Department of Physics & Astronomy , University College London , Gower Street , London WC1E 6BT , United Kingdom.
Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX) , University College London , Gower Street , London WC1E 6BT , United Kingdom.
J Phys Chem B. 2019 Jun 6;123(22):4705-4717. doi: 10.1021/acs.jpcb.9b01236. Epub 2019 May 22.
Two-photon absorption (2PA) finds widespread application in biological systems, which frequently exhibit heterogeneous fluorescence decay dynamics corresponding to multiple species or environments. By combining polarized 2PA with time-resolved fluorescence intensity and anisotropy decay measurements, we show how the two-photon transition tensors for the components of a heterogeneous population can be separately determined, allowing structural differences between the two fluorescent states of the redox cofactor NAD(P)H to be identified. The results support the view that the two states correspond to alternate configurations of the nicotinamide ring, rather than folded and extended conformations of the entire molecule.
双光子吸收（2PA）在生物系统中得到了广泛的应用，生物系统通常表现出与多种物质或环境相对应的异质荧光衰减动力学。通过将偏振 2PA 与时间分辨荧光强度和各向异性衰减测量相结合，我们展示了如何分别确定异质群体成分的双光子跃迁张量，从而能够识别氧化还原辅因子 NAD(P)H 的两个荧光态之间的结构差异。结果表明，这两种状态对应于烟酰胺环的交替构象，而不是整个分子的折叠和扩展构象。
