Effects Of Carotenoids On The Absorption Spectral And Fluorescence Quenching Of Chlorophyll A

In photosynthesis,the function of most chlorophyll is to absorb and transmit light energy.There are several different chlorophyll in nature.There are several different chlorophyll in nature,and most of them are chlorophyll a and b.These two chlorophyll are mainly found in higher class plants and green algae,while chlorophyll c and d are mainly found in various kinds of algae,and often co-exist with chlorophyll a.This paper mainly researches chlorophyll a.The chlorophyll a absorption band is mainly located in the red and blue-violet range.As a result,our study that researching the absorption spectrum of chlorophyll a in different solution environments and the quenching of fluorescence can provide a foundation for the study in organism area.Carotenoids are the most common natural complexes.The fast internal conversion and short excited state lifetime make carotenoids an excellent quencher that dissipates the excited state quickly and without radiation.In this paper,we first studied the effect of aii-trans-?-carotenoids on the absorption and fluorescence spectrum of chlorophyll a.With UV-Vis absorption spectroscopy,fluorescence spectroscopy and Raman spectroscopy,it was observed that the absorption spectrum of chlorophyll a would be enhanced and the degree of fluorescence quenching will increase carotenoids concentration increases.We analyzed the physical mechanism of this phenomenon.Then we compared the absorption spectroscopy and fluorescence quenching of carotenoids and chlorophyll mixed solution with different structures.Finally,we further analyzed and elucidated the fluorescence quenching,with the Stern-Volmer curve,and the absorption spectra of carotenoids and chlorophyll mixture.It was found that exciplex was produced during the quenching process.The innovative results we achieved are as follows:1.The fluorescence quenching of chlorophyll a will make be more and more pronounced as the concentration of all-trans-?-carotenoid increases.The chlorophyll a molecule and the all-trans beta-carotene molecule in the system produce an exciplex without fluorescence radiation,and an increase in the number of carotenoid molecules results in an increasing number of non-fluorescent species.As the all-trans-?-carotene molecule increases,the non-fluorescent exciplex increases.Secondly,the fluorescence spectra of three kinds of carotenoids mixed with chlorophyll a were studied.The linear relationship between the S₀-S₂ electronic transition of carotenoids,the decay rate of S1 and the position of?₁and the effective conjugate length These three factors are the main factors affecting the mixed system of chlorophyll a and carotenoids.2.When studying the absorption spectra of a mixed solution of chlorophyll and all-trans--carotene in ethanol solution,it can be seen that as the concentration of carotenoids increases,the absorption peak of and are significantly improved.Subsequently,the comparison of three kinds of carotenoids with different effective conjugate lengths and chlorophyll a was found.As the effective conjugate length of carotenoids decreased,the absorption spectra of carotenoids and chlorophyll a appeared blue shift.3.The absorption spectra and fluorescence quenching of chlorophyll a and carotenoids were studied in a solvent environment.It was found that the absorption of carotenoids and chlorophyll a showed a red shift as the polarity of the solution increased,and fluorescence quenching was more obvious.This is because that an electric field is applied between molecules,and an intrinsic dipole moment is generatedin a solvent environment,resulting in an increase in intermolecular dispersion.There is a clear linear relationship between the electronic transition of carotenoids S₀-S₂ and the polarizability of the solvent,and the conjugate length of the carotenoid molecules is slightly extended as the polarizability of the solvent increases.Therefore,as the polarity of the solution increases,the fluorescence quantum yield of the excited state will decrease,and even and the fluorescence phenomenon of the excited state in the strong polar solvent is more obvious.In summary,the paper studies the absorption and fluorescence quenching properties of the mixed system of chlorophyll and carotenoids.We observed the physical mechanism of interaction between carotenoids and chlorophyll.It provides new considerations for the study of chlorophyll a in photosynthesis and energy transfer in plants,and also provides a reference for the fluorescence study of exciplex.