Immunoprecipitation is a technique in which an antigen is isolated by binding to a specific antibody attached to a sedimentable matrix. It is also used to analyze protein fractions separated by other techniques such as gel filtration or density gradient sedimentation. The source of antigen for immunoprecipitation can be unlabeled cells or tissues, metabolically or intrinsically labeled cells, or in vitro-translated proteins. This unit describes a wide range of immunoprecipitation techniques, using either suspension or adherent cells lysed by various means.Usually, plasmas transfected cells or natural cells are ideal sample for immunoprecipitation.
Extracellular proteins called plasma proteins are especially important in determining tonicity and fluid movement due to their ability to create oncotic pressure. While cell membranes are readily permeable to water, not all solutes will diffuse easily across cell walls. Water will, however, flow in or out of cells from an area of lower solute concentration to an area of higher solute concentration in order to achieve balance in the body.
Due to its diverse nature and composition, the Extracellular proteins can serve many functions, such as providing support, segregating tissues from one another, and regulating intercellular communication. The extracellular matrix regulates a cell's dynamic behavior. In addition, it sequesters a wide range of cellular growth factors and acts as a local store for them. Changes in physiological conditions can trigger protease activities that cause local release of such stores. This allows the rapid and local growth factor-mediated activation of cellular functions without de novo synthesis.
Formation of the extracellular matrix is essential for processes like growth, wound healing, and fibrosis. An understanding of Extracellular proteins structure and composition also helps in comprehending the complex dynamics of tumor invasion and metastasis in cancer biology as metastasis often involves the destruction of extracellular matrix by enzymes such as serine proteases, threonine proteases, and matrix metalloproteinases.
The stiffness and elasticity of the Extracellular proteins has important implications in cell migration, gene expression, and differentiation. Cells actively sense Extracellular proteins rigidity and migrate preferentially towards stiffer surfaces in a phenomenon called durotaxis. They also detect elasticity and adjust their gene expression accordingly which has increasingly become a subject of research because of its impact on differentiation and cancer progression.