The influence of epitope availability on atomic-force microscope studies of antigen-antibody interactions.
The ability of the atomic-force microscope (AFM) to detect interaction forces between individual biological molecules has recently been demonstrated. In this study, force measurements have been obtained between AFM probes functionalized with the beta-subunit of human chorionic gonadotrophin (betahCG) and surfaces functionalized with anti-betahCG antibody. A comparison of the obtained results with previous anti-ferritin antibody-binding data identifies differences when the antigen molecule expresses only a single epitope (betahCG), rather than multiple epitopes (ferritin), for the monoclonal antibodies employed. Specifically, the probability of observing probe-sample adhesion is found to be higher when the antigen expresses multiple epitopes. However, the periodic force observed in the adhesive-force distribution, due to the rupture of single antigen-antibody interactions, is found to be larger and more clearly observed for the mono-epitopic system. Hence, these findings indicate the potential of the AFM to distinguish between multivalent and monovalent antibody-antigen interactions, and demonstrate the influence of the number of expressed epitopes upon such binding studies.
Allen
S
S
Laboratory of Biophysics and Surface Analysis, School of Pharmaceutical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
Davies
J
J
Davies
M C
MC
Dawkes
A C
AC
Roberts
C J
CJ
Tendler
S J
SJ
Williams
P M
PM
D000268:Adhesiveness; D000906:Antibodies / Q000276:immunology; D000937:Antigen-Antibody Reactions; D000941:Antigens / Q000276:immunology; D006063:Chorionic Gonadotropin / Q000276:immunology* / Q000648:ultrastructure; D000939:Epitopes; D005293:Ferritins / Q000276:immunology / Q000648:ultrastructure; D006801:Humans; D018625:Microscopy, Atomic Force; D018448:Models, Immunological; D011485:Protein Binding
D000906:Antibodies; D000941:Antigens; D006063:Chorionic Gonadotropin; D000939:Epitopes; D005293:Ferritins