Yuan Weize, Casier Remi, Duhamel Jean
Institute for Polymer Research, Waterloo Institute of Nanotechnology, Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Polymers (Basel). 2021 May 22;13(11):1690. doi: 10.3390/polym13111690.
The denaturation undergone by α-helical poly(-glutamic acid) (PGA) in ,-dimethylformamide upon addition of guanidine hydrochloride (GdHCl) was characterized by comparing the fluorescence of a series of PGA constructs randomly labeled with the dye pyrene (Py-PGA) to that of a series of Py-PGA samples prepared from a racemic mixture of ,-glutamic acid. The process of pyrene excimer formation (PEF) was taken advantage of to probe changes in the conformation of α-helical Py-PGA. Fluorescence Blob Model (FBM) analysis of the fluorescence decays of the Py-PGA and Py-PGA constructs yielded the average number (<>) of glutamic acids located inside a , which represented the volume probed by an excited pyrenyl label. <> remained constant for randomly coiled Py-PGA but decreased from ~20 to ~10 glutamic acids for the Py-PGA samples as GdHCl was added to the solution. The decrease in <> reflected the decrease in the local density of PGA as the α-helix unraveled in solution. The changes in <> with GdHCl concentration was used to determine the change in Gibbs energy required to denature the PGA α-helix in DMF. The relationship between <> and the local density of macromolecules can now be applied to characterize the conformation of macromolecules in solution.
通过比较一系列用芘（Py-PGA）随机标记的聚谷氨酸（PGA）构建体与由谷氨酸外消旋混合物制备的一系列Py-PGA样品的荧光，对α-螺旋聚（谷氨酸）（PGA）在加入盐酸胍（GdHCl）时在N，N-二甲基甲酰胺中发生的变性进行了表征。利用芘激基缔合物形成（PEF）过程来探测α-螺旋Py-PGA构象的变化。对Py-PGA和Py-PGA构建体的荧光衰减进行荧光斑点模型（FBM）分析，得到位于一个“blob”内的谷氨酸平均数量（<>），该“blob”代表一个被激发的芘标记探测的体积。对于无规卷曲的Py-PGA，<>保持恒定，但随着向溶液中加入GdHCl，Py-PGA样品的<>从约20个谷氨酸减少到约10个谷氨酸。<>的减少反映了随着α-螺旋在溶液中解开，PGA局部密度的降低。利用<>随GdHCl浓度的变化来确定使DMF中的PGAα-螺旋变性所需的吉布斯自由能变化。现在，<>与大分子局部密度之间的关系可用于表征溶液中大分子的构象。
