Protein spots with differential abundance patterns on gels
were manually excised from gels, washed with Millipore pure
water for three times, destained twice with 30 mM K3Fe (CN) 6
for silver staining spots, reduced with 10 mM DTT in 50 mM
NH4HCO3, alkylated with 40 mM iodoacetamide in 50 mM
NH4HCO3, driedtwice with 100% acetonitrile and digested
overnight at 37 ◦C with sequencing grade modified trypsin
(Promega, Madison, WI, USA) in 50 mM NH4HCO3.