Department of Biophysics, Pavol Jozef Šafárik University, Jesenná 5, Košice 041 54, Slovak Republic.
J Phys Chem B. 2013 Feb 7;117(5):1280-6. doi: 10.1021/jp3114539. Epub 2013 Jan 23.
Fluorescence experiments were carried out to investigate the interaction of hypericin (Hyp), a natural hydrophobic photosensitizer, with artificial bilayer lipid membranes. The spatial orientation of Hyp monomers incorporated in diphytanoyl phosphatidylcholine (DPhPC) membranes was determined by measuring the dependence of the Hyp fluorescence intensity on the angle of incidence of p- and s-polarized excitation laser beams. Inside of the membrane, Hyp monomers are preferentially located in the layers near the membrane/water interface and are oriented with the S(1) ← S(0) transition dipole moments perpendicular to the membrane surface. Transport of Hyp anions between the two opposite sides of the lipid bilayer was induced by applying rectangular electric field pulses to the membrane. The characteristic time for Hyp transport through the membrane center was evaluated by the analysis of the Hyp fluorescence signal during the voltage pulses. In the zero-voltage limit, the transport time approached 70 ms and gradually decreased with higher voltage applied to the membrane. In addition, our measurements indicated an apparent pK(a) constant of 8 for Hyp deprotonation in the membrane.
荧光实验用于研究天然疏水性光敏剂金丝桃素（Hyp）与人工双层脂质膜的相互作用。通过测量 Hyp 荧光强度对 p 和 s 偏振激发激光束入射角的依赖性，确定了二植烷酰基磷脂酰胆碱（DPhPC）膜中 Hyp 单体的空间取向。在膜内，Hyp 单体优先位于靠近膜/水界面的层中，并以 S(1) ← S(0)跃迁偶极矩垂直于膜表面的方式取向。通过向膜施加矩形电场脉冲来诱导 Hyp 阴离子在脂质双层的两个相对侧之间的传输。通过分析电压脉冲期间的 Hyp 荧光信号来评估 Hyp 通过膜中心的传输时间。在零电压极限下，传输时间接近 70 ms，并且随着施加到膜的电压升高而逐渐减小。此外，我们的测量结果表明 Hyp 在膜中去质子化的表观 pK(a)常数为 8。
