Chaotropic anion-phosphatidylcholine membrane interactions: an ultra high field NMR study

Abstract NMR studies on the interaction of the linear chaotropic anions, SCN − and SeCN − , with sonicated egg phosphatidylcholine (EPC) vesicles have been carried out at field strenghts up to 14.1 Tesla. At 600 MHz, both anions cause splitting or increased splitting of the choline N + (CH 3 ) 3 , CH 2 N + and O 3 POCH 2 1 H resonances with SeCN − being somewhat more effective in this action than is SCN − . No changes were observed in the glycerol CH 2 OP and CH 2 OCO 1 H resonances and the phosphate 31 P resonance of the headgroup region. The 13 C spectrum was unchanged by the presence of the anions. After 18 h of exposure to the anion, the 1 H resonance splittings but not the chemical shift values returned to those prior to anion exposure. Increasing the temperature of the vesicles decreased the anion-induced splitting, but, upon return to the beginning temperature, the chemical shifts did not return to their original values. The results are considered in terms of the ‘molecular electrometer’ model recently developed by Seelig and co-workers [1].