Cell Biology Essay Example | Topics and Well Written Essays - 1750 words

Cell Biology - Essay Example Average-sized molecules travel through the gel with different degrees of facility. Electrophoresis is done in a thin vertical slab of polyacrylamide. The course of protein movement is from top to bottom. Protein molecules can be isolated on the basis of their individual mass through use of electrophoresis in a polyacrylamide gel under protein denaturing process. The mixture of protein macromolecules is initially denatured in a homogeneous mixture of sodium dodecyl sulfate (SDS), which is an anionic emulsifier with the ability of disrupting almost all noncovalent interactions in native proteins macromolecules. SDS forms complexes with the denatured proteins which are then subjected to electrophoresis. After the process of electrophoresis, the proteins in the gel are imaged after silver or dye stains are applied. The product is visualized as series of bands. Tiny proteins molecules travel faster through the gel, while bigger molecules of proteins remain at the top where the samples are applied or put. Mobility of most polypeptide chains under these settings is linearly proportional to the logarithm of their mass. SDS polyacrylamide gel electrophoresis (SDS-PAGE) is very fast, sensitive, and has capacity of a high degree of resolution. As tiny as 0.1 Â µg which is equivalent to 2 pmol of a protein produces a discrete band when it is stained with Coomasie blue or less (~0.02 Â µg) can be determined with the use of a silver stain. Protein molecules which vary in mass by about 2% are commonly detected (Berg, et al., 2002). It is essential to detect minute quantities of a specific protein molecule in the presence of several other protein molecules, like for instance the presence of viral proteins in blood circulation. Very minute quantities of a protein molecule of interest concern in a cell or in the human blood can be determined by an immunoassay procedure which is called Western blotting. A sample is subjected to electrophoresis on an SDS-polyacrylamide gel. Blot ting or more commonly called electroblotting moves the resolved protein molecules on the SDS-polyacrylamide gel to the surface of a polymer sheet in order to have the proteins more obtainable during the reaction. A specific antibody for the protein of concern is incorporated to the polymer sheet containing the resolved protein which then forms complexes with the specific antibody. The antibody-antigen complex on the polymer sheet can be determined via rinsing the sheet with the use of a second specific antibody for the first antibody. A radioactive label that is located on the second antibody causes an illumination of dark band on an x-ray film. An alternative procedure using the ELISA method is through the use of an enzyme that is also located on the second antibody which produces a colored product. The use of Western blotting has been a breakthrough in finding a specific protein molecule in a complex mixture of different proteins. Currently, it is not only used as the basis for te sting infection of hepatitis C, wherein it is utilized to determine a core protein of the virus but the technique is also now very purposeful in genetic cloning (Berg, et al., 2002). The objective of this activity is to demonstrate stimulation of the epidermal growth factor receptor-signaling pathway by virtue of SDS-PAGE and Western blotting