Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA.
Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Geongbyuk, 37673, Republic of Korea.
Chemphyschem. 2021 Jan 18;22(2):197-203. doi: 10.1002/cphc.202000881. Epub 2020 Dec 18.
Mechanisms for the spontaneous transformation of achiral chemical systems into states of enantiomeric purity have important ramifications in modern pharmacology and potential relevance to the origins of homochirality in life on Earth. Such mechanisms for enantiopurification are needed for production of chiral pharmaceuticals and other bioactive compounds. Previously proposed chemical mechanisms leading from achiral systems to near homochirality are initiated by a symmetry-breaking step resulting in a minor excess of one enantiomer via statistical fluctuations in enantiomer concentrations. Subsequent irreversible processes then amplify the majority enantiomer concentration while simultaneously suppressing minority enantiomer production. Herein, equilibrium adsorption of amino acid enantiomer mixtures onto chiral and achiral surfaces reveals amplification of surface enantiomeric excess relative to the gas phase; i. e. enantiopurification of chiral adsorbates by adsorption. This adsorption-induced amplification of enantiomeric excess is shown to be well-describe by the 2D Ising model. More importantly, the 2D-Ising model predicts formation of homochiral monolayers from adsorption of racemic mixtures or prochiral molecules on achiral surfaces; i. e. enantiopurification with no apparent chiral driving force.
手性化学体系自发转化为对映体纯态的机制在现代药理学中具有重要意义，并且可能与地球上生命起源的手性有关。手性药物和其他生物活性化合物的生产需要对映体纯化的这种机制。以前提出的从非手性体系到近手性的化学机制是通过对称破缺步骤引发的，该步骤导致通过对映体浓度的统计波动以少量过量的一种对映体。随后的不可逆过程然后放大主要对映体浓度，同时抑制少数对映体的产生。本文通过将氨基酸对映体混合物平衡吸附到手性和非手性表面上，揭示了相对于气相，表面对映体过量的放大；即手性吸附剂通过吸附进行对映体纯化。实验表明，二维伊辛模型很好地描述了这种对映体过量的放大。更重要的是，二维伊辛模型预测从外消旋混合物或前手性分子在非手性表面上的吸附形成同手性单层；即没有明显手性驱动力的对映体纯化。
