Are there any other methods other than gel electrophoresis to determine if protein has been extracted out of the samples?
Sure, actually much more specific would be either mass spec analysis or activity measurement. Others would be binding of some compound etc. That depends on your protein (e.g. is it enzyme or structural protein?)
There are many methods to find out the if there is leftover protein in your sample. You can perform a routine protein estimation test by Folin Lowry method. You can perform Biuret test.
The question is that what is your protocol OR protein of interest OR method of Extraction of Protein.
Thanks all for your answers. I am actually extracting proteins from saliva samples and just want to confirm if the crude protein got extracted. Though SDS PAGE is a method, but prior to that, I wanted to confirm if my sample has any protein or not.
I have performed Lowry and Bradford, but sometimes they also give false results. Hence, wanted to know if any other alternate method is also there.
It sounds like you are facing the problem of determining protein content from very diluted solutions (saliva). MS is the most sensitive technique for determining total protein content if you can work with someone expert in the field. You can even quantify how much total protein you have through acid hydrolysis of your sample and determination of amino acid content. None of this is trivial, though.
Good luck!
Carlo
In order to see if any protein at all is present, you could try to spot-blot (just pipet 1 µl onto the membrane) or dot-blot (with a vacuum manifold, ensures that all samples cover the same area) your sample onto a protein-binding membrane (PVDF, nitrocellulose), wash away contaminants and then stain for example with amidoblack or CBB. Often eyeballing the result is good enough, but the staining can be quantified if necessary by scanning or by extraction with alcoholic NaOH followed by photometry.
That method is particularly suitable to quickly and cheaply check fractions during purification. If you have an antibody against your protein, you can also develop the blot just like a western.
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