Abstract:

A series of firefly oxyluciferin analogues were designed, in which the N and S atoms of benzothiazole of firefly oxyluciferin were substituted by other atoms. In aqueous solution and virtual protein environment, the absorption and emission spectrum were calculated by TD B3LYP/6-31+G(d). The results of the calculation indicate that the absorption spectra of complexes with the O atom at X₁-site show more blue-shift than that with the S atom, while the spectra of complexes in which the S atom is replaced by the N atom show red-shift. The six complexes have similar orbital distributions and the overlapping volume between HOMO and LUMO is high. That benefits to the maintain of high fluorescence efficiency. Deprotonation can enhance the π orbital component of benzene fragment and make emission spectra shift to red. Thus electronic transition probability can be improved. Replaced by different atoms at X₁ and X₂ sites, the emission spectra can be adjusted to move to long wave up to 44 nm and move to short wave up to 41 nm(in virtual protein environment). The emission wavelength range of the six complexes is wide. So they can be used in biological imaging as new potential chemical luminescent material.

Key words: Firefly oxyluciferin analogue, Spectrum property, Density functional theory