extracted thylakoid membrane proteins from spinach chloroplasts. Intact chloroplasts from spinach were isolated by isopycnic Percoll gradient centrifugation. Thylakoids were separated from stromal proteins after osmotic shock of chloroplasts. Thylakoids were washed in Tricine/Sucrose/MgCl 2 -containing buffer and broken twice by a French Press. The thylakoid membrane proteins were separated from lumenal proteins by ultra centrifugation and following washing steps of thylakoid membranes.