Lester Agnieszka, Orlikowska-Rzeznik Hanna, Krok Emilia, Piatkowski Lukasz
Poznan University of Technology, Faculty of Materials Engineering and Technical Physics, Institute of Physics, Piotrowo 3, Poznan 61-138, Poland.
J Phys Chem B. 2025 Jun 26;129(25):6233-6240. doi: 10.1021/acs.jpcb.5c02384. Epub 2025 Jun 10.
For over 40 years, Laurdan has been widely used as a universal fluorescent probe for the study of lipid membranes. However, recent molecular dynamics simulations have uncovered previously unknown properties of Laurdan, revealing that it can adopt distinct conformations within the lipid bilayer, thereby influencing its molecular orientation. Despite these findings, experimental and quantitative validation has been lacking. Here, we present the first experimental study of the orientation of Laurdan in a phase-separated supported lipid bilayer, directly linking its spatial orientation to its emission spectra in liquid-ordered (L) and liquid-disordered (L) phases. Using azimuthally and radially polarized excitation beams, we show that in the L phase, Laurdan molecules align more parallel to the membrane normal, whereas in the L phase, they adopt a more planar orientation within the membrane. Interestingly, the emission spectra for both excitation modes converge at shorter wavelengths, but show deviations at longer wavelengths, particularly in the L phase. By refining our understanding of the behavior of Laurdan in lipid membranes, this study underlines the critical role of the molecular orientation of the dye in fluorescence-based membrane studies and highlights the need for orientation-sensitive analysis in biophysical investigations.
40多年来，劳丹一直被广泛用作研究脂质膜的通用荧光探针。然而，最近的分子动力学模拟揭示了劳丹以前未知的特性，表明它可以在脂质双层中采取不同的构象，从而影响其分子取向。尽管有这些发现，但一直缺乏实验和定量验证。在这里，我们首次对相分离的支撑脂质双层中劳丹的取向进行了实验研究，直接将其空间取向与其在液相有序（L）相和液相无序（L）相中的发射光谱联系起来。使用方位角和径向偏振激发光束，我们表明在L相中，劳丹分子更平行于膜法线排列，而在L相中，它们在膜内采取更平面的取向。有趣的是，两种激发模式的发射光谱在较短波长处收敛，但在较长波长处出现偏差，特别是在L相中。通过完善我们对劳丹在脂质膜中行为的理解，这项研究强调了染料分子取向在基于荧光的膜研究中的关键作用，并突出了生物物理研究中对取向敏感分析的需求。
