Westberry Benjamin P, Mansel Bradley W, Lundin Leif, Williams M A K
School of Natural Sciences, Massey University, Palmerston North, New Zealand; MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand.
National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu, 30076, Taiwan, ROC.
Carbohydr Polym. 2023 Feb 15;302:120417. doi: 10.1016/j.carbpol.2022.120417. Epub 2022 Dec 5.
Recent molecular dynamics simulations, verified experimentally by solution-state x-ray scattering experiments, have found that κ-carrageenan chains contain helical secondary structure, akin to that found in the solid-state, even in aqueous solution. Furthermore, upon the addition of ions to single chains the simulations found no evidence that any conformational transitions take place. These findings challenge the long-held assumption that the so-called disorder-to-order transition in carrageenan systems involves a uni-molecular 'coil-to-helix transition'. Herein, the results of further molecular dynamics simulations undertaken using pairs of κ-carrageenan chains in 0.1 M NaI solutions are reported, and are validated experimentally using state-of-the-art solution-state WAXS experiments. From initially separated chains double-helices are shown to form, leading the authors to propose 'two single helices-to-stabilized double-helix' as a description of the molecular events taking place during the disorder-to-order transition.
最近的分子动力学模拟通过溶液态X射线散射实验得到了实验验证，结果发现，即使在水溶液中，κ-卡拉胶链也含有螺旋二级结构，这与固态中的情况类似。此外，在单链中添加离子后，模拟结果未发现任何构象转变发生的证据。这些发现挑战了长期以来的一种假设，即卡拉胶体系中所谓的无序到有序转变涉及单分子的“线圈到螺旋转变”。本文报道了在0.1M NaI溶液中使用成对的κ-卡拉胶链进行的进一步分子动力学模拟结果，并通过最先进的溶液态广角X射线散射实验进行了实验验证。结果表明，从最初分离的链开始会形成双螺旋结构，这使得作者提出用“两个单螺旋到稳定双螺旋”来描述无序到有序转变过程中发生的分子事件。
