Control of porphyrin interactions via structural changes of a peptoid scaffold,Organic & Biomolecular Chemistry

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Control of porphyrin interactions via structural changes of a peptoid scaffold
Organic & Biomolecular Chemistry ( IF 2.9 ) Pub Date : 2017-10-31 00:00:00 , DOI: 10.1039/c7ob02398g
Woojin Yang _{1,

2,

3,

4,

5} , Boyeong Kang _{1,

2,

3,

4,

5} , Vincent A. Voelz _{1,

6,

7,

8} , Jiwon Seo _{1,

2,

3,

4,

5}

Affiliation

Nature utilizes optimally organized pigments in light-harvesting complexes. To mimic the natural photosynthetic proteins, effective control over inter-pigment interactions is necessary to attain the desired photophysical properties. Previously, we developed porphyrin–peptoid conjugates (PPC_amide) and displayed two porphyrins at defined positions on an α-helical peptoid using a flexible n-butyl linker. Herein, we synthesized new porphyrin–peptoid conjugates (PPC_C–C), where porphyrins are conjugated through a rigid C–C linkage to the helical peptoid via the Suzuki–Miyaura cross-coupling reaction. With PPC_C–C, we studied the effects of backbone conformation, inter-porphyrin distance, and the linker flexibility on porphyrin interactions. When the rigid C–C linkage was used, conformational homogeneity of the PPC increased, providing more effective intramolecular excitonic couplings between the porphyrins; however, the intermolecular porphyrin J-aggregation decreased. In PPC_C–C with a nonameric peptoid backbone, the formation of a threaded loop conformation was observed, which could be switched back to a helical conformation by N-terminal acetylation or by the addition of a protic solvent. This threaded loop-to-helix conversion restored the intramolecular porphyrin interactions. Our results suggest that PPCs represent an excellent system for control over porphyrin interactions and therefore are useful as a model system to elucidate pigment interactions in nature or as a molecular construct with switchable photophysical properties.

中文翻译：

通过类肽支架的结构变化控制卟啉相互作用

大自然在采光复合物中利用了最佳组织的颜料。为了模拟天然的光合作用蛋白，必须有效控制颜料间的相互作用才能获得所需的光物理性质。以前，我们开发了卟啉-类肽结合物（PPC_酰胺），并使用柔性正丁基接头在α-螺旋类肽的确定位置展示了两个卟啉。在这里，我们合成了新的卟啉-类肽结合物（PPC _C-C），其中卟啉通过Suzuki-Miyaura交叉偶联反应通过刚性C-C键与螺旋类肽结合。使用PPC _C–C，我们研究了骨架构象，卟啉间距离和接头柔性对卟啉相互作用的影响。当使用刚性C–C连接时，PPC的构象同质性增加，从而在卟啉之间提供了更有效的分子内激子偶联。但是，分子间卟啉J的聚集减少。在PPC _C–C中对于非肽基类肽骨架，观察到螺纹环构象的形成，该构象可以通过N末端乙酰化或添加质子溶剂转换回螺旋构象。这种螺纹环到螺旋的转化恢复了分子内卟啉的相互作用。我们的结果表明，PPCs是控制卟啉相互作用的极佳系统，因此可用作阐明自然界中色素相互作用的模型系统或具有可切换光物理性质的分子构建体。

更新日期：2017-11-09

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