| 1. |
- Accardo, Antonella, et al.
(författare)
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High-relaxivity supramolecular aggregates containing peptides and Gd complexes as contrast agents in MRI
- 2007
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 1432-1327 .- 0949-8257. ; 12:2, s. 267-276
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Tidskriftsartikel (refereegranskat)abstract
- Mixed supramolecular aggregates, obtained by assembling together two amphiphilic monomers (C18H37)2NCO(CH2)2CO(AdOO)5-G-CCK8 (AdOO is 8-amino-3,6-dioxaoctanoic acid, CCK8 is C-terminal octapeptide of cholecystokinin) and (C18H37)2NCO(CH2)2COLys(DTPAGlu)CONH2 (DTPAGlu is N,N-bis[2-[bis(carboxyethyl)amino]ethyl]-l-glutamic acid), are characterized for their structural parameters by dynamic light scattering and for their relaxometric properties, in the absence and in the presence of 0.9 wt% NaCl. Two different aggregates (micelles and bilayer structures) are present in the absence of NaCl, while only bilayer structures are observed at physiological ionic strength. The presence of NaCl increases the ionic strength, promoting a decrease in the repulsions between the polar heads and among the aggregates in solution, thus supporting the formation of large-curvature aggregates such as bilayer structures like vesicles. In these conditions the closed, vesicular shape and the large size (hydrodynamic radius of about 300 Å) of the aggregates allow a high number of paramagnetic gadolinium complexes and bioactive peptides to be accommodated on the inner and external surfaces . The presence of the salt causes a variation in the structural arrangement of the molecules and a partial rigidification of the assembled Gd(III) complexes on the surface vesicles, reducing their internal motions and giving an approximately 15% higher relaxivity value (r 1p = 21.0 and 18.6 Mm−1 s−1 in the presence and in the absence of NaCl, respectively). The vesicles obtained, for the high relaxivity of each gadolidium complex and for the presence of a surface-exposed bioactive peptide, are very promising candidates as target-selective MRI contrast agents.
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| 2. |
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| 3. |
- Komitov, Lachezar, 1944, et al.
(författare)
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Alignment layer for LCD
- 2009
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The polymer of the invention promotes homeotropic alignment of liq. crystal materials. A polymer for use in an alignment layer for a liq. crystal material is provided. The polymer comprises a polymer backbone comprising a plurality of repeating units, said repeating units being divided into at least two groups, wherein each repeating unit in a first group of said repeating units is functionalized with a pendant side chain of a first type S1; each repeating unit in a second group of said repeating units is functionalized with a pendant side chain of a second type S2; said first type of side chain S1 comprising a fluorine-substituted hydrocarbon group; and said second type of side chain S2 comprising a siloxane. The polymer of the invention promotes homeotropic alignment of liq. crystal materials.
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| 4. |
- Sanna, Daria, et al.
(författare)
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Mendelian breeding units versus standard sampling strategies: Mitochondrial DNA variation in southwest Sardinia
- 2011
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Ingår i: Genetics and Molecular Biology. - 1678-4685. ; 34:2, s. 187-194
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Tidskriftsartikel (refereegranskat)abstract
- We report a sampling strategy based on Mendelian Breeding Units (MBUs), representing an interbreeding group of individuals sharing a common gene pool. The identification of MBUs is crucial for case-control experimental design in association studies. The aim of this work was to evaluate the possible existence of bias in terms of genetic variability and haplogroup frequencies in the MBU sample, due to severe sample selection. In order to reach this goal, the MBU sampling strategy was compared to a standard selection of individuals according to their surname and place of birth. We analysed mitochondrial DNA variation (first hypervariable segment and coding region) in unrelated healthy subjects from two different areas of Sardinia: the area around the town of Cabras and the western Campidano area. No statistically significant differences were observed when the two sampling methods were compared, indicating that the stringent sample selection needed to establish a MBU does not alter original genetic variability and haplogroup distribution. Therefore, the MBU sampling strategy can be considered a useful tool in association studies of complex traits.
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| 5. |
- Tesauro, Diego, et al.
(författare)
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Peptide Derivatized Lamellar Aggregates as Target-Specific MRI Contrast Agents
- 2007
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Ingår i: ChemBioChem. - : Wiley. - 1439-4227 .- 1439-7633. ; 8:8, s. 950-955
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Tidskriftsartikel (refereegranskat)abstract
- The relaxivity behaviour and the structural characterization of new supramolecular aggregates (bilayer structures and micelles) obtained by combining two different amphiphilic monomers are reported. One monomer, (C18)2DTPAGlu-Gd, contains a very stable gadolinium complex, and the other, DSPE-PEG2000-CCK8, contains the bioactive CCK8 peptide. Samples that contained only DSPE-PEG2000-CCK8, or up to 50 % (C18)2DTPAGlu-Gd, aggregated as double-layer structures (lamellar aggregates) with a thickness of80-100 Å, as evaluated by SANS measurement and Cryo-TEM imaging. A transition to micelle formation was observed when the amount of (C18)2DTPAGlu-Gd in the aggregate was increased. These were rod-like micelles 40 Å in radius and >200 Å in length. The proton relaxivities for both lamellar aggregates and rod-like micelles were the same (17.2 mM-1 s-1), although the values were the results of different combinations of local and global contributions. The in vitro target selectivity of aggregates that contained the CCK-8 peptide was demonstrated by using nuclear medicine techniques.
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| 6. |
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| 7. |
- Vaccaro, Mauro, et al.
(författare)
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Peptide and Gd Complexes Containing Colloidal Assemblies as Tumor-Specific Contrast Agents in MRI: Physicochemical Characterization
- 2007
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Ingår i: Biophysical Journal. - : Elsevier BV. - 1542-0086 .- 0006-3495. ; 93:5, s. 1736-1746
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation behavior of an amphiphilic supramolecular system, with potential application as a tumor-specific magnetic resonance imaging contrast agent, has been studied in detail by dynamic light scattering, small-angle neutron scattering and cryotransmission electron microscopy. The system was constituted of mixed aggregates formed by an anionic unimer containing the DTPAGlu, a chelating agent for the paramagnetic Gd3+ ion, and an uncharged unimer containing the bioactive peptide CCK8, capable of directing the assembly toward tumor cells. Mixed aggregates formed by both unimers, and in the case of the DTPAGlu unimer with the chelating agent as free base or as Gd3+ complex, have been investigated. A number of interesting features of the aggregation behavior were revealed: at physiological pH, micelles and bilayer structures were present, whereas upon decreasing solution pH or increasing ionic strength, the formation of bilayer structures was favored. On the basis of the above observations, the aggregating mechanism has been elucidated by considering the screening effect on intra- and interaggregate electrostatic repulsions.
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| 8. |
- Vaccaro, Mauro, et al.
(författare)
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Supramolecular aggregates of amphiphilic gadolinium complexes as blood pool MRI/MRA contrast agents: Physicochemical characterization
- 2006
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 22:15, s. 6635-6643
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the development of a new potential blood pool contrast agent for magnetic resonance imaging applications (MRA/MRI) based on gadolinium complexes containing amphiphilic supramolecular aggregates. A novel amphiphilic unimer, containing the DTPAGlu chelating agent covalently bound to two C18 alkylic chains, has been synthesized. DTPAGlu is a well-known chelating agent for a wide number of ions such as the paramagnetic metal ion Gd3+ used as contrast agent in MRA/MRI. The wide aggregation behavior of this surfactant, as free base or as gadolinium complex, has been studied and compared by means of dynamic light scattering, small-angle neutron scattering and cryogenic transmission electron microscopy techniques. Near neutral pH in both cases, the dominant aggregates are micelles. The high negative actual charge of the surfactant headgroup causes a strong headgroups repulsion, promoting the formation of large and high curvature aggregates. By decreasing pH and less markedly increasing the ionic strength, we observe a micelle-to-vesicle transition driven by a decreased electrostatic repulsion. A straightforward switch between different aggregation states can be particularly useful in the development of pH-responsive MRA/MRI contrast agents.
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