Visualization of an immunological reaction between single antigen and antibody molecules by optical chromatography

Optical chromatography, which is a technique for the separation of microsco pic particles using a radiation force, is applied to kinetic studies of an immunoreaction. Polystyrene beads coated with antibodies react with antigen s to produce conjugated beads, which comprise two beads and some antigens. The resulting conjugated beads are separated from the single beads. The det ection limit of the antigen is <1 ng ml(-1), which is smaller than that rep orted in a previous paper [T. Hatano, T Kaneta, T. Imasaka, Anal. Chem. 69 (1997) 2711], and can be achieved using 2 mu m-diameter beads. The sensitiv ity in the present method can be further enhanced by increasing the particl e size. In addition, the dissociation reaction of the conjugated beads is e valuated by using an on-column reaction technique, which allows the direct monitoring of the formation and dissociation of the conjugated beads. The r ate constant for the dissociation of the conjugated beads is determined to be 4.0 x 10(-3) s(-1) for the case of conjugated beads combined by a single bond. (C)2000 Elsevier Science B.V. All rights reserved.