Immunoaffinity chromatography is a method for separating target antibodies or antigens from a heterogenous solution. It is column-based, which means that the solution is flowed through a column and eluted at the other end. The column is pre-functionalized with the capture antibody or antigen. The target protein is adsorbed onto the resin-bound capture protein and is retained in the column while the remaining solution is eluted. The fraction containing the target protein is later eluted and purified.
Size exclusion chromatography columns are used to separate molecules by size, molecular weight, and hydrodynamic volume. The technique can be used with proteins, polymers, and other macromolecules. It can also be used for buffer exchange or desalting a sample. The principle behind size exclusion chromatography columns is simple, but the technique only works when the correct resin-bound column is matched to the experimental goal.
Proteins are essential components of cells, tissue, and organisms. These macromolecules are made of long strings of amino acids arranged specifically into three dimensional configurations. The side chains of these 22 amino acids create pockets of potential for chemical interactions as the polypeptides fold into their tertiary structures and interact with each other. Proteins initiate and mediate the thousands of biochemical pathways that govern an organism’s function. The careful study of proteins can reveal information about the function of our bodies, the pathways of disease, and the expression of the genetic code. The main challenge to overcome when studying proteins is to choose the most appropriate method of protein extraction.
From the clinical laboratory ELISA to the home pregnancy test, the conjugated antibody is integral to the function of many diagnostic assays. We know about the specificity of antigen-antibody interactions and their role in mounting the innate immune response to a pathogen. This antigen recognition specificity has been utilized by clever scientists and engineers to create biosensors capable of detecting the presence of antigens in biological samples. Biosensors come in many shapes and sizes, and have varying levels of complexity, but one fundamental concept is the need to covalently attach antibodies to a substrate.
Protein A vs Protein G both are bacterial cell wall proteins that have primary binding sites for human and mammalian immunoglobulin G (IgG) antibodies. Protein G was first isolated from Streptococcal bacteria strains C and G. Similarly, protein A was originally found on the cell wall of the bacteria Staphylococcus aureus. These proteins have primary binding domains for the Fc region of (IgG) antibodies, but can also recognize the Fab region of certain IgG subclasses. For the bacteria this is useful because binding IgG’s at the Fc region prevents macrophages from recognizing them, which in turn prevents phagocytosis of the invading bacteria by the host immune system.
The binding specificity between antibody and antigen drive our immune systems to successfully fight infection. When a viruses or bacteria invade a body they are engulfed by macrophages, which break them down and present their epitopes to the B cells lymphocytes. These B cells read the epitope and create antibodies with an antigen binding site, or paratope, that specifically recognizes the invading pathogen, binds to it, and signals to the rest of the immune system that the pathogen/antigen should be destroyed. This antibody affinity to antigen is similar to the specificity of a key in a lock.
The business value of potentially large production capacities coupled to lower capital expenditures (CapEx) requirements and manufacturing costs may reduce the gap between production volumes and patient needs for potentially life-saving drugs. This is the reason because pharmaceutical companies are continuously seeking for new technologies. An economically efficient alternative to bioreactor-based technologies is the use of living biofactories such as transgenic animals, plants or insects.
A need for rapid, reproducible, small-scale purification
For many recombinant protein applications, such as expression clone screening and for optimizing expression conditions, there is a crucial need for a rapid, reproducible, small-scale purification process. Traditionally, protein purification from E. coli consists of four distinct phases: harvest, bacterial cell lysis, lysate clarification and protein purification. You will find the whole process explained step by step in our protein purification handbook.
The search for alternatives to chromatographic resins is not new. With the continuous increase in expression levels in recombinant protein purification, columns are struggling with crude lysates. The need to clarify suspensions containing high levels of expressed protein for post-purification re-concentration no longer appears to be the most efficient strategy. You will find much more information about this topic in our protein purification handbook.