title: Fluidity of bacterial membrane lipids monitored by intramolecular excimerization of 1.3-di(2-pyrenyl)propane.
abstract: Intramolecular excimer formation of 1,3-di(2-pyrenyl)propane was used to study the fluidity of liposomes prepared from membrane polar lipids of Bacillus stearothermophilus. On the basis of spectral data, local polarity and polarizability parameters were established suggesting that the probe molecules are located well inside the membranes, but displaced towards the polar head groups of the phospholipid molecules. The excimerization rate is very sensitive to lipid phase transitions and pretransitions of synthetic pure lipid bilayers. In bacterial lipids from cultures grown at 55 and 68 degrees C, thermal profiles of excimer to monomer intensity ratios (I'/I) show a broad transition which is displaced to higher temperatures in response to the increase of the growth temperature; these results correlate well with differential scanning calorimetry data and fluorescence polarization of diphenylhexatriene. Additionally, lipid bilayers of bacteria grown at 68 degrees C exhibit a decreased membrane fluidity, as monitored by both fluorescent probes.
authors.affiliation: Departamento de Zoologia, Universidade de Coimbra, Portugal.
authors.forename: A S
authors.initials: AS
authors.lastname: Jurado
authors.forename: L M
authors.initials: LM
authors.lastname: Almeida
authors.forename: V M
authors.initials: VM
authors.lastname: Madeira
mesh_terms: D002152:Calorimetry, Differential Scanning; D002462:Cell Membrane / Q000502:physiology; D005456:Fluorescent Dyes; D001411:Geobacillus stearothermophilus / Q000502:physiology*; D008051:Lipid Bilayers; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000032:analysis; D008722:Methods; D010743:Phospholipids / Q000032:analysis; D011721:Pyrenes; D013050:Spectrometry, Fluorescence
chemical_list: D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D008563:Membrane Lipids; D010743:Phospholipids; D011721:Pyrenes; C035116:1,3-di-(1-pyrenyl)propane