Sawato Tsukasa, Yuzawa Ryosuke, Kobayashi Higashi, Saito Nozomi, Yamaguchi Masahiko
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University Aoba Sendai 980-8578 Japan
RSC Adv. 2019 Sep 18;9(50):29456-29462. doi: 10.1039/c9ra06073a. eCollection 2019 Sep 13.
A 1 : 1 mixture of the ethynylhelicene pseudoenantiomers ()-tetramer and ()-pentamer, which possess hydrophilic terminal tri(ethyleneglycol) (TEG) groups, changes their structures in the water-THF (10 μM) solvent system between dissociated random-coils and an associated hetero-double-helix upon heating and cooling. A small change in water content between 30 and 33% significantly affects the dynamics of structural changes. At 30% water content, heating to 60 °C causes rapid formation of random-coil and cooling to 10 °C causes the rapid formation of hetero-double-helix, accompanied by repeated changes in Δ at 369 nm between 0 and -2000 cm M. Heating and cooling experiments at constant rates between 60 and 10 °C resulted in sigmoidal curves in Δ/temperature profiles, which indicate rapid structural changes. Different phenomena occurred at 33% water content. Heating to 60 °C and cooling to 0 °C initially induced changes in Δ between 0 and -2000 cm M, and repeated cycles gradually reduced the range between 0 and -500 cm M. Heating and cooling experiments at constant rates between 60 and 10 °C caused small changes in Δ, and repeated cycles at 10 °C gradually increased Δ to -500 cm M. These phenomena involved rapid changes in molecular structure and slow structural changes in the water-THF solvent system. The sharp switching of the dynamics of structural changes at water content between 30 and 33% indicated discontinuous structural changes in the hydration of TEG and/or in water clusters in the vicinity of oligomer molecules.
乙炔基螺旋烯假对映体（）-四聚体和（）-五聚体的1:1混合物含有亲水性末端三（乙二醇）（TEG）基团，在水-四氢呋喃（10μM）溶剂体系中，加热和冷却时，其结构会在解离的无规卷曲和相关的杂双螺旋之间发生变化。含水量在30%至33%之间的微小变化会显著影响结构变化的动力学。在含水量为30%时，加热至60°C会导致无规卷曲迅速形成，冷却至10°C会导致杂双螺旋迅速形成，同时在369nm处的Δ在0至-2000cm M之间反复变化。在60°C至10°C之间以恒定速率进行的加热和冷却实验在Δ/温度曲线上产生了S形曲线，这表明结构发生了快速变化。在含水量为33%时出现了不同的现象。加热至60°C并冷却至0°C最初会引起Δ在0至-2000cm M之间的变化，重复循环会逐渐减小0至-500cm M之间的范围。在60°C至10°C之间以恒定速率进行的加热和冷却实验导致Δ变化较小，在10°C下重复循环会逐渐将Δ增加至-500cm M。这些现象涉及分子结构的快速变化以及水-四氢呋喃溶剂体系中的缓慢结构变化。含水量在30%至33%之间时结构变化动力学的急剧转变表明TEG水合和/或低聚物分子附近水簇中的结构变化是不连续的。
