Hi im an honours student trying to pull out a clone library.

 

I have a question conserning the colour of X-gal.

 

I was required to make a solution of X-gal and it is clear in colour. When i compare the colouring of my x-gal to that of my supervisors, i can see that his is yellow in colour. Does this difference mean anything? Could it cause any differences wen spreading it on an Ampicillan-LB plate for the growth of clone colonies? Why is mine not yellow?

 

Any help appreciated

 

THank you!!

Have you asked your supervisor why there might be a colour difference?

 

I make up cell culture media and a difference in colour is an indication of a pH problem.

No, Xgal is dissolved in dimethylformamide, pH does not play a role. You did not use water, did you?

I think I recalled that my stock solution also was yellowish, but it was rather highly concentrated. What was your concentration?

 

And yes, this would be something to discuss with your supervisor. It is important (from the viewpoint of the supervisor) that the students communicate and give feedback.

I am using X-gal dissolved in DMSO (20mg/ml). I observed that it turns yellow after storing for long time (around 2 months). I found one book saying that the yellow color does not affect the reaction.

Hi,

Your manager`s solution might be yellow because of potassium ferro?ferrycianide...I can`t remember properly.

The xgal solution should be clear (if it`s mad e up in DMF).Only yellow is the LacZ staining solution, which contains Xgal in DMF...or DMSO.

Hope this helps!

Best wishes,

Zsombor

I would hope the OP had finished their honors by now, but perhaps your post will help someone else.

 

Also, potassium ferricyanide is a bright orange-red, whereas the equivalent ferrocyanide salt is pale yellow.