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Parasassi, Tiziana; Krasnowska, Ewa K.; Bagatolli, Luís A.; Gratton, Enrico

doi:10.1023/a:1020528716621

Cited by 561 publications

(348 citation statements)

References 24 publications

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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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Section: Discussionmentioning

confidence: 99%

Thermotropic Phase Transition in Soluble Nanoscale Lipid Bilayers

et al. 2005

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“…The slope of the GP excitation spectrum can be exploited to ascertain the coexistence of lipid phases. A negative or positive slope indicates a single liquid-crystalline phase or coexisting gel and liquid-crystalline phase domains, respectively (20).…”

Section: Melanoma and Peripheral Blood Mononuclear Cells (Pbmcs)-mentioning

confidence: 99%

Microenvironmental pH Is a Key Factor for Exosome Traffic in Tumor Cells

Parolini

Federici

Raggi

et al. 2009

Journal of Biological Chemistry

1,249

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Exosomes secreted by normal and cancer cells carry and deliver a variety of molecules. To date, mechanisms referring to tumor exosome trafficking, including release and cell-cell transmission, have not been described. To gain insight into this, exosomes purified from metastatic melanoma cell medium were labeled with a lipid fluorescent probe, R18, and analyzed by spectrofluorometry and confocal microscopy. A low pH condition is a hallmark of tumor malignancy, potentially influencing exosome release and uptake by cancer cells. Using different pH conditions as a modifier of exosome traffic, we showed (i) an increased exosome release and uptake at low pH when compared with a buffered condition and (ii) exosome uptake by melanoma cells occurred by fusion. Membrane biophysical analysis, such as fluidity and lipid composition, indicated a high rigidity and sphingomyelin/ganglioside GM3 (N-acetylneuraminylgalactosylglucosylceramide) content in exosomes released at low pH. This was likely responsible for the increased fusion efficiency. Consistent with these results, pretreatment with proton pump inhibitors led to an inhibition of exosome uptake by melanoma cells. Fusion efficiency of tumor exosomes resulted in being higher in cells of metastatic origin than in those derived from primary tumors or normal cells. Furthermore, we found that caveolin-1, a protein involved in melanoma progression, is highly delivered through exosomes released in an acidic condition. The results of our study provide the evidence that exosomes may be used as a delivery system for paracrine diffusion of tumor malignancy, in turn supporting the importance of both exosomes and tumor pH as key targets for future anti-cancer strategies.

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“…As shown in Figure 1, laurdan (6-dodecanoyl-2-dimethylaminonaphtalene) exhibits dual fluorescence from the locally excited (LE) and ICT states, where the ratio depends sensitively on the solvent polarity. This feature has been exploited to probe the local polarity by generalized polarization images [1,2]. Laurdan, an analogue of DMABN (4-dimethylaminobenzonitrile), which is the benchmark system of ICT reaction, consists of an electron-donating dimethylamino group and an electron-withdrawing carbonyl group on the opposite side of the naphthalene.…”

Section: Introductionmentioning

confidence: 99%