Fig. 6.

UV–visible absorption spectra of the purified WT (colored in brown), V331A (dark green), V331F (light green), I333F (orange), F366A (dark blue), F366Y (light blue) QBS point mutants and C-terminal α-helix deletion mutant (colored in red) TrSqrF variants (8.2 µM, 25.7 µM, 31.9 µM, 9.5 µM, 9.1 µM, 14.8 µM, and 11.4 µM, respectively). The absorption spectra of the protein samples were normalized to the absorption value at 280 nm