NMR-based quantification of human lipoprotein (sub)classes is a powerful high-throughput method for medical diagnostics. We evaluated select proton NMR signals of serum lipoproteins for elucidating the physicochemical features and the absolute NMR visibility of their lipids. We separated human lipoproteins of different subclasses by ultracentrifugation and analyzed them by ¹H NMR spectroscopy at different temperatures (283-323 K) and pressures (0.1-200 MPa). In parallel, we determined the total lipid content by extraction with chloroform/methanol. The visibility of different lipids in the ¹H NMR spectra strongly depends on temperature and pressure: it increases with increasing temperatures but decreases with increasing pressures. Even at 313 K, only part of the lipoprotein is detected quantitatively. In LDL and in HDL subclasses HDL2 and HDL3, only 39%, 62%, and 90% of the total cholesterol and only 73%, 70%, and 87% of the FAs are detected, respectively. The choline head groups show visibilities of 43%, 75%, and 87% for LDL, HDL2, and HDL3, respectively. The description of the NMR visibility of lipid signals requires a minimum model of three different compartments, A, B, and C. The thermodynamic analysis of compartment B leads to melting temperatures between 282 K and 308 K and to enthalpy differences that vary for the different lipoproteins as well as for the reporter groups selected. In summary, we describe differences in NMR visibility of lipoproteins and variations in biophysical responses of functional groups that are crucial for the accuracy of absolute NMR quantification.

中文翻译：

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1H NMR 光谱可量化不同温度和压力下脂蛋白、亚类和脂质的可见性。

基于 NMR 的人类脂蛋白（亚）类定量是一种强大的高通量医学诊断方法。我们评估了血清脂蛋白的精选质子 NMR 信号，以阐明其脂质的理化特征和绝对 NMR 可见性。^{我们通过超速离心分离不同亚类的人类脂蛋白，并在不同温度（283-323 K）和压力（0.1-200 MPa）下通过1} H NMR 光谱对其进行分析。同时，我们通过氯仿/甲醇提取测定了总脂质含量。¹ H NMR 光谱中不同脂质的可见度很大程度上取决于温度和压力：它随着温度的升高而增加，但随着压力的增加而降低。即使在 313 K 下，也只能定量检测到部分脂蛋白。在 LDL 和 HDL 亚类 HDL2 和 HDL3 中，分别仅检测到总胆固醇的 39%、62% 和 90%，以及仅检测到 73%、70% 和 87% 的 FA。胆碱头组的 LDL、HDL2 和 HDL3 可见度分别为 43%、75% 和 87%。脂质信号 NMR 可见性的描述需要三个不同区室 A、B 和 C 的最小模型。区室 B 的热力学分析导致​​熔化温度在 282 K 到 308 K 之间，并导致不同程度的焓差。脂蛋白以及所选报告基团。总之，我们描述了脂蛋白 NMR 可视性的差异和功能组生物物理响应的变化，这对于绝对 NMR 定量的准确性至关重要。