ABSTRACT
The use of therapeutic proteins to replace or supplement endogenous protein molecules has been a long established treatment for diseases such as diabetes, growth hormone deficiency, and hemophilia. This chapter describes the differences between the primary, secondary, and tertiary structure of proteins. It also describes major pathways of protein degradation, their chemistry, and the corresponding stabilization strategies. The primary structure of a protein refers to the sequence of amino acids and the location of disulfide bonds in the constituent polypeptide chain(s). Secondary structure can be described as the local spatial conformation of a polypeptide's backbone, excluding the constituent amino acid's side chains. Tertiary structure of a protein refers to the exact three-dimensional structure of its constituent polypeptide chain(s). Quaternary structures are the highest level of protein organization that can be achieved by proteins that have more than one noncovalently linked constituent polypeptide chain. Under physiological conditions, solubility of proteins can vary from the very soluble to the virtually insoluble.
