Biological Activation of Heteropoly Complex of Molybdotungstosilicate Containing Lanthanum K10H3La(SiMo6W5O39)2⋅26H2O: Spectroscopic Approach and Microcalorimetry

In this paper, the biological activation of heteropoly complex of molybdotungstosilicate containing lanthanum K₁₀H₃La(SiMo₆W₅O₃₉)₂?26H₂O (LaW₅) was investigated by spectroscopic approach and microcalorimetry under the human physiological conditions. Fluorescence spectroscopy in combination with UV–Vis absorption spectroscopy was employed to investigate the binding of LaW₅ to bovine serum albumin (BSA). In the mechanism discussion, it was proved that the fluorescence quenching of BSA by LaW₅ is a result of the formation of LaW₅–BSA complex. Binding parameters were determined using the Stern–Volmer equation. The results of thermodynamic parameters ?G, ?H, ?S at different temperatures indicate that van der Waals interactions and hydrogen bonds play a major role for LaW₅–BSA association. The distance r between donor (BSA) and acceptor (LaW₅) was obtained according to fluorescence resonance energy transfer. Furthermore, the calorimetric method was used to monitor the biological activity of LaW₅ in Escherichia coli.     

Structure,molecular modification and anti-tumor activity of melanin from Lachnum singerianum

Intracellular melanin (LIM) was extracted from Lachnum singerianum YM296 mycelium. LIM-a, LIM-b and LIM-c were resolved from LIM by Sephadex G-15 column chromatography, in which LIM-a was the main homogeneous component with a molecular weight of 530 Da. Based on the elemental analysis, mass spectrometry, infrared spectroscopy and NMR analysis, the molecular formula (C₂₈H₂₀N₂O₇S₂) and possible structural formula of LIM-a were proposed. In order to increase its water solubility, non-water-soluble LIM-a was modified by histidine, lysine and arginine, and histidine-melanin (HLIM-a) had the highest water solubility, being 47.7 mg mL⁻¹ in distilled water at room temperature. Infrared spectroscopy, mass spectroscopy and ¹H NMR analysis of HLIM-a indicated that histidine-melanin was formed by conjugating LIM-a molecule with histidine molecule. In vivo test showed that both LIM-a and HLIM-a had significant anti-tumor activity, in which HLIM-a showed better efficacy. Immunohistochemistry analysis and cytokines detection suggested that LIM-a and HLIM-a may repress tumor growth through activating the immune response.     

NirN Protein from Pseudomonas aeruginosa is a Novel Electron-bifurcating Dehydrogenase Catalyzing the Last Step of Heme d1 Biosynthesis

Heme d₁ plays an important role in denitrification as the essential cofactor of the cytochrome cd₁ nitrite reductase NirS. At present, the biosynthesis of heme d₁ is only partially understood. The last step of heme d₁ biosynthesis requires a so far unknown enzyme that catalyzes the introduction of a double bond into one of the propionate side chains of the tetrapyrrole yielding the corresponding acrylate side chain. In this study, we show that a Pseudomonas aeruginosa PAO1 strain lacking the NirN protein does not produce heme d₁. Instead, the NirS purified from this strain contains the heme d₁ precursor dihydro-heme d₁ lacking the acrylic double bond, as indicated by UV-visible absorption spectroscopy and resonance Raman spectroscopy. Furthermore, the dihydro-heme d₁ was extracted from purified NirS and characterized by UV-visible absorption spectroscopy and finally identified by high-resolution electrospray ionization mass spectrometry. Moreover, we show that purified NirN from P. aeruginosa binds the dihydro-heme d₁ and catalyzes the introduction of the acrylic double bond in vitro. Strikingly, NirN uses an electron bifurcation mechanism for the two-electron oxidation reaction, during which one electron ends up on its heme c cofactor and the second electron reduces the substrate/product from the ferric to the ferrous state. On the basis of our results, we propose novel roles for the proteins NirN and NirF during the biosynthesis of heme d₁.     

Preparation and separation of asymmetric tripodal iron complexes of tren and selected aldehydes

Reaction of iron salts with the tripodal ligands formed from the condensation of tris-(2-aminoethyl)amine (tren) with the following mixtures of aldehydes, 2-pyridinecarboxaldehyde (py) and 6-methyl-2-pyridinecarboxaldehyde (6-CH₃py), salicylaldehyde (sal) and 2-hydroxy-5-methylbenzaldehyde (5-CH₃sal), salicylaldehyde and pyrrole-2-carboxaldehyde (pyr), and 4-methyl-5-imidazolecarboxaldehyde (4-CH₃ImH) and salicylaldehyde yielded mixtures of all four possible iron complexes, [Fe(tren)L_xL′_y]^z (x +y = 3), where L and L′ represent different aldehydes. Preliminary indication of mixtures of products was provided by IR and UV-Vis spectroscopy. Conclusive proof of the existence of all four components (x = 0-3) in each of the reaction mixtures is provided by mass spectroscopy. Separation of the [Fetren(sal)_x(4-CH₃ImH)_y](ClO₄)_y mixture can be achieved using a Sephadex ion exchange column. Treatment of the two observed fractions with base yields greatly enriched [Fetren(sal)₂(4-CH₃Im)] and [Fetren(sal)(4-CH₃Im)₂], which were identified by mass spectroscopy.     

Design and Evaluation of a Novel Evodiamine-Phospholipid Complex for Improved Oral Bioavailability

A novel evodiamine (EVO)-phospholipid complex (EPLC) was designed to improve the bioavailability of EVO. A central composite design approach was employed for process optimization. EPLC were characterized by differential scanning calorimetry, ultraviolet spectroscopy, Fourier transformed infrared spectroscopy, ¹H-NMR spectroscopy, matrix-assisted laser desorption/ionization time-of-flight spectroscopy, apparent solubility, and dissolution rate. After oral administration of EPLC, the concentrations of EVO at different time points were determined by high-performance liquid chromatography. The optimal formulation for EPLC was obtained where the values of X₁, X₂, and X₃ were 2, 0.5, and 2.5 mg/mL, respectively. The average particle size and zeta potential of EPLC with the optimized formulation were 246.1 nm and −26.94 mV, respectively. The EVO and phospholipids in the EPLC were associated with non-covalent interactions. The solubility of EPLC in water and the dissolution rate of EPLC in phosphate-buffered solution (pH 6.8) were substantially enhanced. The plasma EVO concentration-time curves of EPLC and free EVO were both in accordance with the two-compartment model. The peak concentration and AUC_0−∞ of EPLC were increased, and the relative bioavailability was significantly increased to 218.82 % compared with that of EVO.KEY WORDS: bioavailability, evodiamine, phospholipid complex, process optimization     

Carboranyl-Chlorin e6 as a Potent Antimicrobial Photosensitizer

Antimicrobial photodynamic inactivation is currently being widely considered as alternative to antibiotic chemotherapy of infective diseases, attracting much attention to design of novel effective photosensitizers. Carboranyl-chlorin-e₆ (the conjugate of chlorin e₆ with carborane), applied here for the first time for antimicrobial photodynamic inactivation, appeared to be much stronger than chlorin e₆ against Gram-positive bacteria, such as Bacillus subtilis, Staphyllococcus aureus and Mycobacterium sp. Confocal fluorescence spectroscopy and membrane leakage experiments indicated that bacteria cell death upon photodynamic treatment with carboranyl-chlorin-e₆ is caused by loss of cell membrane integrity. The enhanced photobactericidal activity was attributed to the increased accumulation of the conjugate by bacterial cells, as evaluated both by centrifugation and fluorescence correlation spectroscopy. Gram-negative bacteria were rather resistant to antimicrobial photodynamic inactivation mediated by carboranyl-chlorin-e₆. Unlike chlorin e₆, the conjugate showed higher (compared to the wild-type strain) dark toxicity with Escherichia coli ΔtolC mutant, deficient in TolC-requiring multidrug efflux transporters.     

Urea-induced modification of cytochrome c flexibility as probed by cyanide binding

Cyanide binding to cytochrome c was monitored by absorption spectroscopy from neutral to acidic pH in the presence of urea. These results were compared with acid-induced unfolding at corresponding urea concentration monitored by absorption spectroscopy and circular dichroism. The association rate constant k_a increased 20-fold when the concentration of urea was raised from 0 M to 6 M at neutral pH. However, the secondary structure of the protein was not affected, i.e. there was no striking conformational change in these urea concentrations at neutral pH. At the pH that was very close to the pK of acid-induced unfolding, the k_a value reached its maximum (k_a,max) in all urea concentrations. Interestingly, the k_a,max value increased exponentially with increasing urea concentrations. These results are interpreted in terms of a change in the flexibility of the least stable part of the cyt c structure that is responsible for the Fe–S(Met80) bond disruption and for ligand binding to heme iron.     

Comparison of molecular weight determination of sodium alginate by sedimentation-diffusion and light scattering

The weight average molecular weight, M̄_w, of sodium alginates were determined by the sedimentation-diffusion technique using photon correlation spectroscopy rather than boundary spreading in the analytical ultracentrifuge to determine the translational diffusion coefficients. This enables the diffusion coefficients to be determined easily and accurately. Excellent correlation is found between the observed zero concentration translational diffusion coefficient, D_O and the M̄_W values in a emphirical power law. The M̄_W obtained by sedimentation-diffusion and laser light scattering compare very favourably. The concentration dependence of the photon correlation spectroscopy data allowed determination of the coil overlap concentration, c*. The inverse proportionality of c* to both M̄_W and [η] is demonstrated.     

Biosynthesis of abscisic acid from [1,2-13C2]acetate in Cercospora rosicola

[1,2-¹³C₂]Sodium acetate was converted to abscisic acid (ABA) by Cerospora rosicola. The labelling pattern, determined by NMR spectroscopy,     

Extraction and characterization of pepsin-solubilized collagen from snakehead (Channa argus) skin: Effects of hydrogen peroxide pretreatments and pepsin hydrolysis strategies

The effects of hydrogen peroxide (H₂O₂) pretreatments and pepsin hydrolysis strategies on the extraction of pepsin-solubilized collagen (PSC) from the skin of snakehead (Channa argus) were studied. The dependences of H₂O₂ bleaching on H₂O₂ concentrations (1%, 3%, and 6% (w/v)) and pH (6, 8, and 10) were examined, while the difference between the conventional and unconventional pepsin hydrolysis methods was compared. Results showed that the yield of snakehead skin PSC was highly dependent on the parameters of both H₂O₂ pretreatments and pepsin hydrolysis processes. The color of PSC was affected by pH more greatly than by H₂O₂ concentration. Compared with the conventional pepsin hydrolysis of fish skins, the use of pepsin after extraction of acid-solubilized collagen (ASC) could improve the color of PSC. Moreover, the electrophoretic study, infrared spectroscopy, and fibril formation measurement showed that the structural integrity of PSC was largely influenced by the pH of H₂O₂ pretreatments, suggesting that the H₂O₂ solution (3% (w/v), pH 10) was suitable for the bleaching of snakehead skins. Finally, the amino acid analysis, ultraviolet spectroscopy, and differential scanning calorimetry confirmed that the prepared collagen had high purity and thermal stability. The light-color collagen might be used as an alternative for mammalian collagens.     

From iodoindium(III) phthalocyanine to the π-radical indium(III) diphthalocyanine and magnetically frustrated indium diacetate hydroxide coordination polymer

Two different compounds, the π-radical double-decker indium diphthalocyanine benzonitrile solvate (InPc₂·2BN) and indium diacetate monohydroxide (In(OH)(CH₃COO)₂), have been obtained in a crystalline form from iodoindium phthalocyanine (InPcI). The first compound is monoclinic with centrosymmetric space group P2₁/m, while the second compound is orthorhombic with space group Cmcm. The indium cation in InPc₂·2BN is eight coordinated by N atoms of two phthalocyaninate rings, one of which is Pc(2−) and the other one is the π-radical one-electron oxidised Pc(1⁻). The unpaired electron has been identified by the EPR spectroscopy (g = 2.0025). The InPc₂·2BN compound was also characterised by UV-Vis spectroscopy. The second compound forms 1D coordination polymer of {In(OH)(CH₃COO)₂}_n bridged through the hydroxyl group and the acetate anions. In the 1D-polymeric chain the indium cation with slightly distorted octahedral geometry is coordinated in plane by four acetate ions having longer In-O bonds and two axial O atoms of hydroxyl groups with shorter In-O bonds. Additionally, the In(OH)(CH₃COO)₂ compound was characterised by IR spectroscopy. The magnetic measurements of In(OH)(CH₃COO)₂ point to the orientational frustration and below 2.5 K the compound exhibits transition to the superconducting phase.     

Dammarane saponins of leaves of Panax pseudo-ginseng subsp. himalaicus

From dried leaves of Panax pseudo-ginseng subsp. himalaicus collected in Eastern Himalaya, new dammarane saponins, named pseudo-ginsenosides-F₁₁ and -F₈ were isolated along with the known Ginseng-root saponins, ginsenosides-Rb₃, Rd and -Re. Pseudo-ginsenoside-F₈ was proved to be a mono-acetyl-ginsenoside-Rb₃ and the location of its acetyl group was established mainly by ¹³C NMR spectroscopy. Pseudo-ginsenoside-F₁₁, was identified as the 6-O-α-rhamnopyransyl(1 → 2)-β-glucopyranoside of 3β,6α,12β,25-tetrahydoxy-(20S,24R)-epoxy-dammarane. The C-24 configuration of ocotillone and its related triterpenes was confirmed to be 24R excluding the recent comment by Lavie et al.     

Acetate in mixotrophic growth medium affects photosystem II in Chlamydomonas reinhardtii and protects against photoinhibition

Chlamydomonas reinhardtii is a photoautotrophic green alga, which can be grown mixotrophically in acetate-supplemented media (Tris–acetate–phosphate). We show that acetate has a direct effect on photosystem II (PSII). As a consequence, Tris–acetate–phosphate-grown mixotrophic C. reinhardtii cultures are less susceptible to photoinhibition than photoautotrophic cultures when subjected to high light. Spin-trapping electron paramagnetic resonance spectroscopy showed that thylakoids from mixotrophic C. reinhardtii produced less ¹O₂ than those from photoautotrophic cultures. The same was observed in vivo by measuring DanePy oxalate fluorescence quenching. Photoinhibition can be induced by the production of ¹O₂ originating from charge recombination events in photosystem II, which are governed by the midpoint potentials (E_m) of the quinone electron acceptors. Thermoluminescence indicated that the E_m of the primary quinone acceptor (Q_A/Q_A⁻) of mixotrophic cells was stabilised while the E_m of the secondary quinone acceptor (Q_B/Q_B⁻) was destabilised, therefore favouring direct non-radiative charge recombination events that do not lead to ¹O₂ production. Acetate treatment of photosystem II-enriched membrane fragments from spinach led to the same thermoluminescence shifts as observed in C. reinhardtii, showing that acetate exhibits a direct effect on photosystem II independent from the metabolic state of a cell. A change in the environment of the non-heme iron of acetate-treated photosystem II particles was detected by low temperature electron paramagnetic resonance spectroscopy. We hypothesise that acetate replaces the bicarbonate associated to the non-heme iron and changes the environment of Q_A and Q_B affecting photosystem II charge recombination events and photoinhibition.     

Structure and dynamic behaviour of lanthanide nitrate complexes with bis(diphenylphosphorylmethyl)mesitylene in solutions: The nature of unexpected P NMR spectra

The solution structures of the lanthanide complexes, [Ln(L)(NO₃)₃] and [Ln(L)₂(NO₃)₃], where L = bis(diphenylphosphorylmethyl)mesitylene and Ln = La, Ce, Nd, Er, were investigated by ³¹P NMR and IR spectroscopy, conductivity and sedimentation analysis. Variable-temperature ³¹P{¹H} NMR spectroscopy was used to identify species present in solution and to monitor their interconversions. The results indicate that equilibrium between molecular complexes [Ln(L)_n(NO₃)₃]⁰ and cationic species (as ion pairs [Ln(L)_n(NO₃)₂]⁺ · (NO₃)⁻ and as free ions [Ln(L)_n(NO₃)₂]⁺, throughout n = 1, 2) in solutions can be observed by ³¹P{¹H} NMR spectroscopy due to separate detection of the molecular complexes and cationic species. The chelate coordination of the ligand and nitrate ions is retained in all complex species at ambient temperature except for [Er(L)₂(NO₃)₃]. The crystal structure of [Nd(L)(NO₃)₃(MeCN)]MeCN was determined by X-ray diffraction.     

Fabrication and characterization of noble crystalline silver nanoparticles from Pimenta dioica leave extract and analysis of chemical constituents for larvicidal applications

The current works report the bio-efficacy of Pimenta dioica leaf derived silver nanoparticles (Pd@AgNPs) and leaf extract obtained trough different solvents against the larvae of malaria, filarial and dengue vectors. Synthesis of silver nanoparticles (AgNPs) was done by adding 10 ml of P. dioica leaf extract into 90 ml of 1 mM silver nitrate solution, a slow colour change was observed depicting the formation of AgNPs. Further, Pd@AgNPs was confirmed through Ultraviolet–visible spectroscopy which exhibited characteristic absorption peak at 422 nm wavelength. X-ray diffraction and selected area electron diffraction analysis confirmed monodispersed and crystalline nature of Pd@AgNPs with 32 nm an average size. Scanning electron microscopy and transmission electron microscopy showed the most of Pd@AgNPs were spherical and triangular in shape and energy-dispersive X-ray spectroscopy revealed silver elemental nature of nanoparticles. Zeta potential of Pd@AgNPs is highly negative which confirmed its stable nature. Pd@AgNPs showed prominent absorption peaks at 1015, 1047, 1243, 1634, 2347, 2373, 2697 and 3840 cm^?1 which are corresponding to following compounds polysaccharides, carboxylic acids, water, alcohols, esters, ethers, amines, amides and phenol, respectively as reported by Fourier-transform infrared spectroscopy analysis. Gas chromatography–mass spectrometry and Liquid chromatography–mass spectrometry analysis revealed 39 and 70 compounds, respectively, which might be contributed for bio-reduction, capping, stabilization and larvicidal behavior of AgNPs. A comparable lethality (LC₅₀ and LC₉₀) was observed in case of Pd@AgNPs over leaf extract alone. The potential larvicidal activity of Pd@AgNPs was observed against the larvae of Aedes aegypti,(LC_50, 2.605; LC_90, 5.084 ppm) Anopheles stephensi (LC_50, 3.269; LC_90, 7.790 ppm) and Culex quinquefasciatus (LC_50, 5.373; LC_90, 14.738 ppm without affecting non-targeted organism, Mesocyclops thermocyclopoides after 72 hr of exposure. This study entails green chemistry behind synthesis of AgNPs which offers effective technique for mosquito control and other therapeutic applications.     

Electronic and molecular structures of C60-based polyanionic high-spin molecular clusters: Direct spin identification and electron spin transient nutation spectroscopy for high-spin chemistry

C₆₀-based polyanionic high-spin clusters (S = 1–3) in their ground state have been prepared by successive chemical reductions of pristine C₆₀ fullerene with potassium in the presence of dicyclohexano-18-crown-6-ether in solution. Intermolecular spin-triplet, quintet, and septet states arising from the C₆₀-based polyanionic molecular clusters have been generated at ambient temperature and identified by CW-ESR and pulse-ESR-based two-dimensional (2D) electron spin transient nutation (2D-ESTN) spectroscopy in organic rigid glasses, for the first time. Intermolecular exchange interactions between mono- and polyanionic C₆₀ fullerenes are ferromagnetic via bridging potassium metal cations. The molecular structures of the polyanionic high-spin C₆₀ clusters in solution have been proposed by a well-established phenomenological spin Hamiltonian approach in terms of the D-tensor-based calculations for the high-spin clusters. The findings of the C₆₀-based high-spin molecular clusters evidence the occurrence of an intramolecular triplet C₆₀ dianion in the ground state. Unequivocal spin identification for molecular high-spin entities by 2D-ESTN spectroscopy and its powerfulness have been illustrated, emphasizing that the 2D-ESTN spectroscopy is useful for mixtures of molecular species with different spin multiplicities, characterized by a small g-anisotropy, for which the powerfulness of advanced high-frequency ESR spectroscopy is hampered.     

Comparative investigations on a series of [hexakis(1-(tetrazol-1-yl)alkane-N4)iron(II)] bis(tetrafluoroborate) spin crossover complexes: Methyl- to butyl-substituted species

A series of 1-(tetrazol-1-yl)alkanes [ntz] with n = 1-4 were synthesised as ligands for iron(II) spin crossover complexes. Within this series 1-(tetrazol-1-yl)butane [4tz] was prepared for the first time, whereas 1-(tetrazol-1-yl)methane [1tz], 1-(tetrazol-1-yl)ethane [2tz], 1-(tetrazol-1-yl)propane [3tz] and the [hexakis(ntz)iron(II)]bis(tetrafluoroborate) complexes were prepared according to the literature. Aiming for a comparative study we characterized all four compounds by XRPD, magnetic susceptibility measurements, ⁵⁷Fe-Moessbauer spectroscopy and IR spectroscopy. [Fe(4tz)₆](BF₄)₂ yielded appropriate single crystals and an X-ray structure of the new compound [Fe(4tz)₆](BF₄)₂ is presented. The magnetic and structural properties of all [Fe(ntz)₆](BF₄)₂ are compared and discussed.     

Mixed ligand octahedral Co3+ β-diketonates,with acetylacetone,benzoylacetone and dibenzoylmethane. Synthesis,separation of isomers and characterization

Three series of complexes were studied: Co(acetylacetonate)_n(dibenzoylmethanato)_3-n, Co(acetylacetonate)_n(benzoylacetonate)_3-n and Co(dibenzoylmethanato)_n(benzoylacetonate)_3-n. The product mixtures were separated by thin-layer chromatography. Complete separation of all compounds and stereoisomers was obtained. No attempt was made to separate optical isomers which exist for each single stereoisomer. Characterization was by elemental analyses, NMR spectroscopy and the separation characteristics. Electronic absorption spectra were measured in acetonitrile in the 200–800 nm region. Interpretation of the spectral data is provided in terms of ∏ → ∏^*, d → ∏^*, d → d^* transitions. The influence of geometrical isomerism is discussed.     

The identification of dimethylphenylarsine as a microbial metabolite using a simple method of chemofocusing

Candida humicola acts on benzenearsonic acid to produce dimethylphenylarsine, which was identified by mass spectroscopy following the chemofocusing of the volatile metabolite onto a mercuric chloride impregnated filter. The same technique established that trimethylarsine is the volatile metabolic product obtained from C. humicola treated with 4-NH₂-2-OHC₆H₃AsO(OH)₂ and (CH₃)₃AsO. Arsanilic acid, 4-NH₂C₆H₄AsO(OH)₂, is not metabolized to a volatile arsine.     

Synthesis and NMR characterization of the novel mixed-ligand Pt(II) complexes cis- and trans-Pt(Ypy)(pyrimidine)Cl2 and trans,trans-Cl2(Ypy)Pt(μ-pyrimidine)Pt(Ypy)Cl2 (Ypy = pyridine derivative)

Mixed-ligand complexes of the type cis- and trans-Pt(Ypy)(pm)Cl₂ where Ypy = pyridine derivative and pm = pyrimidine were synthesized and characterized by IR spectroscopy and by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The cis compounds were prepared from the reaction of K[Pt(Ypy)Cl₃] with pyrimidine (1:1 proportion) in water, while most of the trans isomers were synthesized from the isomerization of the cis compounds. The cis isomers could not be isolated with the Ypy ligands containing two -CH₃ groups in ortho positions. When the aqueous reaction of K[Pt(Ypy)Cl₃] with pyrimidine was performed in a Pt:pm ratio = 2:1, the pyrimidine-bridged dinuclear species were formed. Only the most stable trans-trans isomers could be isolated pure. In IR spectroscopy, the cis monomers showed two ν(Pt-Cl) bands, while the trans monomers and dimers showed only one ν(Pt-Cl) band. The ¹⁹⁵Pt NMR signals of the cis monomers were found at slightly higher fields than those of the corresponding trans isomers. The δ(¹⁹⁵Pt) of the dimers were found close to those of the trans monomers. The NMR results were interpreted in relation to the solvent effect, which seems important in these complexes. The coupling constants J(¹⁹⁵Pt-¹H) and J(¹⁹⁵Pt-¹³C) are larger in the cis geometry. The crystal structures of the compounds cis-Pt(2,4-lut)(pm)Cl₂, trans-Pt(2,6-lut)(pm)Cl₂ and trans,trans-Cl₂(2,6-lut)Pt(μ-pm)Pt(Ypy)Cl₂ were studied by X-ray diffraction methods and the results have confirmed the configurations suggested by IR and NMR spectroscopies.