Fourier transform infrared (FTIR) spectroscopy was employed to examine the thermal denaturation of the Fe(III), Fe(II), and Fe(II)-CO forms of cytochrome c peroxidase and horseradish peroxidase in phosphate buffer at pD 7.0. The amide I' regions of the deconvolved spectra are consistent with predominantly alpha-helical secondary structure around room temperature, but the alpha-helical absorptio...