Phase fluctuation in phospholipid membranes revealed by Laurdan fluorescence

Parasassi, Tiziana; Stasió, Gelsomina De; D'Ubaldo, A; Gratton, Enrico

doi:10.1016/s0006-3495(90)82637-0

Cited by 715 publications

(802 citation statements)

References 13 publications

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“…LAURDAN emission was analyzed by calculating the GP value [28,29] at each pixel, thus producing a pseudo-color GP image. Figure 2A is a pseudo-color representative image of the LAUR-DAN GP, in the aorta cross-section ring, where red (high GP) endothelial cells are facing the lumen and yellowgreen (low GP) smooth muscle cells are visible in the space between the matrix fibers.…”

Section: Resultsmentioning

confidence: 99%

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Two-photon microscopy of aorta fibers shows proteolysis induced by LDL hydroperoxides

Parasassi

Durbin

et al. 2000

Free Radical Biology and Medicine

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Abstract-Oxidatively modified LDL mimics several aspects of atherogenesis. In this disease, degradation of the matrix proteins' network also occurs. By a new morphological ex vivo approach, not requiring sample processing, we explored the relationship between the degradation of matrix protein and oxidatively modified LDL. Two-photon excitation fluorescence microscopy images of fresh cross-section rings of rat aorta, acquired while the sample was maintained in a glucose-and oxygen-supplemented buffer, showed straight, parallel, thick, long extracellular matrix proteins. Traditional microscopic examination, requiring sample fixation and staining, shows smaller and curved fibers. Instead, we observed curved and broken fibers after a 30-min incubation of aorta with either LDL containing lipid hydroperoxides, or tert-butyl-hydroperoxide. The adhesion of LDL to the endothelium and its internalization was directly visualized by using a lipid fluorophore. The damage to aorta matrix proteins induced by LDL and tert-butylhydroperoxide was fully prevented by antioxidants, such as ascorbate or Trolox C, or inhibitors of proteases. The image spectroscopy of the fibers' autofluorescence (polarization and lifetime) revealed an increased mobility of the fluorescent cross-link in fibers. Damaged matrix proteins were also imaged in aorta samples from apolipoprotein E knock-out mice. Our ex vivo images directly visualized the activation of a fast redox-sensitive proteolytic process in the arterial wall triggered by lipid hydroperoxides in LDL.

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Section: Resultsmentioning

confidence: 99%

“…From the images at the two emissions, the generalized polarization (GP) [28] image was calculated as previously described [29]. The lifetime images were obtained using the microscope configuration described in [19] and using the harmonic response technique.…”

Section: Microscopy Measurementsmentioning

confidence: 99%

Two-photon microscopy of aorta fibers shows proteolysis induced by LDL hydroperoxides

Parasassi

Durbin

et al. 2000

Free Radical Biology and Medicine

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“…Laurdan generalized polarization (GP) is a convenient probe for nanosecond relaxation changes correlated with the phase behavior of lipid bilayers [58][59][60] . From the results shown in Table 2 it can be seen that the parameters of the phase transition detected by this method are similar for Nanodiscs of different sizes.…”

Section: Discussionmentioning

confidence: 99%

Thermotropic Phase Transition in Soluble Nanoscale Lipid Bilayers

et al. 2005

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The role of lipid domain size and protein-lipid interfaces in the thermotropic phase transition of dipalmitoyl phosphatidylcholine (DPPC) and dimyristoyl phosphatidylcholine (DMPC) bilayers in Nanodiscs was studied using small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and generalized polarization (GP) of the lipophilic probe Laurdan. Nanodiscs are watersoluble, monodisperse self-assembled lipid bilayers encompassed by a helical membrane scaffold protein (MSP). MSPs of different lengths were used to define the diameter of the Nanodisc lipid bilayer from 76 to 108 Å and the number of DPPC molecules from 164 to 335 per discoidal structure. In Nanodiscs of all sizes, the phase transitions were broader and shifted to higher temperatures relative to those observed in vesicle preparations. The size dependences of the transition enthalpies and structural parameters of Nanodiscs reveal the presence of a boundary lipid layer in contact with the scaffold protein encircling the perimeter of the disc. The thickness of this annular layer was estimated to be approximately 15 Å, or two lipid molecules. SAXS was used to measure the lateral thermal expansion of Nanodiscs and a steep decrease of bilayer thickness during the main lipid phase transition was observed. These results provide basis for the quantitative understanding of cooperative phase transitions in membrane bilayers in confined geometries at the nanoscale.

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“…As the GP of the Laurdan probe accounts for the variations of polarity of the solvent mainly arising in the region of the acyl chains of the phospholipids, 40 and the CH 2 stretching mode accounts for the variations of the vibrational modes in the same region of the phospholipids when a phase transition takes place, we applied a logistic equation to fit both GP and FTIR curves, as described. 40,55 The applied sigmoidal function was the following:…”

Section: ■ Concluding Remarksmentioning

confidence: 99%

Impact of Embedded Endocannabinoids and Their Oxygenation by Lipoxygenase on Membrane Properties

Dainese

Sabatucci

Angelucci

et al. 2012

ACS Chem. Neurosci.

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N-Arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol are the best characterized endocannabinoids. Their biological activity is subjected to metabolic control whereby a dynamic equilibrium among biosynthetic, catabolic, and oxidative pathways drives their intracellular concentrations. In particular, lipoxygenases can generate hydroperoxy derivatives of endocannabinoids, endowed with distinct activities within cells. The in vivo interaction between lipoxygenases and endocannabinoids is likely to occur within cell membranes; thus, we sought to ascertain whether a prototypical enzyme like soybean (Glycine max) 15-lipoxygenase-1 is able to oxygenate endocannabinoids embedded in synthetic vesicles and how these substances could affect the binding ability of the enzyme to different lipid bilayers. We show that (i) embedded endocannabinoids increase membrane fluidity; (ii) 15-lipoxygenase-1 preferentially binds to endocannabinoid-containing bilayers; and that (iii) 15-lipoxygenase-1 oxidizes embedded endocannabinoids and thus reduces fluidity and local hydration of membrane lipids. Together, the present findings reveal further complexity in the regulation of endocannabinoid signaling within the central nervous system, disclosing novel control by oxidative pathways.

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Phase fluctuation in phospholipid membranes revealed by Laurdan fluorescence

Cited by 715 publications

References 13 publications

Two-photon microscopy of aorta fibers shows proteolysis induced by LDL hydroperoxides

Two-photon microscopy of aorta fibers shows proteolysis induced by LDL hydroperoxides

Thermotropic Phase Transition in Soluble Nanoscale Lipid Bilayers

Impact of Embedded Endocannabinoids and Their Oxygenation by Lipoxygenase on Membrane Properties

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