With the aid of MD analysis on TACC3518-532 (Figs. S15-S17), we identified accessible solventexposed L520/R526, K521/D528, and S524/E530 residue pairs as promising options for introduction of cysteines and then addition of a constraint with a variety of linkers. When these TACC3518-532-based variants were tested, up to 4-fold improved IC50 values were found for two of the biphenyl-constrained peptides, both showing inhibitory concentrations in the range of IC50 ~ 30 µM (TACC3518-532-L/R-Bph and TACC3518-532-S/E-Bph; Fig. ). In comparison, larger IC50 values were observed for the corresponding reduced and oxidized species, or when using alternative more flexible, and/or hydrophobic constraints such as octanoyl and polyethylene glycol-based linkers (Table ; Fig. and