Hudson Benjamin C, Battigelli Alessia, Connolly Michael D, Edison John, Spencer Ryan K, Whitelam Stephen, Zuckermann Ronald N, Paravastu Anant K
Department of Chemical and Biomolecular Engineering , Georgia Institute of Technology , Atlanta , Georgia 30332-0100 , United States.
Molecular Foundry , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
J Phys Chem Lett. 2018 May 17;9(10):2574-2578. doi: 10.1021/acs.jpclett.8b01040. Epub 2018 May 2.
Peptoid nanosheets are supramolecular protein-mimetic materials that form from amphiphilic polypeptoids with aromatic and ionic side chains. Nanosheets have been studied at the nanometer scale, but the molecular structure has been difficult to probe. We report the use of C-C dipolar recoupling solid-state NMR measurements to reveal the configuration of backbone amide bonds selected by C isotopic labeling of adjacent α-carbons. Measurements on the same molecules in the amorphous state and in nanosheets revealed that amide bonds in the center of the amino block of peptoid (NaeNpe)-(NceNpe) (B28) favor the trans configuration in the amorphous state and the cis configuration in the nanosheet. This unexpected result contrasts with previous NMR and theoretical studies of short solvated peptoids. Furthermore, examination of the amide bond at the junction of the two charged blocks within B28 revealed a mixture of both cis and trans configurational states, consistent with the previously predicted brickwork-like intermolecular organization.
类肽纳米片是一种超分子蛋白质模拟材料，由具有芳香族和离子侧链的两亲性类肽形成。纳米片已在纳米尺度上进行了研究，但分子结构一直难以探测。我们报告了使用碳 - 碳偶极重耦合固态核磁共振测量来揭示通过相邻α - 碳原子的碳同位素标记选择的主链酰胺键的构型。对处于无定形状态和纳米片中的相同分子进行的测量表明，类肽（NaeNpe） - （NceNpe）（B28）氨基嵌段中心的酰胺键在无定形状态下有利于反式构型，而在纳米片中有利于顺式构型。这一意外结果与之前对短溶剂化类肽的核磁共振和理论研究形成对比。此外，对B28中两个带电嵌段交界处的酰胺键进行检查发现了顺式和反式构型状态的混合物，这与之前预测的砖状分子间组织一致。
