Avilés-Moreno Juan Ramón, Berden Giel, Oomens Jos, Martínez-Haya Bruno
Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, E-41013 Seville, Spain.
Phys Chem Chem Phys. 2018 Feb 7;20(6):4067-4073. doi: 10.1039/c7cp07975c.
The recognition of arginine plays a central role in modern proteomics and genomics. Arginine is unique among natural amino acids due to the high basicity of its guanidinium side chain, which sustains specific interactions and proton exchange biochemical processes. The search for suitable macrocyclic ionophores constitutes a promising route towards the development of arginine receptors. This study evaluates the conformational features involved in the binding of free arginine by the polyether macrocycle (18-crown-6)-tetracarboxylic acid. Infrared action vibrational spectroscopy and quantum-chemical computations are combined to characterize the complexes with net charges +1 and +2. The spectrum of the +1 complex can be explained in terms of a configuration predominantly stabilized by a robust bidentate coordination of guanidinium with a carboxylate group formed from the deprotonation of one side group of the crown ether. The released proton is transferred to the amino terminus of arginine, which then coordinates with the crown ether ring. In an alternative type of conformation, partly consistent with experiment, the amino terminus is neutral and the guanidinium group inserts into the crown ether cavity. In the +2 complexes, arginine is always doubly protonated and the most stable conformations are characterized by a tripodal coordination of the ammonium -NH group of arginine with the oxygen atoms of the macrocycle ring, while the interactions of the amino acid with the side carboxylic acid groups of the crown ether acquire a remarkable lesser role.
精氨酸的识别在现代蛋白质组学和基因组学中起着核心作用。精氨酸在天然氨基酸中独一无二，因其胍基侧链具有高碱性，可维持特定的相互作用和质子交换生化过程。寻找合适的大环离子载体是开发精氨酸受体的一条有前景的途径。本研究评估了聚醚大环（18-冠-6）-四羧酸与游离精氨酸结合时涉及的构象特征。结合红外作用振动光谱和量子化学计算来表征净电荷为 +1 和 +2 的配合物。+1 配合物的光谱可以用一种构型来解释，该构型主要通过胍基与由冠醚一个侧基去质子化形成的羧酸根基团的强双齿配位而稳定。释放的质子转移到精氨酸的氨基末端，然后该末端与冠醚环配位。在另一种构象类型中，部分与实验一致，氨基末端呈中性，胍基插入冠醚腔中。在 +2 配合物中，精氨酸总是双质子化的，最稳定的构象特征是精氨酸的铵 -NH 基团与大环环的氧原子形成三脚架式配位，而氨基酸与冠醚侧羧酸基团的相互作用作用显著较小。
