title: Structural investigation of bilayers formed by 1-palmitoyl-2-oleoylphosphatidylnucleosides.
abstract: Bilayers of palmitoyl-oleoylphosphatidylnucleoside derivatives (1-palmitoyl-2-oleoyl-phosphatidyl-adenosine and 1-palmitoyl-2-oleoyl-phosphatidyl-uridine) were synthesized and investigated in the low-water content regime by a combination of neutron diffraction and Fourier transform infrared linear dichroism (LD-FTIR). Attention was focused on the modulation of structural properties operated by the presence of nucleic acid bases (either adenosine or uridine, a purine and a pyrimidine that are complementary in RNA). Base substitution causes major differences in phase behavior of the phospholipids, i.e., water sorption from a controlled humidity atmosphere and smectic periodicity. The profile of scattering length density can be inferred from five diffraction orders for 1-palmitoyl-2-oleoyl-phosphatidyl-uridine lamellar phase. 1-Palmitoyl-2-oleoyl-phosphatidyl-adenosine is characterized by lower and less ready hydration, giving rise to a powder-like sample. A linear dichroism FTIR investigation on the same lamellar phases was undertaken with the purpose of gathering details at the submolecular level on different portions of the molecule. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers were also investigated with the same technique for the sake of comparison. Besides a confirmation of the diffraction data interpretation, FTIR has provided evidence that the same chemical groups at the bilayer interface (namely the sugar-phosphate) have a different orientation depending on whether the base is a purine or a pyrimidine. A very simple geometrical optimization agrees with this observation. This indicates that a different pattern of base interaction is operating in the two cases and that base substitution acts as a modulator of the phase properties.
authors.affiliation: Department of Chemistry and CSGI (Consorzio Interuniversitario per lo sviluppo dei Sistemi a Grande Interfase), University of Florence, Florence, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Milani
authors.forename: Francesca Baldelli
authors.initials: FB
authors.lastname: Bombelli
authors.forename: Debora
authors.initials: D
authors.lastname: Berti
authors.forename: Thomas
authors.initials: T
authors.lastname: Hauss
authors.forename: Silvia
authors.initials: S
authors.lastname: Dante
authors.forename: Piero
authors.initials: P
authors.lastname: Baglioni
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000737:chemistry; D020404:Glycerophospholipids / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D033363:Neutron Diffraction; D044367:Phase Transition; D010712:Phosphatidic Acids / Q000737:chemistry*; D011687:Purines / Q000737:chemistry; D011743:Pyrimidines / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014529:Uridine / Q000031:analogs & derivatives* / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: C509561:1-palmitoyl-2-oleoyl-phosphatidyl-3-adenosine; C509562:1-palmitoyl-2-oleoyl-phosphatidyl-uridine; D020404:Glycerophospholipids; D008051:Lipid Bilayers; D010712:Phosphatidic Acids; D011687:Purines; D011743:Pyrimidines; D014867:Water; D000241:Adenosine; C030986:pyrimidine; C030985:purine; D014529:Uridine