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Sensing the anomeric effect in a solvent-free environment

机译:在无溶剂的环境中感应异头效果

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摘要

The anomeric effect is a chemical phenomenon that refers to an observed stabilization of six-membered carbohydrate rings when they contain an electronegative substituent at the C1 position of the ring. This stereoelectronic effect influences the three-dimensional shapes of many biological molecules. It can be manifested not only in this classical manner involving interaction of the endocyclic oxygen atom (O5) found in such sugars with the C1 substituent (endo-anomeric effect) but also through a corresponding inter-action of the electronegative exocydic substituent with O5 (exo-anomeric effect). However, the underlying physical origin(s) of this phenomenon is still not clear. Here we show, using a com-bination of laser spectroscopy and computational analysis, that a truncated peptide motif can engage the two anomers of an isolated sugar in the gas phase, an environment lacking extraneous factors which could confound the analysis. (Anomers are isomers that dif-fer in the orientation of the substituent at C1.) Complexes formed between the peptide and the α- or β-anomers of D-galactose are nearly identical structurally; however, the strength of the polariza-tion of their interactions with the peptide differs greatly. Natural bond order calculations support this observation, and together they reveal the dominance of the exo- over the endo-anomeric effect. As interactions between oxygen atoms at positions C1 and C2 (O1 and 02, respectively) on the pyranose ring can alter the exo/endo ratio of a carbohydrate, our results suggest that it will be important to re-evaluate the influence, and biological effects, of substituents at position C2 in sugars.
机译:端基异构作用是一种化学现象,是指当六元碳水化合物环在环的C1位置包含负电取代基时,观察到的稳定。这种立体电子效应影响许多生物分子的三维形状。它不仅可以以这种经典方式体现出来,包括在此类糖中发现的内环氧原子(O5)与C1取代基的相互作用(内-端异头作用),而且还可以通过负电外来取代基与O5的相应相互作用来体现(外来异头作用)。但是,这种现象的潜在物理起源仍然不清楚。在这里,我们结合激光光谱学和计算分析结果表明,截短的肽基序可以在气相中结合分离糖的两个端基异构体,而该环境缺乏可能混淆分析的外部因素。 (异构体是在C1处取代基的方向不同的异构体。)肽与D-半乳糖的α-或β-异头物之间形成的复合物在结构上几乎相同;它们在结构上几乎相同。然而,它们与肽相互作用的极化强度差异很大。天然键序计算支持了这一观察结果,它们一起揭示了外显子在内端异头作用中的优势。由于吡喃糖环上C1和C2位上的氧原子之间的相互作用(分别为O1和02)可以改变碳水化合物的外/内比,因此我们的结果表明,重新评估其影响和生物学效应将非常重要是糖中C2位的取代基。

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  • 来源
    《Nature》 |2011年第7328期|p.76-79|共4页
  • 作者单位

    Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford 0X1 3QZ UK,Departamento de Quimica Fisica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco (UPV-EHU), Apartado 644,E-48940, Bilbao, Spain;

    Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford 0X1 3QZ UK,Institut des Sciences Moleculaires d'Orsay-CNRS, Universite Paris Sud, F91405 Orsay Cedex, France;

    Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford 0X1 3QZ UK,Department of Chemistry and Biochemistry, Rowan University,201 Multica Hill Road, Glassboro, New Jersey 08028, USA;

    Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford 0X1 3QZ UK;

    Chemistry Research Laboratory, Department of Chemistry,University of Oxford, Mansfield Road, Oxford 0X1 3TA, UK;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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