title: A simple sheathless CE-MS interface with a sub-micrometer electrical contact fracture for sensitive analysis of peptide and protein samples.
abstract: Online coupling of capillary electrophoresis (CE) to electrospray ionization mass spectrometry (MS) has shown considerable potential, however, technical challenges have limited its use. In this study, we have developed a simple and sensitive sheathless CE-MS interface based on the novel concept of forming a sub-micrometer fracture directly in the capillary. The simple interface design allowed the generation of a stable ESI spray capable of ionization at low nanoliter flow-rates (45-90 nL/min) for high sensitivity MS analysis of challenging samples like those containing proteins and peptides. By analysis of a model peptide (leucine enkephalin), a limit of detection (LOD) of 0.045 pmol/μL (corresponding to 67 attomol in a sample volume of ∼15 nL) was obtained. The merit of the CE-MS approach was demonstrated by analysis of bovine serum albumin (BSA) tryptic peptides. A well-resolved separation profile was achieved and comparable sequence coverage was obtained by the CE-MS method (73%) compared to a representative UPLC-MS method (77%). The CE-MS interface was subsequently used to analyse a more complex sample of pharmaceutically relevant human proteins including insulin, tissue factor and α-synuclein. Efficient separation and protein ESI mass spectra of adequate quality could be achieved using only a small amount of sample (30 fmol). In addition, analysis of ubiquitin samples under both native and denatured conditions, indicate that the CE-MS setup can facilitate native MS applications to probe the conformational properties of proteins. Thus, the described CE-MS setup should be useful for a wide range of high-sensitivity applications in protein research.
authors: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
authors: Tam T T N
authors: TT
authors: Nguyen
authors: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: Nickolaj.Petersen@sund.ku.dk.
authors: Nickolaj J
authors: NJ
authors: Petersen
authors: Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark. Electronic address: Kasper.Rand@sund.ku.dk.
authors: Kasper D
authors: KD
authors: Rand
mesh_terms: D000818:Animals; D002417:Cattle; D004560:Electricity; D019075:Electrophoresis, Capillary; D006801:Humans; D007328:Insulin / Q000032:analysis*; D012710:Serum Albumin, Bovine / Q000032:analysis*; D021241:Spectrometry, Mass, Electrospray Ionization; D013925:Thromboplastin / Q000032:analysis*; D051844:alpha-Synuclein / Q000032:analysis*
chemical_list: D007328:Insulin; D051844:alpha-Synuclein; D012710:Serum Albumin, Bovine; D013925:Thromboplastin
keywords: Native MS; Peptide mapping; Protein ESI-MS; Protein/peptide analysis; Sheathless CE-MS interface; Sub-micrometer fracture