| 1. |
- Bastiat, Guillaume, et al.
(författare)
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Development of Non-Phospholipid Liposomes Containing a High Cholesterol Concentration
- 2007
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 23:14, s. 7695-7699
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Tidskriftsartikel (refereegranskat)abstract
- We present a novel formulation of non-phospholipid liposomes formed from cholesterol and palmitic acid. Despite the fact that these two lipidic species do not form individually fluid bilayers, we show that once mixed together, fluid bilayers can be obtained and, moreover, these can be extruded using classical extrusion processes to form liposomes. The chem. anal. indicates that these liposomes contain 70 mol % cholesterol, a content that is considerably higher that the satn. limit generally reported for phospholipid bilayers. These cholesterol-rich liposomes, formed with mols. that have low toxicity in vivo, display an improved impermeability relative to that of traditional phospholipid liposomes. In addn., because of the presence of palmitic acid, the stability of the liposomes is pH-dependent, and it is possible to trigger the release of encapsulated materials by pH stimuli.
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| 2. |
- Cui, Zhong-Kai, et al.
(författare)
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Impact of interfacial cholesterol-anchored polyethylene glycol on sterol-rich non-phospholipid liposomes
- 2014
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 428, s. 111-120
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Tidskriftsartikel (refereegranskat)abstract
- HypothesisLiposomes made of single-chain amphiphiles and a large amount of sterols display several advantages including a limited permeability. In the present paper, we examine the possibility to prepare such non-phospholipid liposomes with interfacial polyethylene glycol (PEG) in order to improve their circulation in the blood stream. Cholesterol (Chol) was chosen as the PEG anchor.ExperimentsThe phase behavior of mixtures of palmitic acid (PA) and cholesterol including various proportions of PEGylated cholesterol (PEG-Chol) was characterized. In conditions leading to the formation of fluid bilayers, properties of the resulting liposomes were assessed.FindingsUp to 20 mol% of PEGylated cholesterol could be introduced without significant perturbations in fluid bilayers made of PA and cholesterol. With 10 mol% PEG-Chol, PA/Chol/PEG-Chol liposomes showed a very limited permeability to calcein and doxorubicin. Doxorubicin could be actively loaded in PA/Chol/PEG-Chol liposomes with a high drug loading efficiency and a high drug to lipid ratio. Pharmaco-kinetic experiments in rats indicated that interfacial PEG reduced the clearance of PA/Chol liposomes compared to the naked ones. However the lifetime of these non-phospholipid liposomes in the blood circulation was considerably shorter than that observed for control PEGylated phospholipid liposomes, a phenomenon associated with the negative interfacial charge of the PA/Chol/PEG-Chol liposomes.
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| 3. |
- Lafleur, Jean-Michel, et al.
(författare)
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The political choices of emigrants voting in home country elections : A socio-political analysis of the electoral behaviour of Bolivian external voters
- 2015
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Ingår i: Migration Studies. - : Oxford University Press (OUP). - 2049-5838 .- 2049-5846. ; 3:2, s. 155-181
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Tidskriftsartikel (refereegranskat)abstract
- What variables influence the electoral behaviour of citizens voting in home country elections from abroad? Despite the growing interest of migration scholars for the topic of external voting, this question remains largely unanswered. Basing ourselves on the existing political science literature on electoral behaviour and on the migration literature on immigrants' participation in host country politics, we isolate different hypotheses that explain emigrants' preferences in home country politics. We then build four models of voters based on these hypotheses: the social group voter, the ideological voter, the interest-driven voter, and the transnational voter. In the second part of the paper, we verify the validity of these models using the results of a survey carried out with Bolivian emigrants who took part in the 2009 Bolivian presidential election from abroad. Overall, this article identifies the drivers of immigrant transnational political participation and contributes to current debates on social remittances.
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| 4. |
- Lafleur, Michel, et al.
(författare)
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Bovine binder-of-sperm protein BSP1 promotes protrusion and nanotube formation from liposomes
- 2010
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 399:3, s. 406-411
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Tidskriftsartikel (refereegranskat)abstract
- Binder-of-sperm (BSP) proteins interact with sperm membranes and are proposed to extract selectively phosphatidylcholine and cholesterol from these. This change in lipid composition is a key step in sperm capacitation. The present work demonstrates that the interactions between the protein BSP1 and model membranes composed with phosphatidylcholine lead to drastic changes in the morphology of the lipidic self-assemblies. Using cryo-electron microscopy and fluorescence microscopy, we show that, in the presence of the protein, the lipid vesicles elongate, and form bead necklace-like structures that evolve toward small vesicles or thread-like structures. In the presence of multilamellar vesicles, where a large reservoir of lipid is available, the presence of BSP proteins lead to the formation of long nanotubes. Long spiral-like threads, associated with lipid/protein complexes, are also observed. The local curvature of lipid membranes induced by the BSP proteins may be involved in lipid domain formation and the extraction of some lipids during the sperm maturation process.
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| 5. |
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| 6. |
- Vankova, Zvezda, et al.
(författare)
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Diaspora Policies, Consular Services and Social Protection for Bulgarian Citizens Abroad
- 2020
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Ingår i: Migration and Social Protection in Europe and Beyond. - Cham : Springer International Publishing. - 9783030512446 - 9783030512453 ; Volume 2
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Bokkapitel (refereegranskat)abstract
- This chapter demonstrates that the Bulgarian diaspora policy is characterized by inconsistent implementation and dissonant institutional context. It is intertwined with the country’s migration policy which is focused, among other priorities, on attracting historic kin communities and Bulgarian emigrants, in order to overcome its demographic decline. Against this backdrop, the country lacks overall social protection policies towards Bulgarians abroad and prioritizes providing information rather than financial support. Firstly, the chapter presents the general institutional framework by which home country authorities interact with nationals abroad, as well as the main engagement policies with this population outside of the area of social protection. Secondly, the chapter focuses on the policies, programmes and services offered by home country authorities in response to social protection needs of Bulgarian nationals abroad across five specific policy areas: unemployment, health care, pensions, family-related benefits and economic hardship.
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| 7. |
- Vankova, Zvezda, et al.
(författare)
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Migrants’ Access to Social Protection in Bulgaria
- 2020
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Ingår i: Migration and Social Protection in Europe and Beyond. - Cham : Springer International Publishing. - 9783030512408 - 9783030512415 ; Volume 1
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Bokkapitel (refereegranskat)abstract
- This chapter aims to discuss the link between migration and welfare in Bulgaria. Firstly, it presents the main characteristics of the Bulgarian welfare system and discusses access to social benefits for resident and non-resident nationals, and resident non-nationals. Secondly, it examines Bulgaria’s migration history and key migration policy developments. Finally, the chapter provides a detailed analysis of access to social benefits of these different groups across five policy areas – unemployment, health care, family benefits, pensions, and guaranteed minimum resources – and the links to Bulgaria’s migration policy.
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| 8. |
- Wessman, Per, 1976-
(författare)
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Physico-Chemical Investigations of, and Characterization of Model Membranes for, Lipid-Peptide Interactions
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this thesis is on the effects caused by α-helical peptides on liposome structure, the impact of cholesterol on the peptide-membrane interactions, and the effect of aggregate curvature on the peptide affinity. Results of the studies show that the membrane destabilizing effect of the cationic α-helical peptide melittin is modulated by cholesterol. Melittin induces leakage from pure phospholipid liposomes in a manner that is compatible with the presence of small pores. In the case of cholesterol-supplemented liposomes leakage coincides, however, with major structural transformations and rupture of the liposomes. Cholesterol decreases the affinity of melittin for phospholipid bilayers, but once the peptide has adsorbed to the membrane the presence of cholesterol does not offer any resistance against melittin-induced membrane destabilization. Our investigations indicate that cholesterol affects the alamethicin-lipid bilayer interactions in a similar way. PEG-stabilized bilayer disks are formed upon addition of polyethylene glycol (PEG)-lipids to lipid mixtures with high bending rigidity. The partial segregation of components within the bilayer disk, suggested by theoretical calculations and experimental observations, was verified by small angle neutron scattering. By means of a novel competitive binding assay it was shown that the three α-helical peptides melittin, alamethicin, and magainin have high affinity for the curved rim of PEG-stabilized bilayer disks. The bilayer disks have structural, and other properties, that make them interesting for the formulation of peptides and membrane-associated proteins. For stability reasons dry formulations are often preferred. The PEG-stabilized bilayer disks were shown to retain their structure in rehydrated samples that had been freeze- or spray-dried in the presence of lactose.
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