共查询到20条相似文献,搜索用时 15 毫秒
1.
M. Eugenia Sesto Cabral Fanny I. Schabes E. Elizabeth Sigstad 《Thermochimica Acta》2010,497(1-2):14-20
The effect of the CHCl3 and MeOH extracts from aerial parts from the Northwestern Argentina endemic species Ixorhea tschudiana Fenzl. on germination of the dicot tomato and the monoct onion and on soil microbial activity was studied by calorimetric and calorespirometric experiments. The CHCl3 extract inhibited seedling growth of tomato which increased with increasing concentrations. Seeds imbibed with 250 mg dm?3 extract germinated 24 h later than control and those imbibed with 100 and 500 mg dm?3 extract. This was reflected in the calculated low specific seedling growth rate (pSGΔHB) as determined from calorespirometric experiments. On the other hand, seedlings obtained in 500 mg dm?3 extract showed shorter and thicker hairy roots than control with significantly higher pSGΔHB. Probably, the extract induces inhibition of water uptake by seedling roots. Germination was reduced 50% in onion seeds imbibed with 500 mg dm?3 CHCl3 extract which apparently is due to higher rate of imbibition during the first stages as determined for calorimetry. On the other hand, 83 and 250 mg kg?1 of the MeOH and CHCl3 extract seem to selectively inhibit the growth of certain microorganisms and to enhance the activity of soil actinomycetes. Two actinobacteria were isolated from soil treated with these concentrations of both extracts: Kocuria sp. and Kocuria rosea; this latter species is known as a keratinolytic agent and seems to degrade complex carbon compounds of the soil and those incorporated by the MeOH extract. Both Kocuria specie seem to be beneficial for the soil converting substrate into biomass and thus I. tschudiana could be used as a soil phytoremediator. 相似文献
2.
Thermogravimetric (t.g.) and differential scanning calorimetric (d.s.c.) data have been used to study metal–amino acid interactions in adducts of general formula MnCl2 · ngly (gly = glycine, n = 0.7, 2.0, 4.0 and 5.0). All the prepared adducts exhibit only a one step mass loss associated with the release of glycine molecules, except for the 0.7gly adduct, which exhibits two glycine mass loss steps. From d.s.c. data, the enthalpy values associated with the glycine mass loss can be calculated: MnCl2 · 0.7gly = 409 and 399 kJ mol–1, MnCl2 · 2.0gly = 216 kJ mol–1, MnCl2 · 4.0gly = 326 kJ mol–1 and MnCl2 · 5.0gly = 423 kJ mol–1, respectively. The enthalpy associated with the ligand loss, plotted as function of the number of ligands for the n = 2.0, 4.0 and 5.0 adducts, gave a linear correlation, fitting the equation: H (ligand loss)/kJ mol–1 = 67 × (number of ligands, n) + 76. A similar result was achieved when the enthalpy associated with the ligand loss was plotted as a function of the
a(COO–) bands associated with the coordination through the carboxylate group, 1571, 1575 and 1577 cm–1, respectively, for the n = 2.0, 4.0 and 5.0 adducts, giving the equation H (ligand loss) /kJ mol–1 = 33.5 ×
a(COO–) /cm–1 – 52418.5. This simple equation provides evidence for the enthalpy associated with the ligand loss being very closely related to the electronic density associated with the metal–amino acid bonds. 相似文献
3.
El-Kemary M Sobhy S El-Daly S Abdel-Shafi A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1904-1908
We report on steady-state UV-visible absorption and emission characteristics of Paracetamol, drug used as antipyretic agent, in water and within cyclodextrins (CDs): β-CD, 2-hydroxypropyl-β-CD (HP-β-CD) and 2,6-dimethyl-β-CD (Me-β-CD). The results reveal that Paracetamol forms a 1:1 inclusion complex with CD. Upon encapsulation, the emission intensity enhances, indicating a confinement effect of the nanocages on the photophysical behavior of the drug. Due to its methyl groups, the Me-β-CD shows the largest effect for the drug. The observed binding constant showing the following trend: Me-β-CD>HP-β-CD>β-CD. The less complexing effectiveness of HP-β-CD is due to the steric effect of the hydroxypropyl-substituents, which can hamper the inclusion of the guest molecules. The solid state inclusion complex was prepared by co-precipitation method and its characterization was investigated by Fourier transform infrared spectroscopy, 1H NMR and X-ray diffractometry. These approaches indicated that Paracetamol was able to form an inclusion complex with CDs, and the inclusion compounds exhibited different spectroscopic features and properties from Paracetamol. 相似文献
4.
Marcelo Kobelnik Douglas Lopes Cassimiro Clóvis Augusto Ribeiro Diógenes dos Santos Dias Marisa Spirandeli Crespi 《Journal of Thermal Analysis and Calorimetry》2010,102(3):1167-1173
Two ONNO type naphtaldehyde derivative Schiff base compounds were reduced and two symmetric phenol-amine ligands containing
naphthalene groups were obtained; bis-N,N′[(2-hydroxy-1-naphtyl) methyl]-1,3-propanediamine (NAFLH) and bis-N,N′[(2-hydroxy-1-naphtyl) methyl]-2,2′-dimetyhyl-1,3-propanediamine (NAFLDMH). Homotrinuclear Ni(II) complexes of these ligands were prepared. The solid-state molecular structures of representative
nickel complex of NAFLDMH were determined using single crystal X-ray diffraction analysis. The terminal Ni(II) ions were found to be situated in between
the donor atoms of the organic ligand. The central Ni(II) ion was observed to be bonded via two different μ-bridges. The phenolic
oxygens and carboxylate ion were seen to form two different μ-bridges. TG analysis proved that the compounds have different
thermal characteristics than those cited in literature. The complexes showed extreme exothermic degradation reactions in inert
atmosphere. The complexes are ruptured with a two stepped exothermic reaction which appears huge heat over 300 °C. The heat
appeared in O2 atmosphere is observed to be higher than the heat appeared in inert atmosphere. Revealed heat is observed to be higher than
the conventional explosive materials. 相似文献
5.
The interaction of DNA with Copper(II)-Glutathione (CuGSH) has been investigated by various biophysical methods. The interaction
ratio of DNA and Copper(II)-Glutathione in solution phase has been determined spectrophotometrically and found to be 0.25.
EPR spectroscopy and UV–Vis findings suggest that Cu(II)-Glutathione neither bound to the DNA bases covalently nor intercalated,
this has further been substantiated by the determination of intrinsic binding constant (2.1 × 102). Viscometric measurements also support this type of binding to DNA by Cu(II)-Glutathione. EPR studies and visible d–d spectra
of CuGSH after interaction with DNA, suggested that Copper remained in the Copper(II) state. DNA conformations after interaction
with Cu(II)-Glutathione has been determined spectroscopically. Circular dichroism studies revealed that the B conformation
of DNA is changed to A after interaction with Cu(II)-Glutathione. This has further been substantiated by thin film IR (Infrared)
studies. 相似文献
6.
We have described here the self-assembling properties of the synthetic tripeptides Boc-Ala(1)-Aib(2)-Val(3)-OMe 1, Boc-Ala(1)-Aib(2)-Ile(3)-OMe 2 and Boc-Ala(1)-Gly(2)-Val(3)-OMe 3 (Aib=α-amino isobutyric acid, β-Ala=β-alanine) which have distorted β-turn conformations in their respective crystals. These turn-forming tripeptides self-assemble to form supramolecular β-sheet structures through intermolecular hydrogen bonding and other noncovalent interactions. The scanning electron micrographs of these peptides revealed that these compounds form amyloid-like fibrils, the causative factor for many neurodegenerative diseases including Alzheimer's disease, Huntington's disease and Prion-related encephalopathies. 相似文献
7.
《Journal of membrane science》2002,207(2):199-207
The mass of γ-globulin deposited onto an Anodisc® alumina membrane with a nominal pore diameter of 0.1 μm has been measured at several concentrations and pH. This deposition resulted from filtering through the membrane in a continuous recirculation device.The low concentration deposition can be assigned mainly to adsorption, that can be studied as a function of the electrostatic forces between the solute and the membrane. A sharp maximum in the adsorbed mass for zero electrostatic force was obtained. At high concentrations, accumulation (non-adsorptive deposition) has also to be taken into account at alkaline pH as confirmed by flux decay experiments and retention measurements.The irreversible deposition (understanding irreversible as referring to deposition that do not disappear when the flux through the membrane stops) has been studied by imaging the surface of the membrane after filtration using atomic force microscopy (AFM). These images give insights into how and where adsorption takes place. 相似文献
8.
《Electrochemistry communications》2000,2(5):301-306
Copper and iron hexacyanoferrate form a continuous series of substitutional solid solutions, which have been studied by solid-state electrochemistry, X-ray powder diffraction, IR and ESR spectroscopy. All methods unambiguously prove the formation of solid solutions. The results show the different capabilities of these techniques to study such systems. Especially in the case of poor crystallinity and strongly magnetically interacting metal ions, voltammetry of immobilized microparticles offers a powerful tool for the determination of the composition and properties of solid solutions. 相似文献
9.
Cobalt–iron cyanide (Cox[Fe(CN)6]) nanoparticles have been synthesized by a novel solid–solid reaction in the confined space of dry sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reversed micelles dispersed in n-heptane. The reaction has been carried out by mixing two dry AOT/n-heptane solutions containing CoCl2 and K4Fe(CN)6 or K3Fe(CN)6 nanoparticles in the micellar core, respectively. By UV-Vis spectroscopy it was ascertained that, after the mixing process, the formation of stable nanoparticles is fast and complete. Microcalorimetric measurements of the thermal effect due to the Cox[Fe(CN)6] nanoparticle formation allowed the determination of the stoichiometric ratio (x) and of the molar enthalpy of reaction in the core of AOT reversed micelles. The observed behavior suggests the occurrence of confinement effects and surfactant adsorption on the nanoparticle surface. Further structural information was achieved by small-angle X-ray scattering (SAXS) measurements. From all liquid samples, interesting salt/AOT composites were prepared by simple evaporation of the apolar solvent. Size, crystal structure, and electronic properties of Cox[Fe(CN)6] nanoparticles containing composites were obtained by wide-angle X-ray scattering (WAXS) and X-ray photoelectron spectroscopy (XPS). 相似文献
10.
11.
《Polyhedron》1999,18(5):699-706
Bond valence as the function of inter-nuclear distance for Cu–O and Cu–N bonds were estimated. Based on the developed bond-valence theory a mutual dependence between the bond length in copper coordination sphere with chromophores CuO6, CuO5, CuN6 and CuN4O2 has been derived and compared with the experimental structural correlations. The discontinued transition from chemical bonding to the nonbonding state in the direction of the elongated bond was estimated. The shortest bond lengths are dependent on the copper atom valence. The supreme manifestation of coordination sphere plasticity is estimated as semicoordination. The semicoordinative Cu–O and Cu–N bonds are 3.07 and 2.78 Å long. 相似文献
12.
13.
Lemouchi C Simonov S Zorina L Gautier C Hudhomme P Batail P 《Organic & biomolecular chemistry》2011,9(23):8096-8101
A methodology is proposed to provide direct access in good yields to peptide residues-appended perylenediimides PDI-(Cl(4))-[Gly-Ala(OEt)](2), 2a, PDI-(Cl(4))-[Gly-Val(OEt)](2), 2b and PDI-(Cl(4))-[Gly-Gly(OEt)](2), 2c from a generic perylenediimide (PDI) platform symmetrically functionalized with carboxylic acids at the imide sites, PDI-(Cl(4))-[Gly(OH)](2), 1. The latter is obtained in good purity by a non classical two-steps route avoiding the many, notoriously cumbersome successive chromatography steps typical of PDI chemistry, and including a single final purification allowing to crystallize the water soluble pure diacid 1, of great interest in its own right for further developments in a variety of fields. Then, the synthesis, crystallization and analysis of the crystal structures of 2a and 2b reveal a common pattern of self-assembly of the outer peptide residues based on collections of parallel N-H···O peptidic hydrogen bonds running alongside stacks where the constraints imposed upon on the inner PDI skeletons by long range interaction of these parallel electric dipoles reduce the dihedral angles around the bay regions by as much as 11% down to 32°. 相似文献
14.
《Chemical physics letters》2003,367(5-6):633-636
Gas–solid interactions between hydrogen and single-walled carbon nanotubes (SWNTs) were investigated using highly purified SWNTs. The activation energy of hydrogen desorption, measured to be 0.21 eV, indicates that hydrogen is physisorbed in the pores and that inter-tube pores have an adsorption potential of about −0.21 eV, which induces hydrogen physisorption at ambient temperature. The total amount of adsorbed hydrogen, about 0.3 wt% at 9 MPa, shows that 38% of the inter-tube sites are occupied. These findings are interpreted in terms of the chemical potential of hydrogen and the adsorption potential of the inter-tube pores. 相似文献
15.
Ulf Ryde Mats H. M. Olsson Björn O. Roos Antonio Carlos Borin 《Theoretical chemistry accounts》2001,105(6):452-462
The accuracy of theoretical calculations on models of the blue copper proteins is investigated using density functional theory
(DFT) Becke's three-parameter hybrid method with the Lee–Yang–Parr correlation functional (B3LYP) and medium-sized basis sets.
Increasing the basis set to triple-zeta quality with f-type functions on all heavy atoms and enlarging the model [up to Cu(imidazole-CH3)2(SC2H5) (CH3SC2H5)0/+] has only a limited influence on geometries and relative energies. Comparative calculations with more accurate wave-function–based
methods (second-order M?ller–Plesset perturbation theory, complete-active-space second-order perturbation theory, coupled-cluster
method, including single and double replacement amplitudes and in addition triple replacement perturbatively) and a variety
of basis sets on smaller models indicate that the DFT/B3LYP approach gives reliable results with only a small basis set dependence,
whereas the former methods strongly depend on the size of the basis sets. The effect of performing the geometry optimizations
in a continuum solvent is quite small, except for the flexible Cu-SMet bond. The results of this study confirm the earlier results that neither the oxidized nor the reduced copper site in the
blue proteins is strained to any significant degree (in energy terms) by the protein surrounding.
Received: 7 July 2000 / Accepted: 17 November 2000 / Published online: 21 March 2001 相似文献
16.
《Fluid Phase Equilibria》2002,202(1):49-66
The thermodynamic behaviour of a number of real substances is determined by dipolar as well as quadrupolar interactions of the molecules. In equations of state (EOS) like, e.g. BACKONE separate contributions to the Helmholtz energy for the dipolar and the quadrupolar interactions are considered but no cross contributions. Here, the concept of effective dipole and quadrupole contributions is suggested in which the effective dipole strength μe is influenced by the quadrupole cross interaction. Similarily, the effective quadrupole strength Qe takes into account the dipole cross interaction. In order to arrive at these effective dipolar and quadrupolar strengths, molecular simulations are performed. From the simulation results correlation equations are derived which are used in combination with BACKONE for the calculation of vapour–liquid equilibria (VLE) of real mixtures. By using these effective moments, the only required binary mixing rule parameter kij tends to small values of about 0.01 and becomes temperature-independent. Moreover, the VLE pressures are predicted now considerably better than without consideration of the cross contributions. 相似文献
17.
Yu Ogawa Hitomi Hidaka Satoshi Kimura Ung-Jin Kim Shigenori Kuga Masahisa Wada 《Cellulose (London, England)》2014,21(2):999-1006
We investigated the crystal structure of alkali-celluloses, Na-cellulose IIA and II(Cu), formerly known as Na-cellulose IIB, by synchrotron X-ray diffraction. Na-cellulose IIA, formed from cellulose I by high-concentration NaOH treatment, has a fiber repeat of 15 Å and a threefold-like helical conformation. Na-cellulose II(Cu), prepared by treating cellulose I with copper-saturated alkali solution, also has a fiber repeat of 15 Å with threefold helical symmetry. Incorporation of Cu(II) ions into cellulose was confirmed by multiwavelength anomalous diffraction. Monitoring by X-ray diffraction revealed that the formation of this complex from cellulose I is remarkably slow, probably because of the involvement of copper ion. The stability of alkali-cellulose II(Cu) was tested to estimate the influence of the presence of copper in the crystal. Na-cellulose II(Cu) characteristically dissolved in aqueous ammonia solution, indicating strong coordination of copper ion to cellulose. 相似文献
18.
Magdalena Ogrodowczyk Katarzyna Dettlaff Waldemar Bednarski Barbara Ćwiertnia Maciej Stawny Grzegorz Spólnik Juliusz Adamski Witold Danikiewicz 《Chemical Papers》2018,72(2):349-357
Nadolol ((2R*,3S*)-5-{[(2R*)-3-(tert-butylamino)-2-hydroxypropyl]oxy}-1,2,3,4 tetrahydronaphthalene-2,3-diol) in substantia was exposed to ionizing radiation generated by a beam of high-energy electrons in an accelerator, in the standard sterilisation dose of 25 kGy and in higher doses of 50 ? 400 kGy. The irradiated and non-irradiated (control) samples were analysed by the infrared spectrophotometry, electron paramagnetic resonance, differential scanning calorimetry (DSC) and ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC–MS). The irradiated samples were found to contain free radicals in concentrations much higher than that observed for the other irradiated β-blockers. On the basis of UHPLC–MS results, it was possible to establish structures of 11 compounds of the impurities and/or products of nadolol decomposition. The main product of radiodegradation was concluded to be formed as a result of abstraction of the hydroxyl group and aromatization of the tetrahydronaphthalene ring. The results of DSC measurements confirmed the presence of radiolysis products in the irradiated samples of nadolol. A shift of the endothermic peak corresponding to melting towards lower temperatures (by 4.4 °C at the dose of 400 kGy) was directly proportional to the doses of radiation used, which permits concluding that this method is sensitive and suitable for evaluation of radiodegradation of nadolol in solid phase. 相似文献
19.
M. Bosacka E. Filipek P. ?ulcova ?. Dohnalová A. Paczesna 《Journal of Thermal Analysis and Calorimetry》2012,109(2):605-610
Phase equilibria up to solidus line in CuO?CIn2O3 system have been investigated using XRD and DTA/TG methods. According to the results, only one compound of the formula Cu2In2O5 formed in the system studied. Its thermal stability was determined in the air and argon proving that the compound did not melt but underwent decomposition. The decomposition of Cu2In2O5 in the air atmosphere began at 1080?°C, while in argon at 835?°C. Additional studies were undertaken to determine the hitherto unknown colour properties of samples representing the CuO?CIn2O3 system in the equilibrium state. 相似文献
20.
Carbohydrate recognition is clearly present throughout nature, playing a major role in the initial attachment of one biological
entity to another. The important question is whether these prevalent interactions could provide a real suitable alternative
to the use of antibodies or nucleic acid for detection and identification. Currently, examples of carbohydrates being employed
in biological detection systems are limited. The challenges of using carbohydrate recognition for detection mainly come from
the weak affinity of carbohydrate–protein interactions, the lack of versatile carbohydrate scaffolds with well-defined structures,
and the less developed high-information-content, real-time, and label-free assay technology. In this review, we focus on discussing
the characteristics of carbohydrate–protein interactions in nature and the methods for carbohydrate immobilization based on
surface coupling chemistry in terms of their general applicability for developing carbohydrate- and lectin-based label-free
sensors. Furthermore, examples of innovative design of multivalent carbohydrate–protein interactions for sensor applications
are given. We limit our review to show the feasibility of carbohydrate and lectin as recognition elements for label-free sensor
development in several representative cases to formulate a flexible platform for their use as recognition elements for real-world
biosensor applications. 相似文献