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Overview of cell biology and its importance

The main two categories of cells are prokaryotic and eukaryotic cells. Prokaryotic cells are what make up bacteria and archaea while eukaryotic cells make up organisms of the domain eukaryota. The inside of the prokaryotic cell houses it’s genetic material, DNA, in a region called the nucleoid region. There are also ribosomes within the central region of the bacteria. The next layer is the plasma membrane, a bi-lipid layer like you will see for eukaryotic cells. Unlike eukaryotic cells, prokaryotic cells will have a cell wall and a capsule surrounding the cell membrane. The eukaryotic cell is surrounded by a lipid membrane, and has membrane-bound organelles. The genetic material, DNA, is stored in the nucleus which is a membrane bound organelle. In research, many different types of cells are used. Bacterial cells are used in protein purification to grow a plasmid to express a protein of interest. You can read about this in our article protein expression and purification. Many types of Eukaryotic cells are used to do in vivo studies. Depending on your research interests, you might use muscle cells, or skin cells, or cancer cells. 

The capability of 1 μm and 2.8 μm magnetic particles to intracellularly deliver cargo proteins

In a recently published paper, researchers of the CIBER-BBN and the University Autonoma de Barcelona demonstrated that magnetic microparticles of 1 and 2.8 μm of diameter, in combination with an appropriate magnetic force, could greatly decrease the time needed to interact with and enter target cells, a clear advantage over other types of drug delivery systems.

Enzymes: an overview

Enzymes are proteins with the ability to catalyze chemical reactions. We have several articles you can read to learn more about proteins, their uses, and isolating them for research and clinical purposes. Check out our protein isolation article if you are thinking about how to best purify your protein of interest or read our protein assay article to learn more about working with proteins. Enzymes are particularly interesting and useful due to their catalytic activity. The molecule that goes into the enzyme for manipulation is called the substrate. You will often see this interaction called the “lock and key” interaction as the substrate has to fit just right into the pocket of the enzyme for it to work properly (enzymes are highly specific!), the way a key is very specific to the lock it goes into.

Protein A

Protein A is the name of a protein found on certain bacterial cell walls. The protein has a binding site for Immunoglobulin G (IgG). This ability to bind IgG has been protein A a useful tool for research laboratories. Protein A has many uses. If conjugated to a detectable marker, such as a fluorescent marker or an enzyme, it can be used to detect antibodies. Protein A can also be used to purify total IgG from a solution. Also it can be used for immunoprecipitation as a way to purify a molecule of interest using a solid support system.

Column chromatography is a method used in many areas of science to isolate a single compound from a mixture. The basic principle of column chromatography is the adsorption of target to the column by designing a column with specific affinity to the target. The target compound adsorbs to the column resin while the remaining mixture easily flow through the column and out the other end. A similar method is used to purify protein and nucleic acids, and it is generally referred to as affinity chromatography. Affinity chromatography requires a solid support (typically a magnetic bead or a resin column) on which to covalently attach a capture molecule which has affinity to the target protein or nucleic acid. 

Cell lysis is the act of breaking the cell membrane to enable the study of specific proteins, nucleic acids, and other molecules inside of cells. When cell lysis is successful, the undamaged contents of the cell escape through the damaged cell membrane. These contents are then separated out of the mixed sample and used for further study. The methods used for separation of the lysed cell contents are dependent on the goal of the study. Careful investigation of these inner workings can reveal disease patterns, improve our understanding of normal cellular function, and elucidate biochemical pathways and therapeutic targets. Protein isolation is different from nucleic acid separation, and the reagents used vary drastically. There are a few ways to lyse the cell membrane; these include mechanical disruption, liquid homogenization, freeze/thaw cycles, manual griding, and the use of detergents. Sonication cell lysis is an example of mechanical disruption used for releasing the contents of cells.  

An antigen is a molecule that is part of an object that is foreign to the body. The body uses antibodies to recognize the foreign object by its antigens and stimulates an immune response, activating white blood cells to produce more antibodies and other immune pathways. Antigens can be proteins or sugars that are located on the outer surfaces of pathogenic cells. All cells have antigens including the ones inside the body, bacteria, and even viruses. The antibodies produced by the immune system are custom-fitted to the antigen that initially stimulated the immune response. The antibodies have an antigen recognition site (paratope) that is highly specific affinity for a region on the antigen called the epitope.  

General overview of ELISA

There are a few more considerations for optimizing the CLIA assay that in this chapter will be discussed. The following considerations are related to the performance of your assay.