Triiodothyronine: the 3'iodine is proximal to the  -ring in crystal structure conformation.
The crystal and molecular structure of the thyroid hormone L-triiodothyronine has been determined by x-ray diffraction. The two phenyl rings are almost perpendicular to each other, the acute angle between their normals being 82 degrees. The 3'-iodine is situated proximal to the alpha-ring, rather than distal as inferred from chemical studies. Theoretical calculations indicate this proximal conformation to be energetically favored over the distal one.
D007455:Iodine / Q000032:analysis; D008956:Models, Chemical; D011487:Protein Conformation; D014284:Triiodothyronine / Q000032:analysis*; D014961:X-Ray Diffraction
D014284:Triiodothyronine; D007455:Iodine