I have done Y2H screening with normalized human cDNA library with protein of interest. I have got some positive colonies with blue colour on Leu, Trp, His, Ade dropout + Aureobasidin A and X alpha Gal selection plate then I tried to isolate plasmid from those positive colonies but I am not getting the plasmids. I tried different plasmid isolation protocols but nothing is working. What could be the problem? Anyone faced this problem? Suggestions please.