Subramanian E, Lalitha V, Bordner J
Int J Pept Protein Res. 1984 Jul;24(1):55-9. doi: 10.1111/j.1399-3011.1984.tb00927.x.
L-tyrosyl-L-tyrosine crystallizes as a dihydrate in the orthorhombic system, space group C222(1), with a = 12.105(2), b = 12.789(2), c = 24.492(3) A, Z = 8. The structure was solved by direct methods and refined to a final R-value of 0.059 for 1740 observed reflections. The molecule exists as a zwitterion, the peptide unit is trans planar, and the backbone torsion angles correspond to an extended conformation, with psi 1 = 149.4 degrees, phi 2 = -161.2 degrees, psi 2 = 158.3 degrees. The values of the side-chain torsion angles (chi 1, chi 2) are (-58.8 degrees, -63.1 degrees) for the first tyrosine and (-171.7 degrees, -116.5 degrees) for the second. The planes of the aromatic rings are nearly parallel (dihedral angle of 6.1 degrees), and their centers are separated by 10.9 A. The carboxyl plane forms a dihedral angle of 23.8 degrees with the plane of the peptide bond.
L-酪氨酰-L-酪氨酸以二水合物形式结晶，属于正交晶系，空间群为C222(1)，a = 12.105(2) Å，b = 12.789(2) Å，c = 24.492(3) Å，Z = 8。结构通过直接法解析，对1740个观测反射进行精修后最终R值为0.059。分子以两性离子形式存在，肽单元为反式平面结构，主链扭转角对应伸展构象，ψ1 = 149.4°，φ2 = -161.2°，ψ2 = 158.3°。第一个酪氨酸侧链扭转角（χ1，χ2）的值为（-58.8°，-63.1°），第二个酪氨酸的为（-171.7°，-116.5°）。芳香环平面近乎平行（二面角为6.1°），其中心间距为10.9 Å。羧基平面与肽键平面形成23.8°的二面角。
