The anionic phospholipid DMPG (dimyristoyl phosphatidylglycerol) may exhibit in water, instead of a unique melting transition of the hydrocarbon chains, a "melting regime" for pH values above 5, where the phosphate groups are deprotonated, and for low ionic strength, where charge screening is weak. The chain-melting process of DMPG starts at Tmon (onset of the melting regime at ∼ 20°C), but the complete fluid phase exists only above Tmoff (offset of the melting regime at ∼ 30°C). In a recent paper we developed a SAXS model for a bilayer with pores to explain SAXS results obtained for concentrations up to 70 mM DMPG (F. Spinozzi, L. Paccamiccio, P. Mariani, and L. Q. Amaral, Langmuir, in print, 2010). A new lamellar phase with pores, starting 3°C above T mon and existing up to 4°C above Tm off, was also identified at the higher investigated DMPG concentrations (up to 300 mM DMPG). In this paper we focus in more detail the SAXS curves obtained in the concentration interval 70-300 mM DMPG. The slope of the scattering profile in the very small q range, as well as the anomalous increase in the intensity of the bilayer band centered around 0.12 Å-1 after Tmoff, have been in particular analyzed. By using a model of water-penetrated bilayers, the volume fractions of DMPG and water molecules inside the bilayer was derived as a function of temperature.

New lamellar phase with pores in the chain-melting regime of an anionic phospholipid dispersion / Spinozzi, Francesco; Mariani, Paolo; L., Paccamiccio; L. Q., Amaral. - In: JOURNAL OF PHYSICS. CONFERENCE SERIES. - ISSN 1742-6588. - STAMPA. - 247:(2010), pp. 012019-1-012019-13.

New lamellar phase with pores in the chain-melting regime of an anionic phospholipid dispersion

SPINOZZI, Francesco;MARIANI, Paolo;
2010-01-01

Abstract

The anionic phospholipid DMPG (dimyristoyl phosphatidylglycerol) may exhibit in water, instead of a unique melting transition of the hydrocarbon chains, a "melting regime" for pH values above 5, where the phosphate groups are deprotonated, and for low ionic strength, where charge screening is weak. The chain-melting process of DMPG starts at Tmon (onset of the melting regime at ∼ 20°C), but the complete fluid phase exists only above Tmoff (offset of the melting regime at ∼ 30°C). In a recent paper we developed a SAXS model for a bilayer with pores to explain SAXS results obtained for concentrations up to 70 mM DMPG (F. Spinozzi, L. Paccamiccio, P. Mariani, and L. Q. Amaral, Langmuir, in print, 2010). A new lamellar phase with pores, starting 3°C above T mon and existing up to 4°C above Tm off, was also identified at the higher investigated DMPG concentrations (up to 300 mM DMPG). In this paper we focus in more detail the SAXS curves obtained in the concentration interval 70-300 mM DMPG. The slope of the scattering profile in the very small q range, as well as the anomalous increase in the intensity of the bilayer band centered around 0.12 Å-1 after Tmoff, have been in particular analyzed. By using a model of water-penetrated bilayers, the volume fractions of DMPG and water molecules inside the bilayer was derived as a function of temperature.
2010
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11566/33171
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