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Q. What are Antibodies?
A. Antibodies are proteins produced in response to the presence of foreign molecules, organisms, or other agents in the body (antigens). Antibodies are synthesized predominantly by plasma cells (differentiated B-lymphocytes), and are found mostly in the blood and lymph where they bind to antigens. The bound antigen-antibody complex is scavenged through phagocytosis, resulting in the removal of potentially harmful agents.
Summary of antibody characteristics:
- The region of an antigen that binds to an antibody is called the epitope
- Epitopes on protein antigens are local surface structures that can be formed by continuous or non-continuous amino acid sequences
- Sometimes the binding of an antibody to an antigen results in a large structural change in the antigen or the antibody or both
- The antigen binds to the antibody by multiple non-covalent bonds
- Antibodies can bind to a wide variety of chemical structures and can discriminate among related compounds
- Antibody-antigen binding is reversible
- The affinity of an antibody for its antigen, which determines the amount of antibody/antigen complex at equilibrium, can be very different for different antibodies. The higher the affinity the "stronger" the antibody
- Antibodies with an affinity of 106 liter/mol will not work for immunoprecipitation, and will give a weak signal for cell staining and Western blotting. Affinities greater than 108 will give strong signals
Q. What can antibodies be used for?
A. An antibody interacts with a specific epitope, which forms the basis of all immunochemical techniques. The specific antigen-antibody interaction has been exploited by researchers to accomplish a variety of processes: precisely locate a specific antigen within the cell, pull out an antigen from a mixture of thousands, find out other proteins that the antigen is associated with, block the action of a protein, and determine the exact concentration of an antigen.
Antibody-based assays have been designed to quantify the level of narcotics in urine or blood, detect pregnancy, classify cancerous cells, study the expression of genes at the protein level, and determine the function of proteins.
Antibodies are generally used for:
- Identification of Proteins on Western blots (Immunoblots)
- Identification of Proteins in Cells (Immunocytochemistry)
- Semi-quantitative in-situ analysis -Confocal Microscopy
- Quantitative and semi-quantitative analysis in a single cell -Flow Cytometry
- Functional Assays
- Immunoaffinity Purification and Antigen Trapping
Q. Can the BioGenex antibodies be labeled?
A. The BioGenex antibodies are not suitable for labeling as they come in a solution that contains other proteins that might interfere with the reaction. Also, they are not suitable for in vivo studies (either in animals or in tissue culture) or cell-based assays since they contain sodium azide (15 mM or 0.09%), unless the customer can dilute them to a concentration that is safe for this kind of applications.
Q. Which enzyme system should I choose?
A. BioGenex offers Alkaline Phosphatase (AP) and Horseradish Peroxidase (HRP) enzyme systems. Both offer equivalent sensitivity. For some tissues with a high amount of endogenous peroxidase activity, such as liver and plants, alkaline phosphatase systems should be used. Alkaline phosphatase also produces a stronger color reaction on prolonged incubation.
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