Display omitted
Sodium deoxycholate is a natural bile salt produced by animals and fulfilling important physiological processes. It is also used as dispersive surfactant and building block for ...self-assembled architectures in biology and material science. Although long debated, the study of its self-assembly in water is hereto incomplete and the models of the known aggregates are still controversial. This background suggests a complex scenario likely missing of additional mesophases.
Electron and optical microscopy techniques were crossed with SAXS data for the research.
Novel rod, sponge, vesicle, lamellae, nanotube phases and reversible transitions among them arise at conditions (concentration, pH, temperature, ionic strength, ionic composition) fitting the physiological working environment of sodium deoxycholate. These findings enlarge the perspective towards different directions. The integration of the previous literature with this work removes any interpretative contradiction since all the structures cover the entire spectrum of phases expected for surfactants, thus being explained according to the Israelachvili’s scheme. It is not trivial that a single molecule can show such a high structural variability. This fact highlights a very versatile system. Probably it is not a coincidence that it occurs in a multitasking biomolecule. These results furnish fundamental knowledge to clarify the bile salts’ role in vivo.
Naturally occurring single crystals having a multidomain morphology are a counterintuitive phenonomon: the macroscopic appearance is expected to follow the symmetry of the unit cell. Growing such ...crystals in the lab is a great challenge, especially from organic molecules. We achieve here uniform metallo-organic crystals that exhibit single crystallinity with apparently distinct domains and chirality. The chirality is present at both the molecular and macroscopic levels, although only achiral elements are used. "Yo-yo"-like structures having opposite helical handedness evolve from initially formed seemingly achiral cylinders. This non-polyhedral morphology coexists with a continuous coordination network forming homochiral channels. This work sheds light on the enigmatic aspects of fascinating crystallization processes occurring in biological mineralization. Our findings open up opportunities to generate new porous and hierarchical chiral materials.
The coexistence of single-crystallinity with a multidomain morphology is a paradoxical phenomenon occurring in biomineralization. Translating such feature to synthetic materials is a highly ...challenging process in crystal engineering. We demonstrate the formation of metallo-organic single-crystals with a unique appearance: six-connected half-rods forming a hexagonal-like tube. These uniform objects are formed from unstable, monodomain crystals. The monodomain crystals dissolve from the inner regions, while material is anisotropically added to their shell, resulting in hollow, single-crystals. Regardless of the different morphologies and growth mechanism, the crystallographic structures of the mono- and multidomain crystals are nearly identical. The chiral crystals are formed from achiral components, and belong to a rare space group (P622). Sonication of the solvents generating radical species is essential for forming the multidomain single-crystals. This process reduces the concentration of the active metal salt. Our approach offers opportunities to generate a new class of crystals.
Inorganic nanoparticle–chiral molecule coupling may produce chiroptical effects at the inorganic particles’ excitation wavelengths. In this work, we demonstrate that low concentrations of glutathione ...molecules adsorbed to cube-shaped silver nanoparticles lead to the appearance of new circular dichroism signals in the plasmon resonance absorption range. Moreover, for pH values of <4.5, the nanoparticle surface promotes reversible thiol group oxidation, leading to the formation of diglutathione and consequent reversible modification of both the molecular and plasmonic circular dichroism and absorption spectra. This study demonstrates the importance of chiroptical effects as probes of molecule–inorganic nanocrystal interaction.
Physiology and Physical Chemistry of Bile Acids di Gregorio, Maria Chiara; Cautela, Jacopo; Galantini, Luciano
International journal of molecular sciences,
02/2021, Letnik:
22, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Bile acids (BAs) are facial amphiphiles synthesized in the body of all vertebrates. They undergo the enterohepatic circulation: they are produced in the liver, stored in the gallbladder, released in ...the intestine, taken into the bloodstream and lastly re-absorbed in the liver. During this pathway, BAs are modified in their molecular structure by the action of enzymes and bacteria. Such transformations allow them to acquire the chemical-physical properties needed for fulling several activities including metabolic regulation, antimicrobial functions and solubilization of lipids in digestion. The versatility of BAs in the physiological functions has inspired their use in many bio-applications, making them important tools for active molecule delivery, metabolic disease treatments and emulsification processes in food and drug industries. Moreover, moving over the borders of the biological field, BAs have been largely investigated as building blocks for the construction of supramolecular aggregates having peculiar structural, mechanical, chemical and optical properties. The review starts with a biological analysis of the BAs functions before progressively switching to a general overview of BAs in pharmacology and medicine applications. Lastly the focus moves to the BAs use in material science.
We show that metal–organic frameworks, based on tetrahedral pyridyl ligands, can be used as a morphological and structural template to form a series of isostructural crystals having different metal ...ions and properties. An iterative crystal‐to‐crystal conversion has been demonstrated by consecutive cation exchanges. The primary manganese‐based crystals are characterized by an uncommon space group (P622). The packing includes chiral channels that can mediate the cation exchange, as indicated by energy‐dispersive X‐ray spectroscopy on microtome‐sectioned crystals. The observed cation exchange is in excellent agreement with the Irving–Williams series (Mn<Fe<Co<Ni< Cu>Zn) associated with the relative stability of the resulting coordination nodes. Furthermore, we demonstrate how the metal cation controls the optical and magnetic properties. The crystals maintain their morphology, allowing a quantitative comparison of their properties at both the ensemble and single‐crystal level.
Quantitative exchange of metal cations has resulted in a variety of crystals having different optical and magnetic properties but with retention of the crystal shape. Crystals isolated during the exchange exhibited higher concentrations of the incoming metal cations at the hexagonal basal faces, which suggests that the nanochannels are mediating the process.
Conclusion Bonebridge (BB) and Sophono (SP) devices improved hearing; with the BB implant showing a better performance at medium and high frequencies. Furthermore, the BB, as an active implant, ...showed higher functional gain and increased time of use, when compared to the SP, a passive system. Objectives This study aims to compare surgical and audiological outcomes of SP and BB devices in order to assess and further differentiate the indication criteria. Methods Fourteen patients with conductive and mixed hearing loss were evaluated pre- and post-operatively (BB or SP) (period 2013-2014). Age, gender, surgical history, cause and type of hearing loss, implant use per day, levels of bone and air conduction, and functional gain were recorded. Data was analysed by Wilcoxon singed-rank and Wilcoxon rank-sum tests. Results Fourteen patients (BB; n = 10 and SP; n = 4) with an average age = 25.42 years (CI95 = 12.41-38.43) were evaluated. The gender relation was equal (1:1), with pre-implantation osseous thresholds of 20.42 dB (CI95 = 11.15-29.69), and pre-implantation aerial thresholds of 70.83 dB (CI95 = 62.52-79.14). The SP wearing time was significantly lower than that of the BB (SP = 7-10 h/day, BB = 8-12 h/day; p = 0.0323). The functional gain did not differ significantly between the two devices (BB = 40.00 ± 13.19 dB, SP = 34.06 ± 15.63 dB; p = 0.3434), but a significant improvement from pre- to post-implantation was observed (p < 0.05). BB and SP decreased auditory thresholds at 1 and 2 kHz (< 0.01), respectively. The BB even significantly decreased thresholds at 0.5 kHz (p = 0.0140) and 4 kHz (p < 0.0001). No relevant surgical complications were found.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK, VSZLJ
An approach for tailoring self‐assembled tubular structures is described. By controlling the relative composition of a two‐component surfactant mixture comprising the natural bile salt lithocholate ...and its bolamphiphilic derivative, it was possible to finely tune the nanotube cross‐section of the mixed tubular aggregates that self‐associated spontaneously in aqueous solution at pH 12. The diameter was found to vary up to 50 % when the stoichiometric ratio of the two bile salts was changed. The tuning of supramolecular nanochannels with such remarkable precision is of significant interest for technological applications of these materials.
The perfect fit: The tailoring of self‐assembled nanotube cross‐sections is described for two‐component mixtures of a bile acid and its derivative. By controlling the stoichiometry, diameters were found to vary by up to 50 %. Starting from pure tubules with a parallel arrangement of the monomer, a progressive inclusion of the second component in an antiparallel orientation is proposed to explain the variation in size.
Cortical subarachnoid hemorrhage is an infrequent subtype of non-aneurysmal subarachnoid hemorrhage, rarely reported in watershed territories (wSAH) after carotid stenting. It has never been reported ...after treatment of middle cerebral artery stenosis (MCAS) that is increasingly used in selected patients, as rescue treatment of failed mechanical thrombectomy, due to recent advancements in endovascular interventions. We present a series of patients with MCAS that developed a wSAH after stenting.
Formation of highly interpenetrated frameworks is demonstrated. An interesting observation is the presence of very large adamantane‐shaped cages in a single network, making these crystals new entries ...in the collection of diamondoid‐type metal–organic frameworks (MOFs). The frameworks were constructed by assembling tetrahedral pyridine ligands and copper dichloride. Currently, the networks’ degree of interpenetration is among the highest reported and increases when the size of the ligand is increased. Highly interpenetrated frameworks typically have low surface contact areas. In contrast, in our systems, the voids take up to 63 % of the unit cell volume. The MOFs have chiral features but are formed from achiral components. The chirality is manifested by the coordination chemistry around the metal center, the structure of the helicoidal channels, and the motifs of the individual networks. Channels of both handednesses are present within the unit cells. This phenomenon shapes the walls of the channels, which are composed of 10, 16, or 32 chains correlated with the degree of interpenetration 10‐, 16‐, and 32‐fold, respectively. By changing the distance between the center of the ligand and the coordination moieties, we succeeded in tuning the diameter of the channels. Relatively large channels were formed, having diameters up to 31.0 Å×14.8 Å.
Tetrahydral achiral ligands and copper ions assemble into a record number of interpenetrating diamondoid networks. The networks intertwine akin to strands of a molecular rope to shape the chiral channels. The design of the ligand “arms” allows modulating their degree of interpenetration and the channel properties. The concurrent presence of such numerous interpenetrated networks and porosity is unprecedented for metal–organic frameworks.
PDF
