Synthetic Biology of Autofluorescent Proteins - Fluorescent Proteins: From Understanding to Design - page 115

Fig. 7 Examples for the conformation of (2-F)Tyr and (3-F)Tyr residues in EGFP. Whereas in
case of EGFP[(2-F)Tyr] all fluorinated Tyr residues adopt only one conformation, some of the
(3-F)Tyr residues in EGFP[(3-F)Tyr] exhibit two conformations [ 17 , 57 ]. This might be explained
by different spatial demands of the two regioisomers
the ring carbons of Phe64, whereas (3-F)Tyr143 seems not to be involved in any
interaction [ 17 , 57 ].
The existence of two conformations of fluorinated amino acids in protein struc-
tures was also reported for Trp analogs such as (4-F)Trp, (5-F)Trp, and (6-F)Trp
[ 58 ]. For instance, in the 19 F NMR spectra of EGFP (contains a single W57 residue)