A-factor is pretty hydrophobic and not very soluble. Therefore alpha
factor is used for synchronization instead.
I usually use 1mg/l final conc. of alpha factor. If you use bar- strains,
you can even go further down with the alpha factor conc. The stock is
1000x conc. in 70 % MeOH and stored at -20C.
Early log pahase cells are incubated with alpha factor for 2-3 h, til >90%
of the cells show a shmoo. Remove the alpha factor with 2 quick washes
and resuspend in fresh medium.
Hope this helps!