Crystal structures and conformations of the cyclic dipeptides cyclo-(Glycyl-L-tyrosyl) and cyclo-(L-seryl-L-tyrosyl) Monohydrate.
Crystal structures and conformations of the cyclic dipeptides cyclo-(Glycyl-L-tyrosyl) and cyclo-(L-seryl-L-tyrosyl) Monohydrate.
复制标题
环状二肽环-(甘氨酰-L-酪氨酰)和环-(L-丝氨酰-L-酪氨酰)一水合物的晶体结构和构象。
DOI：
10.1021/ja00801a046
复制
发表时间：
1973
影响因子：
15
通讯作者：
Webb Le
中科院分区：
文献类型：
--
作者：
Chi;Webb Le
用单晶X-射线衍射技术测定了cycZO-（glycyl-L-tyrosyl）（cycfo-（Gly-L-Tyr））和cycZO-（L-Ser-L-Tyr）一水合物的晶体和分子结构。两种肽均为折叠构象（1= 55），酪氨酸侧链中的芳香环朝向二酮哌嗪环。这一发现是在协议的质子磁共振和分子轨道研究的一些环二肽含有芳甲基侧链。在cycZ 〇-（Gly-L-Tyr）中，二酮哌嗪环呈现船形构象，其中Ca-C5键处于准轴向“旗杆”位置，但在cycZ 〇-（L-Ser-L-Tyr）中，该环几乎是平面的，其中α碳偏离通过两个肽键的最小二乘平面约0.2 π。目前可用的晶体学和核磁共振环二肽数据的分析表明，在一般情况下，二酮哌嗪环有利于构象，最大化二酮哌嗪芳香环吸引力的相互作用，而不允许侧链之间的空间干扰。cycZo-（Gly-L-Tyr）的晶体为正交晶系，空间群为P2\2J。其中a= 7.775±0.003，B= 21.475±0.001，c= 6.170±0.001，Z= 4。cycZo-（L-Ser-L-Tyr）晶体属单斜晶系，空间群为P2 U，a= 11.445±0.002，B- 6.191±0.001，c= 8.828±0.001 A，δ = 99.10±0.01，Z = 2。用四圆衍射仪收集了X射线强度数据，用最小二乘法进行了修正，前者的R因子为9.9%，后者为5.3%。（2，5-哌嗪二酮）的发现始于通过质子磁共振研究，芳甲基侧链倾向于芳环朝向二酮哌嗪（DKP）环的折叠构象。2-4由于这两个环之间稳定这种构象的吸引力可能在生物学感兴趣的分子中起作用，我们已经寻找了X射线晶体学证据，
The crystal and molecular structures of cycZo-(glycyl-L-tyrosyl)(cycfo-(Gly-L-Tyr)) and cyclo-(L-seryl-L-tyrosyl)(cycZo-(L-Ser-L-Tyr)) monohydrate were determined by single crystal X-ray diffraction techniques. Both peptides are in the foldedconformation (1= 55), with the aromatic ringin the tyrosine side chain facing the diketopiperazine ring. This finding is in agreement with proton magnetic resonance and molecular orbital studies of a number of cyclic dipeptides containing arylmethyl side chains. In cycZo-(Gly-L-Tyr), the diketopiperazine ring assumes a boat conformation with the Ca-C5 bond in a quasi-axial “flagpole” position, but in cyc/o-(L-Ser-L-Tyr), this ring is nearly planar with the a carbons deviating about 0.2 Á from the least-squares plane through the two peptide bonds. Analysis of presently available crystallographic and nmr cyclic dipeptide data indicates that, in general, the diketopiperazine ring favors a conformation which maximizesthe diketopiperazine-aromaticring attractive interaction without allowing steric interference between side chains. Crystals of cycZo-(Gly-L-Tyr) are orthorhombic, space group P2\2J.\with a= 7.775±0.003, b= 21.475±0.001, c= 6.170±0.001 Á, and Z= 4. The crystals of cycZo-(L-Ser-L-Tyr) are monoclinic, space group P2U with a= 11.445±0.002, b- 6.191±0.001, c= 8.828±0.001 A, 8= 99.10±0.01, andZ= 2. The X-ray intensity data were collected with a four circle diffractometer and refined byleast-squares procedures to an R factor of 9.9% for the former compound and 5.3% for the latter.The current interest in conformations of cyclic di-peptides (2, 5-piperazinediones) began with the discovery, through proton magnetic resonance studies, that an arylmethyl side chain prefers the folded con-formation with the aromatic ring facing the diketopiperazine (DKP) ring. 2-4 Since the attractive force between these two ringswhich stabilizes this conforma-tion may play a role in molecules of biological interest, we have sought X-ray crystallographic evidence for the