[Press Release] Spin states of hemoprotein in physiological conditions probed by nitrogen K-edge X-ray absorption spectroscopy
Figure 1 Nitrogen K-edge X-ray absorption spectra of (a) oxyMb, (b) deoxyMb, and (c) metMb in aqueous solutions at 25 °C within the energy regions of the porphyrin C=N π* peaks. The spin states of heme irons were studied from the inner-shell calculations using the molecular structures shown in the figure. (Credit: Masanari Nagasaka, Restriction: CC BY)
Release Summary
Spin states of myoglobin, which is one of hemoproteins, in aqueous solutions at room temperature were probed from the porphyrin C=N π* peaks of heme using nitrogen K-edge X-ray absorption spectroscopy combined with inner-shell quantum chemical calculations. Although the protein polypeptide chains include numerous nitrogen atoms, the porphyrin C=N π* peaks were analyzed to distinguish them from the protein polypeptide peaks. Oxymyoglobin with an Fe2+ ion connected to an oxygen molecule is in the S = 0 state. Deoxymyoglobin with an Fe2+ ion shows a spin equilibrium between the S = 2 and 1 states. Metmyoglobin with an Fe3+ ion connected to a water molecule also shows a spin equilibrium between the S = 5/2 and 3/2 states. These results clearly propose that the spin states of hemoproteins should be investigated in physiological conditions because these are influenced by factors such as liquid temperature, solvent, gas adsorption, and protein structure.
Journal Title: Spin states of myoglobin heme iron in aqueous solutions at room temperature probed from porphyrins using nitrogen K-edge X-ray absorption spectroscopy
Authors: Yasunobu Sugimoto, Shota Tsuru, and Masanari Nagasaka
