DMF-MALDI: droplet based microfluidic combined to MALDI-TOF for focused peptide detection.

We present an automated droplet microfluidic system (DMF) to generate monitored nanoliter aqueous droplets in oil and their deposition on a commercial stainless steel plate for MALDI-TOF analysis of peptides or protein digests. We demonstrate that DMF-MALDI combination focuses the analyte on the MALDI plate, increasing considerably the homogeneity of the dried material. This results in a 30times enhanced MALDI-TOF MS signal for a model peptide, allowing a significant improvement of the detection sensitivity limit (down to few tens of attomoles).

Capillary electrophoretic focusing of covalently derivatized protein induced by surfactant.

In this communication, we present a very simple strategy to focus covalently derivatized proteins for high sensitivity CE analysis by LIF detection. We demonstrated that the covalently tagged protein can be focused just by adding SDS at a concentration above the CMC in the derivatized sample. Under specific injection conditions, SDS concentration below the CMC is also sufficient to induce the focusing of the tagged protein.

Neutral polymers as coatings for high resolution electrophoretic separation of Aβ peptides on glass microchips.

This study reports a comparison of the performances of two neutral polymers, poly ethylene-oxide (PEO) and poly(dimethylacrylamide-co-allyl glycidyl ether) (EpDMA), in glass microchips to achieve zone electrophoresis separation of several truncated forms of beta amyloid (Aβ) peptides, sharing very similar structures. The peptides were derivatized by FluoProbes 488 NHS to allow their fluorescence detection. Two protocols based either on PEO or EpDMA led to good pH stabilities in addition to a significant reduction of the electroosmotic flow.

On-line capillary electrophoresis derivatization method for high sensitivity analysis of ubiquitin in filtered cerebrospinal fluid.

Electrophoretically mediated microanalysis was implemented for on-line fluorescence derivatization of ubiquitin (UBI), a potential biomarker of Alzheimer disease. Ubiquitin was labeled on its amino groups by the Fluoprobes® 488 N-hydroxysuccinimide. The pH of the BGE, the applied electric field, and the washing process of the capillary were optimized.

Contribution of CE to the analysis of protein or peptide biomarkers.

Biomarker analysis is pivotal for disease diagnosis and one important class of biomarkers is constituted by proteins and peptides. This review focuses on protein and peptide analyses from biological fluids performed by capillary electrophoresis. The various strategies that have been reported to prevent difficulties due to the handling of real samples are described.