title: Material properties of matrix lipids determine the conformation and intermolecular reactivity of diacetylenic phosphatidylcholine in the lipid bilayer.
abstract: Photopolymerizable phospholipid DC(8,9)PC (1,2-bis-(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine) exhibits unique assembly characteristics in the lipid bilayer. Because of the presence of the diacetylene groups, DC(8,9)PC undergoes polymerization upon UV (254 nm) exposure and assumes chromogenic properties. DC(8,9)PC photopolymerization in gel-phase matrix lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monitored by UV-vis absorption spectroscopy occurred within 2 min after UV treatment, whereas no spectral shifts were observed when DC(8,9)PC was incorporated into liquid-phase matrix 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). Liquid chromatography-tandem mass spectrometry analysis showed a decrease in the amount of DC(8,9)PC monomer in both DPPC and POPC environments without any change in the matrix lipids in UV-treated samples. Molecular dynamics (MD) simulations of DPPC/DC(8,9)PC and POPC/DC(8,9)PC bilayers indicate that the DC(8,9)PC molecules adjust to the thickness of the matrix lipid bilayer. Furthermore, the motions of DC(8,9)PC in the gel-phase bilayer are more restricted than in the fluid bilayer. The restricted motional flexibility of DC(8,9)PC (in the gel phase) enables the reactive diacetylenes in individual molecules to align and undergo polymerization, whereas the unrestricted motions in the fluid bilayer restrict polymerization because of the lack of appropriate alignment of the DC(8,9)PC fatty acyl chains. Fluorescence microscopy data indicates the homogeneous distribution of lipid probe 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-lissamine rhodamine B sulfonyl ammonium salt (N-Rh-PE) in POPC/DC(8,9)PC monolayers but domain formation in DPPC/DC(8,9)PC monolayers. These results show that the DC(8,9)PC molecules cluster and assume the preferred conformation in the gel-phase matrix for the UV-triggered polymerization reaction.
authors: Membrane Structure and Function Section, SAIC-Frederick, Inc., Nanobiology Program, Center for Cancer Research, Frederick, Maryland 21702, USA.
authors: Anu
authors: A
authors: Puri
authors: Hyunbum
authors: H
authors: Jang
authors: Amichai
authors: A
authors: Yavlovich
authors: M Athar
authors: MA
authors: Masood
authors: Timothy D
authors: TD
authors: Veenstra
authors: Carlos
authors: C
authors: Luna
authors: Helim
authors: H
authors: Aranda-Espinoza
authors: Ruth
authors: R
authors: Nussinov
authors: Robert
authors: R
authors: Blumenthal
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry* / Q000378:metabolism; D002627:Chemistry, Physical; D002853:Chromatography, Liquid; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D044367:Phase Transition / Q000528:radiation effects; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000032:analysis; D055668:Photochemical Processes / Q000528:radiation effects; D058105:Polymerization; D012235:Rhodamines / Q000032:analysis; D053719:Tandem Mass Spectrometry; D014466:Ultraviolet Rays
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D012235:Rhodamines; C046703:lissamine-rhodamine-phosphatidylethanolamine; C057168:1,2-di-(heptacosadiynoyl)-sn-glycero-3-phosphocholine; D015060:1,2-Dipalmitoylphosphatidylcholine; C028694:1-palmitoyl-2-oleoylphosphatidylcholine