Fig 1. Dye-labeled B₇ probes.

(A) Biotin-4-fluorescein (BFl) contains a shorter spacer of 10 non-hydrogen atoms between the bicyclic ring and the dye structure. (B) Oregon green 488 Biocytin (BcO) has a spacer of 20 non-hydrogen atoms between the bicyclic ring and the fluorescent dye. Biocytin (Bc) is an amide formed with B₇ and L-lysine. (C) biotinylated DNA labeled at the 3’ end with fluorescein (B₇-DNA_ds*Fl-3’), where B₇ was attached to a 14-mer DNA duplex labeled with fluorescein (Fl) at the 3’ end with 16 non-hydrogen atoms between the bicyclic ring and the thymine cyclic base. Unlabeled B₇ was used to find the reaction rate of the final binding site in AV and compare it with the reaction rates of the initial binding site to assess possible cooperativity.