MALDI
Mass
Spectra
of Protein Digests Before and After Enrichment on a
Modified Plate
Prior to enrichment, the mass spectrum of a sample containing 3 digested phosphoproteins shows only minor signals from phosphopeptides (top spectrum). The large number of non-phosphorylated proteolytic peptides may suppress phosphopeptide signals. After enrichment using a MALDI plate coated with polymer-oxotitanium brushes, many phosphopeptide signals appear from all 3 of the proteins (bottom spectrum).
MALDI
mass
spectra
of model protein digests without
phosphopeptide enrichment (top) and after enrichment on MALDI plates
modified with polymer-oxotitanium brushes (bottom). MS peaks
labeled with α,
β,
and
o
represent phosphopeptides generated from α-casein,
β-casein
and
ovalbumin,
respectively,
and red symbols denote multi-phosphorylated
peptides. For more details see J. Proteome Res. 9, 3005–3015
(2010).