Chemtstrv and Physws of LtpMs 14 (1975) 350-362 © North-Holland Pubhshmg Company SOLVATION OF OXYGEN IN LECITHIN BILAYERS * R KIMMICH and A PETERS Abtetlung fur Expertmentelle Phystk 11, Umversttat Ulm, 7900 Ulm, Postfach 4066, Germany Recewed I~ebruary 10, 1975, accepted May 23, 1975 The solubthty of oxygen m dlpalmltoylleclthm (DPL) and paraffin C19 has been investigated by measurement of the enhanced proton relaxation rates under the influence of oxygen pressure The paraffin shows a noticeable effect m the rotator phase, but not so m the crystalhne phase In contrast to paraffins both phases of DPL-bdayers dissolve oxygen, but the solubdlty m the hqu~d-crystalhne phase ~s greater than m the crystaUme state by a factor ~3 Furthermore, the expenments indicate a distribution of electron relaxation tunes m the crystalhne phase m con- trast to the hquld-crystaUme phase A possible explanation of this behavlour is a mulhphase structure of the "crystaUme" lameUae The biological relevance of these results could be a tnggermg of the gas-transport by the alveolar hmng of lungs, ff cychc phase transitions occur during the breathing-cycle I. Introduction In 1971, H Trauble has suggested a carrier model for the passive transport of small molecules through phosphohpld bllayers [1 ], basing on Pechhold's kink-con- cept of the defect-structure of polymers [2] The idea was that the particles could jump into kink vacancies m the hydrocarbon phase of the bllayer lamellae and penetrate the membrane by a "hltch-hxkmg" process, the enclosed molecule always following the kink m its statistical step sequence (fig I) Ttus mechamsm of passwe transport through membranes could allow the derivation of transport properties on molecular parameters, and ,.s therefore of special interest In order to clarify the relevance of this model, we have investigated two questions (a) Are there dlffuslng defects such as kinks m the hydrocarbon phase of lipid bllayers9 and (b) to what extent can small and electrically neutral molecules be solved in thas phase 9 As an appropriate method for the study of both questions we have chosen nuclear magnetic relaxation expenments In previous papers [3, 4], we have shown that the frequency dependence of the spin-lattice relaxation-time T 1 of the protons m the hydrocarbon phase of DPL * Partially reported on the Vlth International Conference on Magnetlc Resonance m Biological Systems, 16 9 -20 9 1974 in Kandersteg