Gel electrophoresis and X-ray fluorescence: A powerful combination for the analysis of protein metal binding

X-ray absorption spectroscopy of metalloproteins

Metalloproteins are enormously important in biology. While a variety of techniques exist for studying metals in biology, X-ray absorption spectroscopy is particularly useful in that it can determine the local electronic and physical structure around the metal center, and is one of the few avenues for studying "spectroscopically silent" metal ions like Zn(II) and Cu(I) that have completely filled valence bands. While X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) are useful for studying metalloprotein structure, they suffer the limitation that the detected signal is an average of all the various metal centers in the sample, which limits its usefulness for studying metal centers in situ or in cell lysates. It would be desirable to be able to separate the various proteins in a mixture prior to performing X-ray absorption studies, so that the derived signal is from one species only. Here we describe a method for performing X-ray absorption spectroscopy on protein bands following electrophoretic separation and western blotting.

Synchrotron Radiation Spectroscopic Techniques as Tools for the Medicinal Chemist: Microprobe X-Ray Fluorescence Imaging, X-Ray Absorption Spectroscopy, and Infrared Microspectroscopy

This review updates the recent advances and applications of three prominent synchrotron radiation techniques, microprobe X-ray fluorescence spectroscopy/imaging, X-ray absorption spectroscopy, and infrared microspectroscopy, and highlights how these tools are useful to the medicinal chemist. A brief description of the principles of the techniques is given with emphasis on the advantages of using synchrotron radiation-based instrumentation rather than instruments using typical laboratory radiation sources. This review focuses on several recent applications of these techniques to solve inorganic medicinal chemistry problems, focusing on studies of cellular uptake, distribution, and biotransformation of established and potential therapeutic agents. The importance of using these synchrotron-based techniques to assist the development of, or validate the chemistry behind, drug design is discussed.