Laurdan和Prodan设计用于评估周围的水合状态。当插入脂质双层系统时,两种探针都位于不同的位置,它们的荧光特性变化很大,取决于周围的环境。在这项研究中,基于荧光寿命(τ)和发射峰(λ),提出了一种利用上述荧光探针的新方法,称为τ与λ图,通过对其多个荧光衰减的全局分析和这些衰减相关光谱(DAS)的去卷积来确定。根据τ对λ图的评估,膜中存在多种荧光成分。此外,它们的荧光分布特性,在τ与λ图上描述,每个探针倾向于与脂质膜的相态和垂直方向相对应。为了评估环境影响对每种分布的贡献,我们在τ对λ图中定义了区域,它是从一系列溶剂混合物中建模的:己烷,丙酮,乙醇和水,模拟DPPC双层系统中的复杂环境。将Laurdan和Prodan的荧光成分在脂质膜中的分布分为每种溶剂种类,和Prodan分成散装水。在升高温度时还观察到Prodan对DPPC双层体系的相转变的敏感性。值得注意的是,大多数荧光成分被分配到溶剂模型中,除了一个单一的组件,具有较长的寿命和较短的发射波长。该成分在固序相中占主导地位;因此,它被认为是脂质膜中不能用溶剂表示的特定成分。尽管这些仍然是定性分析方法,这项研究中提出的独特方法为膜的多焦点性质提供了新的见解。
Laurdan and Prodan were designed for the evaluation of the surrounding hydration state. When inserted into lipid bilayer systems, both probes are located at different positions and their fluorescence properties are drastically varied, depending on their surrounding environment. In this study, a novel method using the above fluorescence probes was proposed on the basis of fluorescence lifetime (τ) and emission peak (λ), called as τ vs. λ plot, determined by global analysis of their multiple fluorescence decays and deconvolution of these decay-associated spectra. According to the evaluation of τ vs. λ plot, the existence of multiple fluorescence components in the membrane was revealed. In addition, their fluorescence distribution properties, described on τ vs. λ plot, of each probe tended to correspond to the phase state and vertical direction of the lipid membrane. To assess the contribution of environmental effect to each distribution, we defined the region in the τ vs. λ plot, which was modeled from a series of solvent mixtures (hexane, acetone, ethanol and water) to emulate the complex environment in the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine bilayer system. The distributions of fluorescence components of Laurdan and Prodan in lipid membranes were classified into each solvent species, and Prodan partition into bulk water was distinguished. The sensitivity of Prodan to the phase pretransition of the 1,2-dipalmitoyl-sn-glycero-3-phosphocholine bilayer system was also observed in increasing the temperature. Noticeably, most of the fluorescence components was assigned to the solvent model, except for a single component that has longer lifetime and shorter emission wavelength. This component was dominant in solid-ordered phase; hence, it is assumed to be a specific component in lipid membranes that cannot be represented by solvents. Although these are still qualitative analytical methods, the unique approach proposed in this study provides novel insights into the multi-focal property of the membrane.