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首页> 外文期刊>Chemistry: A European journal >Designed peptides with homochiral and heterochiral diproline templates as conformational constraints
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Designed peptides with homochiral and heterochiral diproline templates as conformational constraints

机译：以同手性和异手性双脯氨酸模板为构象约束条件设计的肽

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Diproline segments have been advanced as templates for nucleation of folded structure in designed peptides. The conformational space available to homochiral and heterochiral diproline segments has been probed by crystallographic and NMR studies on model peptides containing L-Pro-L-Pro and D-Pro-L-Pro units. Four distinct classes of model peptides have been investigated: a) isolated D-Pro-L-Pro segments which form type II' beta-turn; b) D-Pro-L-Pro-L-XXX sequences which form type II'-I (beta(II'-I), consecutive beta-turns) turns; C) D-Pro-L-pro-D-XXX sequences; d) L-Pro-L-Pro-L-XXX Sequences. A total of 17 peptide crystal structures containing diproline segments are reported. Peptides of the type Piv-D-Pro-L-Pro-L-Xxx-NHMe are conformationally homogeneous, adopting consecutive P-turn conformations. Peptides in the series Piv-D-Pro-L-Pro-D-Xxx-NHMe and Piv-L-Pro-L-Pro-L-Xxx-NHMe, display a heterogeneity of structures in crystals. A type VIa beta-turn conformation is characterized in Piv-L-Pro-L-Pro-L-Phe-OMe (18), while an example of a 5 1 hydrogen bonded alpha-turn is observed in crystals Of Piv-D-Pro-L-Pro-D-Ala-NHMe (11). An analysis of pyrrolidine conformations suggests a preferred proline puckering geometry is favored only in the case of heterochiral diproline segments. Solution NMR studies, reveal a strong conformational influence of the C-terminal Xxx residues on the structures of diproline segments. In L-Pro-L-Pro-L-Xxx sequences, the Xxx residues strongly determine the population of Pro-Pro cis conformers, with an overwhelming population of the trans form in L-XXX = L-Ala (19).
机译：已经将双脯氨酸片段作为用于设计的肽中的折叠结构成核的模板。通过晶体学和NMR研究，对包含L-Pro-L-Pro和D-Pro-L-Pro单元的模型肽进行了探索，可用于手性和异手性双脯氨酸片段的构象空间。已经研究了四种不同类型的模型肽：a）分离的形成II'型β-转角的D-Pro-L-Pro节段; b）D-Pro-L-Pro-L-XXX序列，形成II'-I型（beta（II'-I），连续的beta圈）圈; C）D-Pro-L-pro-D-XXX序列; d）L-Pro-L-Pro-L-XXX序列。报道了总共17个含有双脯氨酸片段的肽晶体结构。 Piv-D-Pro-L-Pro-L-Xxx-NHMe类型的肽构象均一，采用连续的P-turn构象。 Piv-D-Pro-L-Pro-D-Xxx-NHMe系列和Piv-L-Pro-L-Pro-L-Xxx-NHMe系列中的肽显示晶体结构的异质性。在Piv-L-Pro-L-Pro-L-Phe-OMe（18）中表征了VIa型β-转角构象，而在Piv-D-的晶体中观察到5 1个氢键合的α-转角的例子。 Pro-L-Pro-D-Ala-NHMe（11）。吡咯烷构象的分析表明，仅在杂手性双脯氨酸片段的情况下，优选的脯氨酸褶皱几何形状才是有利的。溶液NMR研究表明，C末端Xxx残基对双脯氨酸片段的结构具有很强的构象影响。在L-Pro-L-Pro-L-Xxx序列中，Xxx残基强烈决定了Pro-Pro顺式构象体的数量，L-XXX = L-Ala则是绝大多数的反式形式（19）。

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