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1.
A thin film of poly(l-serine) was prepared via electropolymerization for the determination of trace levels of estradiol. In pH 5.0 phosphate buffer,
l-serine was oxidized during the cyclic potential sweeps between −0.60 and 2.0 V, forming a thin film at the electrode surface.
The electrochemical behavior of estradiol was investigated. The oxidation peak potential of estradiol shifts negatively at
the poly(l-serine) film-coated glassy carbon electrode (GCE) compared with that at the bare GCE. Otherwise, the oxidation peak current
greatly increases at the poly(l-serine) film-modified GCE. These phenomena suggest that the poly(l-serine) film exhibits catalytic activity towards the electrochemical oxidation of estradiol. Based on this, a sensitive,
rapid and simple electrochemical method was proposed for the determination of estradiol. The limit of detection is evaluated
to be 2.0 × 10−8 mol L−1. Finally, this method was successfully used to determine estradiol in blood serum. 相似文献
2.
A total synthesis ofdl-phosphatidyl-(dilinoleoyl)-l-serine was achieved by the acylation of the barium salt of the phthalimidomethyl ester of glycerophosphoryl-n-anisyloxycarbonyl-l-serine. The dilinoleoyl intermediate was treated with hydrazine to remove the phthalimidomethyl group and with hydrogen chloride
to remove the anisyloxycarbonyl protecting group. The resulting phosphatidylserine was purified by Rouser's methods, solubilized,
and tested for biological activity in the antithromboplastin, recalcification, and Hicks-Pitney tests. It was found to have
about the same anticoagulant activity as beef brain phosphatidylserine and hence was more active than the less unsaturated
phosphatidylserine synthesized earlier.
An abstract of the material in this paper appeared in Fed. Proc.24, No. 727 (1965). 相似文献
3.
M. Takehara H. Moriyuki A. Arakawa I. Yoshimura R. Yoshida 《Journal of the American Oil Chemists' Society》1973,50(7):227-229
The physicochemical properties of sodium long chain N-acylglutamate (AGSn) are described. The wetting power, emulsifying power, dispersing power and calcium ion stability were measured. Monosodium
N-lauroyl-l-glutamate (l-LGS) had good wetting and emulsifying properties, but disodium N-acylglutamate (AGS2) was inferior tol-LGS in those properties. In the dispersing power using carbon black as powder,l-LGS was inferior but AGS2, having a palmitoyl or stearoyl radical, was excellent. The AGSn with a few exceptions had good calcium ion stabilities. 相似文献
4.
Chemo-enzymatic synthesis of amino acid-based surfactants 总被引:5,自引:0,他引:5
Rao Valivety Paula Jauregi Iqbal Gill Evgeny Vulfson 《Journal of the American Oil Chemists' Society》1997,74(7):879-886
The application of lipases to the synthesis of amino acid-based surfactants was investigated. Low yields (2–9%) were obtained
in the acylation of free amino acids, such as l-serine and l-lysine, as well as their ethyl esters and amides with fatty acids, owing in part to low miscibility of the reactants. When
the N-carbobenzyloxy (Cbz)-l-amino acids were used in an effort to improve miscibility of the amino acid derivatives with the acyl donor, a dramatic improvement
was observed for N-Cbz-l-serine (92% yield) but not for N
α-Cbz- or N
ζ-Cbz-l-lysine (7 and 2% yield, respectively). As an alternative, and efficient synthesis of N
ζ-acyl-l-lysines was developed, based on the regiospecific chemical acylation of copper(II) lysinate. In pursuit of a general route
to amino acid-fatty acid surfactants, the utility of a polyol linker was investigated. Thus, the glycerol ester of N
α′
N
ζ-di-Cbz-l-lysine was prepared and evaluated as a substrate for acylation. As expected, this and other glycer-1-yl esters of N-protected amino acids were excellent substrates for lipase-catalyzed acylation. Their reaction with myristic acid in the
presence of Novozyme resulted in the regioselective acylation of the primary hydroxyl group of the glycerol moiety to afford
the corresponding 1-O-(N-Cbz-l-aminoacyl)-3-O-myris-toylglycerols with conversions of 50–90%. These were readily deprotected to give a range of 1-O-(aminoacyl)-3-O-myristoyl-glycerols with overall yields of 27–71%. 相似文献
5.
Saturated acyl (6-O-caproyl, lauroyl, and myristoyl) and unsaturated acyl (6-O-oleoyl, linoleoyl, and arachidonoyl) l-ascorbates were continuously synthesized at 50°C using a system where a column packed with ascorbic acid powder and a packed-bed
reactor with an immobilized lipase from Candida antarctica were connected in series. A productivity of 1.6–1.9 kg/L reactor·d was achieved for at least 11 d. The surface tension of
the caproyl or lauroyl l-ascorbate in aqueous solution was measured at various temperatures and pH to estimate the critical micelle concentration
(CMC) of the acyl l-ascorbate. The CMC values were independent of temperature but dependent on the pH. The value of the caproyl ascorbate increased
with an increase in pH. 相似文献
6.
Lekh Raj Juneja Tsuneo Yamane Shoichi Shimizu 《Journal of the American Oil Chemists' Society》1989,66(5):714-717
An enzymatic method was established to increase the phosphatidylcholine (PC) contents of soybean and egg lecithins. Other
phospholipids of lecithin were phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidic acid (PA). Seven
preparations of phospholipase D (PLD), PLD-1 to PLD-6 ofStreptomyces origin and PLD-7 of cabbage origin, were tested for their ability to increase PC by transphosphatidylation in the presence
of choline chloride (CC). The reactions were carried out at 30 C in a biphasic system that consisted of an aqueous phase containing
PLD along with a buffer (optimum pH) having desired concentration of CC and Ca2+ and an ethyl acetate phase containing lecithin phospholipids. Intermitttent samples were extracted and analyzed by HPLC.
Four of six PLD’s ofStreptomyces origin showed good transphosphatidylation (increase of PC contents of soybean lecithin from approximately 35% to 60–70% on
a phospholipid basis) at 2.5 M CC, but the other two microbial PLD’s completely hydrolyzed the phospholipids to PA. Cabbage
PLD-7 showed poor transphosphatidylation. PLD-3 gave the highest PC contents (70%) at 1.75 M CC. One hundred percent transphosphatidylation
of pure PE to PC was achieved with PLD-3. PI was inert to the attack of most PLD preparations examined with the exception
that PLD-3 hydrolyzed PI significantly. Purified PI could not be transphosphatidylized to PC; 100% PA was formed. Soybean
lecithin containing about 80% PC and purified egg yolk lecithin with 75% PC could be converted to products having 95% PC and
almost 100% PC, respectively, by PLD-3 at 1.75M CC.
Studies on Enzymatic Conversion of Phospholipids (v) 相似文献
7.
Zongyou Pan Yi Lou Guangyong Yang Xiao Ni MoChuan Chen Huazi Xu Xigeng Miao Jianli Liu Chunfeng Hu Qing Huang 《Ceramics International》2013,39(5):5495-5502
Calcium sulfate hemihydrate (CSH) with controlled crystal morphology has attracted broad interests due to its superior physical and chemical properties, as well as excellent biological performance. In this study, calcium sulfate dehydrate (CSD) was firstly synthesized via the reaction of H2SO4 and Ca(OH)2 using ethanol as morphology modifier. The prepared CSD was then converted to CSH through a hydrothermal method. It was found that the precipitation time of CSD powders was dramatically shortened and the morphology of CSD crystals was changed from thick tabular to short-rod with the increment in ethanol addition. The finally-obtained CSH crystals were found to have hexagonal prisms shape with smaller aspect ratios. The CSH powder with the desired crystal morphology would provide improved setting behavior and biological performance of the CSH bone cement. 相似文献
8.
R. Yoshida I. Yoshimurra Y. Usuba A. Shibue 《Journal of the American Oil Chemists' Society》1976,53(4):113-117
An application of sodium N-acyl-l-glutamate for detergent bars is described. The acyl radicals of cocoyl, hydrogenated tallowyl, semihydrogenated tallowyl,
and lauroyl were used in the glutamates. The powder of sodium N-acyl-l-glutamate was mixed with a suitable amount of water and milled; then the mixture was extruded and stamped into a bar. Bars
were examined relating composition of acyl radicals of sodium N-acyl-l-glutamates and properties of the bars or milling and molding properties. The other characteristics of the detergent bars
were examined. It was found that attractive detergent bars can be made by using monosodium N-acyl-l-glutamate as a component; that hardness, solubility, and lather characteristics of bars can be controlled by blending various
monosodium N-acyl-l-glutamates and adding moisture; that adjuvant can be used to improve the milling and stamping properties and characteristics
of the monosodium N-acyl-l-glutamate bar; and that the bars are less irritating and leave the skin feeling good. 相似文献
9.
Yuji Shimada Yoshinori Hirota Takashi Baba Shinichiro Kato Akio Sugihara Shigeru Moriyama Yoshio Tominaga Tadamasa Terai 《Journal of the American Oil Chemists' Society》1999,76(10):1139-1142
l-Menthol has been widely used as a food additive and an ingredient of cosmetics, and it is esterified to moderate the strong
flavor. We attempted esterification of l-menthol with long-chain unsaturated fatty acid in an organic solvent-free enzymatic system. Commercially available lipases
were screened, and Candida rugosa lipase was selected as a catalyst. Several factors affecting the esterification were investigated, and the reaction conditions
were determined as follows: A reaction mixture of l-menthol/fatty acid (1:3, mol/mol), 30% water, and 700 units of the lipase per gram of reaction mixture was incubated at 30°C
with stirring. After 24 h under these conditions, the esterification extents of l-menthol with oleic, linoleic, and α-linolenic acids reached 96, 88, and 95%, respectively. The structure of the esterified
product was confirmed by mass, infrared, and nuclear magnetic resonance spectroscopies. Bacause Candida lipase acted strongly on l-menthol and very weakly on d-menthol, dl-menthol was esterified with oleic acid under the same conditions. The reaction showed high enantioselectivity; the enantiomeric
ratio (E) was 31, and enantiomeric excess (ee) of l-menthyl oleate reached 88% after 32 h. 相似文献
10.
Mohamed S. Hamdy Elinor L. Scott Robert H. Carr Johan P. M. Sanders 《Catalysis Letters》2012,142(3):338-344
Abstract
The photocatalytic conversion of an aqueous solution of l-tryptophan (Trp) to kynurenine (KN) was investigated under the illumination of different light sources. Results show that Trp converted to KN with a selectivity of 64% under the illumination of a medium pressure (MP) Hg lamp. KN selectivity was increased to >90% when black light (BL) was used a light source. The novel use of BL in the photocatalytic conversion of Trp to KN significantly reduces the energy consumption compared with MP light. 相似文献11.
Olive oil microemulsions as a biomimetic medium for enzymatic studies: Oxidation of oleuropein 总被引:1,自引:0,他引:1
Microemulsions consisting of olive oil as the non-polar solvent, lecithin as surfactant, 1-propanol as cosurfactant, and water
were prepared. The choice of the compositions of the microemulsions used was based on the pseudo-ternary phase diagrams of
the system determined at 30°C, for different weight ratios of lecithin/olive oil. Lecithin solubilization and water incorporation
in these microemulsion systems was limited. Tyrosinase, an oxidizing enzyme present in olives, was successfully incorporated
in the water core of these microemulsions. Enzymatic oxidation of oleuropein, the most abundant olive phenolic compound, in
the restricted aqueous environment of olive oil microemulsions was studied. Formation of oleuropein oxidation products was
followed spectrophotometrically at 30°C for several minutes. An absorption maximum was observed at 415 nm. When the enzymatic
reaction was considered at different tyrosinase and oleuropein concentrations, a rapid inactivation of the enzyme was observed.
Addition of l-proline as a coupling reactor did not succeed in preventing enzyme inactivation in the microemulsions, probably owing to
substrate localization and product accumulation around the entrapped enzyme molecules in the micellar interface. 相似文献
12.
Kangyi Zhang Xingguo Wang Yuanfa Liu 《Journal of the American Oil Chemists' Society》2012,89(6):1155-1163
Colorless l-α-glycerylphosphorylcholine (l-α-GPC) was obtained at 98.8% purity, and with a specific rotation of −2.5° via a four-step procedure. l-α-GPC was first produced by phospholipase A1 hydrolysis of phosphatidylcholine in an aqueous medium. Almost all the impurities were then removed using two successive D001 cation and D301-111 anion exchange resin column chromatography procedures, followed by decoloration with active carbon to remove minor pigments and remaining impurities. D001 resin and D301-111 resin showed remarkable ability for l-α-GPC isolation after being used eight times. Thus, this study presents a simple and cost-effective method for preparing l-α-GPC with high purity, low costs, and environmental friendliness, and encourages future investigation into its adaptation for industrial applications. 相似文献
13.
A. Ali Fathima Sabirneeza S. Subhashini A. Shahul Hameed 《Journal of Adhesion Science and Technology》2013,27(24):2648-2678
Parametric optimization was carried out for the mixture of polyvinyl alcohol (PVA) and l-serine using Taguchi statistical approach. L9 orthogonal array of experiments were designed and the results were analyzed with Qualitek software. Synergistic effect of the mixture was enhanced at the Qualitek predicted optimized conditions. The graft polymer, poly(vinyl alcohol-serine) (PVAS), was synthesized using free radical-initiated reactions of l-serine with PVA in order to achieve effective inhibition. PVAS was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and powder X-ray diffraction analysis. The thermal properties of PVAS were studied by thermogravimetry, differential thermal analysis, and differential scanning calorimetry. The corrosion inhibition property of PVAS on mild steel corrosion was continuously monitored using electrochemical techniques. Temperature effect on the inhibition properties of PVAS was studied using electrochemical and gravimetric measurements. AFM studies confirmed the formation of polymeric film on mild steel surface which inhibits the rate of corrosion. Theoretical calculations using Hyperchem 7.0 proved the better corrosion mitigation properties of PVAS compared to PVA. The experimental results and surface analysis confirmed the effective inhibition process of the graft polymer which was also supported by the theoretical calculations. A good correlation was obtained between the results of the electrochemical measurements, conventional gravimetric measurement, surface analysis, and theoretical calculations. All the studies proved the enhanced corrosion inhibition properties of PVA through grafting of polyserine. 相似文献
14.
《Ceramics International》2022,48(6):7522-7532
A procedure for the synthesis of calcium oxide has been developed, which consists in heat treatment of an aqueous solution of calcium acetate and d-glucose at 350 and then at 700 °C. The process parameters have been determined. It has been shown that when d-glucose is used and the reaction mixture is heat treated at 700 °C, highly dispersed calcium oxide with an average particle size of 77 nm is formed. CaO formed has been used as a precursor for the synthesis of priceite (Ca2(B5O7)(OH)5 · H2O) during hydrothermal treatment of CaO in an aqueous solution of boric acid. It has been found that the optimal conditions for the synthesis of monophase priceite under hydrothermal conditions include the temperature range of 170–200 °C and the heating time of 12 h. When heating priceite at 800 °C in air for 1 h, highly dispersed powder calcium bis(borate) Ca(BO2)2 has been isolated as the final product. It is shown that the use of synthesized powder CaO leads to the formation of fine-crystalline powders of calcium borates. Samples obtained at each stage of the proposed synthesis of highly dispersed calcium oxide and calcium borates, using the example of priceite and calcium bis(borate), have been studied by powder X-ray diffraction, SEM, TEM, BET, IR spectroscopy, and DTA. 相似文献
15.
R. Lach K. Haberko M.M. Bu?koM. Szumera G. Grabowski 《Journal of the European Ceramic Society》2011,31(10):1889-1895
The preparation technique of the particulate composite materials in the alumina/YAG system was elaborated. Within alumina particles suspension yttria precursor was precipitated with ammonium carbonate. Drying and calcination at 600 °C resulted in the mixture of alumina and yttria particles, the latter being much finer than alumina particles. This mixture was additionally homogenized by short attrition milling in an aqueous suspension. Sintering of such powders results in the materials composed of YAG inclusions of sizes smaller than shown by alumina grains and evenly distributed within the matrix. YAG particles result from the reaction of Y2O3 with Al2O3 during heat treatment. YAG inclusions limit effectively grain growth of the alumina matrix. Hardness, fracture toughness, strength, Young modulus and wear susceptibility of composites and pure alumina were measured. Composites show higher hardness and in some cases higher fracture toughness and wear resistance than pure alumina polycrystals. 相似文献
16.
Fine hydroxyapatite (HA) powders were prepared by mechanically activating a mixture of calcium oxide and brushite powders in a high-energy shaker mill. A defective HA phase was formed when the starting powder mixture was activated for ≤20 h. When the mixture was calcined at 800°C, it was converted to β-tricalcium phosphate. In contrast, a nanocrystalline HA phase was formed when the mechanical activation was extended to 30 h. The material was transformed to a HA compound (Ca10 (PO4 )6 (OH)2 ) of high crystallinity when it was calcined at 800°C. 相似文献
17.
Influence of pH and Ionic Impurities on the Adsorption of Poly(acrylic) Dispersant onto a Zinc Oxide Surface 总被引:1,自引:0,他引:1
We have studied the properties of aqueous suspensions of ZnO powders with different purities. Our results suggest that powder purity determines the amount of dispersant necessary to form a stable aqueous suspension as well as the maximum adsorption capacity of the dispersant: the higher the positive surface charge of the as-received ZnO powders, the higher the amount of dispersant adsorbed onto the metal oxide surface. The surface charge of the ZnO particles in suspension is affected by the concentration of zinc as well as sulfate ions, which are the major impurities in the supernatant. The pH of the aqueous ZnO suspensions increases with increasing concentration of poly(acrylic) dispersant until the maximum adsorption capacity is attained. Further additions of dispersant do not increase the pH because of a buffer formation with impurity ions. 相似文献
18.
A novel ∈-lysine acylase (N
6-acyl-l-lysine amidohydrolase; EC 3.5.1.17) was isolated from Streptomyces mobaraensis and purified to homogeneity by SDS-PAGE from the culture broth. The purified enzyme was monomeric, with a molecular mass
of approximately 60 kDa. The enzyme was inactivated by the presence of 1,10-phenanthroline and activated in the presence of
Co2+ and Zn2+. The enzyme showed a pH optimum of 8.0 and was stable at temperatures of up to 50°C for 1 h at pH 8.0. The enzyme specifically
catalyzed the hydrolysis of the amide bond of various N∈-acyl-l-lysines. Furthermore, the enzyme efficiently catalyzed the synthesis of N∈-acyl-l-lysines with fatty and aromatic acyl groups in an aqueous buffer. In the syntheses of N∈-decanoyl-l-lysine, N∈-lauroyl-l-lysine, and N∈-myristoyl-l-lysine, the product precipitated and the yield was 90% or higher using 10 mM FA and 0.5 M l-lysine as the substrate. 相似文献
19.
Kinetics of formation of fluorescent condensation products from hexanal andl-lysine (or itsN-acetylated forms) including mass-transfer has been studied in a two-phase system consisting of lysine (or lysine derivative)
in a aqueous phosphate buffer and a 1-octanol solution of hexanal as model for formation of fluorophores between protein and
carbonyl compounds in peroxidizing biological systems. The initial rate of formation of fluorescent products in the aqueous
phase was found to be proportional to the concentration of hexanal and lysine and to increase in both phases with increasing
pH in the aqueous phase, in contrast to a higher-order dependence on hexanal in the octanol phase. At pH=6.8, the temperature
dependence of the appearance of fluorescent products corresponds to apparent energies of activation of 63 kJ·mol−1 and 87 kj·mol−1 in the aqueous phase and the octanol phase, respectively. Fluorescent condensation products appeared faster in the octanol
phase. However, by a kinetic analysis, the fluorescent products were shown to be formed in the aqueous phase, corresponding
to the lower energy of activation and to the simple second-order kinetics, and subsequently distributed between the aqueous
phase and the octanol phase.l-Lysine reacted faster thanN
α-acetyl-l-lysine which reacted faster thanN
ε-acetyl-l-lysine. Using fluorescence quantum yields, determined to be 1.4·10−2 in octanol and 8·10−3 in water at pH 6.8, an apparent partition coefficient of 17 (octanol/water) was determined for the condensation product ofl-lysine. The steady-state fluorescence in the octanol phase was attributed to two components with fluorescence life-time at
25°C of 0.7±0.05 ns and 5.1±0.2 ns, assigned to hexanal and the condensation product, respectively. The emission spectra,
were resolved in the two components using phase-sensitive detection, and the condensation product had emission maximum at
405 nm. 相似文献
20.
Eiko Wada Masato Handa Koreyoshi Imamura Takaharu Sakiyama Shuji Adachi Ryuichi Matsuno Kazuhiro Nakanishi 《Journal of the American Oil Chemists' Society》2002,79(1):41-46
N-Medium- and long-chain acyl-l-amino acids were enzymatically synthesized from the corresponding l-amino acids and fatty acids using a reverse hydrolysis. Enzymes that are suitable for the synthetic reaction of N-acyl-l-amino acids were screened on the basis of hydrolytic activity toward N-lauroyl-l-glutamic acid as an indicator. Acylase I from pig kidney (EC 3.5.1.14) showed the highest N-acyl-l-amino acid hydrolytic activity among 57 commercially available enzymes tested. Acylase I effectively catalyzed the synthesis
of N-lauroyl-l-amino acids except for N-lauroyl-l-proline and N-lauroyl-l-tyrosine in a glycerol-water system. Under the optimized reaction conditions, N-lauroyl-l-arginine and N-lauroyl-l-glutamic acid were obtained in conversions of 82 and 44%, respectively. The equilibrium constants calculated from the conversion
obtained were 5.6, 15.4, 18.0, and 39.4 for the syntheses of N-lauroyl-l-glutamic acid, Nα-lauroyl-l-lysine, N-lauroyl-l-glutamine, and N-lauroyl-l-methionine, respectively. N-Acyl-l-arginines with myristic acid and palmitic acid as the fatty acid were also synthesized using acylase I. 相似文献