Chapter 6: X-ray Absorption Spectroscopy

X-ray absorption spectroscopy (XAS) has been a powerful tool to probe physical and chemical structure for an atom, which includes two regions, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The main object of this chapter is to give the readers a brief idea about XAS and its application, alone or combined with other techniques, in metallomics and metalloproteomics studies. This chapter is divided into five sections. After a brief introduction of X-ray-related techniques in section 1, the basic items about X-ray absorption spectroscopy (XAS) are introduced in section 2, which includes the definition of XAS, the sample preparation and measurement of XAS and how to analyze the data obtained from XAS measurement. The application of XAS in metallomics and metalloproteomics is discussed in section 3, which includes the fingerprints and quantitative speciation through XANES and structural configuration like bond distance and coordination numbers through the extended fine structure (EXAFS). Besides, the application of micro-XAS with focused beam, which can provide spatial information, is also demonstrated in this section. In section 4, the combined application of XAS with other techniques like X-ray fluorescence (XRF), protein crystallography, computational chemistry, neutron scattering, circular dichroism, nuclear magnetic resonance, Raman spectroscopy, and electron spin resonance is illustated which further extend its application in metallomics and metalloproteomics studies. Finally in section 5, an overview on the application of XAS in metallomics and metalloproteomics and its further development as an useful tools are discussed.