Patent ID: 7807407

Claim:
A method comprising: a) providing: i) a first nucleic acid sequence encoding a wild type polypeptide and a second nucleic acid sequence encoding a truncated polypeptide of said wild type polypeptide, said first and second sequences in a ratio greater than 250:1, said truncated polypeptide being between 10 and 150 amino acids in length; and ii) a reconstituted in vitro translation system comprising purified recombinant proteins; b) treating said reconstituted translation system so as to reduce protease activity, wherein said treating comprises the addition of one or more protease inhibitors which does not interfere with translation; c) introducing said nucleic acid sequences into said reconstituted translation system under conditions such that said truncated polypeptide is produced; and d) determining the molecular mass of said truncated polypeptide by mass spectrometry.