... 2,2′-di-p-nitrophenyl-5,5′,-diphenyl-3,3 -[ 3,3′-dimethoxy-4,4′-diphenylene] ditetrazolium chloride and 0.38 mM5-bromo-4-chloro-3-indoxyl phosphate mono-(p-toluidinium) salt in 0.1 M Tris-HCl, ... (5) and (6) unbound free and labeled hapten removed by washing.187From: Methods in Molecular Biology, vol. 178: Antibody Phage Display: Methods and Protocols Edited by: P. M. O’Brien and R. ... containing 10 mM DTT (fraction 2b). 11. For SDS-PAGE measurements, add 10 µL 10X reducing loading buffer to fractions 0 and 1, and load samples (e.g., 10 µL and 50 µL) of fractions 0, 1, and 2a...