For those interested in ultrafast ligations, I would strongly recommend
the ligation kit made by TaKaRa. It only takes 15 minutes at 16C or RT. I
called the company to ask how it works and they told me it is T4 ligase
with a polyionic substance like dextran to increase local DNA end
concentrations. The efficiency is superb in our hands.
Sorry I don't have a phone number or address handy, as I am home now (well,
not when you're reading this, but when I wrote it :) ).
gibbs at husc.harvard.edu