The adsorption and concentration of sugars onto mineral surfaces in geochemical environments, such as hydrothermal systems, may have influenced the evolution of early life on Earth. We conducted batch adsorption experiments between d-Ribose and brucite [Mg(OH)₂], a mineral produced from serpentinite-hosted hydrothermal systems, over variable initial ribose concentrations at four ionic strengths resulting from different Mg²⁺ and Ca²⁺ ion concentrations in the aqueous phase. Ribose adsorption generally increased with greater initial concentration and up to 0.3 μmol·m^–2 ribose attached onto brucite with 0.6 mM Mg²⁺ present. Ribose adsorption decreased over 6-fold (4.9 × 10^–2 μmol·m^–2) when the total Mg²⁺ ion concentration increased to 5.8 mM. Ribose adsorption increased to 0.4 μmol·m^–2 when 4.2 mM CaCl₂ was added to the system. Substantial amounts (over 21 μmol·m^–2) of dissolved Ca also attached to the brucite surface independent of ribose concentration. We characterized the interactions between ribose, Ca, and the brucite surface by fitting a surface complexation model to adsorption data. We propose three types of surface reactions that were consistent with the experimental data and involve (1) a bidentate outer sphere or a “standing” ribose surface species, (2) a monodentate Ca-ribose outer-sphere species, and (3) a monodentate Ca outer-sphere species. Our model predicts brucite particle surface charge is negative at low Mg²⁺ concentrations and further decreases upon the addition of MgCl₂, which may hinder our proposed surface complexation of the ribose species, Rib^–. We predict that brucite becomes positively charged with CaCl₂ addition, which may be a consequence of the significant extent of Ca adsorption. The increase in ribose adsorption with CaCl₂ is likely driven by Ca attachment and the formation of a positively charged, cooperative Ca–ribose species that our model predicts will predominate over the “standing” ribose species on brucite. Our model of the ribose–brucite system, established by a combination of batch adsorption experiments and surface complexation modeling, has enabled predictions of ribose adsorption over a wide range of pH and complex environmental conditions.

中文翻译：

---

d核糖的合作，抑制吸附到水镁石〔Mg的（OH）₂ ]二价阳离子

糖在地球化学环境（例如热液系统）中的矿物表面上的吸附和浓缩可能影响了地球上早期生命的演变。我们在d-核糖和水镁石[Mg（OH）₂ ]（一种由蛇纹石托管的水热系统产生的矿物）之间进行了分批吸附实验，在不同的Mg ²⁺和Ca ²⁺离子浓度产生的四个离子强度下，其初始核糖浓度存在变化在水相中。核糖的吸附通常随着初始浓度的增加而增加，并且在存在0.6 mM Mg ^2+的水镁石上附着至0.3μmol·m ^–2核糖。核糖吸附降低了6倍以上（4.9×10^-2微摩尔·^米-2）当总的Mg ²⁺离子浓度增加至5.8毫米。当向系统中添加4.2 mM CaCl ₂时，核糖吸附增加到0.4μmol·m ^–2。大量（超过21μmol·m ^–2）的溶解钙也附着在水镁石表面，与核糖浓度无关。我们通过将表面络合模型拟合到吸附数据来表征核糖，钙和水镁石表面之间的相互作用。我们提出三种类型的表面反应，这些实验与实验数据一致，涉及（1）双齿外球或“直立”核糖表面物质，（2）单齿Ca-核糖外球物质，以及（3）a单齿钙外球物种。我们的模型预测，在低Mg ²⁺浓度下，水镁石颗粒表面电荷为负，并在加入MgCl ₂时进一步降低，这可能会阻碍我们建议的核糖物种Rib ^–的表面络合。。我们预测，CaCa _2的添加使水镁石带正电，这可能是由于Ca吸附量很大的结果。CaCl ₂吸附核糖的增加可能是由于钙的附着和我们模型预测的带正电荷的协作性核糖核糖物种的形成所驱动，我们的模型预测这些核糖核苷将优于水镁石上的“立式”核糖核素。我们通过分批吸附实验和表面络合建模相结合建立的核糖-微晶石系统模型，可以预测在广泛的pH值和复杂的环境条件下核糖的吸附。