Immunosorbent Analysis (ELISA). The purified NusA-IRAS (10-120aa) , diluted to 10 μg/mL in 50 mM carbonate salt buffer (pH 9.6), was coated on plates at 100 μL aliquot per well, 4 • C overnight. The wells were washed three times with PBS-Tween buffer (0.05% Tween 20 in PBS). The coated wells were blocked with 200 μL of 3% BSA for 1 hour at 37 • C and then incubated with 150 μL monoclonal antibodies against NusA-IRAS (10-120aa) fusion protein with different dilutions (from 1 : 1000 to 1 : 25600). After incubation for 1 hour at 37 • C, the wells were incubated with 150 μL horseradish peroxidase-conjugated goat antimouse IgG (dilution 1 : 5000, Santa Cruz) for 1 hour at 37 • C after thorough washing. Peroxidase activity was detected using o-phenylenediamine and H 2 O 2 as enzyme substrates. Color development was stopped with 2 M of H 2 SO 4 and the absorbance was measured at 490 nm using Microplate Reader (Bio-Rad).