The amino acid serine has long been known to form a protonated "magic-number" cluster containing eight monomer units that shows an unusually high abundance in mass spectra and has a remarkable homochiral preference. Despite many experimental and theoretical studies, there is no consensus on a Ser8H+ structure that is in agreement with all experimental observations. Here, we present the structure of Ser8H+ determined by a combination of infrared spectroscopy and ab initio molecular dynamics simulations. The three-dimensional structure that we determine is ∼25 kcal mol-1 more stable than the previous most stable published structure and explains both the homochiral preference and the experimentally observed facile replacement of two serine units.

中文翻译：

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质子化丝氨酸八聚体的结构

长期以来，人们都知道氨基酸丝氨酸会形成质子化的“幻数”簇，其中包含八个单体单元，在质谱中显示出异常高的丰度，并具有显着的同手性偏好。尽管进行了许多实验和理论研究，但对于与所有实验观察一致的 Ser8H+ 结构还没有达成共识。在这里，我们展示了结合红外光谱和从头算分子动力学模拟确定的 Ser8H+ 的结构。我们确定的三维结构比之前最稳定的已发表结构稳定约 25 kcal mol-1，并解释了同手性偏好和实验观察到的两个丝氨酸单元的容易替换。