ABSTRACT
This chapter provides an introduction to the characteristics of peptides and proteins which determine their retention behavior in high-performance liquid chromatography (HPLC). The properties of peptides and proteins are characteristic of their amino acid composition and sequence. The acetonitrile concentration range available for practical isocratic separations of peptides/proteins is very narrow compared to smaller organic molecules. Peptides and proteins are a unique class of molecules consisting of amino acids as the fundamental units, or building blocks. The hydrophobicity/hydrophilicity as well as the number of charged groups present becomes important factors in the separation of peptides and proteins. The distinction between a peptide, polypeptide, or protein is somewhat arbitrary with peptides usually defined as molecules containing 50 amino acids or less. Most polypeptides and proteins contain tyrosine residues, which provide a rapid means of estimating their concentrations in solution. Due to the difference in the mechanism of interaction of peptides/proteins with hydrophobic stationary phases compared to small organic molecules.
