Resonance Raman spectroscopic studies in copper reconstituted and hybrid hemoglobins: probe into subunit heterogeneity

Abstract

Copper reconstituted hemoglobin (CuHb), copper containing T-state hybrid hemoglobins like α₂(Ni)β₂(Cu), and α₂(Cu)β₂(Ni), and intermediate R-state hybrids like α₂(CO-Fe)β₂(Cu) and α₂(Cu)β₂(Fe-CO) are studied using resonance Raman (RR) spectroscopy at two different excitation wavelengths. The high frequency RR region in CuHb indicates the presence of both 4- and 5-coordinate forms of Cu(II). In hybrid Hbs, the presence of two distinct metal ion environments within one particular subunit is evident. This is also consistent with previous findings using EPR spectroscopy and sulfydryl reactivity studies on these hybrid Hbs. The low frequency RR region on these copper derivatives of HbA further suggests the existence of two different heme moieties within the subunit.