frag() function can be used within a
proteinAbundance() term to specify a protein fragment, e.g., a product of proteolytic cleavage. Protein fragment expressions take the general form:
<range> (required) is an amino acid range, and <descriptor> (optional) is any additional distinguishing information like fragment size or name.
For these examples, HGNC:YFG is ‘your favorite gene’. For the first four examples, only the
<range> argument is used. The last examples include use of the optional