Stepišnik Janez
Faculty of Mathematics and Physics, University of Ljubljana, 1000 Ljubljana, Slovenia.
Molecules. 2023 Jul 19;28(14):5506. doi: 10.3390/molecules28145506.
Velocity correlation spectra (VAS) in binary mixtures of water and glycerol (G/W), obtained by measurements using the modulated gradient spin echo (MGSE) NMR method, were explained by the interactions of water molecules with clusters formed around the hydrophilic glycerol molecule, which drastically change the molecular dynamics and rheology of the mixture. It indicates a thickening of the shear viscosity, which could affect the dynamics of submerged macromolecules. The calculation of the polymer dynamics with the Langevin equations according to the Rouse model, where the friction was replaced by the memory function of the retarded friction, gave the dependence of the dynamics of the polymer on the rate of shear viscous properties of the solvent. The obtained formula was used to calculate the segmental VAS of the polymer when immersed in pure water and in a G/W mixture with 33 vol% glycerol content, taking into account the inverse proportionality between the solvent VAS and friction. The spectrum shows that in the G/W mixture, the fast movements of the polymer segments are strongly inhibited, which creates the conditions for slow processes caused by the internal interaction between the polymer segments, such as interactions that cause disordered polypeptides to spontaneously fold into biologically active protein molecules when immersed in such a solvent.
通过使用调制梯度自旋回波（MGSE）核磁共振方法测量得到的水和甘油二元混合物（G/W）中的速度相关谱（VAS），可以用水分子与亲水性甘油分子周围形成的簇之间的相互作用来解释，这种相互作用极大地改变了混合物的分子动力学和流变学。这表明剪切粘度增加，这可能会影响浸没大分子的动力学。根据劳斯模型，用朗之万方程计算聚合物动力学，其中摩擦力被延迟摩擦力的记忆函数所取代，得到了聚合物动力学对溶剂剪切粘性特性速率的依赖性。考虑到溶剂VAS与摩擦力之间的反比例关系，所得到的公式用于计算聚合物浸没在纯水和甘油含量为33体积%的G/W混合物中的链段VAS。光谱表明，在G/W混合物中，聚合物链段的快速运动受到强烈抑制，这为聚合物链段之间的内部相互作用引起的缓慢过程创造了条件，例如当浸没在这种溶剂中时，导致无序多肽自发折叠成生物活性蛋白质分子的相互作用。
