1,721,037 research outputs found
Structural Features of β-Cyclodextrin Solvation in the Deep Eutectic Solvent, Reline
Full text linkThe inherently amphiphilic nature of native cyclodextrins (CDs) determines their peculiar molecular encapsulation features, enabling applications such as targeted drug nanodelivery, aroma protection, etc. On the contrary, it may also lead to poor solubility in water and other organic solvents and to potentially detrimental flocking in these media, thus posing limitations to more extensive usage. Here we use small angle X-ray scattering to show that deep eutectic solvent reline (1:2 choline chloride:urea) succeeds in dissolving large amounts of β-CD (at least 800 mg/mL, compared with the solubility in water of 18 mg/mL), without aggregation phenomena occurring. At the microscopic level, molecular dynamics simulations highlight the complex interplay of hydrogen bonding-mediated hydrophilic interactions and hydrophobic force mitigation occurring between β-CD and reline components, leading to energetically favorable β-CD solvation. The possibility of achieving very high concentration conditions for unaggregated β-CD in an environmentally responsible media, such as reline, can open the way to new, so far unpredictable applications, addressing multiple societal challenges
Liquid structure of a water-based, hydrophobic and natural deep eutectic solvent: The case of thymol-water. A Molecular Dynamics study
Full text linkThe structural organization of the first example of a water-based, type V, hydrophobic, natural deep eutectic solvent (DES) is investigated in this work, exploiting the synergy of X-ray scattering and compu- tational techniques. The stoichiometric mixture of thymol:water (4.8:1) has been recently reported to behave as a DES, with a melting point at 6 C, well below the one foreseen for the ideal liquid mixture. Our study provides an atomistic insight into the structural correlations in this system, highlighting the major role played by hydrogen bonding (HB) correlations in affecting morphology as well as the solid– liquid equilibrium. Thymol engages HB-mediated interactions with both thymol and water molecules: evidences of conventional HB interactions involving the hydroxyl group are found, together with indica- tions of p HAO hydrogen bonding correlations with both thymol and water. Overall, in the mixture, thymol is involved in a larger number of HB interactions than in its neat liquid state. Such a strong inter- ference of water into thymol structural organization strongly hinders the development of HB-mediated thymol hexamers that is the structural leitmotif in crystalline thymol. On the other hand, only 30 % of the present water molecule can engage into correlations with at least another water molecule, thus pre- venting the formation of an extended HB network among water molecules that would result incompat- ible with the otherwise hydrophobic environment. Evidences of mesoscopic organization are observed experimentally and confirmed by simulations: these are related to the clustering of thymol hydroxyl groups with water molecules, leading to the formation on polar nano-pools embedded into the apolar matrix. This new solvent extends the range of water based, type V, hydrophobic DES, and represents an additional contribution to the development of sustainable technologies, with appealing properties
Solubility and solvation features of native cyclodextrins in 1-ethyl-3-methylimidazolium acetate
No full textThe comprehension of the mechanism entailing efficient solvation of cyclodextrins (CD) by green solvents is of great relevance to boost environmentally sustainable usages of smart supramolecular systems. Here, 1-ethyl-3-methylimidazolium acetate, an ecofriendly ionic liquid (IL), is considered as an excellent solvent for native CDs. This IL efficiently dissolves up to 40 wt.% β- and γ-CD already at ambient temperature and X-ray scattering indicates that CDs do not tend to detrimental flocculation under these drastic concentration conditions. Simulation techniques reveal the intimate mechanism of CD solvation by the ionic species: while the strong hydrogen bonding acceptor acetate anion interacts with CD's hydroxyl groups, the imidazolium cation efficiently solvates the hydrophobic CD walls via dispersive interactions, thus hampering CD's hydrophobic driven flocking. Overall the amphiphilic nature of the proposed IL provides an excellent solvation environment for CDs, through the synergic action of its components
Dissolution of nitrones in alkylphosphates: A structural study
No full textNitrones are chemical compounds with well-established anti-oxidant and spin-trapping properties. Their low solubility in water for many of them limits their applications, so opportune solvents must be found. In this study, two recently synthetized oxindole nitrones with proven antiproliferative and antioxidant activity have been dissolved in several liquid amphiphiles, chosen as model solvents. The effect of the polar head nature and the alkyl chain length/type have been investigated by a combined experimental (solubility, UV–vis spectroscopy) / computational (molecular dynamics) approach. The different chemical structures of the various solvents offer different chemical environments to the nitrones. The intermolecular interactions involved in the nitrone stabilization in the considered solvents have been highlighted, furnishing precious information for the ad-hoc design of specific carrier for nitrones delivery
Morphology of Poly(Ethylene Oxide)-Rtils Mixtures: Saxs and MD Studies
No full textPoly (ethylene oxide) is one of the few polymers that are soluble in room temperature ionic liquids. These mixtures can find several applications such as polymer electrolytes or separation media.
A few years ago, we highlighted the good solvent nature of RTILs towards PEO, using SANS technique [1], and Ribeiro simulated the morphology and dynamics of PEO-rich mixtures [2]. Recently the activities of Watanabe’s [3], Rogers’s [4] and Lodge’s [5] groups focused on the phase diagram of PEO-RTIL binary mixtures, detecting the existence of a Lower Critical Solution Temperature for these systems and screening the role of RTIL’s chemical details on this complex behavior.
Here we show recently obtained results from both Small Angle X-ray and Neutron Scattering from PEO-RTILs mixtures at ambient temperature, as a function of polymer concentration, for a variety of RTILs. We screened the role of alkyl chain length, methylation of position 2 in the imidazolium ring and other chemical details of the RTIL on the morphology of the macromolecule, extracting information as interesting as its average size, the persistence length and chain rigidity.
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These results have been complemented with MD simulation study of oligo (ethylene oxide) dissolved in C2mimTf2N and C2C1mimTf2N, in order to explore the role of hydrogen bonding on microscopic organization in such mixtures.
SAXS data for another polymer/IL mixture (namely PMMA/C2mimTf2N) will also be presented and compared with the findings for PEO/C2mimTf2N
Structure and vibrational features of the protic ionic liquid 1,8-diazabicyclo[5.4.0]-undec-7-ene-8-ium bis(trifluoromethanesulfonyl)amide, [DBUH][TFSI]
Full text linkThe Protic Ionic Liquid (PIL) formed by neutralization of the super-strong base 1,7-diazabicyclo[5.4.0]undec-7-ene (DBU) with the super-strong acid bis(trifluoromethanesulfonyl)-imide (TFSI), indicated as [DBUH][TFSI], has been investigated. Its chemical physical properties and structural features have been explored using a synergy of experimental and computational tools. Molecular Dynamics-rationalised X-ray diffraction patterns highlight the major role played by hydrogen bonding (HB) in affecting morphology in this PIL. A comparison between HB features in this and in related PILs has been presented, on the base of far-IR experiments and DFT analysis. Indications of a weaker HB interaction in [DBUH][TFSI] in comparison with [DBUH][TfO], consistently with their ΔpKa difference, have been observed and rationalised in terms of geometrical properties of the main conformers contributing to the experimental spectra. In the liquid phase of [DBUH][TFSI] a particularly large conformational disorder is observed and the corresponding large dispersion of the frequencies of the HB stretching modes leads to a broad absorption band without a well defined peak. On the contrary, well detectable HB related absorptions are observable in the solid phase of [DBUH][TFSI] and at all temperatures in [DBU][TfO], where less configurational disorder occurs
Structural features of selected protic ionic liquids based on a super-strong base
No full textProtic ionic liquids (PIL) were prepared from a super-strong base 1,7-diazabicyclo[5.4.0]undec-7-ene (DBU) and super-strong acids, trifluoromethane sulfonic acid (TfOH), and (trifluoromethanesulfonyl)-(nonafluorobutylsulfonyl)imide, (IM14H), ([DBUH][TfO] and [DBUH][IM14], respectively; the latter for the first time) and their chemical and physical properties and structural features have been explored using a synergy of experimental and computational tools. The short range order in neat DBU, as well as the long range structural correlations induced by charge correlation and hydrogen bonding interactions in the ionic liquids, have been explored under ambient conditions, where these compounds are proposed for a variety of applications. Similar to other [DBUH]-based PILs, the probed ones behave as good ionic liquids. Molecular dynamics-rationalised X-ray diffraction patterns show the major role played by hydrogen bonding in affecting morphology in these systems. Additionally, we find further evidence for the existence of fluorous domains in [DBUH][IM14], thus potentially extending the range of applications for these PILs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Green tea catechins induce inhibition of ptp1b phosphatase in breast cancer cells with potent anti-cancer properties: In vitro assay, molecular docking, and dynamics studies
Full text linkThe catechins derived from green tea possess antioxidant activity and may have a potentially anticancer effect. PTP1B is tyrosine phosphatase that is oxidative stress regulated and is involved with prooncogenic pathways leading to the formation of a.o. breast cancer. Here, we present the effect of selected green tea catechins on enzymatic activity of PTP1B phosphatase and viability of MCF-7 breast cancer cells. We showed also the computational analysis of the most effective catechin binding with a PTP1B molecule. We observed that epigallocatechin, epigallocatechin gallate, epicatechin, and epicatechin gallate may decrease enzymatic activity of PTP1B phosphatase and viability of MCF-7 cells. Conclusions: From the tested compounds, epigallocatechin and epigallocatechin gallate were the most effective inhibitors of the MCF-7 cell viability. Moreover, epigallocatechin was also the strongest inhibitor of PTP1B activity. Computational analysis allows us also to conclude that epigallocatechin is able to interact and bind to PTP1B. Our results suggest also the most predicted binding site to epigallocatechin binding to PTP1B
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