CHEMICAL ENVIRONMENT HETEROGENEITY AROUND THE 2 CHLOROPHYLL-A' MOLECULES IN PHOTOSYSTEM-I

Treatment of whole and fractionated plant tissues with hydrophilic and hydrophobic solvent mixtures of varied volume ratio liberates two chl orophyll (Chl) a' molecules from the photosystem (PS)I core when the s olvent hydrophilicity exceeds a critical level, whereas only one molec ule is extracted in hydrophobic media. The PSI core proteins, PSI-A an d PSI-B, which form a heterodimer, appear to bind one Chl a' molecule each, in local environments significantly different regarding their hy drophilicity or hydrophobicity.