B23-Circular Dichroism
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Diamond Proposal Number(s):
[14708, 16031]
Open Access
Abstract: Polyphenols are an important constituent of wines and they are largely studied due to their antioxidant properties and for their effects on wine quality and stability, which is also related to their capacity to bind to proteins. The effects of some selected polyphenols, including procyanidins B1 and B2, tannic acid, quercetin, and rutin, as well as those of a total white wine procyanidin extract on the conformational properties of the major wine protein VVTL1 (Vitis vinifera Thaumatin-Like-1) were investigated by Synchrotron Radiation Circular Dichroism (SRCD). Results showed that VVTL1 interacts with polyphenols as demonstrated by the changes in the secondary (far-UV) and tertiary (near-UV) structures, which were differently affected by different polyphenols. Additionally, polyphenols modified the two melting temperatures (TM) that were found for VVTL1 (32.2 °C and 53.9 °C for the protein alone). The circular dichroism (CD) spectra in the near-UV region revealed an involvement of the aromatic side-chains of the protein in the interaction with phenolics. The data demonstrate the existence of an interaction between polyphenols and VVTL1, which results in modification of its thermal and UV denaturation pattern. This information can be useful in understanding the behavior of wine proteins in presence of polyphenols, thus giving new insights on the phenomena that are involved in wine stability.
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Apr 2020
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B21-High Throughput SAXS
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Open Access
Abstract: Ellagic acid (EA) is a potent antioxidant substance of natural origin characterized by poor biopharmaceutical properties and low solubility in water that limit its use. The aim of the present study was to develop lipid-based nanoparticle formulations able to encapsulate EA for dermal delivery. The EA-loaded nanoparticles were prepared using two different lipid compositions, namely tristearin/tricaprylin (NLC-EA1) and tristearin/labrasol (NLC-EA2). The influence of formulations on size, entrapment efficiency, and stability of EA-loaded nanoparticles was investigated. Cryo-TEM and small-angle X-ray scattering (SAXS) analyses showed that no morphological differences are evident among all the types of loaded and unloaded nanostructured lipid carriers (NLCs). The macroscopic aspect of both NLC-EA1 and NLC-EA2 did not change with time. No difference in size was appreciable between empty and drug-containing NLC, thus the nanoparticle diameter was not affected by the presence of EA and in general no variations of the diameters occurred during this time. The entrapment efficiency of both EA-loaded nanoparticles was almost quantitative. In addition, NLC-EA1 maintained EA stability for almost two months, while NLC-EA2 up to 40 days. FRAP (Ferric reducing ability of plasma) assay showed an antioxidant activity around 60% for both the loaded NLC, as compared to the solution. Although both types of NLC are characterized by some toxicity on HaCaT cells, NLC-EA1 are less cytotoxic than NLC-EA2. Taken together these results demonstrated that the inclusion of EA within NLC could improve the water solubility, allowing for a reduction of the dosage. Moreover, both types of NLC-EA maintained a high antioxidant effect and low toxicity.
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Mar 2020
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I22-Small angle scattering & Diffraction
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Diamond Proposal Number(s):
[17191]
Open Access
Abstract: Owing to their unique structural features, non-lamellar liquid crystalline nanoparticles comprising cubosomes and hexosomes are attracting increasing attention as versatile investigative drug carriers. Background: Depending on their physiochemical characteristics, drug molecules on entrapment can modulate and reorganize structural features of cubosomes and hexosomes. Therefore, it is important to assess the effect of guest molecules on broader biophysical characteristics of non-lamellar liquid crystalline nanoparticles, since drug-induced architectural, morphological, and size modifications can affect the biological performance of cubosomes and hexosomes. Methods: We report on alterations in morphological, structural, and size characteristics of nanodispersions composed from binary mixtures of glycerol monooleate and vitamin E on thymoquinone (a molecule with wide therapeutic potentials) loading. Results: Thymoquinone loading was associated with a slight increase in the mean hydrodynamic nanoparticle size and led to structural transitions from an internal biphasic feature of coexisting inverse cubic Fd3m and hexagonal (H2) phases to an internal inverse cubic Fd3m phase (micellar cubosomes) or an internal inverse micellar (L2) phase (emulsified microemulsions, EMEs). We further report on the presence of “flower-like” vesicular populations in both native and drug-loaded nanodispersions. Conclusions: These nanodispersions have the potential to accommodate thymoquinone and may be considered as promising platforms for the development of thymoquinone nanomedicines.
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Dec 2019
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[22240]
Open Access
Abstract: A simple protocol yielding ortho-substituted nitrosophenols from phenols is demonstrated,
in the form of copper(II) bis(nitrosophenolato) complexes. The developed methodology was applied
to a range of substrates, confirming the role of the copper in both the formation and protection of the
challenging 1, 2-substitution pattern. Using polymer supported thiourea, the Cu could be stripped
from the complexes and thus enabled the isolation or identification of the uncoordinated ligands
and their decomposition products, in yields generally low in line with the intrinsic high reactivity of
2-nitrosophenols. The product complexes are useful intermediates as demonstrated in revisiting a
formal [4 + 2] cycloaddition with dimethylacetylene dicarboxylate to synthesise bicyclic products in
variable yields, revealing the product has a novel structure di erent from those previously reported
in the literature.
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Nov 2019
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I04-1-Macromolecular Crystallography (fixed wavelength)
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Diamond Proposal Number(s):
[8421]
Open Access
Abstract: Since hyperactivity of the protein kinase DYRK1A is linked to several neurodegenerative disorders, DYRK1A inhibitors have been suggested as potential therapeutics for Down syndrome and Alzheimer’s disease. Most published inhibitors to date suffer from low selectivity against related kinases or from unfavorable physicochemical properties. In order to identify DYRK1A inhibitors with improved properties, a series of new chemicals based on [b]-annulated halogenated indoles were designed, synthesized, and evaluated for biological activity. Analysis of crystal structures revealed a typical type-I binding mode of the new inhibitor 4-chlorocyclohepta[b]indol-10(5H)-one in DYRK1A, exploiting mainly shape complementarity for tight binding. Conversion of the DYRK1A inhibitor 8-chloro-1,2,3,9-tetrahydro-4H-carbazol-4-one into a corresponding Mannich base hydrochloride improved the aqueous solubility but abrogated kinase inhibitory activity.
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Nov 2019
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I07-Surface & interface diffraction
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Diamond Proposal Number(s):
[17042]
Open Access
Abstract: Due to the characteristic chain rigidity and weak intermolecular interactions of perfluorinated substances, the phase diagram of Langmuir monolayer formed by perfluorinated molecules has been interpreted so far as displaying only two phases, a 2D gas (G) and a liquid condensed (LC). However, in this work, we presented Grazing Incidence X-ray Diffraction measurements, which exhibit two diffraction peaks on the transition plateau: One is the signature of the hexagonal structure of the LC phase, the second one is associated to the low-density fluid phase and is thus more ordered than expected for a 2D gas or a typical fluid phase. Atomistic molecular dynamics simulations, performed on the transition plateau, revealed the existence of clusters in which domains of vertical molecules organized in a hexagonal lattice coexist with domains of parallel lines formed by tilted molecules, a new structure that could be described as a “2D smectic C” phase. Moreover, the diffraction spectrum calculated from the simulation trajectories compared favorably with the experimental spectra, fully validating the simulations and the proposed interpretation. The results were also in agreement with the thermodynamic analysis of the fluid phase and X-ray Reflectivity experiments performed before and after the transition between these two phases.
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Oct 2019
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[16139]
Open Access
Abstract: The n-paraphenylene family comprises chains of phenylene units linked together by C-C bonds that are between single- and double-bonded, and where n corresponds to the number of phenylene units. In this work, we compare the response of the optical properties of different phenylene arrangements. We study linear chains (LPP), cyclic systems (CPPs), and non-conjugated cyclic systems with two hydrogenated phenylenes (H4[n]CPP). Particularly, the systems of interest in this work are [6]LPP, [12]- and [6]CPP and H4[6]CPP. This work combines Raman and infrared spectroscopies with absorption and fluorescence (one- and two-photon excitations) measured as a function of pressure up to maximum of about 25 GPa. Unprecedented crystallographic pressure-dependent results are shown on H4[n]CPP, revealing intramolecular π-π interactions upon compression. These intramolecular interactions justify the H4[n]CPP singular optical properties with increasing fluorescence lifetime as a function of pressure.
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Oct 2019
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I19-Small Molecule Single Crystal Diffraction
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Diamond Proposal Number(s):
[15000]
Open Access
Abstract: Single-component molecular conductors form an important class of materials showing exotic quantum phenomena, owing to the range of behavior they exhibit under physical stimuli. We report the effect of high pressure on the electrical properties and crystal structure of the single-component crystal [Ni(dddt)2] (where dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate). The system is isoelectronic and isostructural with [Pd(dddt)2], which is the first example of a single-component molecular crystal that exhibits nodal line semimetallic behavior under high pressure. Systematic high pressure four-probe electrical resistivity measurements were performed up to 21.6 GPa, using a Diamond Anvil Cell (DAC), and high pressure single crystal synchrotron X-ray diffraction was performed up to 11.2 GPa. We found that [Ni(dddt)2] initially exhibits a decrease of resistivity upon increasing pressure but, unlike [Pd(dddt)2], it shows pressure-independent semiconductivity above 9.5 GPa. This correlates with decreasing changes in the unit cell parameters and intermolecular interactions, most notably the π-π stacking distance within chains of [Ni(dddt)2] molecules. Using first-principles density functional theory (DFT) calculations, based on the experimentally-determined crystal structures, we confirm that the band gap decreases with increasing pressure. Thus, we have been able to rationalize the electrical behavior of [Ni(dddt)2] in the pressure-dependent regime, and suggest possible explanations for its pressure-independent behavior at higher pressures.
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May 2019
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I03-Macromolecular Crystallography
I04-1-Macromolecular Crystallography (fixed wavelength)
I24-Microfocus Macromolecular Crystallography
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Diamond Proposal Number(s):
[1358]
Open Access
Abstract: Thymidylate synthase (TS) is an enzyme of paramount importance as it provides the only de novo source of deoxy-thymidine monophosphate (dTMP). dTMP, essential for DNA synthesis, is produced by the TS-catalyzed reductive methylation of 2′-deoxyuridine-5′-monophosphate (dUMP) using N5,N10-methylenetetrahydrofolate (mTHF) as a cofactor. TS is ubiquitous and a validated drug target. TS enzymes from different organisms differ in sequence and structure, but are all obligate homodimers. The structural and mechanistic differences between the human and bacterial enzymes are exploitable to obtain selective inhibitors of bacterial TSs that can enrich the currently available therapeutic tools against bacterial infections. Enterococcus faecalis is a pathogen fully dependent on TS for dTMP synthesis. In this study, we present four new crystal structures of Enterococcus faecalis and human TSs in complex with either the substrate dUMP or the inhibitor FdUMP. The results provide new clues about the half-site reactivity of Enterococcus faecalis TS and the mechanisms underlying the conformational changes occurring in the two enzymes. We also identify relevant differences in cofactor and inhibitor binding between Enterococcus faecalis and human TS that can guide the design of selective inhibitors against bacterial TSs.
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Mar 2019
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I19-Small Molecule Single Crystal Diffraction
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Open Access
Abstract: An in silico study has been conducted upon (3′RS,5′SR)-5-[2′-benzyl-5′-hydroxymethyl-1′,2′-isoxazolidin-3′-yl]uracil through a molecular dynamics/docking approach that highlights its potential inhibitory activity upon the wild-type pseudouridine 5′-monophosphate glycosidase. The crystal structure of this compound has been solved by means of X-ray single crystal diffraction and the data inferred were used to predict its crystal morphology. These data were compared with optical microscopy images and confirmed the validity of the computed models. This robust approach, already used for several other different compounds, provides a fast and reliable tool to standardize a crystallization method in order to get similar and good quality crystals. As different crystal shapes could be associated with different polymorphic forms, this method could be considered a fast and cheap screening to choose among different and coexistent polymorphic forms. Furthermore, a match with the original crystal structure of pseudouridine 5′-monophosphate is provided.
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Dec 2018
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