Understanding the role of polymers rich in aspartic acid (Asp) and glutamic acid (Glu) is the key to gaining precise control over mineralization processes. Despite their chemical similarity, experiments revealed a surprisingly different influence of Asp and Glu sequences. We conducted molecular dynamics simulations of Asp and Glu peptides in the presence of calcium and chloride ions to elucidate the underlying phenomena. In line with experimental differences, in our simulations, we indeed find strong differences in the way the peptides interact with ions in solution. The investigated Asp pentapeptide tends to pull a lot of ions into its vicinity, and many structures with clusters of calcium and chloride ions on the surface of the peptide can be observed. Under the same conditions, comparatively fewer ions can be found in proximity of the investigated Glu pentapeptide, and the structures are characterized by single calcium ions bound to multiple carboxylate groups. Based on our simulation data, we identified three reasons contributing to these differences, leading to a new level of understanding additive–ion interactions.

中文翻译：

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天冬氨酸和谷氨酸序列对矿化具有惊人不同影响的三个原因

了解富含天冬氨酸 (Asp) 和谷氨酸 (Glu) 的聚合物的作用是精确控制矿化过程的关键。尽管它们的化学相似性，实验揭示了 Asp 和 Glu 序列的惊人不同的影响。我们在钙离子和氯离子存在下对 Asp 和 Glu 肽进行了分子动力学模拟，以阐明潜在的现象。与实验差异一致，在我们的模拟中，我们确实发现肽与溶液中离子相互作用的方式存在很大差异。所研究的 Asp 五肽倾向于将大量离子吸引到其附近，并且可以观察到许多在肽表面具有钙离子和氯离子簇的结构。在同等条件下，在所研究的 Glu 五肽附近可以发现相对较少的离子，并且该结构的特征在于单个钙离子与多个羧酸根基团结合。根据我们的模拟数据，我们确定了导致这些差异的三个原因，从而对加性离子相互作用的理解达到了一个新的水平。