Bruzzi E, Stace A J
Department of Physical and Theoretical Chemistry, School of Chemistry , University of Nottingham , University Park, Nottingham NG7 2RD , UK.
R Soc Open Sci. 2017 Jan 4;4(1):160671. doi: 10.1098/rsos.160671. eCollection 2017 Jan.
Further understanding of the biological role of the Ca ion in an aqueous environment requires quantitative measurements of both the short- and long-range interactions experienced by the ion in an aqueous medium. Here, we present experimental measurements of binding energies for water molecules occupying the second and, quite possibly, the third solvation shell surrounding a central Ca ion in [Ca(HO) ] complexes. Results for these large, previously inaccessible, complexes have come from the application of finite heat bath theory to kinetic energy measurements following unimolecular decay. Even at = 20, the results show water molecules to be more strongly bound to Ca than would be expected just from the presence of an extended network of hydrogen bonds. For > 10, there is very good agreement between the experimental binding energies and recently published density functional theory calculations. Comparisons are made with similar data recorded for [Ca(NH) ] and [Ca(CHOH) ] complexes.
要进一步了解钙离子在水性环境中的生物学作用，需要对该离子在水性介质中经历的短程和长程相互作用进行定量测量。在此，我们给出了在[Ca(HO) ]配合物中，围绕中心钙离子的第二溶剂化层（很可能还有第三溶剂化层）中水分子结合能的实验测量结果。这些大型的、以前无法获得的配合物的结果来自于有限热浴理论在单分子衰变后动能测量中的应用。即使在 = 20时，结果也表明水分子与钙的结合比仅由氢键扩展网络的存在所预期的更强。对于 > 10，实验结合能与最近发表的密度泛函理论计算结果非常吻合。还与[Ca(NH) ]和[Ca(CHOH) ]配合物记录的类似数据进行了比较。
