X-ray absorption near-edge structure study on the configuration of Cu super()

The local configurations around metal ions in metalloproteins are of great significance for understanding their biological functions. Cu super(2+)/histidine (His) is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional (3D) structural configurations of Cu super(2+)/His complexes at different pH values (2.5, 6.5, and 8.5) are quantitatively determined by x-ray absorption near-edge structure (XANES). Generally Cu super(2+)/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu super(2+). It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the O sub(carboxyl), N sub(am), and N sub(im) from hisitidine molecules. Furthermore, the symmetries of Cu super(2+)/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5.