Which of the following is true for ELISA? I. An antibody, antibody 1, specific to the analyte of interest is dissolved in aqueous solution.; II. Analyte is incubated with antibody 1, binding to form a complex. The fraction of antibody 1 sites bound to analyte is proportional to the concentration.; III. Unbound substances are flushed from the ELISA surface and a second antibody, antibody 2, which binds to a different region of the analyte, is applied to the antibody 1-analyte complexes.; IV. Antibody 2 is chemically modified to include an enzyme that converts a colorless reagent to a colored reagent. The more bound analyte, the more intense the color generated.
