[15] Protein structure from ultraviolet resonance Raman spectroscopy

Ultraviolet resonance Raman (UVRR) spectroscopy provides a technique- to gain vibrational spectroscopic information on the aromatic amino acid side chains and on the amide and proline groups in any protein. The vibrational spectrum obtained from UVRR spectroscopy can yield information on details of the state of protonation, hydrogen bonding, and conformation of a particular side chain; it can also yield estimates of the secondary structure of the proteins. Through the effect of resonance Raman enhancement, UVRR spectroscopy has a distinct advantage over conventional (visible) Raman spectroscopy and infrared spectroscopy, as more dilute protein solutions can be employed; moreover, tuning the excitation wavelength permits selective enhancement of specific chromophores (e.g., tryptophan or tyrosine side chains). These advantages have caused a rapid expansion of the field over the 1980s, and a number of lengthy reviews have been written. This chapter concentrates on the experimental requirements for a UVRR experiment and on the type of information available in a protein UVRR spectrum. A few examples of the application to the study of metalloproteins are described.