Identifying a particular protein or fragment of nucleic acid can be accurately achieved by one of two methods.
Antibodies and antibody-related methods (e.g. ELISA or Western Blotting) use immunoglobulins to accurately bind a peptide with a unique sequence, within a protein solution or lysate.
Alternatively, products such as pathogen detection kits use PCR to identify a specific sequence exclusive to a particular bacterium, virus or fungi.
An antibody (aka immunoglobulin) is a glycoprotein produced and secreted by plasma cells. Antibodies play a vital role in regulating the immune system as they can accurately identify particular molecules originating from pathogens and toxins. Each antibody is specified to recognize a specific molecule, referred to as an antigen. Once an antibody has identified its corresponding antigen, it binds to it, which activates the immune response to neutralize and eliminate the invading pathogen.
Detection tests for the presence and concentration of a molecule in a sample, whether it is a nucleic acid, peptide, antibody, or antigen. Typical methods include immunoassays, the use of fluorophores and microarrays.
(Pathogen) Detection kits
Detection methods may vary depending on the nature of your sample (e.g. RNA, DNA, protein or tissue) and the source of the molecule, i.e. the organism. Specific kits are adapted to unique sample types, from an array of tissues and bodily fluids, including; urine, cell culture, blood, and food.
As an example, detection of a plant-based viroid differs in technique and equipment to that required aimed at testing for the presence of E.coli in a water sample. Fortunately, pathogen detection kits now exist with dedicated technology for identifying a certain bacterium or virus.
Protein quantification verifies peptide concentration; it is an essential step before downstream analyses such as Western blotting. Only small loading volumes are required. However, it is recommended to perform quantification before protein purification to reduce variability in further experiments.
Immunodetection Kits help determine which specific proteins are within a sample via the use of specific complementary antibodies. The two most commonly used techniques are Western blotting and ELISA; both analyze proteins (either qualitatively or quantitatively); utilizing serum, plasma, or tissues. ELISA is simpler and quicker than Western blotting but requires highly specific antibodies. ELISA also mainly works on native proteins, while Westerns works on denatured proteins (and identifies the purity of your proteins).
For processes such as ELISA, molecular labeling is necessary to determine the success of the experiment. Additionally, labeling nucleic acids and proteins can identify their position within the cell or the genome, their presence and concentration can also be determined.