Edible Supramolecular Chiral Nanostructures by Self-Assembly of an Amphiphilic Phytosterol Conjugate (original) (raw)
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Chiral effect on the self-assembly of chiral molecules synthesized from cholesterol
Journal of the Taiwan Institute of Chemical Engineers, 2018
One predesigned chiral steroid base compound cholesteryl 4-(carbonyloxy) 4-(hexyloxyl) benzoate (CCH *) and two achiral compounds with various alkyl chain length oxalyl acid N',N'-di(4-(hexyloxy)benzoyl)hydrazide (AG6) and oxalyl acid N',N'-di(4-(undecyloxy)benzoyl)-hydrazide (AG11) have been successfully synthesized. Formation of asymmetric self-assembled constructions via self-assembly of achiral molecules in chiral environment was investigated. Due to steric hindrance, CCH * could not form gel in any kind of organic solvents. On the other hand, AG6 and AG11 formed achiral gels in many kinds of solvent. The results suggest that polarity, side branch and intermolecular forces are the key factors for the gelation. Temperature-dependent 1 H NMR analysis of the fabricated gels show that van der Waals forces and ππ interactions are key factors leading to self-assembly of molecules result in three-dimensional networks. In addition, CCH * was used as a chiral dopant added into achiral compounds forming asymmetric selfassembled constructions. The results indicate that doping of CCH * into achiral gelators giving a chiral environment leads to the formation of helical constructions. The fabricated asymmetric constructions were confirmed using circular dichroism (CD) spectroscopy and small angle X-ray scattering (SAXS).
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Proceedings of the National Academy of Sciences, 2010
A challenging target in the noncovalent synthesis of nanostructured functional materials is the formation of uniform features that exhibit well-defined properties, e.g., precise control over the aggregate shape, size, and stability. In particular, for aqueousbased one-dimensional supramolecular polymers, this is a daunting task. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing out attractive noncovalent forces within the hydrophobic core of the polymerizing building blocks with electrostatic repulsive interactions on the hydrophilic rim we managed to switch from elongated, rod-like assemblies to small and discrete objects. Intriguingly this rod-tosphere transition is expressed in a loss of cooperativity in the temperature-dependent self-assembly mechanism. The aggregates were characterized using circular dichroism, UV and 1H-NMR spectroscopy, small angle X-ray scattering, and cryotransmission electron microscopy. In analogy to many systems found in biology, mechanistic details of the self-assembly pathways emphasize the importance of cooperativity as a key feature that dictates the physical properties of the produced supramolecular polymers.
Configuration of a single centre determines chirality of supramolecular carotenoid self-assembly
Tetrahedron Letters, 2001
Card-pack and head-to-tail types of self-assembly are formed upon aqueous dilution of capsantholon 6%-epimers dissolved in water-miscible organic solvents. Slow transformation of head-to-tail assembly into card-pack type is observed. Induced supramolecular chirality is seen upon addition of achiral b-carotene, as judged from the increased intensity of exciton signal detected in circular dichroism spectra.
Advanced Fiber Materials
Molecular recognition of simple sugars is crucial due to their essential roles in most living organisms. However, it remains extremely challenging to achieve a visual recognition of simple sugars like sucrose in water media under physiological conditions. In this article, the visual recognition of sucrose is accomplished by a chiral supramolecular hydrogel formation through the co-assembly of a two-component fibrous solution (l-phenylalanine based gelator co-diaminopyridine, LDAP) and sucrose. H-bonding between the amino group of LDAP and the hydroxyl group of sucrose facilitates the gelation by loading sucrose into the LDAP solution. The formed hydrogel showed an amplified inversion of circular dichroism (CD) signals as compared to the corresponding LDAP solution. In addition, the effective chirality transfer was accompanied by a bathochromic shift in UV-Vis and FL spectra of the gel. Such a simple and straightforward chiral co-assembled strategy to visually recognize sucrose will have the potential use of smart gelators in saccharides separation and proteomics to be further applied in medical diagnostics and cell imaging.
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The self-assembly of biologically based amphiphiles into potentially useful nanostructures has been the subject of intense study in recent years. Many types of amphiphilic molecules self-assemble to form cylindrical tubules and helical ribbons. 1-4 In most cases, these systems consist of ...
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Increasing knowledge on the link between diet and human health has generated a lot of interest in the development of functional foods. However, several challenges, including discovering of beneficial compounds, establishing optimal intake levels, and developing adequate food delivering matrix and product formulations, need to be addressed. A number of new processes and materials derived from nanotechnology have the potential to provide new solutions in many of these fronts. Nanotechnology is concerned with the manipulation of materials at the atomic and molecular scales to create structures that are less than 100 nm in size in one dimension. By carefully choosing the molecular components, it seems possible to design particles with different surface properties. Several food-based nanodelivery vehicles, such as protein-polysaccharide coacervates, multiple emulsions, liposomes and cochleates have been developed on a laboratory scale, but there have been very limited applications in rea...
Soft Matter, 2016
We report that star-shaped molecules with cholic acid cores asymmetrically grafted by low molecular weight polymers with hydrogen bonding end-groups undergo aggregation to nanofibers, which subsequently wrap into micrometer spherical aggregates with low density cores. Therein the facially amphiphilic cholic acid (CA) is functionalized by four flexible allyl glycidyl ether (AGE) side chains, which are terminated with hydrogen bonding 2-ureido-4[1H]pyrimidinone (UPy) end-groups as connected by hexyl spacers, denoted as CA(AGE 6-C 6 H 12-UPy) 4. This wedge-shaped molecule is expected to allow the formation of a rich variety of solvent-dependent structures due to the complex interplay of interactions, enabled by its polar/nonpolar surface-active structure, the hydrophobicity of the CA in aqueous medium, and the possibility to control hydrogen bonding between UPy molecules by solvent selection. In DMSO, the surfactant-like CA(AGE 6-C 6 H 12-UPy) 4 self-assembles into nanometer scale micelles, as expected due to its nonpolar CA apexes, solubilized AGE 6-C 6 H 12-UPy chains, and suppressed mutual hydrogen bonds between the UPys. Dialysis in water leads to nanofibers with lateral dimensions of 20-50 nm. This is explained by promoted aggregation as the hydrogen bonds between UPy molecules start to become activated, the reduced solvent dispersibility of the AGE-chains, and the hydrophobicity of CA. Finally, in pure water the nanofibers wrap into micrometer spheres having low density cores. In this case, strong complementary hydrogen bonds between UPy molecules of different molecules can form, thus promoting lateral interactions between the nanofibers, as allowed by the hydrophobic hexyl spacers. The wrapping is illustrated by transmission electron microscopy tomographic 3D reconstructions. More generally, we foresee hierarchically structured matter bridging the length scales from molecular to micrometer scale by sequentially triggering supramolecular interactions.
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Asia-pacific Journal of Molecular Biology and Biotechnology, 2023
Lipids such as glyceryl monooleate, phosphatidylcholine, and monoglyceride (CITREM) possess an amphipathic property that allows them to self-assemble into a complex internal structure when interacting with an aqueous solution. Since amphiphilic molecules possess hydrophilic heads and lipophilic tails, hydrophobic effects cause the spontaneous activity of the molecular rearrangement. The selforganization of the molecules often results in the phases of lipid polymorphism, for example microemulsion, inverse bicontinuous cubic (Q2), discontinuous hexagonal (H2), and micellar cubic (I2) Fd3m. Interestingly, these lamellar and non-lamellar phases have been applied in the development of nanocarriers for drug delivery due to their ability to provide a sustained drug release system, better drug bioavailability, and improved overall treatment. However, the attention that they are receiving from their application is not comparable to our understanding of the mechanisms involved in their synthesis. Elucidation of the spontaneous process helps in predicting and tuning the internal structure of an amphiphilic molecule to suit its application. Therefore, this review discusses the formation of lipid polymorphism from the thermodynamic point of view, critical packing parameter, and modified stalk theory.