Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya Suruga-ku, Shizuoka 422-8529, Japan.
J Am Chem Soc. 2011 Oct 26;133(42):16770-3. doi: 10.1021/ja206898j. Epub 2011 Oct 5.
To elucidate how the protein-ligand docking structure affects electronic interactions in the electron-transfer process, we have analyzed time-resolved electron paramagnetic resonance spectra of photoinduced charge-separated (CS) states generated by light excitation of 9,10-anthraquinone-1-sulfonate (AQ1S(-)) bound to human serum albumin at a hydrophobic drug-binding region. The spectra have been explained in terms of the triplet-triplet electron spin polarization transfer model to determine both the geometries and the exchange couplings of the CS states of AQ1S(2-•)-histidine-242 radical cation (H242(+•)) and AQ1S(2-•)-tryptophan-214 radical cation (W214(+•)). For the CS state of the former, it has been revealed that, due to the orthogonal relationship between the singly occupied molecular orbitals of AQ1S(2-•) and H242(+•), the electronic coupling (5.4 cm(-1)) is very weak, contributing to the prevention of energy-wasting charge recombination, even at a contact edge-to-edge separation.
为了阐明蛋白质-配体对接结构如何影响电子转移过程中的电子相互作用，我们分析了通过光激发结合在人血清白蛋白疏水药物结合区域的 9,10-蒽醌-1-磺酸盐（AQ1S(-)）产生的光致电荷分离（CS）态的时间分辨电子顺磁共振（EPR）谱。通过三重态-三重态电子自旋极化转移模型解释了这些光谱，以确定 AQ1S(2-•)-组氨酸-242 自由基阳离子（H242(+•)）和 AQ1S(2-•)-色氨酸-214 自由基阳离子（W214(+•)）的 CS 态的几何形状和交换耦合。对于前一个 CS 态，已经揭示由于 AQ1S(2-•)和 H242(+•)的单占据分子轨道之间的正交关系，电子耦合（5.4 cm(-1)）非常弱，有助于防止能量浪费的电荷复合，即使在接触边缘到边缘的分离下也是如此。
