Fig. 1.

Structure of [³H]BG. Counting efficiency was determined as described in Materials and methods. Stoichiometry was derived from the counting efficiency and definitions; Avogadro’s number = 6.022 × 10²³ mol^-1 and 1 μCi = 2.22 × 10⁶ dpm. Because mass spectrometry indicated that [³H]BG consisted of a mixture of unlabeled, ³H-mono-labeled, ³H-di-labeled, and ³H-tri-labeled materials, ³H was placed in the center of the benzene ring to indicate that ³H was located in the benzene ring of O⁶-BG.