Fluorescence Kinetics Of Fluorescence Resonance Energy Transfer Between Tryptophan And Biomolecules

As one of the eight essential amino acids for human and animals,tryptophan plays an important role in their growth,development and metabolism,and has been widely used in medicine,feed additives,environmental monitoring and other fields.Studies have shown that fluorescence resonance energy transfer can occur between tryptophan and some biomolecules.The fluorescence lifetime distribution and intermolecular energy transfer efficiency of tryptophan under this action can be used to observe the changes of metabolic activity in biological cells.However,in organisms,tryptophan mainly exists as monomeric tryptophan and multiple tryptophans in many proteins.Whether these two types of tryptophan can transfer fluorescence resonance energy between these biomolecules is unknown.To solve this problem,based on the theory of fluorescence resonance energy transfer,we study the interaction between tryptophan in different structural types and coenzyme NADH,folic acid,and explore the conditions for fluorescence resonance energy transfer between tryptophan-coenzyme NADH and tryptophan-folic acid.Furthermore,the protein peptide chain usually contains more than one tryptophan,and the fluorescence contribution of each tryptophan to the interaction between protein and coenzyme NADH/folic acid is different.Time correlation single photon counting technique was used to study the fluorescence kinetics of resonance energy transfer between tryptophan and coenzyme NADH,folic acid together with UV-Vis absorption and steady-state fluorescence spectroscopy.By analyzing the time-resolved fluorescence spectra and the lifetime fitting data,it can be found that not all structural types of tryptophan can undergo fluorescence resonance energy transfer between coenzyme NADH,folic acid.Meanwhile,the fluorescence contribution of different tryptophan molecules on the protein peptide chain during the fluorescence resonance energy transfer of proteincoenzyme NADH was analyzed by decay-associated spectra spectroscopy.The decrease of the average fluorescence lifetime of protein is mainly due to the fluorescence resonance energy transfer between tryptophan long-lifetime component and coenzyme NADH.