Surfactant-induced stabilization of four-coordinated hemes in reconstituted hemoglobins

Abstract

A transition from 5-coordination to 4-coordination metal centres of porphyrins in carbonmonoxy Fe(II), Cu(II) and Ni(II) hemoglobins is observed as a consequence of ionic surfactant interactions with metalloproteins through UV-Vis studies. SDS (anionic) and CTAB (cationic) surfactants are used. Values of heme partition coefficient (K) between globin and surfactant show that, in both CTAB and SDS, partitioning increases proportionately with surfactant concentration for a fixed concentration of hemoglobin. The interactions seem to be mainly hydrophobic in nature with metalloproteins, though coordination and coulombic interactions may also play a minor role in CTAB and SDS respectively. The present study provides new insight into reconstituted hemoglobin-surfactant interaction.