*4.1. Materials*

Reagents were purchased from Sigma (Milan, Italy), and an anti-phospho-tyrosine (P-Tyr) (clone PY20) mouse monoclonal antibody was obtained from Biosource-Invitrogen (Camarillo, CA, USA). Anti-mouse secondary antibody conjugated with horseradish peroxidase (HRP) was obtained from BioRad Laboratories (Irvine, CA, USA), and DDS-NHOH from Toronto Research Chemicals Inc. (North York, ON, Canada).
