Hello wise scientific community,

I am trying to measure the concentration of Spike Protein ( whole protein) expressed by my cell line transfected with a pC DNA 3.1. I can see a nice band by Western Blot, but when using the same cell extracts ( RIPA buffer plus PI cocktail) in ELISA there is no way to see protein, no matter how much I try to concentrate them. I am using 500 ng of recombinant S protein as a standard to start... I might think the amount of protein expressed is out of the detection range of my assay ( only picograms?), but before deciding that, I wanted to see if anybody has an input about it. A more sensitive assay, a different and more efficient way to extract the protein from the cells lysates... Has anybody tried a transmembrane extraction reagent such as Tm Per-50?

Thanks a lot for your help!

Laura