Design, expression, and characterization of clusterin QconCAT. (A). Clusterin QconCAT includes five Q peptides (shown in green) with 6-amino acid long flanking regions (shown in yellow) concatenated into the sequence with N-terminal Met and C-terminal His6-tag. (B) Coomassie R250 stained clusterin QconCAT after 15% polyacrylamide gel separation. (C) Stable isotope incorporation into the clusterin. MRM spectra for two representative transitions per Q1, Q4, and Q5 peptides are shown. The pair transitions for light (unlabeled) and heavy (labeled) form of each Q peptide are color coordinated. Isotope incorporation factor for clusterin QconCAT was calculated based on combined data for all three peptides and presented as mean ± SD.