title: X-ray absorption spectroscopy using synchrotron radiation for structural investigation of organometallic molecules of biological interest.
abstract: The technique of x-ray absorption spectroscopy using tuneable, very intense x-rays from a high energy electron storage ring has been applied to study of the estended x-ray absorption fine structure for Cu and Ni tetraphenylporphyrin and methemoglobin. Preliminary analysis shows that the spectra may be interpreted as a super-position of modulations arising from the nearest neighbor nitrogen and pyrrole alpha-carbon coordination sheels of the metal atoms. We estimate that with the observed magnitude of noise to modulation amplitude, relative shifts of 0,5% in the metal-nitrogen to metal-carbon bond distances in the prophyrins should be observable using extended x-ray absorption fine structure and that this technique may provide a method of observing these types of structural changes in solution.
mesh_terms: D003300:Copper; D008433:Mathematics; D008706:Methemoglobin; D008968:Molecular Conformation; D009532:Nickel; D009942:Organometallic Compounds; D011166:Porphyrins; D013057:Spectrum Analysis; D014965:X-Rays
chemical_list: D009942:Organometallic Compounds; D011166:Porphyrins; D003300:Copper; D009532:Nickel; D008706:Methemoglobin