Fig. 4. Fertilization stimulates protein-tyrosine phosphorylation in LD-DIM fractions. Sucrose density gradient fractions (20 µl of each fraction per lane) were prepared from (A) unfertilized, (B) fertilized (5 minutes after insemination) and (C) H₂O₂-treated (10 mM, 5 minutes) eggs and analyzed by immunoblotting with anti-phosphotyrosine antibody (pTyr, 1 µg/ml of PY99) or anti-pY416 antibody (pY416, 5 µg/ml). Fractions 3-6 of unfertilized and fertilized eggs were concentrated ten times before the experiment. Asterisks indicate the positions of tyrosine-phosphorylated Xyk.