Lu Jiaqi, Straub Joshua S, Nowotarski Mesopotamia S, Han Songi, Xu Xiang, Jerschow Alexej
Department of Chemistry, New York University, New York, USA.
Department of Physics, University of California, Santa Barbara, California, USA.
NMR Biomed. 2024 Feb;37(2):e5057. doi: 10.1002/nbm.5057. Epub 2023 Oct 18.
Phosphate is an essential anion in the human body, comprising approximately 1% of the total body weight, and playing a vital role in metabolism, cell membranes, and bone formation. We have recently provided spectroscopic, microscopic, and computational evidence indicating that phosphates can aggregate much more readily in solution than previously thought. This prior work provided indirect evidence through the observation of unusual P NMR relaxation and line-broadening effects with increasing temperature. Here, we show that, under conditions of slow exchange and selective RF saturation, additional features become visible in chemical exchange saturation transfer (CEST) experiments, which appear to be related to the previously reported phosphate clustering. In particular, CEST shows pronounced dips several ppm upfield of the main phosphate resonance at low temperatures, while direct P spectroscopy does not produce any signals in that range. We study the pH dependence of these new spectroscopic features and present exchange and spectroscopic parameters based on fitting the CEST data. These findings could be of importance in the investigation of phosphate dynamics, especially in the biological milieu.
磷酸盐是人体中一种重要的阴离子，约占总体重的1%，在新陈代谢、细胞膜和骨骼形成中起着至关重要的作用。我们最近提供了光谱、显微镜和计算证据，表明磷酸盐在溶液中比以前认为的更容易聚集。这项先前的工作通过观察随着温度升高异常的磷核磁共振弛豫和谱线展宽效应提供了间接证据。在这里，我们表明，在慢交换和选择性射频饱和条件下，化学交换饱和转移（CEST）实验中会出现其他特征，这些特征似乎与先前报道的磷酸盐聚集有关。特别是，CEST在低温下主磷酸盐共振峰上方几ppm处显示出明显的凹陷，而直接磷光谱在该范围内不产生任何信号。我们研究了这些新光谱特征对pH值的依赖性，并基于对CEST数据的拟合给出了交换和光谱参数。这些发现可能对研究磷酸盐动力学很重要，尤其是在生物环境中。
