ABSTRACT
A simple means of determining whether differences in protein composition exist in different tissues involves investigating the expression of individual known proteins in such tissues. These methods might involve the isolation of widely differing amounts of an individual protein (or none of the protein at all) from different tissues, using an established purification procedure, or the detection of an enzymatic activity associated with the protein in extracts of only one particular tissue. We shall consider in detail, however, only methods where the expression of a specific protein is monitored by the use of a specific antibody to it. Normally, such an antibody is produced by injecting the protein into an animal such as a rabbit or mouse. The resulting immune response results in the presence in the animal’s blood of antibodies which specifically recognize the protein and can be used to monitor its expression in particular tissues.
