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1.
Pauliukaite R Zhylyak G Citterio D Spichiger-Keller UE 《Analytical and bioanalytical chemistry》2006,386(2):220-227
An amperometric biosensor has been developed for measurement of Umami, or the taste based on the amount of L-glutamate, in tomato foods. The biosensor is based on an enzyme-mediator system in which L-glutamate oxidase is used for biochemical oxidation of L-glutamate and a tetrafulvalene-tetracyanoquinodimethane (TTF-TCNQ) paste, prepared from the mixture of TTF-TCNQ salt, graphite powder, and silicone oil, serves as the mediator. The limit of detection, calculated by use of a four-parameter logistic model, was 0.05 mmol L(-1), and the limit of quantification was 0.15 mmol L(-1). The correlation coefficient (R2) was 0.990 and the relative standard deviation was no more than 1% (n=5). The response time (tau (95)) was 20-50 s, depending on concentration. The repeatability of the sensor was better than 5% (n=10). The sensor developed was stable for more than ten days. 相似文献
2.
Pedraza A Sicilia MD Rubio S Pérez-Bendito D 《Analytical and bioanalytical chemistry》2007,389(7-8):2297-2302
A selective method for the determination of l-glutamate in foodstuffs has been developed. It was based on the competition established between the analyte and the dye Coomassie
brilliant blue G (CBBG) to interact with the surfactant didodecyldimethylammonium bromide (DDABr). The measurement parameter
was the amount of DDABr required to reach a given dye-to-surfactant binding degree. It was obtained by photometric titration
on the basis of the changes observed in the spectral characteristics of the dye when CBBG–DDABr aggregates were formed. The
calibration graph obtained was linear in the l-glutamate concentration interval 0.2–5 mM (detection limit 0.05 mM). The high selectivity of the proposed method (other amino
acids and food additives did not interfere at the concentrations present in foodstuffs) permitted the direct analysis of food
samples after dissolution of the analyte in hot water. The accuracy of the surfactant to the dye binding degree method was
demonstrated by determining l-glutamate in different kinds of foodstuffs (liquid and dried soups, seasonings, pasta sauces and dried mushroom creams) and
comparing the results obtained with those provided by the commercial Boehringer Mannheim essay. 相似文献
3.
Qing-Shan Li Juan-Juan Xu Jian-Jiang Zhong 《Applied biochemistry and biotechnology》1997,62(2-3):243-250
Effects of water content and carbon and nitrogen sources on the production ofL-glutamate oxidase (GOD) by solid state fermentation (SSF) ofStreptomyces sp. N1 were investigated in a 250-mL shake flask. The results show that in the solid medium containing wheat bran 98% (w/w), KCl
0.2% (w/w), and MgCl2 0.2% (w/w), addition of 2.0-mL water per gram solid medium and 0.4% (w/w) (NH4)2SO4 was the best for GOD production. In this work, we also developed a simple technique forin situ measuring oxygen uptake rate (OUR) and carbon dioxide evolution rate (CER) in SSF in a shake flask based on the principle
of Warburg manometer. The method was successfully applied to determine OUR and CER values in SSF ofStreptomyces sp. N1. The results indicate that the largest OUR value was detected about one or two days ahead of the highest GOD activity reached
depending on the fermentation conditions, and the OUR may be used as anin situ indicator of GOD production in the SSF process. 相似文献
4.
A chiral liquid chromatographic method for determination of the enantiomeric purity of both l-carnitine and acetyl-l-carnitine is described. Separation of the enantiomers of dl-carnitine and acetyl-dl-carnitine was achieved on a commercial chiral column (Chiralcel OD-R) after derivatization with (alpha-bromo)methyl phenyl ketone. Introduction of this lipophilic UV chromophoric group to the carnitine and acetylcarnitine molecules improved their retention, resolution, and UV detection. The mobile phase was 74:26 (v/v) 0.5 mol L-1 sodium perchlorate–acetonitrile, pH 3.8, and the flow rate was 0.4 mL min-1. Detection was performed at 235 nm. The method is selective and reliable for determination of the enantiomeric purity of bulk drug substances l-carnitine and acetyl-l-carnitine. 相似文献
5.
Hamase K Takagi S Morikawa A Konno R Niwa A Zaitsu K 《Analytical and bioanalytical chemistry》2006,386(3):705-711
Using a column-switching HPLC system combining a micro-ODS column and a chiral column, the amounts of d-proline (d-Pro) have been determined in 18 tissues, plasma and urine of mice. To avoid the enzymatic degradation of d-amino acids in vivo, a mutant mouse strain lacking d-amino acid oxidase activity (ddY/DAO− mouse) was used. In the brain, relatively large amounts of d-Pro were observed in the anterior pituitary, posterior pituitary and pineal glands. In the peripheral tissues, the amounts
of d-Pro were high in the pancreas and kidney. Above all, it is surprising that the ddY/DAO− mice excreted large amounts of d-Pro in their urine (433 nmol/mL, 20 times that of l-Pro). The origin of d-Pro has also been investigated. By comparing germ-free mice and gnotobiotic mice, intestinal bacteria were shown to have
no effect on the urinary d-Pro amount. Concerning the dietary origin, a notable amount of d-Pro was still excreted in the urine after starvation for 4 days, suggesting that some of the d-Pro is produced in the mice. Age-dependent changes in the urinary d-Pro amount have also been investigated from the postnatal 1st month up to 12 months, and ddY/DAO− mice were found to excrete large amounts of d-Pro in the urine constantly throughout their lives.
Kenji Hamase is Associate Professor in the Department of Bioanalytical Chemistry, Graduate School of Pharmaceutical Sciences at Kyushu
University. His current research interests focus on the development of analytical methods for d-amino acids and the study of their physiological functions and diagnostic values. He received the Japanese Society for Analytical
Chemistry Award for Young Scientists in 2003, and the PSJ Award for Young Scientists in 2006. 相似文献
6.
N. V. Zyk E. K. Beloglazkina S. E. Sosonyuk M. N. Bulanov R. L. Antipin 《Russian Chemical Bulletin》2005,54(6):1488-1491
Electrophilic sulfenylation, selenenation, and halogenation of bicyclo[2.2.1]heptenes containing CF3 or NO2 group in position endo-5 were studied. The sulfenylation and selenenation were accomplished by arylsulfene- and arylselenenamides activated by POHal3 (Hal = Br, Cl), and iodination was performed by KICl2. The reactions are regiospecific and involve an exo-attack of the electrophilic fragment (arylthio or arylseleno group or iodine) on the C=C bond atom located closer to the
CF3 or NO2 group.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1445–1448, June, 2005. 相似文献
7.
V. V. Potekhin 《Russian Chemical Bulletin》2007,56(5):875-882
The oxidation of lower aliphatic alcohols C1–C4 with dioxygen to form the corresponding carbonyl compounds in the presence of the PdII tetraaqua complexes and FeII-FeIII aqua ions in an aqueous medium was studied at 40–80 °C. The introduction of an aromatic compound (acetophenone, benzonitrile,
phenylacetonitrile, o-cyanotoluene, nitrobenzene) and FeII aqua ion instead of the FeIII aqua ion into the reaction system increases substantially the catalytic activity and the yield of the carbonyl compound.
The key role of the Pd species in the intermediate oxidation state stabilized by the aromatic additive in the catalytic cycle
of alcohol oxidation with dioxygen to the carbonyl compound was shown. An increase in the kinetic isotope effect with an increase
in the temperature of methanol oxidation indicates a change in the rate-determining step of alcohol oxidation with dioxygen
in the presence of PdII-FeII-FeIII and the aromatic compound. At temperatures below 60 °C, the catalytically active palladium species are mainly formed upon
the reduction of the PdII tetraaqua complex with the FeII aqua ion, whereas at higher temperatures the reaction between the alcohol and PdII predominates. The mechanism and kinetic equation of the process were proposed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 842–848, May, 2007. 相似文献
8.
Shi Nian-Qing Prahl Kristine Hendrick Jim Cruz Jose Lu Ping Cho Jae-Yong Jones Sharon Jeffries Thomas 《Applied biochemistry and biotechnology》2000,84(1-9):201-216
Pichia stipitis CBS 6054 will grow on d-xylose, d-arabinose, and l-arabinose. d-Xylose and l-arabinose are abundant in seed hulls of maize, and their utilization is important in processing grain residues. To elucidate
the degradation pathway for l-arabinose, we obtained a mutant, FPL-MY30, that was unable to grow on d-xylose and l-arabinose but that could grow on d-arabinitol. Activity assays of oxidoreductase and pentulokinase enzymes involved in d-xylose, d-arabinose, and l-arabinose pathways indicated that FPL-MY30 is deficient in d-xylitol dehydrogenase (D-XDH), d- and l-arabinitol dehydrogenases, and d-ribitol dehydrogenase. Transforming FPL-MY30 with a gene for xylitol dehydrogenase (PsXYL2), which was cloned from CBS 6054 (Gen Bank AF127801), restored the D-XDH activity and the capacity for FPL-MY30 to grow on
l-arabinose. This suggested that FPL-MY30 is critically deficient in XYL2 and that the d-xylose and l-arabinose metabolic pathways have xylitolas a common intermediate. The capacity for FPL-MY30 to grow on d-arabinitol could proceed through d-ribulose. 相似文献
9.
Zhenning Yan Xiaoge Wang Ronghua Xing Jianji Wang 《The Journal of chemical thermodynamics》2009,41(12):1343-1349
Densities and conductivity data for the sodium carboxylate (sodium acetate and sodium butyrate)–dipeptides {(glycyl-l-glutamine and l-alanyl-l-glutamine) + water} systems were determined at T = 298.15 K. The apparent molar volumes of the peptides and the molar conductivity (Λ) of sodium acetate and sodium butyrate have been calculated. These data have been utilized to deduce the standard partial molar volumes (), standard partial molar volumes of transfer for dipeptide from water to aqueous sodium carboxylate solutions (ΔtV°), volumetric interaction coefficient, the limiting molar conductivity (Λ°), and Walden product (Λ°η). Both and ΔtV° for the dipeptides increase with increasing concentration of sodium carboxylate. The interpretation is that this result arises from the dominant interactions of the sodium carboxylate with the charged group and polar groups of peptides. The decrease in Λ° of sodium carboxylate with increasing dipeptide concentration and nonconstant Walden product are attributed to the interactions of sodium carboxylate with peptide and friction resistance of the solvent medium. 相似文献
10.
Mishra A 《Applied biochemistry and biotechnology》2006,135(1):33-42
This article reports the production of high levels of l-asparaginase from a new isolate of Aspergillus niger in solid state fermentation (SSF) using agrowastes from three leguminous crops (bran of Cajanus cajan, Phaseolus mungo, and Glycine max). When used as the sole source for growth in SSF, bran of G. max showed maximum enzyme production followed by that of P. mungo and C. cajan. A 96-h fermentation time under aerobic condition with moisture content of 70%, 30 min of cooking time and 1205–1405 μ range
of particle size in SSF appeared optimal for enzyme production. Enzyme yield was maximum (40.9±3.35 U/g of dry substrate)
at pH 6.5 and temperature 30±2°C. The optimum temperature and pH for enzyme activity were 40°C and 6.5, respectively. The
study suggests that choosing an appropriate substrate when coupled with process level optimization improves enzyme production
markedly. Developing an asparaginase production process based on bran of G. max as a substrate in SSF is economically attractive as it is a cheap and readily available raw material in agriculture-based
countries. 相似文献
11.
Substrate selectivity of Gluconobacter oxydans (ATCC 9937) for 2,5-diketo-d-gluconic acid (2,5-DKG) production was investigated with glucose, gluconic acid, and gluconolactone in different concentrations
using a resting-cell system. The results show that gluconic acid was utilized favorably by G. oxydans as substrate to produce 2,5-DKG. The strain was coupled with glucose dehydrogenase (GDH) and 2,5-DKG reductase for synthesis
of 2-keto-l-gulonic acid (2-KLG), a direct precursor of l-ascorbic acid, from glucose. NADP and NADPH were regenerated between GDH and 2,5-DKG reductase. The mole yield of 2-KLG of
this multienzyme system was 16.8%. There are three advantages for using the resting cells of G. oxydans to connect GDH with 2,5-DKG reductase for production of 2-KLG: gluconate produced by GDH may immediately be transformed into
2,5-DKG so that a series of problems generally caused by the accumulation of gluconate would be avoided; 2,5-DKG is supplied
directly and continuously for 2,5-DKG reductase, so it is unnecessary to take special measures to deal with this unstable
substrate as it was in Sonoyama’s tandem fermentation process; and NADP(H) was regenerated within the system without any other
components or systems. 相似文献
12.
V. N. Leibzon L. V. Michalchenko M. Yu. Leonova V. P. Gultyai 《Russian Chemical Bulletin》2005,54(5):1203-1207
Small additives of iron(II) or copper(II) salts change the regioselectivity of 2,4,6-trinitrotoluene monoreduction with titanium(III) chloride affording predominantly less accessible 2-amino-4,6-dinitrotoluene over 4-amino-2,6-dinitrotoluene (from 25% when
the reduction occurs in the absence of the iron and copper salts to 70% in the presence of these salts). A possible mechanism
of the process is discussed.
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. 1172–1176, May, 2005. 相似文献
13.
Hasegawa H Fukushima T Lee JA Tsukamoto K Moriya K Ono Y Imai K 《Analytical and bioanalytical chemistry》2003,377(5):886-891
d-Lactic and l-lactic acids were simultaneously determined by means of a column-switching high-performance liquid chromatography (HPLC) with fluorescence detection. As a fluorescence reagent, 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ) was employed for the fluorescence derivatization of lactic acid. The proposed HPLC system adopted both octylsilica (Cadenza CD-C8) and amylose-based chiral columns (CHIRALPAK AD-RH), which proved to give a sufficient enantiomeric separation of the lactic acid derivatives with a separation factor () of 1.32 and a resolution (Rs) of 1.98. Moreover, the features of the first elution of d-lactic acid peak in the proposed HPLC were convenient for the determination of trace amount of serum d-lactic acid, which is known to increase under diabetes. Intra-day and inter-day accuracies were in the range of 90.5–101.2 and 89.0–100.7%, and the intra-day and inter-day precisions were 0.3–1.2 and 0.4–4.8%, respectively. The proposed method was applied to determine d-lactic and l-lactic acids in human serum of normal subjects and diabetic patients, showing that both d-lactic and l-lactic acid concentrations were significantly increased in the serum of diabetic patients (n=31) as compared with normal subjects (n=21). This fact was found for the first time owing to the development of the proposed HPLC method which is able to determine d-lactic and l-lactic acid simultaneously. Finally, serum d-lactic acid concentrations determined by the proposed HPLC method were compared with those from a reported enzymatic assay, and the smaller p value between normal subjects and diabetic patients was shown by the proposed HPLC method. 相似文献
14.
Arabinose utilization by xylose-fermenting yeasts and fungi 总被引:1,自引:0,他引:1
Various wild-type yeasts and fungi were screened to evaluate their ability to fermentl-arabinose under oxygen-limited conditions when grown in defined minimal media containing mixtures ofl-ara-binose,d-xylose, andd-glucose. Although all of the yeasts and some of the fungi consumed arabinose, arabinose was not fermented to ethanol by any
of the strains tested. Arabitol was the only major product other than cell mass formed froml-arabinose; yeasts converted arabinose to arabitol at high yield. The inability to fermentl-arabinose appears to be a consequence of inefficient or incomplete assimilation pathways for this pentose sugar. 相似文献
15.
Microalgae were screened from seawater for greenhouse gas CO2 fixation and d-lactic acid production by self-fermentation and tested for their growth rate, starch content, and conversion rate from starch
into d-lactic acid. More than 300 strains were isolated, and some of them were found to have suitable properties for this purpose.
One of the best strains, Nannochlorum, sp. 26A4, which was isolated from Sakito Island, had a starch content of 40% (dry weight), and a conversion rate from consumed
starch into d-lactic acid of 70% in the dark under anaerobic conditions. The produced d-lactic acid showed a high optical purity compared with the conventional one. The proposed new d-lactic acid production system using Nannochlorum sp. 26A4 should also be an effective technology for greenhouse gas CO2 fixation and/or conversion into industrial raw materials. 相似文献
16.
G. Sankar P. R. Sarode A. Srinivasan C. N. R. Rao S. Vasudevan J. M. Thomas 《Journal of Chemical Sciences》1984,93(3):321-334
A detailed investigation of sulphided Co/Mo/Al2O3 catalysts, their oxide precursors and several model oxides and sulphides of cobalt and molybdenum has been carried out using
x-ray photoelectron spectroscopy and x-ray absorption spectroscopy (xanes andexafs). Octahedrally coordinated Co(II) and Mo(IV) are shown to be present in a sulphidic environment on the surfaces of these
catalysts. The surface species contain an excess of sulphur, probably involving disulphide linkages. The surface compositions
of the catalysts examined conform to the general formula Co11 Mo
2n
IV
(2n + 3)S
2
2−
(2n -2)S2−. 相似文献
17.
E. K. Beloglazkina A. G. Majouga A. N. Chernysheva R. D. Rakhimov N. V. Zyk 《Russian Chemical Bulletin》2007,56(7):1374-1379
The reaction of 2,2′-di(2-hydroxybenzaliminoethyl) disulfide (H2L1) and 2-[(2-thioethyl)iminomethyl]phenol (H2L2) with MCl2·xH2O (M = Co, Ni, Cu) afforded the [M2(L1)Cl2] and [M(L2)]2 complexes, respectively. Their structures were determined by the data of electronic and IR spectroscopy and PM3 quantum chemical
calculations. The H2L1 ligand and the complexes were studied by electrochemistry (CV and using a rotating disk electrode). The primary electronic
changes are localized on the ligand fragment upon the electrochemical oxidation and reduction of the complexes.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1325–1330, July, 2007. 相似文献
18.
The reactions of cluster (-H)Os3(CO)10(-OH) with ethyl and isopropyl esters ofl-oxyproline were studied. In the presence of Me3NO intermediate complex (-H)Os3(CO)9(-OH)L (L — isopropyl ester ofl-oxyproline) is formed, which slowly converts to the more stable cluster (-H)Os3(CO)9
. Cluster complexes containing chelate-bridging heterocycles were also obtained by heating (-H)Os3(CO)10(-OH) with esters ofl-oxyproline. In both cases, only one of the possible diastereomeric complexes (-H)Os3(CO)9
(R = Et, Pri) is formed, which indicates that the reactions are stereospecific. Based on analysis of Dreiding's models, an attempt to determine the absolute configuration of the obtained clusters was made.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2021–2025, October, 1995. 相似文献
19.
J. Vliegen J. Yperman J. Mullens J. P. François L. C. Van Poucke 《Journal of solution chemistry》1984,13(4):245-257
The apparent molar volumes of the zwitterion (HL) and the chloride salt form (H2LCl) and their mixtures (HL/H2LCl) of glycine, L-serine and L-proline have been measured in aqueous solutions at 25°C. From these experimental data the excess apparent molar volumes of the HL/H2LCl mixtures have been calculated. An attempt is made to explain these excess volume properties in terms of intermolecular hydrogen bond formation between the solute molecules HL and H2LCl when forming the dimer H3L2Cl. 相似文献
20.
Hongmei Chen Wei Ouyang Bisi Lawuyi Trisna Lim Satya Prakash 《Applied biochemistry and biotechnology》2006,134(3):207-221
Numerous microcapsule systems have been developed for a wide range of applications, including the sustained release of drugs,
cell transplantation for therapy, cell immobilization, and other biotechnological applications. Despite the fact that microcapsule
membrane is a dominant factor governing overall microcapsule performance, its characterization is challenging. We report a
new method for characterizing microcapsule membranes, using the most common alginate-poly-l-lysine-alginate (APA) microcapsule as an example. Our data demonstrate that genipin, a naturally derived reagent extracted
from gardenia fruits, interacts with poly-l-lysine (PLL) and generates fluorescence. This fluorescence allows clear visualization and easy analysis of the PLL membrane
in the APA microcapsules using confocal laser scanning microscopy. The results also show that PLL binding correlates to the
reaction variables during PLL coating such as PLL concentration and coating time. In addition, five other different microcapsule
formulations consisting of PLL and/or chitosan membranes were examined, and the results imply that this method can be extended
to characterize a variety of microcapsule membranes. These findings suggest that genipin can serve as a fluorogenic marker
for rapid characterization of microcapsule membranes, a superior method that would have important implications for microcapsule
research and potential in many other applications. 相似文献