title: Two-layer sample preparation method for MALDI mass spectrometric analysis of protein and peptide samples containing sodium dodecyl sulfate.
abstract: Sodium dodecyl sulfate (SDS) is widely used in protein sample workup. However, many mass spectrometric methods cannot tolerate the presence of this strong surfactant in a protein sample. We present a practical and robust technique based on a two-layer matrix/sample deposition method for the analysis of protein and peptide samples containing SDS by matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The two-layer method involves the deposition of a mixture of sample and matrix on top of a thin layer of matrix crystals. It was found that for SDS-containing samples, the intensity of the MALDI signals can be affected by the conditions of sample preparation: on-probe washing, choice of matrix, deposition method, solvent system, and protein-to-SDS ratio. However, we found that, under appropriate conditions, the two-layer method gave reliable MALDI signals for samples with levels of SDS up to approximately 1%. The applications of this method are demonstrated for MALDI analysis of hydrophobic membrane proteins as well as bacterial extracts. We envision that this two-layer method capable of handling impure samples including those containing SDS will play an important role in protein molecular weight analysis as well as in proteome identification by MALDI-MS and MS/MS.
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Doucette
authors.forename: L
authors.initials: L
authors.lastname: Li
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis*; D004926:Escherichia coli / Q000737:chemistry; D015335:Molecular Probes; D010455:Peptides / Q000032:analysis*; D015203:Reproducibility of Results; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D012997:Solvents; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D001426:Bacterial Proteins; D015335:Molecular Probes; D010455:Peptides; D012997:Solvents; D012967:Sodium Dodecyl Sulfate