a, separation of intact QconCATs by SDS-PAGE to evaluate mass accuracy and purity. i, QconCAT 1; ii, QconCAT 2; iii, QconCAT 3. b, separation of digested QconCATs to test the digestion completeness. i, trypsin; ii, QconCAT 1 digest; iii, QconCAT 2 digest; iv, QconCAT 3 digest.