving target surface that is moved into the mass spectrometer.…”

New directions of miniaturization within the proteomics research area

“…Alternatively so-called hydrophobic anchor points can be applied, which utilizes a hydrophilic spot surrounded by a hydrophobic surface. As a large volume is deposited on the anchor point, the sample is enriched on the predefined spot area through the evaporation process [55]. Such target plates are now commercially available from Bruker Daltonics and Micromass.…”

An Overview of Analytical Applications of Time of Flight-Mass Spectrometric (TOF-MS) Analyzers and an Inductively Coupled Plasma-TOF-MS Technique

“…[36][37][38][39][40][41][42][43][44][45][46][47][48] Coupling of MALDI with liquid chromatography, capillary electrophoresis (CE) and gel chromatography is a way to extend its applicability. 32,[49][50][51][52][53][54][55][56][57][58] The possibility to attain the sensitivity of physical limits (a few atoms or molecules) by laser-assisted reflectron TOF-MS has been stated. 59 The precision of the detection and quantification of metal isotope ratios comparable to ICP-MS and thermal ionization mass spectrometry (TIMS) has been reported.…”