I agree with Virginia in that it sound like you have way too much cellular
material in your sample. Typically when I used to look at E. coli raw samples
on minigels (10 x 8 cm) I usually tried to load approx. 0.04 OD 550 nm units
of cell culture per lane. Generally this worked out to putting 0.2 OD units
worth of culture (eg 10 ul of an OD 20 stationary phase broth culture + 10 ul
5X loading buffer + 30 ul water) in a microfuge tube, boiling, 30 sec spin in
a microfuge, and then loading 10 ul / lane. This typically gave me plenty of
signal on a Coomassie-stained gel. If you go to silver staining the amounts
can be reduced significantly.
Eric
