Pervanadate is a protein tyrosine phosphatase inhibitor that is commonly used to increase tyrosine phosphorylation in cells. When cells are treated with pervanadate for 30 minutes they undergo significant tyrosine phosphorylation, as shown by western blotting using anti-Phosphotyrosine. Confluent cultures of A431 cells were serum starved overnight. Cells were then either left untreated or treated with pervanadate (1 mM) for 30 minutes at 37°C Cells were lysed in 1% SDS, 1.0mM sodium ortho-vanadate, 10mM Tris (pH 7.4) buffer. Protein concentration was determined using the BCA method (Pierce) before diluting to final concentration and buffer.