Studies of some bio-inspired liquid crystals

The main phase transition of lipid bilayers corresponds to a defined change from an ordered (gel) to a disordered (fluid liquid crystal) state of hydrocarbon chains, occurring in general at a defined temperature T-m. However, aqueous dispersions of pure anionic phospholipids, and particularly DMPG, may exhibit a 'melting regime', from T-m(on) until T-m(off), over similar to 10 degrees C. The melting process depends on pH, ionic strength and several details of sample preparation. This paper makes a review on seven papers of the author with different collaborations, with the original proposal of pores in the DMPG melting transition. The focus is on structural results obtained from X-ray scattering, varying concentration and temperature, but integrating with results from other experimental techniques. Initially the effect of salt addition was separated from the effect of DMPG concentration. At DMPG concentrations higher than 70 mM a lamellar phase starts and a detailed study of the temperature variation of 150 mM DMPG allowed arrival to detailed pore model, focused in the surface fractions of pores in the bilayers. The model admits large and small pores in the melting regime and agrees with the new Lamellar Phase with pores (Lp) starting at T-3. The large biological relevance is stressed. [GRAPHICS] .