Recombinant rFRβ is functional in binding folate. (a) Purified rFRβ was resolved on 4% to 12% NuPAGE gel. The rFRβ appears as a tight doublet. Molecular weight markers (in kilodaltons) are on the left side of the gel image. (b) rFRβ is able to bind to folate. Open squares indicate NTA control with FITC-folate, filled squares indicate rFRβ with FICT-folate and 100-fold excess unlabelled folate, and filled diamonds indicate rFRβ with FITC-folate. FITC emission is detected at 518 nm. FITC, fluorescein isothiocyanate; rFRβ, recombinant folate receptor beta.