Enzyme-linked immunosorbent assay (ELISA) is based on an older and very similar technique called enzyme immunoassay (EIA). ELISA Kits allow for the detection of an unknown amount of antigen which is bound to a surface. A specific antibody is applied on the antigen bound to the surface so that it can bind to the antigen. The antibody is linked to an enzyme as reporter agent that produces a detectable signal. Often these reporters produce a light of specific wave-length (fluorescence) if expose to UV-light. The amount of antigen in the sample can be determined by comparing the light intensity to a standard of know concentration. There are several types of ELISA Kits that are based on the same main principle but vary slightly in their approach. Main distinctions are direct and indirect ELISAs. Thereby the ELISA is used to detect the presence of antigens that are recognized by an antibody (direct method) or it can be used to test for antibodies that recognize an antigen (indirect method). Further distinctions include the sandwich ELISA, which measures the amount of antigen between two layers of antibodies. Sandwich assays are restricted because the antigens to be measured must contain at least two antigenic sites, since at least two antibodies act in the sandwich. Testing of suitable pairs of antibodies, development of a solid standard curve and the choice of the right substrate is often not possible when only a small number of probes is available. However, there is no need to limit your research, because antibodies-online offers you over 138,000 ELISA Kits that contain anything you will need for a direct start. Simply search for the protein of your choice and check the reactivity with the species you will require. With high-quality ELISA Kits from antibodies-online you will produce reliable results in no time at all. On antibodies-online you can compare ELISA Kits from different manufacturers and find the right product for your research.