Antibodies against sulphoquinovosyl-diacyl glycerol and their reactions with chloroplasts.

Using immunological techniques we tried to determine the localization and orientation of the sulpholipid of chloroplasts in thylakoids. During immunization of rabbits with lamellar systems of chloroplasts of A n tirrh in u m m ajus antisera were obtained which precipitated sulpholipid emulsions. Antibodies against the sulpholipid were not detected until a second series of intravenous injections. By immunizing purified sulpholipid of F ucus serratus, adsorbed to methylated bovine serum albumin, sulpholipid antisera were acquired. These antisera and the antisera against lam ellar systems of A n tirrh in u m m ajus reacted with preparations of sulpholipid from widely different plant species. The sulpholipid antisera did not react with emulsions of the monoor digalactosyl-diacyl glycerol, of lecithin or the anionic phosphatide phosphatidyl glycerol. Lamellar systems isolated without osmotic shock on a sucrose gradient were not agglutinated by sulpholipid antisera directly, but an indirect agglutination could be achieved in a C o o m b s -test or in a mixed antigen aggluti­ nation after U h l e n b r u c k . Broken chloroplasts, however, were agglutinated directly by sulpho­ lipid antisera, as well lam ellar systems which had been disrupted in a French-press or by ultrasonic treatm ent. From agglutination and agglutination inhibition experiments with lamellar systems prepared by different methods it is concluded that the determinant groups of the sulpholipid are accessible for antibodies in the lam ellar system of chloroplasts. But probably the sulpholipid molecules are located inside the thylakoids.