Dipartimento di Scienze Chimiche, Università di Padova, via Marzolo 1, 35131 Padova, Italy.
J Phys Chem B. 2011 Aug 25;115(33):9980-9. doi: 10.1021/jp205163w. Epub 2011 Aug 4.
We have studied the emission features of the fluorescent polarity-sensitive probes known as Prodan and Laurdan in a liquid-crystalline DPPC bilayer. To this purpose, we have combined high-level quantum mechanical electronic structure calculations with a molecular field theory for the positional-orientational-conformational distribution of the probes, in their ground and excited states, inside of the lipid bilayer, taking into account at both levels the nonuniformity and anisotropy of the environment. Thus, we can interpret the features of the fluorescence spectra of Prodan and Laurdan in relation to the position and orientation of their chromophore in the bilayer. We have found that the environment polarity is not sufficient to explain the large red shifts experimentally observed and that specific effects due to hydrogen bonding must be considered. We show that the orientation of the probe is important in determining the accessibility to water of the H-bond-acceptor group; in the case of Laurdan interesting conformational effects are highlighted.
我们研究了已知的荧光极性探针 Prodan 和 Laurdan 在液晶 DPPC 双层中的发射特性。为此，我们将高级量子力学电子结构计算与分子场理论相结合，用于探针在脂质双层内的位置-取向-构象分布，在这两个层次上都考虑了环境的非均匀性和各向异性。因此，我们可以解释 Prodan 和 Laurdan 荧光光谱的特征与它们在双层中的发色团的位置和取向有关。我们发现，环境极性不足以解释实验观察到的大红移，必须考虑氢键引起的特定效应。我们表明，探针的取向对于确定氢键供体基团与水的可及性很重要；对于 Laurdan，突出了有趣的构象效应。
