Format of Original
6 p.; 26 cm
Journal of Inorganic Biochemistry
Original Item ID
doi: 10.1016/j.jinorgbio.2008.07.005; PubMed Central, PMCID: PMC2605091
Recent progress in generating and stabilizing reactive heme protein enzymatic intermediates by cryoradiolytic reduction has prompted application of a range of spectroscopic approaches to effectively interrogate these species. The impressive potential of resonance Raman spectroscopy for characterizing such samples has been recently demonstrated in a number of studies of peroxo- and hydroperoxo-intermediates. While it is anticipated that this approach can be productively applied to the wide range of heme proteins whose reaction cycles naturally involve these peroxo- and hydroperoxo-intermediates, one limitation that sometimes arises is the lack of enhancement of the key intraligand ν(O–O) stretching mode in the native systems. The present work was undertaken to explore the utility of cobalt substitution to enhance both the ν(Co–O) and ν(O–O) modes of the CoOOH fragments of hydroperoxo forms of heme proteins bearing a trans–axial histidine linkage. Thus, having recently completed RR studies of hydroperoxo myoglobin, attention is now turned to its cobalt-substituted analogue. Spectra are acquired for samples prepared with 16O2 and 18O2 to reveal the ν(M–O) and ν(O–O) modes, the latter indeed being observed only for the cobalt-substituted proteins. In addition, spectra of samples prepared in deuterated solvents were also acquired, providing definitive evidence for the presence of the hydroperoxo-species.