共查询到20条相似文献,搜索用时 15 毫秒
1.
Yukiko Enomoto-Rogers Hiroshi Kamitakahara Kunihiro Nakayama Toshiyuki Takano Fumiaki Nakatsubo 《Cellulose (London, England)》2009,16(3):519-530
Model experiments for synthesis of a comb-shaped copolymer with cellulose side-chains were performed with cellobiose derivatives.
A novel cellobiose monomer, N-(15-methacryloyloxypentadecanoyl)-2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-β-d-glucopyranosylamine (2) was prepared from heptaacetylcellobiosyl- amine. Homopolymerization of cellobiose monomer 2 and copolymerization of monomer 2 with methyl methacrylate (MMA) were performed using 2,2′-azobis(isobutyronitrile) (AIBN) as an initiator to obtain homopolymers
3-i (i = 1–4) and copolymers 3-i (i = 5–7), poly(methyl methacrylate)-graft-(heptaacetylcellobiosylamine-C15). The size exclusion chromatography—multi-angle laser light scattering (SEC-MALS) measurements
revealed that comb-shaped homopolymers 3-i (i = 1–4) had more compact structures compared to copolymers 3-i (i = 5–7) at the same elution volume. Selective deacetylation of polymers 3-i (i = 1–7) gave novel cellobiose polymers 4-i (i = 1–7), poly(methyl methacrylate)-graft-(cellobiosylamine-C15). The amide linkages between cellobiose moiety and long-chain alkyl group, and the ester linkages between
PMMA main-chain and long-chain alkyl group remained after deprotection.
The differential scanning calorimetry (DSC) measurements revealed that the T
gs of the polymers 4-i (i = 1, 5, 6, 7) increased with increasing cellobiose composition in the polymers. It was indicated that cellobiose moieties
of polymers 4-i (i = 1, 5, 6, 7) reduced the mobility of PMMA main-chain. 相似文献
2.
I. A. Opeida M. A. Kompanets O. V. Kushch A. G. Matvienko 《Theoretical and Experimental Chemistry》2010,46(2):107-111
The kinetics of the decomposition of the phthalimid-N-oxyl radical (PINO) in acetic acid has been studied. The rate constants
of the addition of the radical to T bonds of molecules of vinyl compounds – styrene, methyl methacrylate, acrylonitrile, and
methyl acrylate – have been measured. It was shown that electron-donor substituents in the monomer molecule increase, while
electron-acceptor substituents decrease the rate of addition. The reactivity of monomers in the elementary step of addition
of the PINO radical decreases in the order CH2=C(CH3)C6H5 > CH2=CHC6H5 > CH2=C(CH3)COOCH3 > CH2=CHCOOCH3 > CH2=CHCN. 相似文献
3.
Pengyan Liu Lei Liu Li Zhang Ning Jiang Zhanli Liu Yun Wang 《Frontiers of Chemistry in China》2008,3(4):378-383
A molecularly imprinted polymer (MIP), with special molecule recognition properties of ciprofloxacin (CIP), was prepared by
thermal polymerization in which ciprofloxacin acted as template molecule, α-methacrylic acid (MAA) acted as functional monomer and trimethylolpropane trimethylacrylate (TRIM) acted as crosslinker.
The optimized ratio was determined to be n(CIP): n (MMA):n(TRIM)51:6:16 by investigation of the effects of different concentrations of functional monomer and the crosslinker on the
MIP’s recognition properties. Equilibrium binding experiment was used to investigate the adsorption dynamics, the binding
ability to template molecule and the substrate selectivity. Scatchard analysis was used to study the MIP’s binding characteristic
to template molecule. The results indicated that MIP has higher adsorption ability and selectivity. The equilibrium distribution
coefficient K
D was 41.64 and the separation factor α was 1.62. Scatchard analysis showed that two different kinds of binding sites were produced in the polymer matrix and their
dissociation constants were calculated to be K
d1 = 5.249 × 10−5 mol·L−1, K
d2 = 2.237 × 10−3 mol·L−1.
__________
Translated from Chemistry, 2008, 71(2): 132–137 相似文献
4.
A new binary chiral selector system effective for the enantioselective extraction of racemic mandelic acid is presented. While
L-dipentyl tartrate and β-cyclodextrin had a very low enantioselectivity as single selectors, a preferential extraction of D-mandelic acid to the organic phase was found in the binary selector system. Using decanol as organic solvent and pH of a
phoshate buffer equal to 2.3, the distribution coefficients of D-and L-mandelic acids as high as 14.9 and 7.0, respectively, and the enantioselectivity value of 2.1 were found at optimum concentration
of β-cyclodextrin. 相似文献
5.
Natalia García-Otero Carmen Teijeiro-Valiño Jacobo Otero-Romaní Elena Peña-Vázquez Antonio Moreda-Piñeiro Pilar Bermejo-Barrera 《Analytical and bioanalytical chemistry》2009,395(4):1107-1115
Nickel(II) and lead(II) ionic imprinted 8-hydroxyquinoline polymers were synthesized by a precipitation polymerization technique
and were used as selective solid phase extraction supports for the determination of nickel and lead in seawater by flow injection
solid phase extraction on-line inductively coupled plasma-optical emission spectrometry. An optimum loading flow rate of 2.25 mL min−1 for 2 min and an elution flow rate of 2.25 mL min−1 for 1 min gave an enrichment factor of 15 for nickel. However, a low dynamic capacity and/or rate for adsorption and desorption
was found for lead ionic imprinted polymer and a flow rate of 3.00 mL min−1 for 4-min loading and a flow rate of 2.25 mL min−1 for 1-min elution gave a enrichment factor of 5. The limit of detection was 0.33 μg L−1 for nickel and 1.88 μg L−1 for lead, with a precision (n = 11) of 8% (2.37 μg Ni L−1) for nickel and 11% (8.38 μg Pb L−1) for lead. Accuracy was also assessed by analyzing SLEW-3 (estuarine water) and TM-24 (lake water) certified reference materials,
and the values determined were in good agreement with the certified concentrations. 相似文献
6.
He-Yan Jiang Chen-He Zhou Kui Luo Hua Chen Jing-Bo Lan Ru-Gang Xie 《Journal of molecular catalysis. A, Chemical》2006,260(1-2):288-294
Chiral imidazole hydrolytic metalloenzyme models with characteristics of chiral centers directly link to imidazole N-atoms and varieties in both alkyl chain length and number of alkyl chains, have been synthesised and investigated for enantioselective hydrolysis of Boc-α-amino acid esters. The result indicates that both hydrolysis rates and enantioselectivities are increased with increases in the alkyl chain length and the number of the alkyl chains in the lipophilic chiral imidazole-type surfactants in many cases. The lipophilic chiral imidazole 4d ((S)-1-hexadecoxy-2-(1-imidazolyl)-propane), which has one long alkyl chain, shows higher hydrolysis rate and enantioselectivity (kD = 132.5 × 10−5, kD/kL = 5.38), 5d ((S)-1,5-dihexadecoxy-2-(1-imidazolyl)-pentane), which has two long alkyl chains, shows the highest hydrolysis rate and enantioselectivity (kD = 201.5 × 10−5, kD/kL = 11.72). Additionally, the effects of the metals, the additives, the solvents and the substrates on the hydrolysis rates and enantioselectivities are examined. 相似文献
7.
An enzymatic method for determining L-malic acid in wine based on an L-malate sensing layer with nicotinamide adenine dinucleotide (NAD+), L-malate dehydrogenase (L-MDH) and diaphorase (DI), immobilized by sol-gel technology, was constructed and evaluated. The sol-gel glass was prepared
with tetramethoxysilane (TMOS), water and HCl. L-MDH catalyzes the reaction between L-malate and NAD+, producing NADH, whose fluorescence (λ
exc = 340 nm, λ
em = 430 nm) could be directly related to the amount of L-malate. NADH is converted to NAD+ by applying hexacyanoferrate(III) as oxidant in the presence of DI. Some parameters affecting sol-gel encapsulation and the
pH of the enzymatic reaction were studied. The sensing layer has a dynamic range of 0.1–1.0 g/L of L-malate and a long-term storage stability of 25 days. It exhibits acceptable reproducibility [s
r(%)≈10] and allows six regenerations. The content of L-malic acid was determined for different types of wine, and polyvinylpolypyrrolidone (PVPP) was used as a bleaching agent
with red wine. The results obtained for the wine samples using the sensing layer are comparable to those obtained from a reference
method based on UV-vis molecular absorption spectrometry, if the matrix effect is corrected for. 相似文献
8.
de Jesus Rodrigues Santos W Lima PR Tarley CR Kubota LT 《Analytical and bioanalytical chemistry》2007,389(6):1919-1929
Despite the increasing number of applications of molecularly imprinted polymers (MIP) in analytical chemistry, the synthesis
of polymers with hemin introduced as the catalytic center to mimic the active site of peroxidase remains as a challenge. In
the current work, a new type of molecularly imprinted polymer (MIP) was synthesized with 4-aminophenol (4-APh) as the template
and two monomers: hemin, which acts as the catalytic center, and methacrylic acid (MAA), which is used to build the active
sites. This work shows that MIP successfully mimics peroxidase. For this purpose, a flow injection analysis system coupled
to an amperometric detector was investigated through multivariate analysis. The determination of 4-APh was not affected by
the equimolar presence of structurally similar phenol compounds, including catechol, 4-chloro-3-methylphenol, 2-aminophenol,
guaiachol, chloroguaiachol and 2-cresol, thus highlighting the good performance of the imprinted polymer. Under the optimized
experimental conditions, an analytical curve covering a wide linear response range from 0.8 up to 500 μmol L−1 (r > 0.999) was obtained, and the method gave satisfactory precisions (n = 8), as evaluated via the relative standard deviation (RSD), of 4.1 and 3.2% for solutions of 4-APh of 50 and 500 μmol L−1, respectively. Recoveries of 96–111% from water samples (tap water and river water) spiked with 4-APh were achieved, thus
illustrating the accuracy of the proposed system.
Figure Schematic presentation of the synthesis of the MIP 相似文献
9.
Katsuhiro Inomata Reina Doi Erina Yamada Hideki Sugimoto Eiji Nakanishi 《Colloid and polymer science》2007,285(10):1129-1137
Amphiphilic polymers Cn-PHEG consisting of water-soluble poly[N
5-2-(hydroxyethyl) l-glutamine] (PHEG) and hydrophobic alkyl chain (carbon number n = 12, 14, 16, or 18) attached at the PHEG terminal was prepared, and association behavior and structure of associate for
Cn-PHEG in selective solvent (water/ethylene glycol mixed solvent) have been investigated. α-Helix content of PHEG block for
all the polymers increased with weight fraction of ethylene glycol in the mixed solvent (W
EG). By light scattering measurements, formation of a small micelle was suggested for C14-, C16-, and C18-PHEG when W
EG = 0. With the increase in W
EG, appearance of a larger associate was revealed for C16- and C18-PHEG. Evaluated molecular weight and radius of gyration suggested
that the micelle is star-like sphere when W
EG = 0 and worm-like cylinder when W
EG = 0.7. C12-PHEG did not demonstrate any distinct micellization behavior because of the weak hydrophobicity of C12 chain. 相似文献
10.
Covalent imprinted polymer for selective and rapid enrichment of ractopamine by a noncovalent approach 总被引:1,自引:0,他引:1
A novel molecularly imprinted polymer (MIP) for the separation and concentration of ractopamine (RAC) was prepared by a covalent
imprinting approach and the template was removed successfully by hydrolysis, so that four carboxylic acid groups were left
in the cavities and could specifically rebind RAC through noncovalent interaction: hydrogen bonding. The conditions for synthesis
of the MIP were optimized during the polymerization process, and a molar ratio of template–functional monomer complexes to
cross-linker of 1:3 was confirmed. The adsorption capacity of the MIP was 4.1-fold that of the nonimprinted polymer, and the
adsorption reaction reached equilibrium after 25 min at 50 mg L-1 concentration. The results of the competitive adsorption test showed that the MIPs had specific recognition ability for the
analyte RAC. In addition, the important factors affecting the efficiency of the method which was developed using the MIPs
as a solid-phase sorbent for separation and determination of RAC combined with high-performance liquid chromatography with
fluorescence detection were optimized. Under the optimum experimental conditions, the linear range of the calibration curve
in the method was 0.05-5 μg L-1 (R
2 = 0.98) and the limit of detection (signal-to-noise ratio of 3) was 0.01 μg L-1. The proposed method was applied to determination of RAC in spiked feedstuffs and urine samples, with recoveries ranging
from 74.17 to 114.46% and relative standard deviation (n = 3) below 4.55 in all cases. 相似文献
11.
A novel thermal desorption technique using a direct-probe device (Chromatoprobe) attached to a gas chromatograph–mass spectrometer
is presented for the thermal pretreatment, characterisation and analysis of molecularly imprinted polymers. The technique
is demonstrated as effective for the removal of volatile materials, including template and unreacted monomers, from methacrylic
acid–ethylene glycol dimethacrylate copolymers imprinted with 2-aminopyridine. Mass spectrometry is a powerful technique for
polymer bleed characterisation. Thermal desorption studies on reloaded template and related compounds are reported as a means
of assessing polymer morphology, specific binding by imprinted polymers compared with reference non-imprinted polymers and
selective binding by an imprinted polymer for its template. Calibration studies on the thermal desorption technique using
an internal standard are presented with R
2 > 0.999. The technique provides a novel method for assessment of polymer thermal stability, composition and morphology. 相似文献
12.
The K-stearate/glycerol (KC18/Gl) binary system was studied at mole fractions of stearate of x
KC18 = 0.10, 0.25, 0.30 and 0.50. Small- and wide-angle X-ray diffraction (XRD) measurements were combined with differential scanning
calorimetry (DSC) measurements at different temperatures. The investigations were intended to verify the previously published
phase diagram and were targeted at the confirmation of the gel-like (G1) phase and the isotropic (I) phase. The XRD and DSC measurements lead to the conclusion that the G1 phase as well as the I phase, the existence of which had been proposed from texture observations, do in fact not exist. Consequently,
a correction of the preliminary phase diagram is given. This corrected phase diagram reveals the crystalline phase (C) ⇆ gel
phase (G) ⇆ hexagonal phase (Hα) ⇆ isotropic, micellar phase phase transitions for low KC18 concentrations of x
KC18 = 0.15–0.3 and the C ⇆ G ⇆ lamellar phase (Lα) phase transitions for concentrations about or higher than x
KC18 = 0.35. The C, G, Lα and Hα phases have been further characterized by structural parameters (characteristic d values) as a function of temperature. The phase transitions C ⇆ G, G ⇆ Lα and G ⇆ Hα correlate with sharp shifts in the d value of the first small-angle reflections.
Received: 20 April 1999 Accepted: 28 July 1999 相似文献
13.
Zhixiang Xu Shuang Chen Wei Huang Guozhen Fang Hua Pingzhu Shuo Wang 《Analytical and bioanalytical chemistry》2009,393(4):1273-1279
Estrone is one of the important potential endocrine-disrupting compounds, and the sensitive and reliable analytical methods
for the determination of estrone are required for the assurance of human health. In this paper, using estrone as template
molecule, 3-aminopropyltriethoxysilane as function monomer, and tetraethoxysilicane as cross-linker, a highly selective molecularly
imprinted microsphere was synthesized by surface molecular imprinting technique combined with a sol–gel process. The imprinted
material was characterized by the Fourier transform infrared and static adsorption experiments, and the results showed that
it exhibited good recognition and selective ability for estrone. A novel method for separation and determination of trace
estrone in environmental sample was developed using on-line molecularly imprinted solid-phase extraction coupled to high-performance
liquid chromatography. With a sample loading flow rate of 2.6 mL min−1 for a 9.6-min extraction, the enrichment factor obtained by the slopes of the linear portion in comparison with the direct
injection of 10 μL standard sample solution was 1,045. The detection limit (S/N = 3) was 5.7 ng L−1, and the relative standard deviations for nine replicate extractions of 5.0 μg L−1 estrone was less than 10.0%. This method was evaluated for quantitative determination of estrone in well and lake water samples
spiked at two levels (0.5 and 1.0 μg L−1) with recoveries ranging from 86% to 95%.
相似文献
14.
Kuehnelt D Kienzl N Traar P Le NH Francesconi KA Ochi T 《Analytical and bioanalytical chemistry》2005,383(2):235-246
To obtain quantitative information on human metabolism of selenium, we have performed selenium speciation analysis by HPLC/ICPMS
on samples of human urine from one volunteer over a 48-hour period after ingestion of selenium (1.0 mg) as sodium selenite,
L-selenomethionine, or DL-selenomethionine. The three separate experiments were performed in duplicate. Normal background urine from the volunteer
contained total selenium concentrations of 8–30 μg Se/L (n=22) but, depending on the chromatographic conditions, only about 30–70% could be quantified by HPLC/ICPMS. The major species
in background urine were two selenosugars, namely methyl-2-acetamido-2-deoxy-1-seleno-β-D-galactopyranoside (selenosugar 1) and its deacylated analog methyl-2-amino-2-deoxy-1-seleno-β-D-galactopyranoside (selenosugar 3). Selenium was rapidly excreted after ingestion of the selenium compounds: the peak concentrations (∼250–400 μg Se/L, normalized
concentrations) were recorded within 5–9 hours, and concentrations had returned to close to background levels within 48 hours,
by which time 25–40% of the ingested selenium, depending on the species ingested, had been accounted for in the urine. In
all experiments, the major metabolite was selenosugar 1, constituting either ∼80% of the total selenium excreted over the first 24 hours after ingestion of selenite or L-selenomethionine or ∼65% after ingestion of DL-selenomethionine. Selenite was not present at significant levels (<1 μg Se/L) in any of the samples; selenomethionine was
present in only trace amounts (∼1 μg/L, equivalent to less than 0.5% of the total Se) following ingestion of L-selenomethionine, but it constituted about 20% of the excreted selenium (first 24 hours) after ingestion of DL-selenomethionine, presumably because the D form was not efficiently metabolized. Trimethylselenonium ion, a commonly reported urine metabolite, could not be detected
(<1 μg/L) in the urine samples after ingestion of selenite or selenomethionine. Cytotoxicity studies on selenosugar 1 and its glucosamine isomer (selenosugar 2, methyl-2-acetamido-2-deoxy-1-seleno-β-D-glucosopyranoside) were performed with HepG2 cells derived from human hepatocarcinoma, and these showed that both compounds
had low toxicity (about 1000-fold less toxic than sodium selenite). The results support earlier studies showing that selenosugar
1 is the major urinary metabolite after increased selenium intake, and they suggest that previously accepted pathways for human
metabolism of selenium involving trimethylselenonium ion as the excretionary end product may need to be re-evaluated. 相似文献
15.
Jie Cai Jia Guo Minglei Ji Wuli Yang Changchun Wang Shoukuan Fu 《Colloid and polymer science》2007,285(14):1607-1615
Fe3O4/SiO2/poly (N-isopropylacrylamide-co-N,N-dimethylaminoethyl methacrylate) [P(NIPAM-co-DMA)] multiresponsive composite microspheres with core–shell structure were synthesized by template precipitation polymerization.
First, the magnetite nanoparticles were coated with silica and then modified with 3-(trimethoxysilyl)-propyl methacrylate
(MPS). Subsequently, the Fe3O4/SiO2 particles grafted with MPS were used to seed the precipitation copolymerization of NIPAM and DMA. The composite microspheres
with core–shell structure were superparamagnetic, pH-sensitive, and thermoresponsive. The swelling ratio (D25 °C,
pH = 3/D50 °C,
pH = 9)3 coupling of pH and temperature increased up to 21.2, which was much higher than that without comonomer DMA. 相似文献
16.
Giuseppe Cirillo Francesco Puoci Manuela Curcio Ortensia Ilaria Parisi Francesca Iemma Umile Gianfranco Spizzirri Nevio Picci 《Colloid and polymer science》2010,288(6):689-693
The aim of this study is the preparation of molecularly imprinted polymers by employing a redox pair as initiator system.
Bulk molecularly imprinted polymers were synthesized by using Fenton reagents as initiator system. Theophylline, methacrylic
acid, and ethylene glycol dimethacrylate were employed as model template, functional monomer, and crosslinking agent, respectively.
Conventional imprinted polymers were also prepared by using 2,2′-azoisobutyronitrile in order to evaluate the efficiency of
the proposed initiator system. Redox molecularly imprinted polymers and conventional molecularly imprinted polymers were characterized
by water uptake measurement, while the imprinting effect of synthesized polymers were evaluated by performing binding experiments
in organic (acetonitrile) and in water (buffered water solution at pH = 7.4) media. 相似文献
17.
Jun Yao Hong Xu Ningning Shi Xin Cao Xiaohai Feng Sha Li Pingkai Ouyang 《Applied biochemistry and biotechnology》2010,160(8):2332-2341
Bacillus subtilis NX-2 produces γ-polyglutamic acid (γ-PGA) when using glucose and l-glutamate as carbon sources. The conversion of carbon sources into γ-PGA was analyzed with the 13C-NMR method after enriching the media with 13C-labeled glucose. The results showed that the percentage of γ-PGA monomers derived from glucose was relatively low, approximately
6% and 9%, respectively, with an initial glucose concentration of 30 and 40 g L−1. It was concluded that glucose was utilized mainly as the growth-limiting substrate for cell growth and supplied the required
energy during γ-PGA biosynthesis, while l-glutamate was preferred as the main substrate for γ-PGA formation. To achieve an efficient conversion of l-glutamate and enhance the γ-PGA production, a fed-batch culture was proposed by feeding of glucose. By this method, supplied
l-glutamate (40 g L−1) was completely depleted, and γ-PGA yield was attained 42 g L−1. 相似文献
18.
P. I. Abronina L. V. Backinowsky A. A. Grachev S. L. Sedinkin N. N. Malysheva 《Russian Chemical Bulletin》2005,54(5):1287-1293
Methyl 2,4-di-O-benzoyl-α-D-mannopyranoside was used as a key intermediate in the synthesis of 3,6-branched mannopentaoside bearing one terminal D-[1-13C]mannopyranose residue, viz., methyl 6-O-[3,6-di-O-(α-D-mannopyranosyl)-α-D-mannopyranosyl)-3-O-{α -D-[1-13C]mannopyranosyl}-α-D-mannopyranoside.
Dedicated to Academician N. K. Kochetkov on the occasion of his 90th birthday.
__________
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1250–1255, May, 2005. 相似文献
19.
Methyl iodide activated stereospecific α-mannosylations utilising 2-pyridyl-1-thiomannopyranoside derivatives (2,3,4) as donors
and suitably protected myo-inositol derivatives (1,25,27,29) as acceptors to prepare 2-0-α-D-mannopyranosyl-6-[O-α-D-mannopyranosyl-(1–6)-O-α-D-mannopyranosyl-(l-6)-O-α-D-mannopyranosyl]-D-myo-inositol derivative (31) is described.
IICT Commun. No. 3355 相似文献
20.
To obtain a highly selective material for the antibiotic chloramphenicol, which has several harmful side effects in humans,
different molecularly imprinted polymers (MIPs) were prepared. In order to avoid a major traditional drawback associated with
MIPs of residual template bleeding, molecules that are structurally related to chloramphenicol were used as templates for
polymer synthesis. Chromatographic evaluation indicated that the employed template imparted a significant influence on the
recognition properties of the corresponding polymer. A strong retention of chloramphenicol under nonpolar elution conditions
(k = 68.03, IF = 17.72) and under aqueous elution conditions (k = 92.44, IF = 1.35) was achieved. After chromatographic evaluation, the MIP was utilized as the recognition sorbent in a
solid-phase extraction to determine chloramphenicol using either an organic or aqueous washing solvent. Recoveries of nearly
100% from the chloramphenicol standard solution and nearly 90% from honey samples spiked with chloramphenicol were attained.
Furthermore, the applicability of the MIP for sample cleanup was demonstrated. 相似文献