Interactions of Hemoglobin with Vesicles and Tubes Formed from Mixtures of Histidine-Derived Bolaamphiphile and Conventional Surfactants

The interactions between protein and surfactant aggregates have been the subject of intensive studies due to their potential applications in biological systems. Here we report the interactions of hemoglobin (Hb) with vesicles and tube-like aggregates formed from mixtures of a histidine-derived bolaamphiphile and a cconventional surfactant dodecyltrimethylammonium bromide (DTAB). This study was performed using a combination of UV-vis spectroscopy, steady and synchronous fluorescence spectroscopy, circular dichroism, and microcalorimetry measurements. The secondary structure of the protein is disturbed, and then the partially unfolded protein is capable of penetrating the vesicles and tube-like aggregates, this is mainly the result of hydrogen bonding and hydrophobic interactions between Hb and the H2D/DTAB aggregates. The polar portion of the unfolded protein chains is near to the polar head of the amphiphile in the aggregate's membrane. Hb is converted to hemichrome in the vesicles, and the heme monomer is solubilized in tube-like aggregates after escaping from the hydrophobic cavity of Hb.