OEP23 exists in the entire plant lineage starting from green algae till flowering plants. It forms a cation selective single channel in the outer membrane of chloroplasts. It is a single channel and is not a member of a multiple pore complex like other bacterial or mitochondrial ß barrels. For this reason, it is considered a novel member of the ion channels in the outer membrane of chloroplasts that are responsible for solute exchange. CD spectroscopy studies revealed that OEP23 secondary structure constitutes of 42 ∓ 10% alpha-helix, 14 ∓ 5% ß-sheet, 16 ∓ 5% turns and 27 ∓ 5% of unordered structures.