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首页> 外文期刊>Chemistry: A European journal >Shape Persistence of PolyprolineII Helical Oligoprolines
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Shape Persistence of PolyprolineII Helical Oligoprolines

机译：PolyprolineII螺旋寡脯氨酸的形状持久性

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摘要

Oligoprolines are commonly used as molecular scaffolds. Past studies on the persistence length of their secondary structure, the polyprolineII (PPII) helix, and on the fraction of backbone cis amide bonds have provided conflicting results. We resolved this debate by studying a series of spin-labeled proline octadecamers with EPR spectroscopy. Distance distributions between an N-terminal Gd-III-DOTA (DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) label and a nitroxide label at one of five evenly spaced backbone sites allowed us to discriminate between the flexibility of the PPII helix and the cis amide contributions. An upper limit of 2% cis amide bonds per residue was found in a 7:3 (v/v) water/glycerol mixture, whereas cis amides were not observed in trifluoroethanol. Extrapolation of Monte Carlo models from the glass transition to ambient temperature predicts a persistence length of approximate to 3-3.5nm in both solvents. The method is generally applicable to any type of oligomer for which the persistence length is of interest.
机译：寡脯氨酸通常用作分子支架。过去有关其二级结构，聚脯氨酸II（PPII）螺旋的持久性长度以及骨架顺式酰胺键部分的研究提供了矛盾的结果。我们通过研究一系列带有EPR光谱的自旋标记脯氨酸十八酰胺来解决这一争论。 N-末端Gd-III-DOTA（DOTA = 1,4,7,10-四氮杂环十二烷-1,4,7,10-四乙酸）标签和一氧化氮标签之间的距离分布允许在五个均匀间隔的骨架位点之一我们区分PPII螺旋​​的柔韧性和顺酰胺的贡献。在7：3（v / v）水/甘油混合物中发现每个残基2％的顺酰胺键上限，而在三氟乙醇中未观察到顺酰胺。从玻璃化转变到环境温度的蒙特卡洛模型外推法预测两种溶剂中的持久性长度约为3-3.5nm。该方法通常适用于持久性长度令人感兴趣的任何类型的低聚物。

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