Biotin-avidin binding was detected using Xe NMR.

(A) Structures of ABAO derivatives that contain propargyloxy group and biotin. (B) Quantification of the reaction of BABAO with the M13 phage displaying a library of peptides with N-terminal glyoxal and wt phage displaying no aldehyde (1011 PFU/mL each). (C) Phage mixture was exposed to BABAO for the specified time. (D) To measure the reaction rate, we exposed the mixture of phage to 1 mM BABAO and measured biotinylation as a function of time by avidin capture. Error bars represent standard deviations from four independent kinetics experiments.