In vitro studies on the metal sensing capability of annelide hemoglobin

Many studies in the literature suggest that earthworms play an important role in the use and management of soils and are considered good bioindicators of environmental contamination by presenting changes in their behavior and even death when inserted in contaminated environments. In the current study we investigated the in vitro behavior of Amynthas gracilis hemoglobin (HbAg) against copper (Cu) and cadmium (Cd) in concentrations ranging from 0 to 100 µmol L-1, at pH values 5.0 and 7.0 by optical absorption, fluorescence emission, light scattering and circular dichroism techniques. Our results sugest that the HbAg undergoes oxidation in its heme group at both pH values. As from 30 µmol L-1 of copper in pH 7.0 HbAg is oxidized, dissociates and loses part of its secondary structure. In pH 5.0, it undergoes greater oxidation, also near 30 µmol L-1 but without secondary structures loss or dissociation. Regarding the metal cadmium, no significant changes were observed. The results indicate that HbAg has a potential for studies on copper biosensing.