QD labeling of AChRs. (a) Alexa488-BTX and (b) BBQ. Pre-patterned AChR clusters (arrows) were seen with both labels, but diffuse AChRs were only seen after BBQ labeling as individual fluorescent dots. (c) Pretreatment with 5 μM unlabeled BTX for 30 min before BBQ labeling. (d) QD labeling without biotin-BTX. Scale bar, 10 μm.