HELP! -- Protecting DNA on a transilluminator?

[Earl J. Gubbins]

Vern Shellman wrote:
> 
> I am having problems ligating my DNA fragments cut out of a gel.  I
> get variable results that seem to relate  to how long it takes to cut
> out the band.  The fastest I can see and cut out a band is about 15
> seconds and by then I suspect there is already significant UV damage.
> Is there any way to protect my DNA during UV exposure?

A recent article in Biotechniques (Vol. 21 #5, pp. 898 - 903; 1996) 
discussed the use of guanosine or cytidine to protect DNA from UV 
damage.  The authors claim that the addition of 1 mM of either to the 
gel increases cloning efficiencies by 10-100X by protecting the DNA from 
damage.  I have started adding 1 mM cytidine (1:100 dilution of a 100 mM 
stock solution) to my gels, and while I haven't done direct comparisons 
it does seem to yield significantly more colonies after ligation & 
transformation.