Enhanced detection of in-gel released N-glycans by MALDI-TOF-MS.

Many biologically relevant glycoproteins need to be separated on 1D- or 2D-gels prior to analysis and are available in picomole amounts. Therefore, it is important to have optimized methods to unravel the glycome that combine in-gel digestions with MALDI-TOF-MS. In this technical report, we investigated how the detection of in-gel released N-glycans could be improved by MALDI-TOF-MS. First, an AnchorChip target was tested and compared to ground steel target using several reference oligosaccharides. The highest signals were obtained with an AnchorChip target and D-arabinosazone as the matrix; a LOD of 1.3 to 10 fmol was attained. Then, the effect of octyl-β-glucopyranoside, a nonionic detergent, was studied during in-gel peptide-N(4) -(acetyl-ß-glucosaminyl) asparagine amidase F digestion of standard glycoproteins and during glycan extraction. Octyl-β-glucopyranoside increased the intensity and the amount of detected neutral as well as acidic N-glycans. A LOD of under 7 pmol glycoprotein could be achieved.