Determination of Protein Secondary Structures using FTIR Spectroscopy

Introduction

Proteins can perform a wide variety of molecular functions due to their unique conformation. There are two different representations encoding the structural conformation of proteins, which are the secondary structure and tertiary structure. The secondary structure of proteins is characterized by the repetitive folding pattern of helices, sheets, turns and disordered coils. Different techniques such as X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy have been widely used to investigate the conformation and stability of secondary structure in proteins. However, these techniques are costly and require specific and time-consuming sample preparation steps. Fourier transform infrared (FTIR) spectroscopy is suitable to determine the secondary structure of proteins due to its versatility and high sensitivity towards chemical composition of molecules. The secondary structure composition of proteins could be obtained from the amide band I ranging from 1600 cm-1 to 1700 cm-1 of the IR spectrum. Each type of the secondary structure has its specific spectral band which overlaps in this region. Mathematical procedures such as band curve-fitting and second derivatives can be applied to resolve the overlapping amide I band components and to quantify the secondary structure of proteins. In this application news, we examine the secondary structure of proteins by using FTIR transmission spectroscopy and band curve-fitting data analysis.