Physical Chemistry Department, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, India.
Langmuir. 2012 Jul 10;28(27):10230-7. doi: 10.1021/la3014859. Epub 2012 Jun 26.
Picosecond spectroscopy under a confocal microscope is employed to study solvation dynamics of coumarin 153 (C153) inside a single giant lipid vesicle (1,2-dilauroyl-sn-glycero-3-phosphocholine, DLPC) of diameter 20 μm. Fluorescence correlation spectroscopy (FCS) indicates that the diffusion coefficient (D(t)) of the probe (coumarin153, C153) in the immobilized vesicle displays a wide distribution from ~3 to 21 μm(2) s(-1). The distribution of D(t) suggests that the microenvironment of the probe (C153) is highly heterogeneous and the local friction is different for probe molecules in different regions. The values of D(t) is significantly smaller than that for the same dye in bulk water (550 μm(2) s(-1)). This suggests that the probe is located in the interface or membrane region rather than in the water pool of the vesicle. The solvation time of C153 in different regions of the lipid vesicle varies between 750 to 1200 ps. This result clearly shows that a confocal microscope is able to resolve the spatial heterogeneity in local friction (i.e., D(t)) and solvation dynamics within a lipid vesicle.
皮秒共聚焦显微镜光谱法被用来研究香豆素 153（C153）在直径为 20μm 的单个巨大脂质囊泡（1,2-二月桂酰基-sn-甘油-3-磷酸胆碱，DLPC）中的溶剂化动力学。荧光相关光谱（FCS）表明，探针（香豆素 153，C153）在固定囊泡中的扩散系数（D（t））显示出从~3 到 21μm(2) s(-1)的宽分布。D（t）的分布表明探针（C153）的微环境高度不均匀，并且在不同区域的探针分子的局部摩擦力不同。D（t）的值明显小于相同染料在体相水中的值（550μm(2) s(-1)）。这表明探针位于囊泡的界面或膜区域，而不是在囊泡的水相中。C153 在脂质囊泡不同区域的溶剂化时间在 750 到 1200 ps 之间变化。这一结果清楚地表明，共焦显微镜能够分辨脂质囊泡内局部摩擦力（即 D（t））和溶剂化动力学的空间异质性。
