Supramolecular Assembly Of Chlorophyll In Barrel-shaped Protein Nanocages And Its Photocatalytic Properties

Chlorophyll is a natural photocatalyst existing in nature.When it is separated from the biological environment,it is easy to degrade under light irradiation,which limits its application in the field of illumination.The improvement of photostability is a key issue to be solved in the construction of artificial photocatalysts.From the perspective of biomimetic catalysis,introducing chlorophyll into water-soluble proteins with similar natural structures may better regulate the photocatalytic properties of chlorophyll by utilizing their delicate structure and special microenvironment.In this thesis,nano-barrel-shaped GroEL composed of two loops back-to-back and its mutant monocyclic SR1 were selected as target proteins,and chlorophyll a and its derivatives were selected as photocatalyst models.In this research,based on the concept of biomimetic catalysis and the characteristics of supramolecular chemistry,chlorophyll a and its derivatives were introduced into hydrophobic cavities of chaperone GroEL and SR1 by dialysis to construct photocatalysts in the form of pigment-protein complex.The preparation process and properties were investigated.The main contents are as follows:1)Chlorophyll a was introduced into the hydrophobic cavity of GroEL by dialysis to prepare Chl a@GroEL complex.Studies have shown that GroEL can effectively stabilize hydrophobic chlorophyll a.The Chl a@GroEL complex can achieve photoreduction of MV.And Chl a@GroEL complex with a ratio of 1:40 was used to prepare solar sensitized dye cells,showing a good photoelectric conversion efficiency of 0.86%.This pigment-protein form of optical catalyst could provide a theoretical basis for the development of new photoelectric materials.2)Considering that splitting GroEL into single ring for supramolecular assembly of chlorophyll a may be more conducive to mass transfer in catalytic reactions and affect the performance of the assembly,we prepared the Chl a@SR1 complex by dialysis.When SR1 binds more chlorophyll a,the optical stability of the complex is higher,and the reduction of MV can be achieved.The ratio of 1:60 Chl a@SR1 complex was assembled into solar sensitized dye cell,whose photoelectric conversion efficiency can reach 1.09%,and the possible mechanism was discussed.3)On the other hand,chlorophyll a was transformed into Cu-pheo a by replacement reaction,and the Cu-pheo a@GroEL complex was prepared by dialysis method.It was found that GroEL did not improve the optical stability of Cu-pheo a,but could achieve the reduction of MV.The ratio of 1:40 Cu-pheo a@GroEL complex prepared into solar cells has lower photoelectric conversion capacity than the other two complexes.This part reflects the important effect of magnesium ion in chlorophyll a on its stability and photocatalytic performance.