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首页> 外文期刊>RSC Advances >Investigation of the cis–trans structures and isomerization of oligoprolines by using Raman spectroscopy and density functional theory calculations: solute–solvent interactions and effects of terminal positively charged amino acid residues
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Investigation of the cis–trans structures and isomerization of oligoprolines by using Raman spectroscopy and density functional theory calculations: solute–solvent interactions and effects of terminal positively charged amino acid residues

机译：使用拉曼光谱和密度官能理论计算研究寡丙酮的顺式 - 反式结构和异构化：溶液 - 溶剂相互作用及末端带正电荷氨基酸残基的影响

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Using low-wavenumber Raman spectroscopy in combination with theoretical calculations via solid-state density functional theory (DFT)-D3, we studied the vibrational structures and interaction with solvent of poly- L -proline and the oligoproline P12 series. The P12 series includes P12, the positively charged amino acid residue (arginine and lysine) N-terminus proline oligomers RP11 and KP11, and the C-terminus P11R and P11K. We assigned the spring-type phonon mode to 74–76 cm ~(?1) bands for the PPI and PPII conformers and the carbonyl group ring-opening mode 122 cm ~(?1) in the PPI conformer of poly- L -proline. Amide I and II were assigned based on the results of mode analysis for O, N, and C atom displacements. The broad band feature of the H-bond transverse mode in the Raman spectra indicates that the positively charged proline oligomers PPII form H-bonds with water in the solid phase, whereas P12 is relatively more hydrophobic. In propanol, the PPI conformer of the P12 series forms less H-bond network with the solvent. The PPII conformer exhibits a distinct Raman band at 310 cm ~(?1) , whereas the PPI has bands at 365, 660, and 960 cm ~(?1) with reasonable intensity that can be used to quantitatively determine these two conformational forms. The 365 cm ~(?1) mode comprising the motion of a CO group turning to the helix axis was used to monitor the isomerization reaction PPI ? PPII. In pure propanol, RP11 and KP11 were found to have mostly PPI present, but P11R and P11K preferred PPII. After adding 20% water, the PPI in P11R and P11K was completely converted to PPII, whereas a small fraction of PPI remained in RP11 and KP11. The substituted positively charged amino acid affected the balance of the PPI/PPII population ratio.
机译：通过固态密度官能理论（DFT）-D3将低波纹拉曼光谱与理论计算结合使用，我们研究了振动结构和与多-L-脯氨酸和寡丙烯P12系列的溶剂相互作用。 P12系列包括P12，带正电荷的氨基酸残基（精氨酸和赖氨酸）N-末端脯氨酸低聚物RP11和KP11，以及C-末端P11R和P11K。我们将弹簧型声子模式分配到PPI和PPII适系的74-76cm〜（α1）条带中PPI的PPI和PPII符合材料和羰基环开启模式122cm〜（α1）中的POPI-L-PLOLINE 。根据O，N和C原子位移的模式分析结果分配酰胺I和II。拉曼光谱中的H键横向模式的宽带特征表明，带正电荷的脯氨酸低聚物PPII在固相中与水形成H键，而P12相对较为疏水。在丙醇中，P12系列的PPI构象与溶剂形成较少的H键网。 PPII符合材料在310cm〜（α1）处具有不同的拉曼带，而PPI具有365,660和960cm〜（α1）的带，具有合理的强度，可用于定量地确定这两种构象形式。包括CO组转向螺旋轴的运动的365cm〜（α1）模式用于监测异构化反应PPI？ ppii。在纯丙醇中，发现RP11和KP11主要存在PPI，但P11R和P11K优选PPII。加入20％水后，P11R和P11K中的PPI完全转化为PPII，而在RP11和KP11中留下了一小部分PPI。取代的带正电荷的氨基酸影响了PPI / PPII人口比的平衡。

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