Monomeric PSI is found within thermophilic cyanobacteria, i.e., Thermosynechococcus elongatus either in case of iron deficiency or deletion of PsaL subunit. Previous investigations pointed to the role of PsaL in oligomerization of monomeric complexes. Successful isolation of monomeric PSI was achieved only via salt treatment of thylakoid membrane at high temperature (50°C). Here, monomeric PSI was obtained through splitting the purified trimeric PSI in vitro. Selective elimination of carotenoids and Chlorophyll a located in monomer-monemer interface area was performed using a mixture of hexane with different organic solvents.
Hexane-dimethyl sulfoxide mixture was considered the best organic solvent for removal the interface carotenoids and chlorophyll a, where it splatted trimeric PSI completely. Also, the role of carotenoids and chlorophyll a on stabilization of trimeric PSI was proven by sucrose density gradient and blue native gel. 77K spectroscopical emission fluorescence measurements of investigated PSI showed blue shift peaks due to monemerization as well as formation of uncoupled chlorophylls. The efficiency of organic solvents on removing  carotenoids molecules was higher than chlorophyll molecules, where about 12/96 chlorophyll molecules and 12/22 carotenoids molecules have been eliminated in case of complete splitting of trimeric PSI.