Hi Yousra,

It would be easier to troubleshoot if you could provide some more information about the experiment.

1. Did you run your gel at Constant Current, Constant Voltage or Constant Power?

2. Did you run a Protein Molecular Weight Marker along with your sample?

3. What do your samples contain? Are you loading whole cell lysates, or purified protein?

4. How did you prepare your samples prior to loading? Did you quantify the total protein content of your sample?

5. What is the Molecular Weight of the protein of your interest?

6. Did you use Coomassie R250 Staining Solution or was it the colloidal G250 stain? How long did you leave your gel in the staining solution?

Regards,

Bakul

Absolutely Bakul is right.

and one more things, explain steps of your staining and di staining ways and materials.

Many thanks I repeat it again and notice that prot marker disappeared after staining (it's a reused stain)

so I prepare a fresh stain and repeat the gel again and it give goo result

i changed every buffer and samples used but never thought the stain is the cause

thank you for your concern