A.M. Butlerov Institute of Chemistry, Kazan Federal University , Kremlevskaya ul. 18, Kazan, 420008 Russia.
Kazan Zavoisky Physical-Technical Institute, Kazan Scientific Center, Russian Academy of Sciences , Sibirskii trakt 10/7, Kazan, 420029 Russia.
J Phys Chem B. 2017 Sep 14;121(36):8603-8610. doi: 10.1021/acs.jpcb.7b06759. Epub 2017 Aug 30.
Thermal treatment of oligopeptides is one of the methods for synthesis of organic nanostructures. However, heating may lead not only to self-assembly of the initial molecules, but also to chemical reactions resulting in the formation of new unexpected nanostructures or change in the properties of the existing ones. In the present work, the reaction of cyclization of dipeptide l-leucyl-l-leucine in solid state under heating was studied. The change in morphology of dipeptide thin film and formation of nanostructures after heating was visualized using atomic force microscopy. This method also was used for demonstration of differences in self-assembly of linear and cyclic dipeptides. The chemical structure of reaction product was characterized by NMR spectrometry, FTIR spectroscopy and GC-MS analysis. Kinetic parameters of cyclization were estimated within the approaches of the nonisothermal kinetics ("model-free" kinetics and linear regression methods for detection of topochemical equation). The results of present work are useful for explanation the changes in the properties of nanostructures based on short-chain oligopeptides, notably leucyl-leucine, after thermal treatment, as well as for the synthesis of cyclic oligopeptides.
寡肽的热处理是合成有机纳米结构的方法之一。然而，加热不仅可能导致初始分子的自组装，还可能导致化学反应，从而形成新的意想不到的纳米结构或改变现有纳米结构的性质。在本工作中，研究了在加热条件下二肽 l-亮氨酰-l-亮氨酸在固态中的环化反应。使用原子力显微镜可视化了加热后二肽薄膜的形态变化和纳米结构的形成。该方法还用于演示线性和环状二肽自组装的差异。通过 NMR 光谱、FTIR 光谱和 GC-MS 分析对反应产物的化学结构进行了表征。通过非等温热力学方法（“无模型”动力学和用于检测拓扑化学反应方程的线性回归方法）估算了环化的动力学参数。本工作的结果有助于解释基于短链寡肽（尤其是亮氨酰-亮氨酸）的纳米结构在热处理后的性质变化，以及环状寡肽的合成。
