what is the purpose of blocking in western blot
Western blot Since the membrane has been chosen for its ability to bind protein and as both antibodies and the target are proteins, steps must be taken to prevent the interactions between the membrane and the antibody used for detection of the target protein. Blocking of non-specific binding is achieved by placing the membrane in a dilute solution of protein – typically 3–5% bovine serum albumin (BSA) or non-fat dry milk (both are inexpensive) in tris-buffered saline (TBS) or I-Block, with a minute percentage (0.1%) of detergent such as Tween 20 or Triton X-100. Although non-fat dry milk is preferred due to its availability, an appropriate blocking solution is needed as not all proteins in milk are compatible with all the detection bands.[12] The protein in the dilute solution attaches to the membrane in all places where the target proteins have not attached. Thus, when the antibody is added, there is no room on the membrane for it to attach other than on the binding sites of the specific target protein. This reduces background in the final product of the western blot, leading to clearer results, and eliminates false positives.
Western Wall In a broader sense, "Western Wall" can refer to the entire 488-metre-long (1,601 ft) retaining wall on the western side of the Temple Mount. The classic portion now faces a large plaza in the Jewish Quarter, near the southwestern corner of the Temple Mount, while the rest of the wall is concealed behind structures in the Muslim Quarter, with the small exception of a 25 ft (8 m) section, the so-called Little Western Wall. The segment of the Western retaining wall traditionally used for Jewish liturgy, known as the "Western Wall", derives its particular importance to it having never been fully obscured by medieval buildings, and displaying much more of the original Herodian stonework than the "Little Western Wall". In religious terms, the "Little Western Wall" is presumed to be even closer to the Holy of Holies and thus to the "presence of God" (Shechina), and the underground Warren's Gate, which has been out of reach since the 12th century, even more so.