Cody V
Endocr Res Commun. 1979;6(2):123-34. doi: 10.1080/07435807909061100.
In an accurately determined X-ray diffraction study of the thyroid hormone thyroxine (T4), the two independent conformations in the crystal lattice show significant differences in the outer phenyl ring geometry when compared with that of 3,5,3'-triiodothyronine (T3). The major differences between the T4 and T3 structures are a shortened C4'-O4' bond, contraction of the C3'-C4'-C5' angle and an increase in the C3' and C5' angles of T4. These changes can be correlated with the difference in acidity of the 4'-OH of T4 and T3 and help to explain binding affinity differences among thyroactive compounds. The hydrogen bond directionality observed in T4 and other thyroid structures offers an insight into the molecular details of the hormone-receptor site. The conformation of one T4 molecule is cisoid, that of the other transoid, the first such instance of different overall conformations to be found in the same crystal lattice. One T4 molecule has the side chain nearly coplanar with the inner ring, an unusual conformation among thyroid structures.
在对甲状腺激素甲状腺素（T4）进行的一项精确测定的X射线衍射研究中，与3,5,3'-三碘甲状腺原氨酸（T3）相比，晶格中的两种独立构象在外苯环几何结构上显示出显著差异。T4和T3结构之间的主要差异在于T4的C4'-O4'键缩短、C3'-C4'-C5'角收缩以及C3'和C5'角增大。这些变化与T4和T3的4'-OH酸度差异相关，并有助于解释甲状腺活性化合物之间的结合亲和力差异。在T4和其他甲状腺结构中观察到的氢键方向性为了解激素 - 受体位点的分子细节提供了线索。一个T4分子的构象为顺式，另一个为反式，这是在同一晶格中发现的不同整体构象的首个此类实例。一个T4分子的侧链几乎与内环共面，这在甲状腺结构中是一种不寻常的构象。
