The sample pad is a chopped glass fiber pad cut to 14 mm width (Ahlstrom-Munksjö, Helsinki, Finland, product 8964). The pad is blocked in 0.05%, 1-day aged casein, 5 mM borate, 0.2% w/v sucrose, 0.05% w/v PVP-40 (Sigma, St Louis, MO, PVP-40) and 1 mg/mL HBR-1 (Scantibodies, Santee, CA). The sample pad was submerged completely in blocking solution with continuous rocking for 15 minutes and then dried at 25°C in a forced-air oven.