Institute of Chemistry, Martin Luther University Halle-Wittenberg, 06120, Halle (Saale), Germany; Department of Chemistry, Hazara University, 21120, Mansehra, Pakistan.
Institute of Chemistry, Martin Luther University Halle-Wittenberg, 06120, Halle (Saale), Germany; Integrative Research Center HALOmem, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, 06120, Halle (Saale), Germany.
Chem Phys Lipids. 2020 Aug;230:104918. doi: 10.1016/j.chemphyslip.2020.104918. Epub 2020 May 15.
The monolayer behavior of a l-DPPC derivative with a single fluorination in one of its terminal methyl groups (F-DPPC) at air-water interface was investigated by epifluorescence microscopy and infrared reflection absorption spectroscopy (IRRAS). Epifluorescence microscopy was utilized to study the shape and morphology of liquid-condensed (LC) domains observed upon compression of the film. IRRAS was employed for the determination of chain order and orientation. The shapes of LC-domains in a monolayer of F-DPPC are more dependent on the rate of compression than those of DPPC. The LC domains of F-DPPC display pronounced fractal growth patterns depending on the compression speed. The evolution of LC domain occurs under dominating electrostatic dipolar forces in F-DPPC. IRRAS measurements with the analysis of the frequency of the methylene stretching vibrations as a function of film compression show that the acyl chains in an F-DPPC monolayer in the LE-phase are more disordered than those in a DPPC film. The reason for the higher chain disorder in LE phase F-DPPC monolayers is a back folding of the fluorinated sn-2 chain terminus towards the air-water interface leading to larger molecular area requirement. Angular dependent IRRA spectra of monolayers at a surface pressure of 30 mN m show that in the LC phase DPPC and F-DPPC exhibit a similar tilt of the acyl chains of ca. 28-30 ° relative to the surface normal. F-DPPC is ideally miscible with l-DPPC-d having the same chirality, as indicated by epifluorescence images and by IRRAS. However, the LC domains in an equimolar mixture of d-DPPC and F-DPPC having opposite chirality show multi-lobed complex domain patterns indicating chiral phase separation within LC domains.
在空气-水界面，通过荧光显微镜和红外反射吸收光谱（IRRAS）研究了一个末端甲基中具有一个氟取代基的 1-DPPC 衍生物（F-DPPC）的单层行为。荧光显微镜用于研究在薄膜压缩时观察到的液晶（LC）畴的形状和形态。IRRAS 用于确定链序和取向。F-DPPC 单层中 LC 畴的形状比 DPPC 更依赖于压缩速度。F-DPPC 的 LC 畴显示出明显的分形生长模式，这取决于压缩速度。LC 域的演化是在 F-DPPC 中占主导地位的静电偶极力作用下发生的。IRRAS 测量结果以及作为薄膜压缩函数的亚甲基伸缩振动频率的分析表明，在 LE 相中的 F-DPPC 单层中的酰基链比 DPPC 膜中的酰基链更无序。在 LE 相 F-DPPC 单层中，链无序度更高的原因是氟取代的 sn-2 链末端向后折叠到空气-水界面，导致更大的分子面积要求。在表面压力为 30 mN m 的单层的角度依赖的 IRRA 光谱表明，在 LC 相中 DPPC 和 F-DPPC 表现出相对于表面法线约 28-30°的相似酰基链倾斜。F-DPPC 与具有相同手性的 l-DPPC-d 完全混溶，如荧光图像和 IRRAS 所示。然而，具有相反手性的 d-DPPC 和 F-DPPC 的等摩尔混合物中的 LC 域显示出多叶复杂的畴图案，表明 LC 域内的手性相分离。
