Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO 80309, USA.
Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15697-701. doi: 10.1073/pnas.1210029109. Epub 2012 Aug 27.
We report unambiguous spectroscopic evidence of peptide bond formation at the air-water interface, yielding a possible mechanism providing insight into the formation of modern ribosomal peptide bonds, and a means for the emergence of peptides on early Earth. Protein synthesis in aqueous environments, facilitated by sequential amino acid condensation forming peptides, is a ubiquitous process in modern biology, and a fundamental reaction necessary in prebiotic chemistry. Such reactions, however, are condensation reactions, requiring the elimination of a water molecule for every peptide bond formed, and are thus unfavorable in aqueous environments both from a thermodynamic and kinetic point of view. We use the hydrophobic environment of the air-water interface as a favorable venue for peptide bond synthesis, and demonstrate the occurrence of this chemistry with in situ techniques using Langmuir-trough methods and infrared reflection absorption spectroscopy. Leucine ethyl ester (a small amino acid ester) first partitions to the water surface, then coordinates with Cu(2+) ions at the interface, and subsequently undergoes a condensation reaction selectively forming peptide bonds at the air-water interface.
我们报告了在气-水界面形成肽键的明确光谱证据，这为现代核糖体肽键的形成提供了一个可能的机制，并为早期地球上肽的出现提供了一种方法。在水相环境中，通过氨基酸的顺序缩合形成肽来促进蛋白质合成，这是现代生物学中普遍存在的过程，也是前生物化学中必要的基本反应。然而，这些反应是缩合反应，每形成一个肽键就需要消除一个水分子，因此从热力学和动力学的角度来看，在水相环境中是不利的。我们利用气-水界面的疏水环境作为合成肽键的有利场所，并使用朗缪尔槽法和红外反射吸收光谱等原位技术证明了这种化学物质的存在。亮氨酸乙酯（一种小的氨基酸酯）首先分配到水表面，然后在界面处与 Cu(2+) 离子配位，随后选择性地在气-水界面处进行缩合反应形成肽键。
