Centre for Advanced Electron Spin Resonance and Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.
Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
J Phys Chem Lett. 2021 Jan 14;12(1):80-85. doi: 10.1021/acs.jpclett.0c02884. Epub 2020 Dec 11.
We present a new technique, light-induced triplet-triplet electron resonance spectroscopy (LITTER), which measures the dipolar interaction between two photoexcited triplet states, enabling both the distance and angular distributions between the two triplet moieties to be determined on a nanometer scale. This is demonstrated for a model bis-porphyrin peptide that renders dipolar traces with strong orientation selection effects. Using simulations and density functional theory calculations, we extract distance distributions and relative orientations of the porphyrin moieties, allowing the dominant conformation of the peptide in a frozen solution to be identified. LITTER removes the requirement of current light-induced electron spin resonance pulse dipolar spectroscopy techniques to have a permanent paramagnetic moiety, becoming more suitable for in-cell applications and facilitating access to distance determination in unmodified macromolecular systems containing photoexcitable moieties. LITTER also has the potential to enable direct comparison with Förster resonance energy transfer and combination with microscopy inside cells.
我们提出了一种新的技术，即光诱导三重态-三重态电子共振光谱（LITTER），它可以测量两个光激发三重态之间的偶极相互作用，从而能够在纳米尺度上确定两个三重态部分之间的距离和角度分布。我们以一种模型双卟啉肽为例进行了演示，该模型呈现出具有强烈取向选择效应的偶极轨迹。通过模拟和密度泛函理论计算，我们提取了卟啉部分的距离分布和相对取向，从而可以确定肽在冷冻溶液中的主要构象。LITTER 消除了当前光诱导电子自旋共振脉冲偶极光谱技术必须具有永久顺磁部分的要求，使其更适合于细胞内应用，并便于在含有光可激发部分的未经修饰的大分子系统中进行距离测定。LITTER 还有可能与Förster 共振能量转移直接比较，并与细胞内显微镜结合使用。
