Determining the particle size and number of lipoprotein components found in blood plasma (HDL, LDL and VLDL) has become an important clinical tool in diagnosing risk of cardiovascular disease. Proton (1H) NMR spectroscopy methods to quantify lipoprotein particle subclasses have been advancing since NMR lineshape analysis of plasma samples was first proposed in the 1990's. NMR methods, including a more recent DOSY-based diffusion spectroscopy test, provide the foundation for the advanced lipoprotein tests, including Lipoprotein® and Liposcale® analyses available for clinical use to determine particle size and number. At the time of this submission, no NMR studies exist which explore physical parameters of individual lipoprotein fractions when they are deformed by pressure. This study reports 1H NMR frequency shifts and T2* measurements for the broad methyl peak attributed to terminal methyls (cholesteryl positions 26, 27 and terminal acyl methyl groups) in three primary lipoprotein fractions as a function of hydraulic pressure. This terminal CH3 resonance shifted linearly upfield as a function of pressure for HDL and VLDL (observed slopes of -0.014 Hz/bar). The LDL terminal CH3 resonance shows segmented behavior, with a shallow slope between 0-900 bar (-0.008 hz/bar) and a slope similar to HDL and VDL across the range from 1000 to 2400 bar (slope -0.016 Hz/bar). 1H T2* values measured for VLDL and HDL dropped linearly with increasing pressure. 1H T2* values for LDL demonstrated segmented behavior as a function of pressure. The unique behavior observed for LDL terminal CH3 frequency and 1H T2* trends suggests an approximate pressure at which phase transition occurs.

中文翻译：

---

挤压脂质：压力下脂蛋白颗粒的核磁共振表征。

测定血浆中脂蛋白成分（HDL、LDL 和 VLDL）的粒径和数量已成为诊断心血管疾病风险的重要临床工具。自 20 世纪 90 年代首次提出对血浆样品进行 NMR 线形分析以来，用于量化脂蛋白颗粒亚类的质子 (1H) NMR 波谱方法一直在不断进步。NMR 方法，包括最近基于 DOSY 的扩散光谱测试，为先进的脂蛋白测试提供了基础，包括可用于临床确定颗粒大小和数量的 Lipo Protein® 和 Liposcale® 分析。在提交本文时，尚无 NMR 研究探索单个脂蛋白组分因压力变形时的物理参数。本研究报告了三种初级脂蛋白组分中由末端甲基（胆固醇位置 26、27 和末端酰基甲基）引起的宽甲基峰的 1H NMR 频移和 T2* 测量值，作为液压的函数。该末端 CH3 共振作为 HDL 和 VLDL 压力的函数线性向上场移动（观察到的斜率为 -0.014 Hz/bar）。LDL 末端 CH3 共振显示分段行为，在 0-900 bar (-0.008 Hz/bar) 之间具有浅斜率，在 1000 至 2400 bar 范围内具有与 HDL 和 VDL 类似的斜率（斜率 -0.016 Hz/bar）。VLDL 和 HDL 的 1H T2* 测量值随着压力的增加而线性下降。LDL 的 1H T2* 值显示了作为压力函数的分段行为。观察到的 LDL 末端 CH3 频率和 1H T2* 趋势的独特行为表明发生相变的大致压力。