Which cells/tissues are your proteins isolated from? The origin of your protein extract could point to the identity of the contaminating agent.

Cheers, Christian

Hi there,

As Ginka mentioned, loading buffer turns yellow when sample is acidic. Loading buffer contains Tris at pH 6.8 which is not buffering that much. So if the samples are acidic they should turn loading buffer into yellow when mixing. If it is the case, add 1-2µL of 1M Tris to neutralize acidity and turn BB back into blue.

HI Rakesh,

Its because of change in pH, you can add few ul of 1 M Tris, as suggested by Dominique. I have faced this situation. Tris works the trick.

Best

Lokesh

I agreed with Lokesh suggestion, But u need to mentioned the source of protein so that we can suggest what u can do..

Dear All

Thanks for your answers, but I don,t observe color change before loading, yes I know that at low pH it turns yellow and by adding tris the color again turns to blue. But the problem starts after loading...

Plz see the 2nd image, where two samples with dye were loaded, and it was blue but as it starts migrating it leaves some colored mark and the blue band is also visible.

The proteins were isolated from a plant system and purified using Ni-NTA collums, and has no DNA-RNA contamination.

Hi again,

As BB is blue during migration ans as MWM are running normally, the problem is specific of your protein samples. What do they contain in terms of proteins and in terms of global composition?

Proteins associated with chlorophyll appear greenish in protein gels (please refer to fig. 7 in the attached publication). Maybe you need to optimize your protein purification method.

Cheers, Christian

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