tailieunhanh - Báo cáo khoa học: Thermal behaviour of cubic phases rich in 1-monooleoyl-rac-glycerol in the ternary system

Using synchrotron X-ray diffraction the thermal behaviour was studied of the cubic phases in the 1-monooleoyl-rac-glycerol (MO)/n-octyl-b-D-glucopyranoside (OG)/ 2 H2O system with 58 or 45 wt % MO concentration and varying OG/ 2 H2O contents. These MO contents correspond to a Pn3mcubic single-phase or aPn3mcubic phase in excess water on the binary MO/water axis of the ternary phase diagram. The cubic liquid crystalline phases are stable with small fractions of OG, while higher OG concentrations trigger a cubic-to-lamellar phase transition. . | Eur. J. Biochem. 270 56-65 2003 FEBS 2003 doi Thermal behaviour of cubic phases rich in 1-monooleoyl-rac-glycerol in the ternary system 1-monooleoyl-rac-glycerol n-octyl-p-D-glucoside water Gerd Persson1 Hakan Edlund1 and Goran Lindblom2 1 Department of Natural and Environmental Sciences Mid Sweden University Sundsvall Sweden department of Biophysical Chemistry Umea University Umeà Sweden Using synchrotron X-ray diffraction the thermal behaviour was studied of the cubic phases in the 1-monooleoyl-rac-glycerol MO n-octyl-b-D-glucopyranoside OG 2H2O system with 58 or 45 wt MO concentration and varying OG 2H2O contents. These MO contents correspond to a Pn3m cubic single-phase or a Pn3m cubic phase in excess water on the binary MO water axis of the ternary phase diagram. The cubic liquid crystalline phases are stable with small fractions of OG while higher OG concentrations trigger a cubic-to-lamellar phase transition. Moreover with increasing OG concentration the initial Pn3m structure is completely converted to an Ia3d structure prior to the La phase being formed. Upon heating this effect is reversed resulting in an Ia3d-to-Pn3m phase transition. For some samples additional peaks were observed in the diffracto-grams upon heating resulting from the metastability notoriously shown by bicontinuous cubic phases. This judgement is supported by the fact that upon cooling these peaks were absent. Remarkably both the Ia3d and the Pn3m cubic structures could be in equilibrium with excess water in this ternary system. A comparison is made with previous results on n-dodecyl-b-D-maltoside DM showing that cubic phases with OG have higher thermal and compositional stability than with DM. Keywords 1-monooleoyl-rac-glycerol n-octyl-b-D-gluco-side monoolein-rich cubic phases thermal behaviour. Access to the complete structure of membrane proteins is one of the cornerstones in obtaining a better understanding of their function in the biological cell.