Improved Proteome and Phosphoproteome Analysis on a Cation Exchanger by a Combined Acid and Salt Gradient

Currently used elution
methods for strong cation exchange (SCX)
chromatography are based on two principles: salt and pH gradient.
In this paper, we report the first observation of peptide elution
by acid gradient. The degree of peptide separation using C18-SCX StageTip
was greatly improved by our acid and salt-based elution method compared
with a salt-based elution method. This development enabled us to identify
over 22 000 phosphopeptides from 2 mg of protein without labor-intensive
sample preparation. Our method is simple, robust, scalable, and low-cost
and can be easily implemented without any special equipment or techniques.