Five species of tRNAs bearing two different fluorescent groups were synthesized. These were suitable for intramolecular distance measurements by singlet-singlet energy transfer. The efficiency of energy transfer was determined from the sensitized emission of the energy acceptor. With the assumption that the relative orientation of donor and acceptor is random, the apparent distances between the 5′-end and the 3′-end, the 4-thiouridine and the 3′-end, the pseudouridine and 3′-end, the pseudouridine and the dihydrouridine in Escherichia coli formyl methionine tRNA, and between the 2-thiouridine (in the anticodon) and the 3′-end in E. coli glutamate tRNA were calculated to be 24 Å, 38 Å, 55 Å, 36 Å, and >65 Å, respectively.

Yang, C.-H., & Söll, D. (1974). Studies of Transfer RNA Tertiary Structure by Singlet-Singlet Energy Transfer. Proceedings of the National Academy of Sciences, 71(7), 2838–2842.