Analysis of Secondary Order Structure by Circular Dichroism (CD) (CAT#: STEM-B-0374-CJ)

Introduction

Structure and conformation of a biological molecule is key for its function. The higher order structure of a biopharmaceutical molecule is, thereby, often directly connected to the quality, stability, safety, and efficacy of a therapy. The higher order structure is considered a critical quality attribute and, thus, a detailed understanding of the higher order structure of a biopharmaceutical compound is critical in every research and development phase. Characterizing the secondary, tertiary and, if present, quaternary structure of a biopharmaceutical compound requires multiple analytical techniques.

The secondary structure of a protein refers to the local folding patterns on the polypeptide chain formed by intramolecular interactions between atoms of the backbone. The formation of the secondary structure is mainly driven by hydrogen bonding between amino groups and carboxyl groups on the polypeptide chain.

The most common types of secondary structure are α helix and β sheet. An α helix is made when the polypeptide chain turns around itself, forming a structural motif that resembles a spiral staircase. A β sheet is generated when multiple segments of a polypeptide chain lie side by side, creating a sheet-like structure held together by hydrogen bonds. Most proteins contain α helices and β sheets. For example, α helices are especially abundant in membrane proteins and hair cells (i.e., α-keratin), and β sheets are the main component of amyloid fibers in both animals and bacteria.