CIRCULAR DICHROISM OF BOVINE PLASMA ALBUMIN - DYE COMPLEXES

We report on the circular dichroism induced in two dyes, 2,7‐dibromo‐4‐hydroxy mercurifluorescein and pyridoxal‐5‐phosphate, bound to bovine plasma albumin. We show that the optical activity induced in 2,7‐dibromo‐4‐hydroxy mercurifluorescein, covalently bound to the unique sulfhydryl residue of the protein, makes it possible to follow the pH dependent transitions of bovine plasma albumin occurring in the pH ranges 3 to 5 and 6 to 8. The optical activity induced in the dye is important only for the contracted state of the protein obtained near the isoionic point. On the other hand we show that the optical activity induced in pyridoxal‐5‐phosphate, a dye probably bound to the ɛ‐amino group of a particular lysine residue, is independent of pH between pH 5 and 8. Copyright © 1969, Wiley Blackwell. All rights reserved