Membrane transport of singlet oxygen monitored by dipole potential measurements.
Membrane transport of singlet oxygen monitored by dipole potential measurements.
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DOI：
10.1529/biophysj.108.135145
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发表时间：
2009-01
影响因子：
3.4
通讯作者：
V. Sokolov;P. Pohl
中科院分区：
文献类型：
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作者：
V. Sokolov;P. Pohl
光动力学反应的效率取决于1）光敏剂进入膜的渗透深度和2）靶的侧性。对单线态氧敏感的分子（（1）O（2））在通过膜与光敏剂分离时受到的损伤较小。由于（1）O（2）在膜环境中的寿命比非激发态氧（O（2））穿过膜所需的时间长几个数量级，这一观察结果表明（1）O（2）和O（2）的渗透性或膜分配之间存在差异。我们通过在平面膜的一侧释放（1）O（2），同时在同一膜的另一侧监测靶损伤的动力学来研究这一假设。以偶极修饰分子（根皮素或根皮苷）为代表的靶点损伤，通过小叶间偶极电位差Deltaphi（B）的变化来指示。一个简单的分析模型允许从Deltaphi（B）变化的速率估计（1）O（2）瓣叶间浓度差异。证实（1）O（2）渗透率的下限约为2 cm/s;即，它大致匹配奥弗顿规则预测的O（2）渗透率。因此，膜不能作为（1）O（2）扩散的屏障。细胞质膜和细胞外膜小叶反应速率的差异可能仅归因于（1）O（2）膜内的猝灭剂。
The efficiency of photodynamic reactions depends on 1), the penetration depth of the photosensitizer into the membrane and 2), the sidedness of the target. Molecules which are susceptible to singlet oxygen ((1)O(2)) experience less damage when separated from the photosensitizer by the membrane. Since (1)O(2) lifetime in the membrane environment is orders of magnitude longer than the time required for nonexcited oxygen (O(2)) to cross the membrane, this observation suggests that differences between the permeabilities or membrane partition of (1)O(2) and O(2) exist. We investigated this hypothesis by releasing (1)O(2) at one side of a planar membrane while monitoring the kinetics of target damage at the opposite side of the same membrane. Damage to the target, represented by dipole-modifying molecules (phloretin or phlorizin), was indicated by changes in the interleaflet dipole potential difference Deltaphi(b). A simple analytical model allowed estimation of the (1)O(2) interleaflet concentration difference from the rate at which Deltaphi(b) changed. It confirmed that the lower limit of (1)O(2) permeability is approximately 2 cm/s; i.e., it roughly matches O(2) permeability as predicted by Overton's rule. Consequently, the membrane cannot act as a barrier to (1)O(2) diffusion. Differences in the reaction rates at the cytoplasmic and extracellular membrane leaflets may be attributed only to (1)O(2) quenchers inside the membrane.