| 1. |
- Gubitosi, M., et al.
(författare)
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On the stability of lithocholate derivative supramolecular tubules
- 2017
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 7:1, s. 512-517
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Tidskriftsartikel (refereegranskat)abstract
- The self-assembly of a mannose-labelled bile salt derivative gives rise to a metastable nematic phase of monodisperse nanotubes in aqueous solutions that are characterized by a crystalline order. This work is addressed to study the relative stability of these tubular aggregates in order to have full control of such a system for possible applications. By using a static light scattering method we evaluate both the solubilities of the metastable nanotubes and of stable nanocrystals, demonstrating that these are remarkably lower than the critical micellar concentration of typical bile salts and other ionic conventional surfactants. A partial stability map is developed by combining solubility and calorimetry data, where a nematic nanotube phase region is highlighted below 60-65 °C.
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| 2. |
- Gubitosi, Marta, et al.
(författare)
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Sugar-Bile Acid-Based Bolaamphiphiles: From Scrolls to Monodisperse Single-Walled Tubules.
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:22, s. 6358-6366
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Tidskriftsartikel (refereegranskat)abstract
- The introduction of a mannose residue on carbon 3 of lithocholic acid gives rise to an asymmetric and rigid bolaamphiphilic molecule, which self-assembles in water to form elongated tubular aggregates with an outer diameter of about 20 nm. These tubular structures display a temporal evolution, where the average tube diameter decreases with time, which can be followed by time-resolved small-angle X-ray scattering experiments. Cryogenic transmission electron microscopy images collected as a function of time show that at short times after preparation tubular scrolls are formed via the rolling of layers, after which a complex transformation of the scrolls into single-walled tubules takes place. At long time scales, a further evolution occurs where the tubules both elongate and become narrower. The observed self-assembly confirms the tendency of bile acids and their derivatives to form supramolecular aggregates with an ordered packing of the constituent molecules. It also demonstrates that scrolls can be formed as intermediate structures in the self-assembly process of monodisperse single-walled tubules.
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| 3. |
- Travaglini, Leana, et al.
(författare)
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A tryptophan-substituted cholic acid : expanding the family of labelled biomolecules
- 2015
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 483:Online 31 March 2015, s. 142-149
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of a novel cholic acid derivative bearing in the C-3 position a residue of tryptophan linked through an amide bond is herein described. Acidic or basic conditions are needed for the solubilization of the derivative in water. In alkaline solutions the molecule shows a self-association similar to the one of its natural precursor leading to the formation of ellipsoidal micelles which does not involve significant Trp–Trp interactions. On the contrary, in acidic conditions strong interactions between the tryptophan moieties occur, leading to the formation of a gel at low temperature. These interactions are broken upon heating and small micelles similar to those observed at high pH are formed. In both cases, fluorescence spectra suggest a polar environment for the amino acid fluorophore not remarkably affected by the self-assembly.
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| 4. |
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| 5. |
- Travaglini, Leana, et al.
(författare)
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Between Peptides and Bile Acids: Self-Assembly of Phenylalanine Substituted Cholic Acids
- 2013
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 117:31, s. 9248-9257
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Tidskriftsartikel (refereegranskat)abstract
- Biocompatible molecules that undergo self-assembly are of high importance in biological and medical applications of nanoscience. Peptides and bile acids are among the most investigated due to their ability to self-organize into many different, often stimuli-sensitive, supramolecular structures. With the aim of preparing molecules mixing the aggregation properties of bile acid and amino acid-based molecules, we report on the synthesis and self-association behavior of two diastereomers obtained by substituting a hydroxyl group of cholic acid with a L-phenylalanine residue. The obtained molecules are amphoteric, and we demonstrate that they show a pH-dependent self-assembly. Both molecules aggregate in globular micelles at high pH, whereas they form tubular superstructures under acid conditions. Unusual narrow nanotubes with outer and inner cross-section diameters of about 6 and 3 um are formed by the derivatives. The diasteroisomer with alpha orientation of the substituent forms in addition a wider tubule (17 nm cross-section diameter). The ability to pack in supramolecular tubules is explained in terms of a wedge-shaped bola-form structure of the derivatives. Parallel or antiparallel face-to-face dimers are hypothesized as fundamental building blocks for the formation of the narrow and wide nanotubes, respectively.
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| 6. |
- Travaglini, Leana, et al.
(författare)
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On the self-assembly of a tryptophan labeled deoxycholic acid
- 2014
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Ingår i: Physical Chemistry Chemical Physics. - 1463-9084. ; 16:36, s. 19492-19504
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembly of peptides and bile acids has been widely investigated because of their biological role and their potential as a tool for the preparation of nanostructured biomaterials. We herein report both the synthesis and the self-association behavior of a compound that combines the aggregation properties of bile acid- and amino acid-based molecules. The derivative has been prepared by introducing a L-tryptophan residue into the C-3 position of the deoxycholic acid skeleton and resulted in an amphoteric fluorescent labeled bile acid that shows a pH-dependent self-assembly. Under alkaline conditions it assembles into 28 nm diameter tubules, thus showing a completely different behavior compared to the precursor bile acid, which forms micelles under similar conditions. Upon heating the tubules break and turn into micelles, leading to an increase in the exposure to water of the tryptophan residue. On the other hand, in acidic solutions it aggregates into elongated micelles that further self-assemble forming a gel network, when an electrolyte is added.
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| 7. |
- Travaglini, Leana, et al.
(författare)
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Twisted nanoribbons from a RGD-bearing cholic acid derivative
- 2017
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Ingår i: Colloids and Surfaces B: Biointerfaces. - : Elsevier BV. - 0927-7765. ; 159, s. 183-190
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Tidskriftsartikel (refereegranskat)abstract
- In light of the biomedical interest for self-assembling amphiphiles bearing the tripeptide Arg-Gly-Gly (RGD), a cholic acid derivative was synthesized by introducing an aromatic moiety on the steroidal skeleton and the RGD sequence on the carboxylic function of its chain 17–24, thus forming a peptide amphiphile with the unconventional rigid amphiphilic structure of bile salts. In aqueous solution, the compound self-assembled into long twisted ribbons characterized by a very low degree of polydispersity in terms of width (≈25 nm), thickness (≈4.5 nm) and pitch (≈145 nm). It was proposed that in the ribbon the molecules are arranged in a bilayer structure with the aromatic moieties in the interior, strongly involved in the intermolecular interaction, whereas the RGD residues are located at the bilayer-water interface. The nanostructure is significantly different from those generally provided by RGD-containing amphiphiles with the conventional peptide-tail structure, for which fibers with a circular cross-section were observed, and successfully tested as scaffolds for tissue regeneration. From previous work on the use of this kind of nanostructures, it is known that features like morphology, rigidity, epitope spacing and periodicity are important factors that dramatically affect cell adhesion and signaling. Within this context, the reported results demonstrate that bile salt-based peptide surfactants are promising building blocks in the preparation of non-trivial RGD-decorated nanoaggregates with well-defined morphologies and epitope distributions.
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