α-Bungarotoxin (α-bgtx)-binding proteins, including certain nicotinic acetylcholine receptors and acetylcholine-binding proteins (AChBPs), are frequently characterized with radioisotope-labeled α-bgtx-binding assays. Such assays, however, preclude investigations of binding interactions in real time and are hampered by the inconveniences associated with radioisotope-labeled reagents. We used surface plasmon resonance-based technology (BIAcore) to investigate the binding of recombinant AChBP to CM-5 sensor chip surfaces with directly immobilized α-bgtx. We validated our BIAcore results by comparing the same biological samples using the traditional 125 I-labeled α-bgtx-binding assay. An α-bgtx sensor chip, as described here, enables detailed, real-time, radioisotope-free interaction studies that can greatly facilitate the characterization of novel α-bgtx-binding proteins and complexes.