The PCR reaction was monitored by agarose gel electrophoresis as follows: A 1.5% agarose (FMC Bioproducts) electrophoresis gel in tris-borate EDTA ("TBE") 1× buffer (89 mM Tris-borate (Fisher Biotech), 89 mM boric acid (Mallinckrodt) and 2 mM EDTA (Mallinckrodt)) was prepared. Five to ten microliters of PCR products were loaded onto the gel with 1 μl dye 10× (0.5% bromophenol blue (Sigma), 0.5% Xylene cyanol (Gibco-BRL), 40% (w/v) sucrose (IBI) in water). Electrophoresis was run in TBE 1× at 120 V for 45 minutes. The gel was stained with ethidium bromide (10 μg/ml, Sigma) for 5 minutes. PCR products were visualized with ultraviolet light.
