DNA scaffold supports long-lived vibronic coherence in an indodicarbocyanine (Cy5) dimer,Chemical Science

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DNA scaffold supports long-lived vibronic coherence in an indodicarbocyanine (Cy5) dimer
Chemical Science ( IF 7.6 ) Pub Date : 2020-07-22 , DOI: 10.1039/d0sc01127d
Sara H. Sohail _{1,

2,

3,

4,

5} , John P. Otto _{1,

2,

3,

4,

5} , Paul D. Cunningham _{6,

7,

8} , Young C. Kim _{6,

7,

8} , Ryan E. Wood _{1,

2,

3,

4,

5} , Marco A. Allodi _{1,

2,

3,

4,

5} , Jacob S. Higgins _{1,

2,

3,

4,

5} , Joseph S. Melinger _{6,

7,

8} , Gregory S. Engel _{1,

2,

3,

4,

5}

Affiliation

Vibronic coupling between pigment molecules is believed to prolong coherences in photosynthetic pigment–protein complexes. Reproducing long-lived coherences using vibronically coupled chromophores in synthetic DNA constructs presents a biomimetic route to efficient artificial light harvesting. Here, we present two-dimensional (2D) electronic spectra of one monomeric Cy5 construct and two dimeric Cy5 constructs (0 bp and 1 bp between dyes) on a DNA scaffold and perform beating frequency analysis to interpret observed coherences. Power spectra of quantum beating signals of the dimers reveal high frequency oscillations that correspond to coherences between vibronic exciton states. Beating frequency maps confirm that these oscillations, 1270 cm⁻¹ and 1545 cm⁻¹ for the 0-bp dimer and 1100 cm⁻¹ for the 1-bp dimer, are coherences between vibronic exciton states and that these coherences persist for ∼300 fs. Our observations are well described by a vibronic exciton model, which predicts the excitonic coupling strength in the dimers and the resulting molecular exciton states. The energy spacing between those states closely corresponds to the observed beat frequencies. MD simulations indicate that the dyes in our constructs lie largely internal to the DNA base stacking region, similar to the native design of biological light harvesting complexes. Observed coherences persist on the timescale of photosynthetic energy transfer yielding further parallels to observed biological coherences, establishing DNA as an attractive scaffold for synthetic light harvesting applications.

中文翻译：

DNA支架可在靛蓝羰花青（Cy5）二聚体中支持长寿命的电子相干性

色素分子之间的振动耦合被认为可以延长光合色素-蛋白质复合物中的相干性。在合成的DNA构建体中使用纤维偶联的生色团重现长寿命的相干性，提供了一条仿生途径来实现有效的人工光收集。在这里，我们目前在DNA支架上的一个单体Cy5构建体和两个二聚Cy5构建体（染料之间0 bp和1 bp）的二维（2D）电子光谱，并进行跳动频率分析以解释观察到的相干性。二聚体的量子跳动信号的功率谱揭示了与振动子激子状态之间的相干性相对应的高频振荡。拍频图确认了这些振荡，即1270 cm ^-1和1545 cm ^-1对于0 bp二聚体，对于1 bp二聚体为1100 cm ^-1，是振动子激子态之间的相干性，并且这些相干性持续了约300 fs。振动激子模型很好地描述了我们的观察结果，该模型预测了二聚体中的激子耦合强度以及由此产生的分子激子状态。这些状态之间的能量间隔紧密对应于观察到的拍频。MD模拟表明，我们构建体中的染料大部分位于DNA碱基堆积区域内部，类似于生物光收集复合物的天然设计。观察到的一致性在光合作用能量转移的时间尺度上持续存在，与观察到的生物一致性进一步相似，从而将DNA建立为合成光收集应用的诱人支架。

更新日期：2020-08-20

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