Lenti vector ligation - (Sep/16/2011 )

Hi,
I am new to this.I need help.
My lenti vector is 7.5kb and insert is 4.5kb. I did ligations but i could not get colonies after transformation. Kindly someone help me in this regard? Please Please.

Regards

If you don't get any colonies after ligation, it can be caused by anything from bad ligation to competent cells.

Hi CloneMan,
Thanks a lot.
I used the same ligation protocol which i always used for other ligations, (that is T4 ligase), and always i got very good results. The only difference at this time is the insert and vector size. I never worked with 4.5 kb insert and 7.5 kb lenti vector. Would you suggest me some protocol to solve this problem.
Thanks in advance.