A laboratory exercise illustrating the sensitivity and specificity of Western blot analysis.

Western blot analysis, commonly known as "Western blotting," is a standard tool in every laboratory where proteins are analyzed. It involves the separation of polypeptides in polyacrylamide gels followed by the electrophoretic transfer of the separated polypeptides onto a nitrocellulose or polyvinylidene fluoride membrane. A replica of the separated polypeptides from the gel is created on the membrane, which is then probed with antibodies or other ligands to identify specific polypeptide(s). Here, we report an undergraduate laboratory exercise involving Western blotting. During the 3-week laboratory exercise, students investigated the likelihood of the presence of a serum albumin in fruit fly (Drosophila melanogaster) homogenate, bovine calf serum (BCS), and fetal bovine serum (FBS). Students isolate proteins from fruit fly larvae and perform sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE), electrophoretic blotting, and immunoassay comparing those proteins with BCS and FBS proteins. Their results indicate that serum albumin is present in BCS and FBS but is absent in fruit flies. In the process, the specificity and sensitivity of Western blot analysis is demonstrated. The laboratory exercise can be easily incorporated into any college-level biochemistry or molecular techniques laboratory. The procedure used can be easily adapted to study other proteins.