Protein or phosphoprotein gel staining and image acquisition were carried out as previously described [21, 22]. Briefly, the gels were fixed three times in 200 ml immobilization solution [10% acetic acid and 50% methanol] for 30 min and washed five times with 200 ml of water for 15 min. Under the dark, the gels were stained with Pro-Q Diamond phosphoprotein gel stain (Life Technologies, Carlsbad, CA) for 120 min at room temperature with gentle agitation and then washed three times with destaining solution [50 mM sodium acetate, pH 4.0 and 20% (v/v) acetonitrile] for 30 min. Image acquisition was performed on Fluorophorestar 3000 image capture system (Anatech, Tokyo, Japan) with a 520 nm excitation and 575 nm emission filter for Pro-Q Diamond detection.