Analysis of Tertiary Order Structure by Cryogenic Electron Microscopy (cryo-EM) (CAT#: STEM-B-0379-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 overall three-dimensional conformation of a single polypeptide chain (a protein molecule) is referred to as the tertiary structure, which typically includes different elements of secondary structures such as α helices, β sheets, random coils, and loops. Bonds between side chains (R groups) of amino acids—including hydrophobic interactions, hydrogen bonds, and ionic bonds —contribute to the tertiary structure.

In addition, there is one type of covalent bond that can also contribute to tertiary structure: the disulfide bond. Disulfide bonds are a type of post-translational modification (PTM) formed between sulfur-containing side chains of cysteine residues, allowing distant parts of the protein to be held together. They are abundantly found in secretory proteins and extracellular domains of membrane proteins.