Protein precipitation by storage - (Oct/13/2013 )

Run some of your re-dissolved protein over a gel-filtration column.

If you get a single, monodisperse peak eluting at the expected molecular weight, then chances are your protein is perfectly fine. If you see some aggregation and polydispersity in the protein sample that by SDS-PAGE is a clean, single band, then I would hesitate to use it for any real application.

If you don't have a gel filtration setup in your lab, then simple alternative is to run Native-PAGE on the sample. If the expected pI of your protein is <7, then all you have to do is run the gel like a normal SDS-PAGE gel except leave out all SDS (in your sample buffer, running buffer and gel itself). Stain with coomassie and if you get a nice tight band then chances are your protein is good. If it comes out as aggregates, oligomers or an uninterpretable smear, then it's no good.

labtastic on Wed Oct 16 12:42:40 2013 said:

Run some of your re-dissolved protein over a gel-filtration column.

 

If you get a single, monodisperse peak eluting at the expected molecular weight, then chances are your protein is perfectly fine. If you see some aggregation and polydispersity in the protein sample that by SDS-PAGE is a clean, single band, then I would hesitate to use it for any real application.

 

If you don't have a gel filtration setup in your lab, then simple alternative is to run Native-PAGE on the sample. If the expected pI of your protein is <7, then all you have to do is run the gel like a normal SDS-PAGE gel except leave out all SDS (in your sample buffer, running buffer and gel itself). Stain with coomassie and if you get a nice tight band then chances are your protein is good. If it comes out as aggregates, oligomers or an uninterpretable smear, then it's no good.

Thank you vary much for your valuable tips.I will try it.