Studies on Chloroplast Membranes. II. ¹³C Chemical Shifts and Longitudinal Relaxation Times of 1,2-Di[(9Z,12Z,15Z)-octadeca-9,12,15-trienoyl]-3-galactosyl-sn-glycerol and 1,2-Di[(9Z,12Z,15Z)-octadeca-9,12,15-trienoyl]-3-digalactosyl-sn-glycerol

Abstract

The ¹³C chemical shift and longitudinal relaxation time (T₁) of the individual carbon atoms in the two major lipids of chloroplast thylakoids, 1,2-di[(9Z,12Z,15Z)-octadeca-9,12,15-trienoyl]-3- galactosyl-sn-glycerol and 1,2-di[(9Z,12Z,15Z)-octadeca-9,12,15- trienoyl]-3-digalactosyl-sn-glycerol, have been measured in the three solvents: methanol[D₄], chloroform[D] and water[D₂]. The longitudinal relaxation time data are interpreted in terms of different secondary structures in the different solvents, a monomeric structure in methanol[D₄], an inverted micellar structure in chloroform[D] and a bilayer structure in water[D₂]. Two possible correlations times can be obtained from the longitudinal relaxation times of the galactosyl and glyceryl carbon atoms in chloroform[D] and water[D₂] and nuclear Overhauser enhancement values have been used to assign the correlation times to these carbon atoms.