Ligations - (Jul/19/2002 )

I have been having problems with ligating a 3,200 bp insert into a 5,000 bp binary vector. Digests and amount of DNA are very good. I have been doing in-gel ligation and E.coli (DH5a) transformation (routin protocols) with no success. Any advise??

You might want to dephosphorylate the vector
dephos enzyme and buffer from Lifetech (GibcoBRL)

1- you can try to dephosphorylate the vector. Be sure you inactivate the enzyme (5min 85C)  before ligation.
2- you could try by PCR. amplify your insert with primers having  enzymatic restriction sites to obtain cohesive ends compatible with your vector.
3- your insert is very big. It can be a problem. You can try to do ligation in two times. Cut you insert in two pieces (1,6Kb) and insert one after each other.