What unit is the length of a protein measured in? Sorry if this question is obvious - I'm not familiar with proteomics so I'm not sure of the standard units.
In this paper, it talks about using the length of a protein to calculate the NSAF value.  However, it doesn't specify the units.  Would it be peptides, amino acids or nucleic acids? Or something else?
As mentioned by others, it's the number of amino acids. Alternative measurements could be in Angstroms or similar, but that would require at least an approximate structure.