Chemical and Biological Systems Simulation Lab, Centre of New Technologies , University of Warsaw , Banacha 2C , 02-097 Warsaw , Poland.
Biomedical Research Institute , Hasselt University , Agoralaan Building C , 3590 Diepenbeek , Belgium.
Langmuir. 2019 Sep 3;35(35):11471-11481. doi: 10.1021/acs.langmuir.9b01840. Epub 2019 Aug 23.
The development of a universal probe to assess the phase of a lipid membrane is one of the most ambitious goals for fluorescence spectroscopy. The ability of a well-known molecule as Laurdan to reach this aim is here exploited as the behavior of the probe is fully characterized in a dipalmitoylphosphatidylcholine (DPPC) solid gel (So) phase by means of molecular dynamics simulations. Laurdan can take two conformations, depending on whether the carbonyl oxygen points toward the β-position of the naphthalene core (Conf-I) or to the α-position (Conf-II). We observe that Conf-I has an elongated form in this environment, whereas Conf-II takes an L-shape. Interestingly, our theoretical calculations show that these two conformations behave in an opposite way from what is reported in the literature for a DPPC membrane in a liquid disordered (Ld) phase, where Conf-I assumes an L-shape and Conf-II is elongated. Moreover, our results show that in DPPC (So) no intermixing between the conformations is present, whereas it has been seen in a fluid environment such as DOPC (Ld). Through a careful analysis of angle distributions and by means of the rotational autocorrelation function, we predict that the two conformers of Laurdan behave differently in different membrane environments.
开发一种通用探针来评估脂质膜的相是荧光光谱学最具挑战性的目标之一。这里利用一种众所周知的分子——胆甾醇作为探针来达到这个目的，通过分子动力学模拟充分表征了探针在二棕榈酰磷脂酰胆碱（DPPC）固体凝胶（So）相中的行为。胆甾醇可以采取两种构象，这取决于羰基氧指向萘核的β-位（Conf-I）还是α-位（Conf-II）。我们观察到，在这种环境中，Conf-I 呈伸长状，而 Conf-II 呈 L 形。有趣的是，我们的理论计算表明，这两种构象的行为与文献中报道的 DPPC 膜在无序液体（Ld）相中的行为相反，在 Ld 相中，Conf-I 呈 L 形，Conf-II 呈伸长状。此外，我们的结果表明，在 DPPC（So）中不存在构象之间的混合，而在 DOPC（Ld）等流体环境中则存在这种混合。通过对角度分布的仔细分析，并通过旋转自相关函数，我们预测胆甾醇的两种构象在不同的膜环境中表现不同。
