The western blot (sometimes called the protein immunoblot) is a widely accepted analytical technique used to detect specific proteins in a sample of tissue homogenate or extract. It uses gel electrophoresis to separate native proteins by 3-D structure or denatured proteins by the length of the polypeptide. The proteins are then transferred to a membrane (typically nitrocellulose or PVDF), where they are stained with antibodies specific to the target protein.[1][2] Gel electrophoresis step is included in Western blot analysis to resolve the issue of the cross-reactivity of antibodies. An improved immunoblot method, Zestern analysis, is able to address this issue without the electrophoresis step, thus significantly improving the efficiency of protein analysis.