An unusual residual dipolar coupling of methylene protons was recorded in NMR spectra because aromatic zephycandidine has preferential orientation at the external magnetic field. The observed ...splitting contains contribution from the dipole-dipole
-coupling and the anisotropic component of
-coupling. Absolute values of the anisotropy of magnetic susceptibility |Δ
| are larger for protic solvents because of the hydrogen-bonding compared to aprotic solvents for which polar and dispersion forces are more important. The energy barrier for the reorientation due to hydrogen-bonding is 1.22 kJ/mol in methanol-
0.85 kJ/mol in ethanol-
and 0.87 kJ/mol in acetic acid-
. In dimethyl sulfoxide-
, 1.08 kJ/mol corresponds to the interaction of solvent lone pair electrons with π-electrons of zephycandidine. This energy barrier decreases for acetone-
which has smaller electric dipole moment. In acetonitrile-
, there is no energy barrier which suggests solvent ordering around the solute due to the solvent-solvent interactions. The largest absolute values of the magnetic anisotropy are observed for aromatic benezene-
and tolune-
which have their own preferential orientation and enhance the order in the solution. The magnetic anisotropy of "isolated" zephycandidine, not hindered by intermolecular interaction could be estimated from the correlation between Δ
and cohesion energy density.
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•Novel polymeric dispersions were prepared using the solvate form of griseofulvin.•Enhanced antifungal properties were found for the dispersions prepared using HPMCAS.•A correlation ...between the interactions in the solid and liquid was found.•Formed solvates attach to the biofilms interface via hydrogen bonding.
Fungal biofilms are invariably recalcitrant to antifungal drugs and thus can cause recurrent serious infections. The aim of this work was to prepare highly effective form of the antifungal drug griseofulvin using the chloroform solvate embedded into different polymeric matrices. Based on their solid solubility, solvated (chloroform) and non-solvated (methanol and acetone) solid dispersions were prepared using different materials: silica, microcrystalline cellulose, polyvinylpyrrolidone and hydroxypropyl methylcellulose acetate succinate (HPMCAS) by which HPMCAS dispersions showed the highest solubility of about 200 μg/mL compared with ∼30 μg/mL for pure griseofulvin. The anti fungal potential of griseofulvin was assessed against the dermatophytes T. rubrum. Metabolic and protease activity of T. rubrum NCPF 935 with and without the presence of GF:HPMCAS chloroform solvates showed significant reduction compared to the untreated control after 24 h period. Confocal laser scanning microscopy showed thin hyphae compared to Control and GF:HPMCAS (non solvated). Dynamic vapour sorption data showed that HPMCAS formed most stable solvate structure preventing recrystallization and solvate expulsion, which could explain the disruptive effect of the biofilms. This could be explained by the formed hydrogen bonds as revealed by the solid and liquid state NMR data, which was further confirmed via thermal and FTIR analyses.
During the past two decades, an improved understanding of the operative particle deformation mechanisms during latex film formation has been gained. For a particular colloidal dispersion, the ...Routh–Russel deformation maps predict the dominant mechanism for particle deformation under a particular set of conditions (evaporation rate, temperature, and initial film thickness). Although qualitative tests of the Routh–Russel model have been reported previously, a systematic study of the relationship between the film-formation conditions and the resulting water concentration profiles is lacking. Here, the water distributions during the film formation of a series of acrylic copolymer latexes with varying glass-transition temperatures, T g (values of −22, −11, 4, and 19 °C), have been obtained using GARField nuclear magnetic resonance profiling. A significant reduction in the rate of water loss from the latex copolymer with the lowest T g was found, which is explained by its relatively low polymer viscosity enabling the growth of a coalesced skin layer. The set of processing parameters where the drying first becomes impeded occurs at the boundary between the capillary deformation and the wet sintering regimes of the Routh–Russel model, which provides strong confirmation of the model’s validity. An inverse correlation between the model’s dimensionless control parameter and the dimensionless drying time is discovered, which is useful for the design of fast-drying waterborne films.
1 H nuclear magnetic resonance (NMR) relaxometry shows that arresting the hydration of cement paste by isopropanol exchange does not involve simple replacement of the pore water with isopropanol. ...Isopropanol fills capillary voids. It removes and replaces the water in the calcium-silicate-hydrate (C-S-H) interhydrate pores. In the C-S-H gel pores, the isopropanol draws water out, but does not replace it to the same extent. The exchange has only a minor impact on C-S-H interlayer water. The connectivity of the interlayer-gel network and interhydrate pores and capillary voids is evidenced by proton–deuteron chemical exchange in the C-S-H pore structure which is observed experimentally for the first time. Isopropanol also reveals the presence of large capillary voids that are not detected in samples saturated with water.
Functionalised nanomaterials are gaining popularity for use as drug delivery vehicles and, in particular, mucus penetrating nanoparticles may improve drug bioavailability via the oral route. To date, ...few polymers have been investigated for their muco-penetration, and the effects of systematic structural changes to polymer architectures on the penetration and diffusion of functionalised nanomaterials through mucosal tissue have not been reported. We investigated the influence of poly(2-oxazoline) alkyl side chain length on nanoparticle diffusion; poly(2-methyl-2-oxazoline), poly(2-ethyl-2-oxazoline), and poly(2-n-propyl-2-oxazoline) were grafted onto the surface of thiolated silica nanoparticles and characterised by FT-IR, Raman and NMR spectroscopy, thermogravimetric analysis, and small angle neutron scattering. Diffusion coefficients were determined in water and in a mucin dispersion (using Nanoparticle Tracking Analysis), and penetration through a mucosal barrier was assessed using an ex vivo fluorescence technique. The addition of a single methylene group in the side chain significantly altered the penetration and diffusion of the materials in both mucin dispersions and mucosal tissue. Nanoparticles functionalised with poly(2-methyl-2-oxazoline) were significantly more diffusive than particles with poly(2-ethyl-2-oxazoline) while particles with poly(2-n-propyl-2-oxazoline) showed no significant increase compared to the unfunctionalised particles. These data show that variations in the polymer structure can radically alter their diffusive properties with clear implications for the future design of mucus penetrating systems.
Abstract
The incorporation of lithium as a filler species in Co
1‐2x
Fe
x
Ni
x
Sb
3
skutterudites was accomplished by intercalation at 60 °C, using
n
‐BuLi as a reducing agent. Solid state
7
Li NMR ...and ICP‐MS analysis confirm the presence of lithium in the product phases and provide an estimate of the lithium content. The maximum uptake of lithium increases as cobalt is progressively substituted by an equimolar mixture of iron and nickel. Difference Fourier maps, calculated during Rietveld structure refinement using powder neutron diffraction data, locate the lithium cations at the 2
a
(0,0,0) sites within the cavities of the skutterudite framework. The intercalation of lithium results in reductions in thermal conductivity of up to 47 %, indicative of phonon glass electron crystal (PGEC) type behaviour. Charge transfer from lithium to the framework that accompanies intercalation results in a substantial decrease in electrical resistivity in lithiated phases and a more metal‐like temperature dependence. The increased carrier concentration also decreases the Seebeck coefficient, with the consequence that modest increases in the figure of merit occur, despite the reduced thermal conductivity.
A procedure based on 13C CPMAS NMR was developed to study procyanidins (PCs) and prodelphinidins (PDs) directly in milled sainfoin plant tissues. Blackcurrant and Tilia samples enabled reference ...spectra of purified proanthocyanidin (PA) fractions, crude extracts, and milled plant tissues, with characteristic resonances at 155, 144, and 132 ppm. PC/PD ratios were estimated from the I132/I155 intensity ratio and differed by 2.5 to 5.9% compared to thiolysis data. Normalization to the 155 ppm signal intensity from reference spectra enabled analysis of PA contents with an error of ca. 8 g PAs/100 g plant tissue. The procedure estimates the lignin contribution and allows for a correction of the PA content. In six sainfoin accessions, estimated PA contents were 1.6- to 20.8-fold higher than the thiolysis and 1.4- to 2.6-fold higher than the HCl–butanol–acetone results. Method differences may reflect the presence of unextractable, possibly high molecular weight PAs in sainfoin.
The blue-light sensitive photoreceptor, phototropin, is a flavoprotein which regulates the phototropism response of higher plants. The photoinduced triplet state and the photoreactivity of the ...flavin-mononucleotide (FMN) cofactor in two LOV domains of Avena sativa, Adiantum capillus-veneris, and Chlamydomonas reinhardtii phototropin have been studied by time-resolved electron paramagnetic resonance (EPR) and UV−vis spectroscopy at low temperatures (T ≤ 80 K). Differences in the electronic structure of the FMN as reflected by altered zero-field splitting parameters of the triplet state could be correlated with changes in the amino acid composition of the binding pocket in wild-type LOV1 and LOV2 as well as in mutant LOV domains. Even at cryogenic temperatures, time-resolved EPR experiments indicate photoreactivity of the wild-type LOV domains, which was further characterized by UV−vis spectroscopy. Wild-type LOV1 and LOV2 were found to form an adduct between the FMN cofactor and the functional cysteine with a yield of 22% and 68%, respectively. The absorption maximum of the low-temperature photoproduct of wild-type LOV2 is red-shifted by about 15 nm as compared with the FMN C(4a)-cysteinyl adduct formed at room temperature. In light of these observations, we discuss a radical-pair reaction mechanism for the primary photoreaction in LOV domains.
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