Effects Of Thylakoid Membrane Lipids On The Structural Properties Of Photosystem I (PSI)

In this work,photosystem I?PSI?was separated from spinach and Spirulina platensis by using sucrose density gradient centrifugation method.The structural integrity,purity and oxygen consumption activity of PSI samples were examined with low temperature fluorescence spectrum,SDS-PAGE and liquid oxygen electrode.The results showed that the structure of the PSI samples obtained was complete and the purity was over 98%.The oxygen consumption activities of PSI samples from spinach and Spirulina platensis were0.492?mol O₂/?mg Chl·min?and 0.92?mol O₂/?mg Chl·min?respectively,which were very close to the highest values in literature.On this basis,the effects of four thylakoid membrane lipids?i.e.MGDG,DGDG,SQDG and PG?on the structural properties of PSI were examined with UV-vis absorption,low temperature fluorescence spectrum,liquid oxygen electrode and circular dichroism.The studied structural properties of PSI include secondary structure analysis,thermal stability,oxygen consumption activity and the effective sizes of PSI in solution.The results show that the addition of thylakoid membrane lipids had a certain influence on the structural properties of PSI.But the same kind of membrane lipid has different influence on the properties of PSI samples from spinach and Spirulina platensis.In addition,the interactions among Chl a,Chl B and some other subunits in spinach PSI will be changed with the addition of thylakoid membrane lipids.