Department of Chemistry and James Franck Institute, University of Chicago, Chicago, Illinois, USA.
Biophys J. 2011 Apr 20;100(8):2043-52. doi: 10.1016/j.bpj.2010.12.3747.
We extend traditional two-dimensional (2D) electronic spectroscopy into a third Fourier dimension without the use of additional optical interactions. By acquiring a set of 2D spectra evenly spaced in waiting time and dividing the area of the spectra into voxels, we can eliminate population dynamics from the data and transform the waiting time dimension into frequency space. The resultant 3D spectrum resolves quantum beating signals arising from excitonic coherences along the waiting frequency dimension, thereby yielding up to 2n-fold redundancy in the set of frequencies necessary to construct a complete set of n excitonic transition energies. Using this technique, we have obtained, to our knowledge, the first fully experimental set of electronic eigenstates for the Fenna-Matthews-Olson (FMO) antenna complex, which can be used to improve theoretical simulations of energy transfer within this protein. Whereas the strong diagonal peaks in the 2D rephasing spectrum of the FMO complex obscure all but one of the crosspeaks at 77 K, extending into the third dimension resolves 19 individual peaks. Analysis of the independently collected nonrephasing data provides the same information, thereby verifying the calculated excitonic transition energies. These results enable one to calculate the Hamiltonian of the FMO complex in the site basis by fitting to the experimental linear absorption spectrum.
我们将传统的二维（2D）电子光谱扩展到第三个傅里叶维度，而无需使用额外的光学相互作用。通过获取一组在等待时间上均匀间隔的 2D 光谱，并将光谱的面积划分为体素，我们可以从数据中消除种群动力学，并将等待时间维度转换为频率空间。所得的 3D 光谱解析了来自激子相干的量子拍频信号，沿着等待频率维度，从而在构建完整的 n 个激子跃迁能量集所需的频率集合中提供多达 2n 倍的冗余。使用这种技术，我们获得了迄今为止第一个 Fenna-Matthews-Olson（FMO）天线复合物的电子本征态的完整实验数据集，可用于改进该蛋白质内能量转移的理论模拟。虽然 FMO 复合物的 2D 重相位光谱中的强对角峰掩盖了 77 K 时所有除一个交叉峰之外的所有交叉峰，但扩展到第三个维度可解析 19 个单独的峰。对独立收集的非重相位数据的分析提供了相同的信息，从而验证了计算出的激子跃迁能量。这些结果使得可以通过拟合实验线性吸收光谱来计算 FMO 复合物在站点基础上的哈密顿量。
