As I said in my post to Dr. A. Rosenthal, we have used this "sonication
ligation" with great success.
We use an ultrasound cleaning bath (Branson 2200 by GWB) which has set
frquency (ie only ON/OFF switch).
Also other people in our institute (Institute of Biotechnology, Helsinki,
Finland) have tried this method, and since they are coming back to use our
bath, I guess they have had good experiences too :)
saren at operoni.helsinki.fi