El Samrout Ola, Mezzetti Alberto, Berlier Gloria, Lambert Jean-François
Department of Chemistry, University of Torino, Via P. Giuria 7, 10125, Torino, Italy.
Laboratoire de Réactivité de Surface, LRS, Sorbonne Université, Place Jussieu, 75005, Paris, France.
Chemistry. 2023 Apr 18;29(22):e202204010. doi: 10.1002/chem.202204010. Epub 2023 Mar 13.
The parameters that determine the formation of linear peptides and cyclic dimers (diketopiperazine, DKP) on silica surfaces of different surface area, silanol and siloxane ring populations, controlled by thermal treatments, are investigated upon glycine deposition from gas and liquid phases. The formed products were characterized by infrared and Raman spectroscopies, X-ray diffraction and thermogravimetric analysis. The results reveal the importance of "nearly-free" silanols to form ester centers as primers for the formation of linear peptides over DKP, on surfaces with medium silanol density (1.4 to 2.7 nm ). Quenched reactivity is seen on isolated silanols (density≤0.7 nm ), while silanols involved in hydrogen bonding (density of 4.5 nm ) weakly interact with Gly resulting in its cyclization to DKP. Deposition of glycine from liquid phase may also form both DKP and linear polymers, depending on its loading and silica surface. These conclusions demonstrate the complexity of glycine surface chemistry in the polymerization reaction and highlight the interest of a surface science approach to evaluate geochemical prebiotic scenarios.
通过气相和液相甘氨酸沉积，研究了在不同表面积、硅醇和硅氧烷环数量的二氧化硅表面上，由热处理控制的线性肽和环状二聚体（二酮哌嗪，DKP）形成的参数。通过红外光谱和拉曼光谱、X射线衍射和热重分析对形成的产物进行了表征。结果表明，在中等硅醇密度（1.4至2.7 nm）的表面上，“近游离”硅醇对于形成酯中心作为线性肽形成的引物而非DKP的形成非常重要。在孤立的硅醇（密度≤0.7 nm）上观察到淬灭反应性，而参与氢键形成的硅醇（密度为4.5 nm）与甘氨酸弱相互作用，导致其环化形成DKP。根据甘氨酸的负载量和二氧化硅表面，从液相沉积甘氨酸也可能形成DKP和线性聚合物。这些结论证明了甘氨酸在聚合反应中表面化学的复杂性，并突出了表面科学方法在评估地球化学前生物情景方面的意义。
