Yun Yongju, Gellman Andrew J
Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Langmuir. 2015 Jun 9;31(22):6055-63. doi: 10.1021/acs.langmuir.5b00707. Epub 2015 May 22.
Gas-phase equilibrium adsorption of D- and L-serine (Ser) mixtures and D- and L-phenylalanine (Phe) mixtures has been studied on the naturally chiral Cu{3,1,17}(R&S) surfaces. (13)C labeling of the l enantiomers (*L-Ser and *L-Phe) has enabled mass spectrometric enantiodiscrimination of the species desorbing from the surface following equilibrium adsorption. On the Cu{3,1,17}(R&S) surfaces, both equilibrium adsorption and the thermal decomposition kinetics of the D and *L enantiomers exhibit diastereomerism. Following exposure of the surfaces to D/*L mixtures, the relative equilibrium coverages of the two enantiomers are equal to their relative partial pressures in the gas phase, θ(D)/θ(*L) = P(D)/P(*L). This implies that adsorption is not measurably enantiospecific. The decomposition kinetics of Ser are enantiospecific whereas those of Phe are not. Comparison of these results with those for aspartic acid, alanine, and lysine suggests that enantiospecific adsorption on the naturally chiral Cu surfaces occurs for those amino acids that have side chains with functional groups that allow strong interactions with the surface. There is no apparent correlation between amino acids that exhibit enantiospecific adsorption and those that exhibit enantiospecific decomposition kinetics.
已在天然手性的Cu{3,1,17}(R&S)表面上研究了D-和L-丝氨酸（Ser）混合物以及D-和L-苯丙氨酸（Phe）混合物的气相平衡吸附。对l-对映体（L-Ser和L-Phe）进行(13)C标记，使得能够对平衡吸附后从表面解吸的物种进行质谱对映体鉴别。在Cu{3,1,17}(R&S)表面上，D和*L对映体的平衡吸附和热分解动力学均表现出非对映异构现象。在将表面暴露于D/*L混合物之后，两种对映体的相对平衡覆盖率等于它们在气相中的相对分压，即θ(D)/θ(*L)=P(D)/P(*L)。这意味着吸附没有可测量的对映体特异性。Ser的分解动力学是对映体特异性的，而Phe的分解动力学则不是。将这些结果与天冬氨酸、丙氨酸和赖氨酸的结果进行比较表明，对于那些具有能与表面发生强相互作用的官能团侧链的氨基酸，在天然手性的Cu表面上会发生对映体特异性吸附。表现出对映体特异性吸附的氨基酸与表现出对映体特异性分解动力学的氨基酸之间没有明显的相关性。
