Abstract5-Bromo-(Br-PBA) and 3,5-dibromo-2-hydroxy-N-phenylbenzamides (Br2-PBA) inhibited photosynthetic electron transport (PET) and their inhibitory efficiency depended on the compound lipophilicity as well as on the electronic properties of the R substituent in the N-phenyl moiety. Br-PBA showed higher PET inhibiting activity than Br2-PBA with the same R substituent. The most effective inhibitors in the tested series were the derivatives with R = 3-F (Br-PBA; IC50 = 4.3 μmol dm−3) and R = 3-Cl (Br2-PBA; IC50 = 8.6 μmol dm−3). Bilinear dependence of the PET inhibiting activity on the lipophilicity of the compounds as well as on the Hammett constant, σ, of the R substituent was observed for both investigated series. Using EPR spectroscopy it was found that the site of action of the tested compounds in the photosynthetic apparatus is situated on the donor side of PS 2, in D· or in the Z·/D· intermediates. Interaction of the studied compounds with chlorophyll a and aromatic amino acids present in the pigment-protein complexes mainly in photosystem 2 was documented by fluorescence spectroscopy.
摘要:5-溴-(Br-PBA)和3,5-二溴-2-羟基-N-苯基苯甲酰胺(Br2-PBA)抑制了光合作用电子传递(PET),它们的抑制效率取决于化合物的亲脂性以及N-苯基基团中R取代基的电子性质。Br-PBA表现出比具有相同R取代基的Br2-PBA更高的PET抑制活性。在测试系列中,具有R = 3-F(Br-PBA; IC50 = 4.3 μmol dm−3)和R = 3-Cl(Br2-PBA; IC50 = 8.6 μmol dm−3)的衍生物是最有效的抑制剂。对于两个研究系列,观察到了PET抑制活性与化合物的亲脂性以及R取代基的Hammett常数σ之间的双线性依赖关系。使用EPR光谱学发现,测试化合物在光合作用器官中的作用位点位于PS 2的给体侧,在D·或在Z·/D·中间体中。通过荧光光谱学证明了研究化合物与叶绿素a和存在于色素蛋白复合物中的芳香氨基酸的相互作用主要发生在光系统2中。