Lalitha V, Subramanian E, Parthasarathy R
Int J Pept Protein Res. 1986 Mar;27(3):223-8. doi: 10.1111/j.1399-3011.1986.tb01814.x.
The tripeptide, L-prolyl-glycyl-glycine, crystallizes in the trigonal space group P3(2), with a = b = 8.682(2) A, c = 12.008(2) and Z = 3. The structure was solved by direct methods and refined to an R-value of 0.07 for 727 reflections (I greater than 1.0 sigma). The molecule exists as a zwitterion in the crystal. The peptide units are trans and show significant deviations from planarity (omega 1 = 169.7 degrees, omega 2 = -170.1 degrees). The peptide backbone adopts a left-handed helical conformation similar to that of polyglycine II and polyproline II.
三肽L-脯氨酰-甘氨酰-甘氨酸结晶于三方空间群P3(2)，a = b = 8.682(2) Å，c = 12.008(2) ，Z = 3。结构通过直接法解析，并对727个反射（I大于1.0σ）精修至R值为0.07。该分子在晶体中以两性离子形式存在。肽单元为反式，且显著偏离平面性（ω1 = 169.7°，ω2 = -170.1°）。肽主链采用类似于聚甘氨酸II和聚脯氨酸II的左手螺旋构象。
