First crystal structures of wild-type and enhanced GFP. Tsien designed T203Y mutant based on crystal structure of S65T GFP. It is yellow fluorescent.

References:

M Ormo, AB Cubitt, K Kallio, LA Gross, RY Tsien, SJ Remington: Crystal structure of the Aequorea victoria green fluorescent protein. Science 273 (1996) 1392-95.

F Yang, LG Moss, GN Phillips: The molecular structure of green fluorescent protein. Nature Biotechnology 14 (1996) 1246-51.

Further reading on Crystal Structures: To Be Added