Conformational analysis of proteins and peptides

To perform its biochemical functions, a protein usually folds into a well defined, highly ordered structure. Subtle changes in conformation are frequently used in nature to modulate or regulate protein's functions. It is, thus, critical to identify these changes in order to fully comprehend how proteins perform their biological functions. A variety of spectrometry techniques, including X-ray crystallography, nuclear magnetic resonance (NMR), circular dichroism (CD), fluorescence, infrared and Raman spectroscopies, and mass spectrometry (MS), are in current use for the conformational analysis of proteins and peptides. These techniques are complementary and provide important information related to the conformation and folding/unfolding dynamics of proteins. CD is well-established for measuring the secondary structural elements of a protein and fluorescence provides information on the environment of aromatic moieties. X-ray crystallography and NMR both provide structural details down to atomic resolution. Mass spectrometry is a recent addition in the field of conformational analysis. Isotope hydrogen exchange, in combination with NMR and MS, has been a highly successful approach in the detection of conformational changes in proteins. In this review article, a short description of the basic principles of these techniques and recent representative examples of their applications in conformational analysis of proteins and peptides are described.