Department of Chemistry, Faculty of Science , Sultan Qaboos University , P.O. Box 36, Postal Code 123 , Muscat , Sultanate of Oman.
Centre for Fundamental and Frontier Sciences in Nanostructure Self-Assembly, Department of Chemistry, Faculty of Science , University of Malaya , 50603 Kuala Lumpur , Malaysia.
Langmuir. 2019 Jul 23;35(29):9584-9592. doi: 10.1021/acs.langmuir.9b01767. Epub 2019 Jul 9.
New designer biofluorophores are being increasingly used in the investigation of complex cellular processes. In this study, we utilized new derivatives of pyrene (Py), i.e., 2--alkyl-pyrenes (Py-C and Py-C), in order to probe different regions inside the hydrophobic tail of -dodecyl β-d-maltoside (βMal-C) in two different phases (cubic ↔ lamellar). Although the sensitivity to the local environment is reduced compared to that of Py, attaching C and C at the 2-position of Py can provide a possible means to probe the local hydrophobicity in different parts of the tail region. The absence of excimer fluorescence and the ratio of the vibronic fluorescence peak intensities (/) in a lipid environment indicate the existence of Py as monomers in the hydrophobic region, similar to hydrophobic solvation, yet close to the headgroup region. When Py is replaced by Py-C and Py-C, there is a small increase in hydrophobicity (reduction in /) as the Py moiety is pulled deeper inside the tail region of both cubic and lamellar phases. The larger space of the tail region in the lamellar phase is reflected as more local hydrophobicity measured by the probes which can penetrate deep inside, whereas the curved structure of the cubic phase limits the available space for the probes. Three fluorescence lifetime components were measured in lipid, indicating the heterogeneous nature of the hydrophobic region. In the lamellar phase, a large reduction in the average lifetime value, led by the long decay component, was measured for Py-C (reduction by 25%) and Py-C (45%) compared to that of the parent Py. This observation suggests the presence of a mechanism of interaction more collisional than static between the Py moiety and the tail region of the bilayer unit due to the ample space provided by the lamellar phase as the probe is buried deeper inside the hydrophobic region. A much smaller effect was observed in the cubic phase and was correlated with the tight environment around the probes, which stems from the increased curvature of the cubic phase. The current results provide a deeper understanding of the hydrophobic region during phase transition of lipid self-assembly which is important for better control during the process of membrane-protein crystallization.
新型生物荧光染料在研究复杂细胞过程中被越来越多地应用。在这项研究中，我们利用了芘（Py）的新衍生物，即 2-烷基芘（Py-C 和 Py-C），以探测β-麦芽糖苷（βMal-C）疏水尾部的不同区域，该实验在两种不同的相态（立方相向层状相）中进行。尽管与 Py 相比，其对局部环境的灵敏度降低，但在 Py 的 2 位连接 C 和 C 可以提供一种可能的方法来探测尾部区域不同部分的局部疏水性。在脂质环境中，无激基缔合物荧光和振动态荧光峰强度比（/）的存在表明，Py 以单体形式存在于疏水区，类似于疏水溶剂化作用，但靠近头部基团区域。当 Py 被 Py-C 和 Py-C 取代时，由于 Py 部分被拉到立方相和层状相的尾部区域更深，疏水性略有增加（/减小）。层状相尾部区域的较大空间反映为可以深入探测的探针所测量的局部疏水性增加，而立方相的弯曲结构限制了探针的可用空间。在脂质中测量了三个荧光寿命成分，表明疏水区具有异质性。在层状相中，与母体 Py 相比，Py-C（减少 25%）和 Py-C（减少 45%）的长衰减分量导致平均寿命值的大幅降低。这一观察结果表明，由于层状相提供了充足的空间，探针被更深地埋在疏水区内，Py 部分与双层单元的尾部区域之间的相互作用机制更具碰撞性而非静态性。在立方相中观察到的效果要小得多，这与探针周围的紧密环境有关，这源于立方相的曲率增加。目前的结果提供了对脂质自组装相变过程中疏水区的更深入了解，这对于更好地控制膜蛋白结晶过程很重要。
