143 research outputs found

    Benzoic acid–3,4-bis­[(pyridin-3-ylmeth­yl)amino]­cyclo­but-3-ene-1,2-dione (1/2)

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    In the title co-crystal, C16H14N4O2·2C7H6O2, the 3,4-bis­[(pyridin-3-ylmeth­yl)amino]­cyclo­but-3-ene-1,2-dione squareamide mol­ecules assemble into chains along the b axis via N—H⋯O hydrogen bonds. The benzoic acid mol­ecules then hydrogen bond to the pyridine rings via O—H⋯N hydrogen bonds, supported by weaker C—H⋯O hydrogen bonds, forming extended ribbons. The asymmetric unit consists of a half squareamide mol­ecule, sitting on a special position around a twofold axis, and one benzoic acid mol­ecule on a general position

    Reactions of halogens with Pt(II) complexes of N-alkyl- and N,N-dialkyl-Nʹ -benzoylthioureas: oxidative addition and formation of an I₂ inclusion compound

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    The treatment of cis-[PtII(L1a/b-S,O)2] complexes of N,N-diethyl- (HL1a) and N,N-di(n-butyl)-N'-benzoylthiourea (HL1b) with I2 or Br2 in chloroform, leads to rapid oxidative addition to yield several geometric isomers of [PtIV(L-S,O)2X2] (X = I, Br); the reactions can be monitored by 195Pt NMR and UV-visible spectrophotometry. The products cis-[PtIV(L1a-S,O)2I2] 6 and cis-[PtIV(L1a-S,O)2Br2] 7, which have been isolated and structurally characterized, are the first-reported crystal structures of complexes of Pt(IV) with this class of ligand. Molecules of 6 pack such that the I–Pt–I axes are essentially aligned, with unusually close nearest-neighbour iodide contacts (3.553(1) A˚ ). These short I···I intermolecular interactions lead to infinite chains of weakly connected molecules in crystals of the compound. No such interactions are evident in the corresponding crystals of 7. Reaction of the Pt(II) complex of N-propyl-N'-benzoylthiourea (H2L2a) cis-/trans-[PtII(H2L2a-S)2Br2] with Br2 also results in oxidative addition, to yield trans-PtIV(H2L2a-S)2Br4 9. By contrast, treatment of cis-/trans-[PtII(H2L2a-S)2I2] with I2 does not lead to an oxidative addition product, yielding instead an interesting iodine inclusion compound of PtII, trans-[PtII(H2L2a-S)2I2]·I2 8. In 8, short intermolecular I···I distances of 3.453(1) A˚ between I2 and coordinated iodide ions in trans-[PtII(H2L2a-S)2I2] molecules, result in infinite chains of weakly linked trans-[PtII(H2L2a-S)2I2] ···I2 groups in the lattice. However, the empirically estimated bond order of 0.75 for the included I2 molecules does not support the possible existence of discrete tetraiodide ions (I42−) in the lattice of compound 8

    Inclusion of Hydroxycinnamic Acids in Methylated Cyclodextrins: Host-Guest Interactions and Effects on Guest Thermal Stability

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    There is ongoing interest in exploiting the antioxidant activity and other medicinal properties of natural monophenolic/polyphenolic compounds, but their generally low aqueous solubility limits their applications. Numerous studies have been undertaken to solubilize such compounds via supramolecular derivatization with co-crystal formation with biocompatible coformer molecules and cyclodextrin (CD) complexation being two successful approaches. In this study, eight new crystalline products obtained by complexation between methylated cyclodextrins and the bioactive phenolic acids (ferulic, hydroferulic, caffeic, and p-coumaric acids) were investigated using thermal analysis (hot stage microscopy, thermogravimetry, differential scanning calorimetry) and X-ray diffraction. All of the complexes crystallized as ternary systems containing the host CD, a phenolic acid guest, and water. On heating each complex, the primary thermal events were dehydration and liberation of the respective phenolic acid component, the mass loss for the latter step enabling determination of the host-guest stoichiometry. Systematic examination of the X-ray crystal structures of the eight complexes enabled their classification according to the extent of inclusion of each guest molecule within the cavity of its respective CD molecule. This revealed three CD inclusion compounds with full guest encapsulation, three with partial guest inclusion, and two that belong to the rare class of ‘non-inclusion’ compounds

    Aqueous Solution Equilibria and Spectral Features of Copper Complexes with Tripeptides Containing Glycine or Sarcosine and Leucine or Phenylalanine

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    Copper(II) complexes of glycyl-L-leucyl-L-histidine (GLH), sarcosyl-L-leucyl-L-histidine (Sar-LH), glycyl-L-phenylalanyl-L-histidine (GFH) and sarcosyl-L-phenylalanyl-L-histidine (Sar-FH) have potential anti-inflammatory activity, which can help to alleviate the symptoms associated with rheumatoid arthritis (RA). From pH 2–11, the MLH, ML, MLH-1 and MLH-2 species formed. The combination of species for each ligand was different, except at the physiological pH, where CuLH-2 predominated for all ligands. The prevalence of this species was supported by EPR, ultraviolet-visible spectrophotometry, and mass spectrometry, which suggested a square planar CuN4 coordination. All ligands have the same basicity for the amine and imidazole-N, but the methyl group of sarcosine decreased the stability of MLH and MLH-2 by 0.1–0.34 and 0.46–0.48 log units, respectively. Phenylalanine increased the stability of MLH and MLH-2 by 0.05–0.29 and 1.19–1.21 log units, respectively. For all ligands, 1H NMR identified two coordination modes for MLH, where copper(II) coordinates via the amine-N and neighboring carbonyl-O, as well as via the imidazole-N and carboxyl-O. EPR spectroscopy identified the MLH, ML and MLH-2 species for Cu-Sar-LH and suggested a CuN2O2 chromophore for ML. DFT calculations with water as a solvent confirmed the proposed coordination modes of each species at the B3LYP level combined with 6-31++G**

    Computer simulation of nickel in blood-plasma following the in vitro investigations of complex formation chemistry with polyamine(amide) ligands

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    In- and out-of-cell potentiometric techniques have been used to determine the formation constants for nickel(II) with 3,3,9,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime (L1), N,N′-bis(2-hydroxyiminopropionyl)propane-1,3-diamine (L2) and 1,15-bis(N,N-dimethyl)-5,11-dioxo-8-(N-benzyl)-1,4,8,12,15-pentaazapentadecane (L3) at 25 °C and an ionic strength of 0.15 mol dm−3. Nickel(II) forms stable complexes with L1 and L2 where square-planar [NiLH−1] and [NiLH−2] species predominate under alkaline conditions. The square-planar coordination of nickel by L1 has been confirmed by a single-crystal X-ray structure, UV/Vis spectrometry and molecular mechanics calculations of the [NiL1H−1] complex. The introduction of a third amine group into L3 dramatically decreases the ligand's ability to complex Ni(II). This results from a change in structure of the complex which decreases the ability of the metal ion to promote the dissociation of the amide protons. Using a model of blood plasma, the high binding ability of L1 towards Ni(II) is calculated to decrease the mobilisation of Cu(II) in plasma by approximately 65%. [CuL1H−1] is currently under investigation as an anti-inflammatory agent

    Cataract in patients with diabetes mellitus—incidence rates in the UK and risk factors

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    Aims: To analyze the risk of incident cataract (diagnosis or extraction) in patients with or without diabetes focusing on other comorbid conditions, antidiabetic drug use, and diabetes duration. Methods: The study population comprised newly diagnosed diabetes patients (≥40 years) from the UK-based Clinical Practice Research Datalink (CPRD) between 2000 and 2015, and a random sample of the general population matched for age, sex, general practice, and year of diabetes diagnosis. We assessed cataract incidence rates (IRs) and performed a nested case-control analysis in the diabetic cohort to assess potential risk factors for a cataract. Results: There were 56,510 diabetes patients included in the study. IRs of cataract were 20.4 (95% CI 19.8-20.9) per 1000 person-years (py) in patients with diabetes and 10.8 (95% CI 10.5-11.2) per 1000 py in the general population. IRs increased considerably around the age of 80 years and with a concomitant diagnosis of macular edema. The incidence rate ratio (IRR) was highest in patients of the age group of 45-54 years. In the nested case-control study, we identified 5800 patients with cataract. Risk of cataract increased with increasing diabetes duration (adj. OR 5.14, 95% CI 4.19-6.30 diabetes for ≥10 years vs. diabetes <2 years). Conclusions: According to our study, diabetes is associated with an approximately two-fold increased detection rate of cataract. The risk of cataract associated with diabetes is highest at younger ages. Patients with diabetic macular edema are at an increased risk for cataract as well as patients with long-standing diabetes

    Automated Three-Dimensional Detection and Shape Classification of Dendritic Spines from Fluorescence Microscopy Images

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    A fundamental challenge in understanding how dendritic spine morphology controls learning and memory has been quantifying three-dimensional (3D) spine shapes with sufficient precision to distinguish morphologic types, and sufficient throughput for robust statistical analysis. The necessity to analyze large volumetric data sets accurately, efficiently, and in true 3D has been a major bottleneck in deriving reliable relationships between altered neuronal function and changes in spine morphology. We introduce a novel system for automated detection, shape analysis and classification of dendritic spines from laser scanning microscopy (LSM) images that directly addresses these limitations. The system is more accurate, and at least an order of magnitude faster, than existing technologies. By operating fully in 3D the algorithm resolves spines that are undetectable with standard two-dimensional (2D) tools. Adaptive local thresholding, voxel clustering and Rayburst Sampling generate a profile of diameter estimates used to classify spines into morphologic types, while minimizing optical smear and quantization artifacts. The technique opens new horizons on the objective evaluation of spine changes with synaptic plasticity, normal development and aging, and with neurodegenerative disorders that impair cognitive function

    Genetic Variation in OAS1 Is a Risk Factor for Initial Infection with West Nile Virus in Man

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    West Nile virus (WNV) is a re-emerging pathogen that can cause fatal encephalitis. In mice, susceptibility to WNV has been reported to result from a single point mutation in oas1b, which encodes 2′–5′ oligoadenylate synthetase 1b, a member of the type I interferon-regulated OAS gene family involved in viral RNA degradation. In man, the human ortholog of oas1b appears to be OAS1. The ‘A’ allele at SNP rs10774671 of OAS1 has previously been shown to alter splicing of OAS1 and to be associated with reduced OAS activity in PBMCs. Here we show that the frequency of this hypofunctional allele is increased in both symptomatic and asymptomatic WNV seroconverters (Caucasians from five US centers; total n = 501; OR = 1.6 [95% CI 1.2–2.0], P = 0.0002 in a recessive genetic model). We then directly tested the effect of this SNP on viral replication in a novel ex vivo model of WNV infection in primary human lymphoid tissue. Virus accumulation varied markedly among donors, and was highest for individuals homozygous for the ‘A’ allele (P<0.0001). Together, these data identify OAS1 SNP rs10774671 as a host genetic risk factor for initial infection with WNV in humans
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