It may well be that 1 ng is below the sensitivity of the blot. Also be careful that the gel is not run too long as the gamma monomer is rather small. Probably not an issue, most likely the quantity . See http://www.abcam.com/index.html?datasheet=24979&tab=abreviews&intabreviewid=13372. They used much, much more and got a faint band

First checks whether the transfection was successful using a fluorescing marker, if it was successful identifies that cell structure is expressing the gene what you are looking for, if the transfection resulted in production of a soluble portion western blot is not the proper method I recommend Elisa

I would concur with Modesto. Western's don't always work and your antibodies would be more reliable in an Elisa.

I am sure about the transfection, I have evaluated the expression with ELisa, I also have evaluated bioactivity of this protein but I also need to show molecular weight of this protein

Did you see anything in your positive control? How much amount (not conc.) of protein did you load?

Yes, about 10 microliter

If you saw your band in the positive control then there is nothing wrong with the antibodies...if your expression is working then there can be a prob only wid the amount which is 10 ng ...the limit of western blotting is 1 ng but it depends on the antibodies and the system used.....if possible try to load more sample ...u can concentrate 100 ul by boiling in lamelli buffer

Thanks, I did not see any band in positive control, Ok i will concentrate samples, thanks again

If all you require is the molecular weight of the protein, try adding Brefeldin A to your cells as this inhibits ER to Golgi transports and allows the protein to accumulate in your cells. Using a cell lysate is always easier than trying to WB from sups