Temperature-controlled polarization modulation near-field scanning optical microscopy measurements of a single supported $L_{{\beta }^{\prime }}$ 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayer are presented. The effective retardance ($S=\frac{2\pi (n_e-n_o)t}{\lambda }$, where $t$ is the thickness of the bilayer and $\lambda$ is the wavelength of light used) and the direction of the projection of the acyl chains ($\theta$) were measured simultaneously. We demonstrate how one is able to align the system over the sample and measure a relative retardance $\mathrm{\Delta }S$, a crucial step in performing temperature-controlled experiments. Maps of $\mathrm{\Delta }S$ and $\theta$, with a lateral resolution on the order of $\sim 100$ nm are presented, highlighting variations deriving from changes in the average molecular orientation across a lipid membrane at room temperature. A discussion of how this information can be used to map the average three-dimensional orientation of the molecules is presented. From $\mathrm{\Delta }S$ and the known thickness of the membrane $t$ the birefringence ($n_e-n_o$) of the bilayer was determined. Temperature-controlled measurements yielded a change of $\mathrm{\Delta }S\sim (3.8\pm 0.3)$ mrad at the main transition temperature ($T_m\sim {41}^{\circ }\mathrm{C}$) of a single planar bilayer of DPPC, where the membrane transitioned between the gel $L_{{\beta }^{\prime }}$ to liquid disorder $L_{\alpha }$ state. The result agrees well with previous values of ($n_e-n_o$) in the $L_{{\beta }^{\prime }}$ phase and translates to an assumed average acyl chain orientation relative to the membrane normal ($\langle \varphi \rangle \sim {32}^{\circ }$) when $T<T_m$ and $0^{\circ }$ when $T>T_m$. Evidence of super heating and cooling are presented. A discussion on how the observed behavior as $T_m$ is approached, could relate to the existence of varying microconfigurations within the lipid bilyer are presented. This conversation includes ideas from a Landau-Ginzburg picture of first-order phase transitions in nematic-to-isotropic systems.

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支持的单脂质双层中各向异性变化和温度诱导的结构变化的近场研究

单支支持的温控偏振调制近场扫描光学显微镜测量 ${\mathrm{大号}}_{{\beta }^{\prime }}$介绍了1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）脂质双层。有效延迟（$\mathrm{小号}=\frac{2\pi （{ñ}_{Ë}-{ñ}_{Ø}）Ť}{\lambda }$，在哪里 $Ť$ 是双层的厚度， $\lambda$ 是所用光的波长）和酰基链的投影方向（$\theta$）同时进行测量。我们演示了如何将系统对准样品并测量相对延迟$\mathrm{\Delta }\mathrm{小号}$，这是进行温度控制实验的关键一步。的地图$\mathrm{\Delta }\mathrm{小号}$ 和 $\theta$，横向分辨率约为 $〜100$给出了nm，突出了在室温下源自脂质膜上平均分子取向变化的变化。讨论了如何将此信息用于绘制分子的平均三维方向。从$\mathrm{\Delta }\mathrm{小号}$ 和已知的膜厚度 $Ť$ 双折射（${ñ}_{Ë}-{ñ}_{Ø}$确定双层的）。温度控制的测量结果发生了变化$\mathrm{\Delta }\mathrm{小号}〜（3.8\pm 0.3）$ 在主要转变温度下的mrad（${Ť}_{米}〜{41}^{\circ }\mathrm{C}$）DPPC的单个平面双层，其中膜在凝胶之间过渡 ${\mathrm{大号}}_{{\beta }^{\prime }}$ 液体紊乱 ${\mathrm{大号}}_{\alpha }$州。结果与（${ñ}_{Ë}-{ñ}_{Ø}$） 在里面 ${\mathrm{大号}}_{{\beta }^{\prime }}$ 相并转化为相对于膜法线的假定平均酰基链取向（$〈\varphi 〉〜{32}^{\circ }$） 什么时候 $Ť<{Ť}_{米}$ 和 $0^{\circ }$ 什么时候 $Ť>{Ť}_{米}$。提供了过热和冷却的证据。讨论如何观察到的行为${Ť}_{米}$接近，可能与脂质胆汁中存在不同的微观构型有关。这次对话包含了Landau-Ginzburg图片中向列相向各向同性系统中一阶相变的构想。