Analyzing the Solution State of Proteins Structure, Interactions and Ligands by Spectroscopic Methods

VERONICA DODERO, PAULA V. MESSINA

Proteins in Solution and at Interfaces: Methods and Applications in Biotechnology and Materials Science

Wiley

Año: 2013; p. 73 - 99

Proteins are the major constituents of the living organisms and perform a wide range of essential functions in cells. Their structural and functional complexity in solution is based on the diverse interactions that existed between their hydrophobic, polar and ionisable side chains. These interactions are responsible not only for the protein structure but also for the association between ligand-protein. Given the vast amount of sequence information obtained from the genome projects, as well as the discovery of aberrant protein structures such as amyloid fibrils, there is an increasing need for a better understanding of protein structure and function at the molecular level. This chapter covers the basic principles of protein structure organization and the more relevant spectroscopic techniques used to determine the secondary structure of proteins in solution. Nuclear Magnetic Resonance (NMR) spectroscopy is the preferred technique to determine protein structure and dynamics in solution with atomic level resolution. However, this high resolution information represents laborious and complex interpretation of the data and it is necessary high concentration samples. Mainly for this reason, other spectroscopic techniques with lower resolution but easier interpretation are used routinely to evaluate protein secondary structure, its changes in response to ligand and/or environmental interaction and also protein tertiary and quaternary structures. Among this ?low resolution? techniques Circular Dichroism (CD), Infrared (FT-IR), Raman and Fluorescence spectroscopy are the most important. Moreover Dynamic Light Scattering (DLS) provide information in order to correlate size and shape distribution. Information given by these techniques, simultaneously with sophisticated molecular modeling methods, allow for refinement of protein structural models as well as rapid assessment of conformational changes resulting from ligand binding or macromolecular interactions. A selected number of examples are given to illustrate the power of these techniques in biological applications.