Question with the molecular weight of my protein - (Apr/09/2015 )

Dear All, 

I have two question:

1. In some factsheet, no predicted molecular weight are written. How one can know it for WB analysis ? 

2. Is the molecular weight in the Ab fact sheet represent the weight for the whole protein or only the epitope to which the primary Ab is binding ? 

Thanks 

1) If it is a known gene/protein, you can go to any of the protein, gene or gene name databases and find this information fairly readily. You can also estimate off the amino acid sequence - there are a number of sites that do this, just google them.

2) Epitopes are usually considered to be less than 8 amino acids (I'm sure there are exceptions) so should only give a MW of 1 kDa or so, but depending on how the anitbody has been prepared, there could be multiple epitopes on the target protein. It would be unlikely to give the MW of the epitope unless the data sheet is showing that the Ab will bind to the antibody (note that this is no indication that the antibody will work on the actual protein target).