Soret peak

A Soret Peak is an intense peak in the blue wavelength region of the visible spectrum. The peak is named after its discoverer Jacques-Louis Soret. The term is commonly used in absorption spectroscopy, corresponding to a wavelength of maximum absorption. The "soret peak" is used to describe the absorption of vividly-pigmented heme-containing moieties, such as various cytochromes. For example, the cytochromes P450, a diverse class of monooxygenase enzymes, exhibit a soret peak at 450 nm in their reduced form when saturated with carbon monoxide. This is called a CO difference spectrum assay: the absorbance spectrum of the solution is subtracted from the spectrum after saturation with carbon monoxide. If the P450 has been denatured, for example due to bad handling, the peak shifts to 420nm. It is possible to see both 420nm and 450nm peaks on the same spectrum if only a portion of the P450 has been denatured.