Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (1): 301-312.doi: 10.3866/PKU.WHXB201512112

• ARTICLE • Previous Articles     Next Articles

Two-Photon Absorption Properties of Chromophores of a Few Fluorescent Proteins: a Theoretical Investigation

Chuan-Xiang YE1,Hui-Li MA2,Wan-Zhen LIANG3,*()   

  1. 1 Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, P. R. China
    2 Department of Chemistry, Tsing University, Beijing 100084, P. R. China
    3 Department of Chemistry, Xiamen University, Xiamen 361005, Fujian Province, P. R. China)
  • Received:2015-10-15 Published:2016-01-13
  • Contact: Wan-Zhen LIANG
  • Supported by:
    the National Natural Science Foundation of China(21373163, 21290193, 21573177)


The experimentally-measured two-photon absorption (TPA) spectra of fluorescent proteins (FPs) show quite different characteristics with one-photon absorption (OPA) spectra in both the low-and high-frequency regions. To reveal the mechanism that results in the discrepancies between OPA and TPA spectra, and to obtain the fundamental structure–property relationships of FPs, here we conduct a theoretical study of OPA and TPA properties of three FP chromophores, including a neutral chromophore in enhanced cyan fluorescent protein (ECFP) and two anionic FP chromophores in DsRed2 and TagRFP. Both the pure electronic and vibrationally-resolved TPA spectra have been calculated. The calculated spectra were found to be highly dependent on the density functional theory exchange-correlation functional used. The experimental spectral lineshapes of vibronic spectra can be well produced when the Franck-Condon (FC) scattering and Herzberg-Teller (HT) vibronic coupling effects were taken into account and the structure parameters produced by CAM-B3LYP were applied in the theoretical calculations. The HT effects affect the low-frequency absorption bands corresponding to the electronic transition from S0 to S1 for two anionic chromophores, leading to a blue-shift of the TPA maximum relative to OPA maximum, while the HT effect is insignificant in the higher-frequency region of the TPA spectra. The intramolecular charge-transfer character of higher-lying excited states explains why the TPA spectra in the higher-frequency region are much stronger than those in the low-frequency region.

Key words: Two-photon absorption, Fluorescent protein chromophore, Vibronic spectrum, Time-dependent density functional theory