Biomimetic phospholipid mixtures are actively used as models of biological membranes and materials for drug delivery in biomedical tasks. One of the essential properties of membranes formed from complex phospholipid mixtures is the equilibrium coexistence of domains of different phases. Studying the conformational state and chemical content of different phases is of great interest in membrane biophysics. We propose an approach for studying phase coexistence in stacked phospholipid bilayers using Raman mapping. For this purpose, phospholipid multilayer films were formed in which the domains of the same phase were self-aligned in stacks. Raman spectra with a high spectral resolution and signal-to-noise ratio obtained on these samples made it possible to estimate the chemical composition and conformational state of lipids in domains of different phases. For the ternary mixture 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (DPPC-d62)/cholesterol (Chol) used in our demonstration, the phase diagram was studied and the effect of hydration on lipid phase separation was revealed. For the hydrated films, the obtained phase diagram is in qualitative agreement with the previous data obtained using ²H NMR. In dry films, phase separation is observed for all investigated compositions, with a tendency to form a phase with a high fraction of DPPC-d62. The use of multilayer phospholipid films makes it possible to release the potential of Raman microspectroscopy to study the phase diagrams of phospholipid mixtures under various experimental conditions.

中文翻译：

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拉曼映射探测多层磷脂膜中脂质相的共存

仿生磷脂混合物被积极用作生物膜模型和生物医学任务中药物输送的材料。由复杂的磷脂混合物形成的膜的基本特性之一是不同相域的平衡共存。研究不同相的构象状态和化学成分在膜生物物理学中具有重要意义。我们提出了一种使用拉曼映射研究堆叠磷脂双层中相共存的方法。为此目的，形成了磷脂多层膜，其中相同相的畴以堆叠的形式自对准。在这些样品上获得的具有高光谱分辨率和信噪比的拉曼光谱使估计不同相域中脂质的化学成分和构象状态成为可能。对于三元混合物 1,2-dioleoyl-sn-甘油-3-磷酸胆碱（DOPC）/1,2-二棕榈酰-d62- sn-甘油-3-磷酸胆碱（DPPC-d62）/胆固醇（Chol）揭示了脂质相分离的水合作用。^{对于水合薄膜，获得的相图与使用2} H NMR获得的先前数据定性一致。在干膜中，观察到所有研究组合物的相分离，倾向于形成具有高比例 DPPC-d62 的相。多层磷脂膜的使用使得释放拉曼显微光谱的潜力成为可能，以研究各种实验条件下的磷脂混合物的相图。