Revisiting Secondary Structures in NCA Polymerization: Influences on the Analysis of Protected Polylysines
Revisiting Secondary Structures in NCA Polymerization: Influences on the Analysis of Protected Polylysines
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DOI：
10.1021/ma5000392
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发表时间：
2014-02-11
期刊：
影响因子：
5.5
通讯作者：
Barz, Matthias
中科院分区：
文献类型：
--
作者：
Huesmann, David;Birke, Alexander;Barz, Matthias
合成了两个系列（聚合度：20-200）具有Z和TFA保护基团的聚赖氨酸，并研究了它们在一系列分析方法中的行为。较小多肽的凝胶渗透色谱显示双峰分布，这在较大的聚合物中丢失。通过GPC、NMR、圆二色性（CD）和MALDI-TOF的分析，证明了双峰分布不是末端链或其他副反应引起的。我们的研究结果表明，双峰性是由生长肽链的二级结构的变化引起的，这种变化发生在聚合度约为15的地方。二级结构的这种变化通过产生双峰分布作为伪影，强烈干扰了聚合物GPC最常用的分析方法。在去保护后，发现多肽表现出完全随机的线圈构象，因此获得了单模GPC图谱。这种效应可以用在螺旋转捩处的水动力体积增加1.6倍来解释。这项工作表明，二级结构需要仔细考虑时，执行多肽系统的标准分析。
Two series (degree of polymerization: 20-200) of polylysines with Z and TFA protecting groups were synthesized, and their behavior in a range of analytical methods was investigated. Gel permeation chromatography of the smaller polypeptides reveals a bimodal distribution, which is lost in larger polymers. With the help of GPC, NMR, circular dichroism (CD), and MALDI-TOF, it was demonstrated that the bimodal distribution is not due to terminated chains or other side reactions. Our results indicate that the bimodality is caused by a change in secondary structure of the growing peptide chain that occurs around a degree of polymerization of about 15. This change in, secondary structure interferes strongly with the most used analysis method for polymers GPC by producing a bimodal distribution as an artifact. After deprotection, the polypeptides were found to exhibit exclusively random coil conformation, and thus a monomodal GPC elugram was obtained. The effect can be explained by a 1.6-fold increase in the hydrodynamic volume at the coil helix transition. This work demostrates that secondary structures need to be carefully considered when performing standard analysis on polypeptidic systems.