Characterization and toxicity of lanthanide complexes with nitrogen- and sulphur-containing Schiff bases

La(III), Ce(III), Pr(III), Nd(III), Gd(III), Dy(III), Ho(III) and Er(III) complexes of Schiff bases derived from sulphamethoxazole and salicylaldehyde (I), and thiophene-2-aldehyde (II) have been characterized on the basis of IR, NMR, UV-Vis spectroscopy, elemental analysis, conductance measurements and molecular weight determinations. The Schiff bases act as monobasic bidentate ligands, rendering the metal eight-coordinated. The equilibrium constants have been studied in solution at 25, 30 and 35 °C. The nephelauxetic effect (1 - β), bonding parameter (β), b^1/2 and Sinha covalency parameter (δ) have been calculated. The positive values indicate the covalent nature of the metal-ligand bond. The covalent nature of the complexes is also supported by molar conductance measurements. The toxicities of the Schiff bases and their complexes were evaluated against insects. The LD₅₀ value for cockroaches and percent growth inhibition of the fungi show greater efficacy for the complexes than the Schiff bases.     

Synthesis, structure and magnetic properties of lanthanide(III) complexes with new imidazole-substituted imino nitroxide radical

Synthesis, characterization and magnetic properties of new lanthanide-radical complexes, [Ln^III(hfac)₃(IM2imH)] (Ln = Gd, Tb; IM2imH = 2-(2-pyridyl)-4,5-dihydro-4,4,5,5-tetramethyl-1H-imidazolyl-1-oxy), are described. The molecular structure of the [Tb(hfac)₃(IM2imH)] has been determined by the X-ray diffraction. The magnetic susceptibility data for [Gd(hfac)₃(IM2imH)] show that the Gd-IM2imH magnetic interaction is antiferromagnetic with an exchange coupling constant J = −2.59 cm⁻¹ in contrast to the ferromagnetic interaction in most of Gd(III) complexes containing paramagnetic center, which will be examined in connection with planarity of the IM2imH chelate.     

Nature and composition of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Dy(III) and Ho(III) complexes of embelin

The isolation and characterization of nine polymeric complexes of the general formula [M(L)_1.5S₂]_n (where M is the metal ion, L the ligand and S the solvent, C₂H₅OH) of La(III) and Ce(III), Pr(III), Nd(III), Sm(III), Gd(III), Tb(III), Dy(III), Ho(III) with.the biologically active compound embelin using elemental and thermal analysis, infrared and electronic spectral studies is reported.     

Role of coarse woody debris in the carbon cycle of Takayama forest,central Japan

Coarse woody debris (CWD) is an important component of the forest carbon cycle, acting as a carbon pool and a source of CO₂ in temperate forest ecosystems. We used a soda-lime closed-chamber method to measure CO₂ efflux from downed CWD (diameter ≥5 cm) and to examine CWD respiration (R _CWD) under field conditions over 1 year in a temperate secondary pioneer forest in Takayama forest. We also investigated tree mortality (input to the CWD pool) from the data obtained from the annual tree census, which commenced in 2000. We developed an exponential function of temperature to predict R _CWD in each decay class (R ² = 0.81–0.97). The sensitivity of R _CWD to changing temperature, expressed as Q ₁₀, ranged from 2.12 to 2.92 and was relatively high in decay class III. Annual C flux from CWD (F _CWD) was extrapolated using continuous air temperature measurements and CWD necromass pools in the three decay classes. F _CWD was 3.0 (class I), 17.8 (class II), and 13.7 g C m^?2 year^?1 (class III) and totaled 34 g C m^?2 year^?1 in 2009. Annual input to CWD averaged 77 g C m^?2 year^?1 from 2000 to 2009. The budget of the CWD pool in the Takayama forest, including tree mortality inputs and respiratory outputs, was 0.43 Mg C ha^?1 year^?1 (net C sink) owing to high tree mortality in the mature pioneer forest. The potential CWD sink is important for the carbon cycle in temperate successional forests.     

Manganese(III) porphyrins complexed with P22 virus-like particles as T 1-enhanced contrast agents for magnetic resonance imaging

Virus-like particles are powerful platforms for the development of functional hybrid materials. Here, we have grown a cross-linked polymer (cross-linked aminoethyl methacrylate) within the confines of the bacteriophage P22 capsid (P22–xAEMA) and functionalized the polymer with various loadings of paramagnetic manganese(III) protoporphyrin IX (MnPP) complexes for evaluation as a macromolecular magnetic resonance imaging contrast agent. The resulting construct (P22–xAEMA–MnPP) has r _1,particle = 7,098 mM^?1 s^?1 at 298 K and 2.1 T (90 MHz) for a loading of 3,646 MnPP molecules per capsid. The Solomon–Bloembergen–Morgan theory for paramagnetic relaxivity predicts conjugating MnPP to P22, a supramolecular structure, would result in an enhancement in ionic relaxivity; however, all loadings experienced low ionic relaxivities, r _1,ionic, ranging from 1.45 to 3.66 mM^?1 s^?1, similar to the ionic relaxivity of free MnPP. We hypothesize that intermolecular interactions between neighboring MnPP molecules block access of water to the metal site, resulting in low r _1,ionic relaxivities. We investigated the effect of MnPP interactions on relaxivity further by either blocking or exposing water binding sites on MnPP. On the basis of these results, future design strategies for enhanced r _1,ionic relaxivity are suggested. The measured r _2,ionic relaxivities demonstrated an inverse relationship between loading and relaxivity. This results in a loading-dependent r ₂/r ₁ behavior of these materials indicating synthetic control over the relaxivity properties, making them interesting alternatives to current magnetic resonance imaging contrast agents.     

Kinetics study of pyridine biodegradation by a novel bacterial strain,Rhizobium sp. NJUST18

Biodegradation of pyridine by a novel bacterial strain, Rhizobium sp. NJUST18, was studied in batch experiments over a wide concentration range (from 100 to 1,000 mg l^?1). Pyridine inhibited both growth of Rhizobium sp. NJUST18 and biodegradation of pyridine. The Haldane model could be fitted to the growth kinetics data well with the kinetic constants μ* = 0.1473 h^?1, K _s = 793.97 mg l^?1, K _i = 268.60 mg l^?1 and S _m = 461.80 mg l^?1. The true μ _max, calculated from μ*, was found to be 0.0332 h^?1. Yield coefficient Y _X/S depended on S _i and reached a maximum of 0.51 g g^?1 at S _i of 600 mg l^?1. V _max was calculated by fitting the pyridine consumption data with the Gompertz model. V _max increased with initial pyridine concentration up to 14.809 mg l^?1 h^?1. The q _S values, calculated from $V_{ \hbox{max} }$ , were fitted with the Haldane equation, yielding q _Smax = 0.1212 g g^?1 h^?1 and q* = 0.3874 g g^?1 h^?1 at S _m′ = 507.83 mg l^?1, K _s′ = 558.03 mg l^?1, and K _i′ = 462.15 mg l^?1. Inhibition constants for growth and degradation rate value were in the same range. Compared with other pyridine degraders, μ _max and S _m obtained for Rhizobium sp. NJUST18 were relatively high. High K _i and K _i′ values and extremely high K _s and K _s′ values indicated that NJUST18 was able to grow on pyridine within a wide concentration range, especially at relatively high concentrations.     

Can uranium follow the iron-acquisition pathway? Interaction of uranyl-loaded transferrin with receptor 1

Transferrin receptor 1 (R_D) binds iron-loaded transferrin and allows its internalization in the cytoplasm. Human serum transferrin also forms complexes with metals other than iron, including uranium in the uranyl form (UO₂ ²⁺). Can the uranyl-saturated transferrin (TUr₂) follow the receptor-mediated iron-acquisition pathway? In cell-free assays, TUr₂ interacts with R_D in two different steps. The first is fast, direct rate constant, k ₁ = (5.2 ± 0.8) × 10⁶ M^?1 s^?1; reverse rate constant, k _?1 = 95 ± 5 s^?1; and dissociation constant K ₁ = 18 ± 6 μM. The second occurs in the 100-s range and leads to an increase in the stability of the protein–protein adduct, with an average overall dissociation constant K _d = 6 ± 2 μM. This kinetic analysis implies in the proposed in vitro model possible but weak competition between TUr₂ and the C-lobe of iron-loaded transferrin toward the interaction with R _D.     

Curium(III) complexation with pyoverdins secreted by a groundwater strain of Pseudomonas fluorescens

Pyoverdins, bacterial siderophores produced by ubiquitous fluorescent Pseudomonas species, have great potential to bind and thus transport actinides in the environment. Therefore, the influence of pyoverdins secreted by microbes on the migration processes of actinides must be taken into account in strategies for the risk assessment of potential nuclear waste disposal sites. The unknown interaction between curium(III) and the pyoverdins released by Pseudomonas fluorescens (CCUG 32456) isolated from the granitic rock aquifers at the Äspö Hard Rock Laboratory (Äspö HRL), Sweden, is the subject of this paper. The interaction between soluble species of curium(III) and pyoverdins was studied at trace curium(III) concentrations (3 × 10^?7 M) using time-resolved laser-induced fluorescence spectroscopy (TRLFS). Three Cm³⁺—P. fluorescens (CCUG 32456) pyoverdin species, M_pH_qL_r, could be identified from the fluorescence emission spectra, CmH₂L⁺, CmHL, and CmL^?, having peak maxima at 601, 607, and 611 nm, respectively. The large formation constants, log β₁₂₁ = 32.50 ± 0.06, log β₁₁₁ = 27.40 ± 0.11, and log β₁₀₁ = 19.30 ± 0.17, compared to those of other chelating agents illustrate the unique complexation properties of pyoverdin-type siderophores. An indirect excitation mechanism for the curium(III) fluorescence was observed in the presence of the pyoverdin molecules.     

Rare earth thiocyanate complexes with tripiperidinophosphine oxide: synthesis and characterization. Crystal structure of Pr(SCN)3(tpppO)3

The synthesis and characterization of rare-earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) thiocyanate adducts with tripiperidinophosphine oxide (tpppO) with general formula (RE)(SCN)₃(tpppO)₃ are reported. Conductance measurements in acetonitrile indicate the non-electrolytic nature of the complexes. Infrared absorption spectra evidence that the SCN⁻ ion coordinates through the nitrogen atom (isothiocyanate form) and that tpppO coordinates through the phosphoryl oxygen. X-ray powder patterns suggest the existence of three different crystal forms: (1) La; (2) an isomorphous series including Ce, Nd and Pr; and (3) another isomorphous series, including Sm, Gd, Eu, Ho, Er, Tb, Lu and Y. The visible spectra of the Nd adduct and the calculated parameters β = 0.98, b^1/2 = 0.072 and δ = 1.06 indicate that the metal-ligand bonds are essentially electrostactic. The emission spectra of the Eu compound showed ⁵D₀ → ⁷F_J bands (J = 0, 1, 2), suggesting a C_3v symmetry for the coordination polyhedron. The lifetime of the ⁵D₀ state is 1.28 ms. The emission spectra of the Tb complex presented ⁵D₄ → ⁷F_J bands (J = 4, 5, 6) and the Dy complex showed the ⁴F_9/2 → ⁶H_13/2 band. The structure of the Pr complex showed that the coordination polyhedron is a trigonal antiprism, with the isothiocyanate anions in one base and three tpppO ligands in the other. Thermal analyses (TG-DTG) were carried out for the Ce, Nd and Gd adducts. Mass losses start between 250 and 334 °C. The final residues at 1300 °C are the corresponding phosphates.     

Analysis of cylindrospermopsin- and microcystin-producing genotypes and cyanotoxin concentrations in the Macau storage reservoir

The Macau storage reservoir (MSR) has experienced algal blooms in recent years, with high levels of Cylindrospermopsis and Microcystis and detectable concentrations of cyanotoxins. To analyze the cyanotoxin-producing genotypes and relate the corresponding cyanotoxins to the water quality parameters, a quantitative real-time polymerase chain reaction was developed and applied to the water samples in three locations of MSR. Cylindrospermopsin polyketide synthetase (pks) gene and a series of microcystin synthetase (mcy) genes were used for identifying and quantifying cylindrospermopsin- and microcystin-producing genes, and the corresponding water parameters were measured accordingly. Our results showed that high concentrations of cylindrospermopsin and low concentrations of microcystin were measured during the study period. There was a strong correlation between the pks gene numbers and cylindrospermopsin concentrations (R ² = 0.95), while weak correlations were obtained between the mcy genes numbers and microcystin concentrations. Furthermore, the pks gene numbers were strongly related to Cylindrospermopsis (R ² = 0.88), cyanobacterial cell numbers (R ² = 0.96), total algae numbers (R ² = 0.95), and chlorophyll-a concentrations (R ² = 0.83), consistent with the dominant species of Cylindrospermopsis among the cyanobacteria existing in MSR. NH₄–N (R ² = 0.68) and pH (R ² = 0.89) were the water quality parameters most highly correlated with the pks gene numbers. These results contribute to monitoring for potential cyanotoxins in raw water.     

Atmospheric nitrogen inputs and losses along an urbanization gradient from Boston to Harvard Forest,MA

Urbanization alters nitrogen (N) cycling, but the spatiotemporal distribution and impact of these alterations on ecosystems are not well-quantified. We measured atmospheric inorganic N inputs and soil leaching losses along an urbanization gradient from Boston, MA to Harvard Forest in Petersham, MA. Atmospheric N inputs at urban sites (12.3 ± 1.5 kg N ha^?1 year^?1) were significantly greater than non-urban (5.7 ± 0.5 kg N ha^?1 year^?1) sites with NH₄ ⁺ (median value of 77 ± 4 %) contributing thrice as much as NO₃ ^?. Proximity to urban core correlated positively with NH₄ ⁺ (R² = 0.57, p = 0.02) and total inorganic N inputs (R² = 0.61, p = 0.01); on-road CO₂ emissions correlated positively with NO ₃ ^? inputs (R² = 0.74, p = 0.003). Inorganic N leaching rates correlated positively with atmospheric N input rates (R² = 0.61, p = 0.01), but did not differ significantly between urban and non-urban sites (p > 0.05). Our empirical measurements of atmospheric N inputs are greater for urban areas and less for rural areas compared to modeled regional estimates of N deposition. Five of the nine sites had NO ₃ ^? leached that came almost entirely from nitrification, indicating that the NO₃ ^? in leachate came from biological processes rather than directly passing through the soil. A significant proportion (17–100 %) of NO ₃ ^? leached from the other four sites came directly from the atmosphere. Surprisingly, the four sites where atmospheric sources made up the largest proportion of leachate NO₃ ^? also had relatively low N leaching rates, suggesting that atmospheric N inputs added to terrestrial ecosystems can move to multiple sinks and losses simultaneously, rather than being lost via leaching only after abiotic and biotic sinks have become saturated. This study improves our understanding of atmospheric N deposition and leaching in urban ecosystems, and highlights the need to incorporate urbanization effects in N deposition models.     

Structured near-infrared Magnetic Circular Dichroism spectra of the Mn4CaO5 cluster of PSII in T. vulcanus are dominated by Mn(IV) d-d ‘spin-flip’ transitions

Photosystem II passes through four metastable S-states in catalysing light-driven water oxidation. Variable temperature variable field (VTVH) Magnetic Circular Dichroism (MCD) spectra in PSII of Thermosynochococcus (T.) vulcanus for each S-state are reported. These spectra, along with assignments, provide a new window into the electronic and magnetic structure of Mn₄CaO₅. VTVH MCD spectra taken in the S₂ state provide a clear g = 2, S = 1/2 paramagnetic characteristic, which is entirely consistent with that known by EPR. The three features, seen as positive (+) at 749 nm, negative (?) at 773 nm and (+) at 808 nm are assigned as ⁴A → ²E spin-flips within the d³ configuration of the Mn(IV) centres present. This assignment is supported by comparison(s) to spin-flips seen in a range of Mn(IV) materials. S₃ exhibits a more intense (?) MCD peak at 764 nm and has a stronger MCD saturation characteristic. This S₃ MCD saturation behaviour can be accurately modelled using parameters taken directly from analyses of EPR spectra. We see no evidence for Mn(III) d-d absorption in the near-IR of any S-state. We suggest that Mn(IV)-based absorption may be responsible for the well-known near-IR induced changes induced in S₂ EPR spectra of T. vulcanus and not Mn(III)-based, as has been commonly assumed. Through an analysis of the nephelauxetic effect, the excitation energy of S-state dependent spin-flips seen may help identify coordination characteristics and changes at each Mn(IV). A prospectus as to what more detailed S-state dependent MCD studies promise to achieve is outlined.     

Environmental variables controlling soil respiration on diurnal, seasonal and annual time-scales in a mixed mountain forest in Switzerland

Studies on soil respiration in mountain forests are rather scarce compared to their broad distribution. Therefore, we investigated daily, seasonal and annual soil respiration rates in a mixed forest (Lägeren), located at about 700 m in the Swiss Jura mountains, during 2 years (2006 and 2007). Soil respiration (SR) was measured continuously with high temporal resolution (half-hourly) at one single point (SR_automated) and periodically with high spatial resolution (SR_manual) at 16 plots within the study site. Both, SR_automated and SR_manual showed a similar seasonal cycle. SR strongly depended on soil temperature in 2007 (R ² = 0.82–0.92), but less so in 2006 (R ² = 0.56–0.76) when SR was water limited during a summer drought. Including soil moisture improved the fit of the 2006 model significantly (R ² = 0.78–0.97). Total annual SR for the study site was estimated as 869 g C m^?2 year^?1 for 2006 and as 907 g C m^?2 year^?1 for 2007 (uncertainty <10% at the 95% confidence interval, determined by bootstrapping). Selected environmental conditions were assessed in more detail: (1) Rapid, but contrasting changes of SR were found after summer rainfall. Depending on soil moisture at pre-rain conditions, summer rain could either cause a pulse of CO₂ from the soil or an abrupt decrease of SR_automated due to water logging of soil pores. (2) Two contrasting winter seasons resulted in SR being about 60–70% (31.2–44.6 g C m^?2) higher during a mild winter (2007) compared to a harsh winter (2006). (3) Analysing SR for selected periods on a diurnal scale revealed a counter-clockwise hysteresis with soil surface temperatures. This indication of a time-lagged response of SR to temperature was further supported by a very strong relationship (R ² = 0.86–0.90) of SR to soil temperature with a time-lag of 2–4 h.     

A functional variant of pre-miRNA-196a2 confers risk for Behcet’s disease but not for Vogt–Koyanagi–Harada syndrome or AAU in ankylosing spondylitis

This study aimed to investigate the predisposition of common pre-miRNA SNPs with Behcet’s disease (BD), Vogt–Koyanagi–Harada (VKH) syndrome and acute anterior uveitis (AAU) associated with ankylosing spondylitis (AS). A two-stage association study was carried out in 859 BD, 400 VKH syndrome, 209 AAU⁺AS⁺ patients and 1,685 controls all belonging to a Chinese Han population. Genotyping, the expression of miR-196a and Bach1 (the target gene of miR-196a), cell proliferation, cytokine production were examined by PCR–RFLP, real-time PCR, CCK8 and ELISA. In the first stage study, the results showed significantly increased frequencies of the miR-196a2/rs11614913 TT genotype and T allele in BD patients (adjusted P _c = 0.024, OR = 1.63; adjusted P _c = 5.4 × 10^?3, OR = 1.45, respectively). However, no significant association of the tested SNPs with VKH and AAU⁺AS⁺ patients was observed. The second stage and combined studies confirmed the association of rs11614913 with BD (TT genotype: adjusted P _c = 6×10^?5, OR = 1.53; T allele: adjusted P _c = 8×10^?6, OR = 1.35; CC genotype: adjusted P _c = 0.024, OR = 0.68). A stratified analysis showed an association of the rs11614913 TT genotype and T allele with the arthritis subgroup of BD (P _c = 5.3 × 10^?3, OR = 1.89; P _c = 0.015, OR = 1.56, respectively). Functional experiments showed a decreased miR-196a expression, an increased Bach1 expression and an increased production of IL-1β and MCP-1 in TT cases compared to CC cases (P = 0.023, P = 0.0073, P = 0.012, P = 0.002, respectively). This study shows that a functional variant of miR-196a2 confers risk for BD but not for VKH syndrome or AAU⁺AS⁺ by modulating the miR-196a gene expression and by regulating pro-inflammatory IL-1β and MCP-1 production.     

Evaluation of Electrostatic Interaction between Lysolecithin and Chitosan in Two-Layer Tuna Oil Emulsions by Nuclear Magnetic Resonance (NMR) Spectroscopy

The main objective of this work was to investigate the electrostatic interaction between lysolecithin and chitosan in two-layer tuna oil-in-water emulsions using nuclear magnetic resonance (NMR) spectroscopy. The influence of chitosan concentration on the stability and properties of these emulsions was also evaluated. The 5 wt% tuna oil one-layer emulsion (lysolecithin-stabilized oil droplets without chitosan) and two-layer emulsions (lysolecithin-chitosan stabilized oil droplets) containing 5 wt% tuna oil, 1 wt% lysolecithin and various chitosan concentrations (0.025–0.40 wt%) were prepared. The one-dimensional (1D) ³¹P and ¹H NMR spectra of emulsions were then recorded at 25 °C. The results showed that addition of chitosan affected the stability and properties of lysolecithin-stabilized one-layer emulsions. The ³¹P NMR peak of the choline head group on lysolecithin molecules disappeared when chitosan was added at concentrations above neutralization concentration (> 0.05 wt%). The ¹H NMR peak intensity monitoring free amino groups (?NH ₃ ⁺) of chitosan showed a strong positive linear relationship to the chitosan concentration with a high correlation coefficient (R² ≈ 0.99). This ¹H NMR peak in emulsions could not be detected for chitosan in emulsions lower than saturation concentration (< 0.15 wt%). These phenomena indicate an electrostatic interaction between lysolecithin and chitosan at droplet surface in emulsion and were consistent with the results from zeta-potential measurements. The T ₂* relaxation time of the choline head group (N-(CH ₃)₃) signal of lysolecithin also confirmed that lysolecithin-chitosan electrostatic interaction occurs at the surface of oil droplets in two-layer emulsions. The results suggest that NMR spectroscopy can be used as an alternative method for monitoring the electrostatic interaction between surfactant and oppositely charged electrolytes or biopolymers in two-layer emulsions.     

Spectroscopic evidence for an all-ferrous [4Fe–4S]<Superscript>0</Superscript> cluster in the superreduced activator of 2-hydroxyglutaryl-CoA dehydratase from <Emphasis Type="Italic">Acidaminococcus </Emphasis><Emphasis Type="Italic">fermentans</Emphasis>

The key enzyme of the fermentation of glutamate by Acidaminococcus fermentans, 2-hydroxyglutarylcoenzyme A dehydratase, catalyzes the reversible syn-elimination of water from (R)-2-hydroxyglutaryl-coenzyme A, resulting in (E)-glutaconylcoenzyme A. The dehydratase system consists of two oxygen-sensitive protein components, the activator (HgdC) and the actual dehydratase (HgdAB). Previous biochemical and spectroscopic studies revealed that the reduced [4Fe–4S]⁺ cluster containing activator transfers one electron to the dehydratase driven by ATP hydrolysis, which activates the enzyme. With a tenfold excess of titanium(III) citrate at pH 8.0 the activator can be further reduced, yielding about 50% of a superreduced [4Fe–4S]⁰ cluster in the all-ferrous state. This is inferred from the appearance of a new Mössbauer spectrum with parameters δ = 0.65 mm/s and ΔE _Q = 1.51–2.19 mm/s at 140 K, which are typical of Fe(II)S₄ sites. Parallel-mode electron paramagnetic resonance (EPR) spectroscopy performed at temperatures between 3 and 20 K showed two sharp signals at g = 16 and 12, indicating an integer-spin system. The X-band EPR spectra and magnetic Mössbauer spectra could be consistently simulated by adopting a total spin S _t = 4 for the all-ferrous cluster with weak zero-field splitting parameters D = ?0.66 cm^?1 and E/D = 0.17. The superreduced cluster has apparent spectroscopic similarities with the corresponding [4Fe–4S]⁰ cluster described for the nitrogenase Fe-protein, but in detail their properties differ. While the all-ferrous Fe-protein is capable of transferring electrons to the MoFe-protein for dinitrogen reduction, a similar physiological role is elusive for the superreduced activator. This finding supports our model that only one-electron transfer steps are involved in dehydratase catalysis. Nevertheless we discuss a common basic mechanism of the two diverse systems, which are so far the only described examples of the all-ferrous [4Fe–4S]⁰ cluster found in biology.     

Crystal structure and ligational aspects of the mesogenic Schiff base, N,N′-di-(4-hexadecyloxysalicylidene)diaminoethane, with some rare earth metal ions

A mesogenic Schiff base, N,N′-di-(4-hexadecyloxysalicylidene)diaminoethane, H₂dhdsde (abbreviated as H₂L¹) that exhibit smectic-C (SmC) mesophase, was synthesized and its structure studied by elemental analyses, mass, NMR & IR spectra and single crystal XRD (triclinic space group with Z = 1) techniques. Bi-dentate bonding of the Schiff base in the mesogenic La^III complex was implied on the basis of IR & NMR spectral data. As per the spectral studies of the complexes, the Zwitterionic species of the ligand (H₂L¹) coordinates to Ln^III ion through two phenolate oxygens rendering the overall geometry around the metal ion to distorted square antiprism (Ln = La, Pr, Nd, Sm, Eu) and monocapped octahedron (Ln = Gd, Tb, Dy, Ho).     

3D-QSAR (CoMFA,CoMSIA), molecular docking and molecular dynamics simulations study of 6-aryl-5-cyano-pyrimidine derivatives to explore the structure requirements of LSD1 inhibitors

Recently, Histone Lysine Specific Demethylase 1 (LSD1) was regarded as a promising anticancer target for the novel drug discovery. And several small molecules as LSD1 inhibitors in different structures have been reported. In this work, we carried out a molecular modeling study on the 6-aryl-5-cyano-pyrimidine fragment LSD1 inhibitors using three-dimensional quantitative structure–activity relationship (3D-QSAR), molecular docking and molecular dynamics simulations. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were used to generate 3D-QSAR models. The results show that the best CoMFA model has q² = 0.802, r²_ncv = 0.979, and the best CoMSIA model has q² = 0.799, r²_ncv = 0.982. The electrostatic, hydrophobic and H-bond donor fields play important roles in the models. Molecular docking studies predict the binding mode and the interactions between the ligand and the receptor protein. Molecular dynamics simulations results reveal that the complex of the ligand and the receptor protein are stable at 300 K. All the results can provide us more useful information for our further drug design.     

Solution studies of lanthanide (III) complexes based on 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and 1,10-phenanthroline Part-I: Synthesis, H NMR, 4f-4f absorption and photoluminescence

Solution studies on the complexes of the type [Ln(hfaa)₃(phen)₂] (Ln = La, Pr and Nd) and [Ln(hfaa)₃phen] (Ln = Nd, Ho, Er and Yb; hfaa stands for the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and phen stands for 1,10-phenanthroline) are presented. These complexes are synthesized in high yields by an in situ method in which hfaa, ammonium hydroxide, lanthanide chlorides and phen were allowed to react in 3:3:1:1 molar ratio in ethanol. In the case of neodymium both eight- and ten-coordinate complexes are isolated. The paramagnetic shifts of the methine protons of β-diketone have their sign opposed to those of paramagnetic shifts of phen protons and the shifts are dominated by dipolar interactions. The inter- and intramolecular shift ratios have been calculated and discussed. The 4f-4f absorption spectra of the complexes of Pr, Nd, Ho and Er are analyzed. The eight- and ten-coordinate neodymium complexes display distinctively different band shapes of the ⁴G_5/2,²G_7/2 ← ⁴I_9/2 hypersensitive transition. The efficient energy transfer from ligand to Pr(III) is reflected by strong red luminescence of this complex at room temperature.     

Synthesis and characterisation of a novel tubulin-directed DO3A-colchicine conjugate with potential theranostic features

Colchicine is a known tubulin binding agent enabling necrosis in tumors. A novel tubulin-directed DO3A-colchicine conjugate and its Gd(III) complex were prepared from N-deacetylcolchicine, coupling alkaloid and polyaza-alicyclic functions via a peptide coupling methodology. The longitudinal proton relaxivity of the Gd(III) complex in water at 4.7 T is 2.86 mM⁻¹ s⁻¹ and a similar efficacy as colchicine towards ovarian carcinoma cells in vitro.