共查询到20条相似文献,搜索用时 24 毫秒
1.
M. R. Ganjali P. Norouzi F. Faridbod S. Riahi M. R. Yaftian A. Zamani D. Matt 《Journal of Applied Electrochemistry》2007,37(7):827-833
A Th4+ ion-selective membrane sensor was fabricated from poly (vinyl chloride) (PVC) matrix membrane containing 2-(diphenylphosphorothioyl)-N′,N′-diphenyl acetamide (DPTD) as a neutral carrier, potassium tetrakis (p-chlorophenyl) borate (KTpClPB) as anionic excluder and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The effects of the membrane composition, pH and additive
anionic influence on the response properties were investigated. The sensor, comprising 30% PVC, 63% solvent mediator, 4% ionophore
and 3% anionic additive demonstrates the best potentiometric response characteristics. It displays Nernstian behavior (15.2 ± 0.5 mV
per decade) over the concentration range 1.0 × 10−2–1.0 × 10−6 M. The detection limit of the electrode is 6.3 × 10−7 M (∼140 ng/ml). The response time of the electrode is 30 s .The sensor can be used in the pH range 3.0–9.0 for about 6 weeks.
The membrane sensor was used as an indicator electrode in the potentiometric titration of Th4+ ions with EDTA. It was successfully applied to the determination of thorium ions in binary mixture. 相似文献
2.
In this study, a novel semi-interpenetrating network (semi-IPN’s) hydrogel, composed of acrylamide (AAm) with N-vinylimidazole (NVI) as comonomer, with poly (ethylene glycol)(PEG) and a multifunctional crosslinker such as trimethylolpropane
triacrylate (TMPTA) was prepared. Highly swollen poly (AAm/NVI) hydrogels and semi-IPN’s were synthesized by free radical
solution polymerization. Swelling experiments were performed in water at 25°C, gravimetrically. The influence of NVI and PEG
content in hydrogels were examined. Poly (AAm/NVI) and poly (AAm/NVI/PEG) hydrogels showed large extents of swelling in aqueous
media the swelling being highly dependent on the chemical composition of the hydrogels. Swelling ratio of poly (AAm/NVI) hydrogels
and poly (AAm/NVI/PEG) hydrogels was shown 7.16–39.85. Diffusion behavior was investigated. Water diffusion into hydrogels
was found to be non-Fickian in character. This study has given the quantitative information on the swelling characteristic of poly (AAm/NVI) hydrogel
and semi-IPN’s as water absorbent in many potential applications. 相似文献
3.
Vasilica Lates Delia Gligor Mircea Darabantu Liana M. Muresan 《Journal of Applied Electrochemistry》2007,37(5):631-636
The electrochemical behavior of a new G-2-s-triazine-based dendrimer, 2,4,6-tris-{4-{4,6-bis-{4-{4,6-bis-[(1S,2S)-1,3-dihydroxy-1-(4-nitrophenyl)-prop-2-ylamino]-s-triazin-2-yl}-piperazin-1-yl}-s-triazin-2-yl}-piperazin-1-yl}-s-triazine, (I), was studied in dimethylsulfoxide solution by cyclic voltammetry, on platinum and graphite electrodes. The electrochemical
properties of I were compared with that of one of its precursor, N-{4,6-bis{4-{4,6-bis[(1S,2S)-1,3-dihydroxy-1-(4-nitrophenyl)-prop-2-ylamino]-s-triazin-2-yl}-piperazin-1-yl}-triazin-2-yl}-piperazine), (II), together with that of the starting material, (1S,2S)-2-amino-1-(4-nitrophenyl)-propane-1,3-diol (“p-nitrophenylserinol”), (III). 相似文献
4.
In this study, N-isopropylacrylamide-based temperature and pH-sensitive hydrogels were synthesized by free radical polymerization for removal
of cationic dyes from aqueous solutions. For this purpose, N-isopropylacrylamide was copolymerized with various amounts of sodium salt of itaconic acid in the presence of crosslinking
agent (N,N-methylene bisacrylamide). The chemical structures of hydrogels were characterized by FT-IR analysis. In order to investigate
swelling properties of the hydrogels, water absorption (swelling) and shrinking (deswelling) kinetics, the equilibrium swelling
ratios in water and different pH buffer solutions, and the temperature dependent swelling ratios were determined. Then, their
adsorption properties such as adsorption capacities, kinetics, isotherms were investigated in case of their usage in removal
of Safranine T (ST), Brilliant Green (BG), and Brilliant Cresyl Blue (BCB) aqueous solutions. According to adsorbed dye amount,
the adsorption capacities are followed the order BG > ST ≅ BCB. In addition, the results indicated that the pseudo-second-order
kinetic model fitted better than the data obtained from pseudo-first-order model for the adsorption of all dyes onto hydrogels.
Furthermore, according to effect of the initial dye concentration findings, it is concluded that, Freundlich isotherm explains
the adsorption better than Langmuir isotherm. 相似文献
5.
3-(3′,4′-Dihydroxyphenyl)-l-alanine (l-DOPA), which is synthesized in velvet bean (Mucuna pruriens), inhibits plant growth. The concentration of l-DOPA in soil is reduced by adsorption and transformation reactions, which can result in the reduction of its plant-growth-inhibitory
activity. To determine which part of the l-DOPA structure is involved in the adsorption and soil transformation reactions, we compared the kinetics of l-DOPA disappearance in a volcanic ash soil with that of l-phenylalanine (3-phenyl-l-alanine) and l-tyrosine (3-(4′-hydroxyphenyl)-l-alanine), compounds that are similar in structure to l-DOPA but do not have a catechol (o-dihydroxybenzene) moiety. l-Phenylalanine and l-tyrosine were not adsorbed and transformed in the soil at equilibrium pH values between 4 and 7. These results suggest that
the adsorption and transformation reactions of l-DOPA in the soil involve the catechol moiety and not the amino and carboxylic acid groups, which are common to all three
compounds. Like l-DOPA, (+)-catechin, another allelochemical that contains a catechol moiety, underwent adsorption and soil transformation
reactions. Thus, we concluded that the concentrations of allelochemicals bearing a catechol moiety in soils will decrease
rapidly owing to adsorption and transformation reactions, and this decrease will be faster in soils with a high pH value or
high adsorption ability. Owing to this decrease in concentration, allelopathic phenomena may not occur. 相似文献
6.
Copolymer hydrogels of N-isopropylacrylamide and itaconic acid (IA), crosslinked with N,N′-methylenebisacrylamide, were prepared by radical copolymerization. These hydrogels were investigated with regard to their
composition to find materials with satisfactory swelling and drug release properties. A paracetamol is used as a model drug
to investigate drug release profile of the hydrogels. It was found that the investigated hydrogels exhibited pH- and temperature-dependent
swelling behaviour with restricted swelling and lower equilibrium degree of swelling at lower pH values and temperatures above
the LCST value of PNIPAM (around 34 °C). The diffusion exponent for paracetamol release indicate that the mechanism of paracetamol
release are governed by Fickian diffusion, while in all release media initial diffusion coefficient was lower than late time
diffusion coefficient. Furthermore, the paracetamol release rate depends on the hydrogel degree of swelling and it increased
in the first stage of diffusion process, whereas was no significant difference thereafter. The presence of the IA moieties
incorporated into the network weakened the shear resistance of the hydrogels. In order to calculate the pore size the characteristic
ratio for PNIPAM, C
n
= 11.7, was calculated. Based on the pore size, the investigated hydrogels can be regarded as microporous. According to the
obtained results swelling behaviour, mechanical properties, drug-loading capacity and the drug release rate could be controlled
by hydrogel composition and crosslinking density, which is important for application of the investigated hydrogels as drug
delivery systems. 相似文献
7.
The effects of key parameters on the preparation and regeneration of protoplast from the β-carotene-producing fungus Blakeslea trispora were discussed in this paper, including the combination of various enzymes, mycelial age, digesting time and temperature,
pH value, osmotic stabilizers, pretreatment, culture medium and culture method. Under the condition of mixed enzymes in osmotic
stabilizer (0.6 M NaCl) combined with 2% lysozyme, 3% cellulase and 3% snailase, the highest protoplast yield, as high as
7.48×106 protoplasts/mL, was obtained when mycelial age was 60 h at pH 5.0–6.0 with digesting for 14–16 h at 28 °C. After
purification of the obtained protoplasts, they were regenerated in PDA regenerative medium using bilayer plate culture method.
To validate the usability of the protoplasts, a novel plasmid with green fluorescent protein (GFP) was used in transformation
for easy visual observation. The results showed that the protoplasts prepared by the optimized method were active and applicable
in further gene manipulation experiments.
This work was presented at 13
th
YABEC symposium held at Seoul, Korea, October 20–22, 2007. 相似文献
8.
Mina Park Sung Soo Park M. Selvaraj Il Kim Chang-Sik Ha 《Journal of Porous Materials》2011,18(2):217-223
The adsorption of cytochrome c has been investigated using two different types of hydrophobic periodic mesoporous organosilicas (PMOs) that have been produced
under mild reaction conditions using 1,4-bis(triethoxysilyl)benzene (PMO-benzene) and 4,4′-bis(triethoxysilyl)biphenyl (PMO-biphenyl)
as the precursors. For comparison studies, the adsorption of cytochrome c has also been investigated using mesoporous SBA-15 as an absorbent. Mesostructured PMOs and SBA-15 have been characterized
by small-angle X-ray scattering (SAXS), N2-adsorption/desorption and transmission electron microscope (TEM). The adsorption rates of the hydrophobic PMOs have been
compared to that of SBA-15 at both pH 7.0 and pH 9.6. From the adsorption studies, it is found that PMO-biphenyl has more
hydrophobicity than PMO-benzene and showed higher adsorption capacity to cytochrome c as compared to PMO-benzene. 相似文献
9.
Hong-Wei Wang In Hae Kim Chang-Su Park Jae-Hwa Lee 《Korean Journal of Chemical Engineering》2008,25(4):801-803
α-amylase from Bacillus licheniformis was successfully immobilized on developed support, which was prepared by coating a chitosan-casein film on silica, at 20
°C, pH 6.0 for 5 hr with microbial transglutaminase (MTG) as the cross-linking factor. The optimal support was obtained when
1% chitosan and 1% casein were used in the coating mixture. The optimal condition for immobilization catalyzed by MTG was
confined to be at MTG concentration of 15 U/mL, pH 6.0, reacting for 6 hr at 20 °C. The highest specific activity of immobilized
α-amylase was achieved as 236 U/g. After immobilization, the obtained enzyme showed broader pH profile and maintained more
than 70% of the original activity after 20 reuses. 相似文献
10.
Superabsorbent hydrogels of chitosan-g-polyacrylamide with N,N′-methylene-bis-acrylamide as a crosslinker were prepared via UV irradiation in the absence of photoinitiator under homogeneous
conditions. The product was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and
scanning electron microscopy to confirm the formation of hydrogels. The transparent hydrogels have been observed to exhibit
as much as 2987% swelling in acidic solution. In addition, the hydrogel which hydrolyzed for 6 h (0.24 × 103 min) can have a water uptake of 106 times its weight (5300% swelling for 0.5 g hydrogel). The effect of several variables
such as time, temperature, pH, acrylamide/chitosan ratio, crosslinker amount, and different media was explored. Finally, the
prepared hydrogel have been used in adsorption of Zn(II) ions from water with high removal efficiency (0.636 meq g−1 or 20.8 mg g−1) at pH = 7. The experimental data of the adsorption equilibrium from Zn(II) solution fit well with the pseudo-second-order
model. 相似文献
11.
Asperamides A (1) and B (2), a sphingolipid and their corresponding glycosphingolipid possessing a hitherto unreported 9-methyl-C20-sphingosine moiety, were characterized from the culture extract of Aspergillus niger EN-13, an endophytic fungus isolated from marine brown alga Colpomenia sinuosa. The structures were elucidated by spectroscopic and chemical methods as (2S,2′R,3R,3′E,4E,8E)-N-(2′-hydroxy-3′-hexadecenoyl)-9-methyl-4,8-icosadien-1,3-diol (1) and 1-O-β-d-glucopyranosyl-(2S,2′R,3R,3′E,4E,8E)-N-(2′-hydroxy-3′-hexadecenoyl)-9-methyl-4,8-icosadien-1,3-diol (2). In the antifungal assay, asperamide A (1) displayed moderate activity against Candida albicans. 相似文献
12.
1,3-Dipalmitoyl-2-oleoyl-sn-glycerol (POP) and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP) are two major molecular species that account for roughly half of the total triacylglycerols in palm oil. The
binary phase behavior of a POP/OOP mixture plays an important role in the crystallization of palm oil. We conducted thermodynamic
and kinetic studies of OOP and its mixtures with POP using differential scanning calorimetry and X-ray diffraction with a
conventional generator and synchrotron radiation. We found that OOP has two polymorphs, α as a metastable form and β′ as the
most stable form, and that the two forms are stacked in a triple-chain-length structure. The POP/OOP mixtures exhibited immiscible
eutectic natures in both their metastable and their most stable states, in contrast to POP/1,2-dipalmitoyl-3-oleoyl-rac-glycerol and POP/1,3-dioleoyl-2-palmitoyl-sn-glycerol mixtures, in which molecular compounds of a double-chain-length structure were formed. A time-resolved synchrotron
radiation X-ray diffraction study undertaken during the cooling and heating processes indicated that the α and β′ forms of
the POP and OOP fractions crystallized and melted in separate manners, and that crystallization of the β′ form and the polymorphic
transformation from α to β′ of POP and OOP are promoted in the presence of another component. The absence of molecular compound
crystals in the binary mixtures of POP/OOP is explained by taking into account the molecular interactions of acyl chain packing,
glycerol conformation, and methyl end stacking, among which glycerol conformation appeared to be most influential. 相似文献
13.
MING CHEN HUI-LAN WANG JING GU GUO-WANG DIAO 《Journal of Applied Electrochemistry》2007,37(3):331-337
The water-soluble p-sulfonated sodium salt of calix[8]arene (III) was synthesized. The product was characterized by FT-IR, NMR and UV–Vis spectra.Then
the electrochemical behaviors of p-sulfonated sodium salt of calix[8]arene in NaAc+HAc (pH = 4) buffer solution was studied. In aqueous solution, p-sulfonated calix[8]arene can be oxidized when the potential is more than 0.7 V vs SCE. It was confirmed that the reaction
was a two-electron irreversible electrochemical reaction. The transfer coefficient, α, was measured as 0.7. At 25°, the diffusion
coefficient of p-sulfonated calix[8]arene was determined as 8.6 × 10−7 cm2 s−1. The diffusion activation energy of p-sulfonated calix[8]arene was 18.9 kJ mol−1 at pH = 4. 相似文献
14.
Five cerebrosides (1–5), including three new ones named cortenuamide A (1), cortenuamide B (2), and cortenuamide C (3), were isolated from the fruiting bodies of the basid-iomycete Cortinarius tenuipes. The structures of those compounds were elucidated as (4E,8E)-N-d-2′-hydroxytetracosanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (1), (4E,8E)-N-d-2′-hydroxytricosanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8 sphingadienine (2), (4E, 8E)-N-d-2′-hydroxydocosanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (3), (4E, 8E)-N-d-2′-hydroxyoctadecanoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (4), and (4E, 8E)-N-d-2′-hydroxypalmitoyl-1-O-β-d-glycopyranosyl-9-methyl-4,8-sphingadienine (5) by spectral and chemical methods. 相似文献
15.
Coccinellid beetles contain a variety of defensive alkaloids that render them unpalatable to predators. Epilachna paenulata (Coleoptera: Coccinellidae) is a South American ladybird beetle that feeds on plants of the Cucurbitaceae family. The defensive
chemistry of E. paenulata has been characterized as a mixture of systemic piperidine, homotropane, and pyrrolidine alkaloids. Whole body extracts of
adult beetles contain four major alkaloids: 2-(2′-oxopropyl)-6-methylpiperidine (1); 1-(6-methyl-2,3,4,5-tetrahydro-pyridin-2-yl)-propan-2-one (2); 1-methyl-9-azabicyclo[3.3.1]nonan-3-one (3); and 1-(2″-hydroxyethyl)-2-(12′-aminotridecyl)-pyrrolidine (4). Comparative studies of the defensive chemistry of eggs, larvae, pupae, and adults showed differences in alkaloid composition
and concentration among life stages. While adults contained mainly the homotropane 1-methyl-9-azabicyclo[3.3.1]nonan-3-one
(3), eggs showed the highest concentration of the piperidine 2-(2′-oxopropyl)-6-methylpiperidine (1). We studied the origin of this alkaloid in the eggs by feeding newly emerged, virgin adult beetles with [2-13C]-labeled acetate, and by performing crosses between 13C-fed and unlabeled males and females. GC-MS analysis of alkaloids from 13C-fed males and females showed high incorporation of 13C into the alkaloids, as evidenced from a 20–30% increase of isotopic peaks in diagnostic fragment ions, confirming the expected
endogenous origin of these alkaloids. In addition, analyses of eggs from different crosses showed that labeled alkaloids from
both parents are incorporated into eggs, indicating that E. paenulata males transfer alkaloids to the females at mating. Biparental endowment of chemical defenses into eggs has been shown previously
in insects that acquire defensive compounds from dietary sources. To our knowledge, this is the first report of biparental
egg endowment of endogenous defenses.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
John H. P. Tyman Robert A. Johnson 《Journal of the American Oil Chemists' Society》2007,84(6):573-578
To study the relationship between structure and properties of members of the lipidic thiobis phenol series, as extreme pressure
additives in lubricants, a series of homologous compounds has been synthesised by the reaction of alkylphenols with sulphur
dichloride. The isomeric n-nonylphenols have been reacted to form the C9 isomeric 2,2′-and 4,4′-thiobisphenols. Longer alkyl side-chains resulted mainly
in the formation of 4,4′-thiobisphenols and some of the 2,2′ isomer. With short alkyl, particularly t-alkyl side-chains, steric hindrance resulted in the 2,2′-compound. Additive studies have indicated that the longer chain
4,4′ compounds possessed antioxidant properties comparable and superior to former commercial branched chain 2,2′ compounds
produced from petrochemical intermediates.
Lipidic alkylthiobisphenols: Long chain phenols, Part 40b (Part 40a, ref 6). 相似文献
17.
Ana Karina Timbola C. D. Souza C. Soldi M. G. Pizzolatti A. Spinelli 《Journal of Applied Electrochemistry》2007,37(5):617-624
We report the electrochemical oxidation of rutin in acetonitrile-sodium phosphate (4:1 (v/v); pH 2.0) in the presence of p-toluenesulfinic acid. Cyclic voltammetry and controlled potential electrolysis were used to study rutin electro-oxidation
and to prepare the sulfone derivatives. Chromatographic methods were employed to separate the products and IR, 1H NMR, 13C NMR, MS and microanalysis to their characterization. Data from cyclic voltammetry allow the identification of three rutin
oxidation processes in the presence of p-toluenesulfinic acid (E
pI = 0.56 V, E
pII = 0.81 V and E
pIII = 1.32 V). Only the electrode process around peak I was exhaustively studied. The first oxidation step leads to the formation
of the corresponding o-quinone, which participates in a Michael addition reaction with the p-toluenesulfinic acid, forming the 6′(4-methylphenylsulfonyl)rutin and 6′(4-methylphenylsulfonyl)quercetin as majority products. 相似文献
18.
Andrzej Piasecki Sławomir Karczewski Irena Maliszewska 《Journal of surfactants and detergents》2007,10(2):93-101
A homologous series of new surface-active 1,1-bis{[3-(N,N-dimethylamino)propyl]amido}alkane-di-N-oxides were synthesized in the reaction of an appropriate diethyl 2-alkylmalonate with N,N-dimethylamino-1,3-propanediamine followed by oxidation with aqueous hydrogen peroxide. The adsorption isotherms of their
aqueous solutions were measured and evaluated to obtain adsorption parameters: critical micelle concentration (CMC), surface
excess concentration (ΓCMC), equilibrium surface tension at the CMC (γCMC), cross-sectional area of the adsorbed surfactant molecule (A
CMC), efficiency of surface adsorption (pC20), standard free energies of adsorption (ΔG°ads), and micellization (ΔG°CMC). All investigated di-amidoamines and di-N-oxides were practically non-toxic to selected bacteria and yeasts. These compounds are readily biodegradable in the Closed
Bottle Test inoculated with activated sludge. Surface and biological properties showed that this group of N-oxide-type compounds has high surface activity and fulfills requirements for environmental acceptance.
相似文献
Andrzej PiaseckiEmail: |
19.
Two antibacterial and xanthine oxidase inhibitory cerebrosides, one of which is chemically new, were characterized from the
chloroform-methanol (1∶1) extract of Fusarium sp. IFB-121, an endophytic fungus in Quercus variabilis. By means of chemical and spectral methods [IR, electrospray ionization MS (ESI-MS), tandem ESI-MS, 1H and 13C NMR, distortionless enhancement by polarization transfer, COSY, heteronuclear multiple-quantum coherence, heteronuclear
multiple-bond correlation, and 2-D nuclear Overhauser effect correlation spectroscopy], the structure of the new metabolite
named fusaruside was established as (2S,2′R,3R,3′E,4E,8E,10E)-1-O-β-d-glucopyranosyl-2-N-(2′-hydroxy-3′-octadecenoyl)-3-hydroxy-9-methyl-4,8,10-sphingatrienine, and the structure of the other was identified as
(2S,2′R,3R,3′E,4E,8E)-1-O-β-d-glucopyranosyl-2-N-(2′-hydroxy-3′-octadecenoyl)-3-hydroxy-9-methyl-4,8-sphingadienine. Both new and known cerebrosides, although inactive to
Trichophyton rubrum and Candida albicans, showed strong antibacterial activities against Bacillus subtilis, Escherichia coli, and Pseudomonas fluorescens, with their minimum inhibitory concentrations being 3.9, 3.9, and 1.9 μg/mL, and 7.8, 3.9, and 7.8 μg/mL, respectively. Furthermore,
both metabolites were inhibitory to xanthine oxidase, with the IC50 value of fusaruside being 43.8±3.6 μM and the known cerebroside being 55.5±1.8 μM. 相似文献
20.
Maleeha Manzoor Farooq Anwar Tahira Iqbal M. I. Bhanger 《Journal of the American Oil Chemists' Society》2007,84(5):413-419
The present work reports the characterization and comparison of Moringa concanensis seed oil from Tharparkar (a drought hit area), Pakistan. The hexane-extracted oil content of M. concanensis seeds ranged from 37.56 to 40.06% (average 38.82%). Protein, fiber, moisture and ash contents were found to be 30.07, 6.00,
5.88 and 9.00%, respectively. The extracted oil exhibited an iodine value of 67.00; a refractive index (40 °C) of 1.4648;
its density (24 °C) was 0.8660 mg mL−1; the saponification value (mg of KOH g−1 of oil) was 179.00; unsaponifiable matter 0.78%; color (1 in. cell) 1.90R + 19.00Y; and acidity (% as oleic acid) 0.34%.
Tocopherols (α, γ, and δ) in the oil accounted for 72.11, 9.26 and 33.87 mg kg−1, respectively. Specific extinctions at 232 and 270 nm were 3.17 and 0.65, respectively. The peroxide and p-anisidine values of the oil were found to be 1.75 and 1.84 meq kg−1, respectively. The induction periods (Rancimat, 20 L h−1, 120 °C) of the crude oil was 10.81 h and reduced to 8.90 h after degumming. The M.
concanensis oil was found to contain high levels of oleic acid (up to 68.00%) followed by palmitic, stearic, behenic, and arachidic acids
up to levels of 11.04, 3.58, 3.44 and 7.09%, respectively. The results of the present analytical study, compared with those
for other Moringa species and different vegetable oils, showed M. concanensis to be a potentially valuable non-conventional seed crop for high quality oil. 相似文献