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Effect of Like Charges on the Conformation and Internal Dynamics of Polypeptides Probed by Pyrene Excimer Fluorescence
Macromolecules ( IF 5.1 ) Pub Date : 2020-06-29 , DOI: 10.1021/acs.macromol.0c00836 Remi Casier 1 , Jean Duhamel 1
Macromolecules ( IF 5.1 ) Pub Date : 2020-06-29 , DOI: 10.1021/acs.macromol.0c00836 Remi Casier 1 , Jean Duhamel 1
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Three series of pyrene-labeled polypeptides, namely, poly(l-lysine) (Py-PLL), poly(l-glutamic acid) (Py-PLGA), and poly(d,l-glutamic acid) (Py-PDLGA), were studied in dimethyl sulfoxide (DMSO) by monitoring their ability to form an excimer between an excited and a ground-state pyrene. The effect that the charges of protonated Py-PLL (Py-PLL·HCl) and deprotonated Py-PLGA (Py-PLGNa) and Py-PDLGA (Py-PDLGNa) had on their conformation and dynamics was assessed by monitoring their fluorescence. The fluorescence decays were analyzed according to the fluorescence blob model (FBM) to determine Nblob, which is the number of structural units in a blob, and kblob, which is the rate constant for diffusive encounters between structural units and their side chains inside a blob. FBM analysis indicated that the blob size for Py-PLGA and Py-PDLGA was unaffected by the presence of anionic charges, yielding Nblob values of 10.3 ± 1.7 and 18.2 ± 1.1 glutamic acid units, respectively. These Nblob values matched the values found for their uncharged counterparts. Molecular mechanics optimizations (MMOs) were then applied to determine the theoretical Nblobth value that could be obtained if Py-PLGA adopted the conformation of a random coil, a polyproline type II helix, a 310-helix, or an α-helix. The agreement found between the Nblob value of 17.9 ± 1.1 for protonated PLGA and deprotonated PLGNa and the Nblobth of 19 found for 310-helical conformation suggested that this was the conformation adopted by the PLGAs in DMSO. Py-PLL·HCl was studied in a similar manner, yielding an Nblob value of 14.3 ± 1.3 lysines, which suggested a coiled conformation according to MMOs. Comparison of kblob between charged and neutral polypeptides demonstrated that the presence of charges slowed the dynamics experienced by the amino acids. Because the polypeptide blobs appeared to have features in terms of their size and dynamics that were similar to those of foldons, this study further supports the notion that blobs and foldons might be identical objects.
中文翻译：
相似电荷对P准分子荧光探测多肽的构象和内部动力学的影响
series标记的多肽的三个系列，即聚（1-赖氨酸）（Py-PLL），聚（1-谷氨酸）（Py-PLGA）和聚（d，1-谷氨酸）（Py-PDLGA）通过监测二甲亚砜在激发态和基态pyr之间形成准分子的能力，对二甲基亚砜（DMSO）进行了研究。通过监测其荧光来评估质子化的Py-PLL（Py-PLL·HCl）和去质子化的Py-PLGA（Py-PLGNa）和Py-PDLGA（Py-PDLGNa）的电荷对其构象和动力学的影响。根据荧光斑点模型（FBM）分析荧光衰减，以确定N斑点（即斑点中的结构单元数）和k斑点，这是斑点内结构单元与其侧链之间发生扩散接触的速率常数。FBM分析表明，Py-PLGA和Py-PDLGA的斑点大小不受阴离子电荷的影响，产生的N斑点值分别为10.3±1.7和18.2±1.1谷氨酸单位。这N个Blob值与为其未充电的对应值找到的值匹配。然后应用分子力学优化（MMO）确定如果Py-PLGA采用无规卷曲，II型多脯氨酸螺旋，3 10螺旋或α螺旋的构象可获得的理论N blob th值。。N之间达成的协议质子化PLGA和去质子化PLGNa的blob值为17.9±1.1，对于3 10螺旋构象发现的N blob th为19，表明这是PLGA在DMSO中采用的构象。以类似的方式研究了Py-PLL·HCl，得到的N斑点值为14.3±1.3赖氨酸，这提示根据MMO呈螺旋状构象。k blob的比较带电和中性多肽之间的相互作用证明了电荷的存在减慢了氨基酸所经历的动力学。因为多肽斑点在大小和动力学方面似乎具有类似于折叠子的特征，所以这项研究进一步支持了斑点和折叠子可能是同一对象的观点。
更新日期：2020-07-14
中文翻译：
相似电荷对P准分子荧光探测多肽的构象和内部动力学的影响
series标记的多肽的三个系列，即聚（1-赖氨酸）（Py-PLL），聚（1-谷氨酸）（Py-PLGA）和聚（d，1-谷氨酸）（Py-PDLGA）通过监测二甲亚砜在激发态和基态pyr之间形成准分子的能力，对二甲基亚砜（DMSO）进行了研究。通过监测其荧光来评估质子化的Py-PLL（Py-PLL·HCl）和去质子化的Py-PLGA（Py-PLGNa）和Py-PDLGA（Py-PDLGNa）的电荷对其构象和动力学的影响。根据荧光斑点模型（FBM）分析荧光衰减，以确定N斑点（即斑点中的结构单元数）和k斑点，这是斑点内结构单元与其侧链之间发生扩散接触的速率常数。FBM分析表明，Py-PLGA和Py-PDLGA的斑点大小不受阴离子电荷的影响，产生的N斑点值分别为10.3±1.7和18.2±1.1谷氨酸单位。这N个Blob值与为其未充电的对应值找到的值匹配。然后应用分子力学优化（MMO）确定如果Py-PLGA采用无规卷曲，II型多脯氨酸螺旋，3 10螺旋或α螺旋的构象可获得的理论N blob th值。。N之间达成的协议质子化PLGA和去质子化PLGNa的blob值为17.9±1.1，对于3 10螺旋构象发现的N blob th为19，表明这是PLGA在DMSO中采用的构象。以类似的方式研究了Py-PLL·HCl，得到的N斑点值为14.3±1.3赖氨酸，这提示根据MMO呈螺旋状构象。k blob的比较带电和中性多肽之间的相互作用证明了电荷的存在减慢了氨基酸所经历的动力学。因为多肽斑点在大小和动力学方面似乎具有类似于折叠子的特征，所以这项研究进一步支持了斑点和折叠子可能是同一对象的观点。
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