bluuebunny/crossref_metadata_2025_split huggingface dataset:
Yeast‐mediated preparation of l‐PAC in an organic solvent
Authors: Kostraby Margaret M. , Smallridge Andrew J. , Trewhella Maurie A. 
Published: September 2002

AbstractThe yeast‐mediated acyloin condensation of benzaldehyde and pyruvic acid to form l‐PAC occurs in a petroleum spirit solvent system at room temperature with moderate conversion (30%) and high enantioselectivity (86%ee) after 24 h. The addition of a small amount of ethanol (0.5% mL) to the reaction mixture inhibits the formation of the side product benzyl alcohol and increases the conversion to l‐PAC. Conducting the reaction using 13C‐labeled pyruvate indicated that the pyruvate was incorporated into the l‐PAC and that the excess pyruvate was converted into ethanol. Conducting the reaction at 5°C results in similar conversion but higher enantioselectivity. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 827–831, 2002; DOI 10.1002/bit.10117
Substrate inhibition mode of ω‐transaminase from Vibrio fluvialis JS17 is dependent on the chirality of substrate
Authors: Shin Jong‐Shik , Kim Byung‐Gee 
Published: September 2002

AbstractSubstrate inhibition is a common phenomenon in enzyme chemistry, which is observed only with a fast‐reacting substrate enantiomer. We report here for the first time substrate inhibition of an enantioselective enzyme by both substrate enantiomers. The enantioselective substrate inhibition, i.e., different mode of inhibition by each substrate enantiomer, of (S)‐specific ω‐transaminase was found with various chiral amines. A kinetic model based on ping‐pong bi‐bi mechanism has been developed and kinetic parameters were measured. The kinetic model reveals that the inhibition by (R)‐amine results from formation of Michaelis complex with enzyme‐pyridoxal 5′‐phosphate, whereas the inhibition by (S)‐amine results from the formation of the complex with enzyme‐pyridoxamine 5′‐phosphate. Substrate inhibition constants (KSI) of each (S)‐enantiomer of four chiral amines showed a linear correlation with those of cognate (R)‐amines. Such a correlation was also found between the KSI values and Michaelis constants of (S)‐amines. These correlations indicate that recognition mechanisms and active site structures of both enzyme‐pyridoxal 5′‐phosphate, enzyme‐pyridoxamine 5′‐phosphate are similar. Taken together with the results, high propensity for non‐productive substrate binding strongly suggests that binding pockets of the ω‐transaminase is loosely defined, which accounts for the enantioselective substrate inhibition. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 832–837, 2002; DOI 10.1002/bit.10165
Application of neural network for simulation of upflow anaerobic sludge blanket (UASB) reactor performance
Authors: Sinha Sucheta , Bose Purnendu , Jawed Mohammed , John Siby , Tare Vinod 
Published: September 2002

AbstractUp‐flow anaerobic sludge blanket (UASB) reactors are being used with increasing regularity all over the world, especially in India, for a variety of wastewater treatment operations. Consequently, there is a need to develop methodologies enabling one to determine UASB reactor performance, not only for designing more efficient UASB reactors but also for predicting the performance of existing reactors under various conditions of influent wastewater flows and characteristics. This work explores the feasibility of application of an artificial neural network‐based model for simulating the performance of an existing UASB reactor. Accordingly, a neural network model was designed and trained to predict the steady‐state performance of a UASB reactor treating high‐strength (unrefined sugar based) wastewater. The model inputs were organic loading rate, hydraulic retention time, and influent bicarbonate alkalinity. The output variables were one or more of the following, effluent substrate concentration (Se), reactor bicarbonate alkalinity, reactor pH, reactor volatile fatty acid concentration, average gas production rate, and percent methane content of the gas. Training of the neural network model was achieved using a large amount of experimentally obtained reactor performance data from the reactor mentioned above as the training set. Training was followed by validation using independent sets of performance data obtained from the same UASB reactor. Subsequently, simulations were performed using the validated neural network model to determine the impact of changes in parameters like influent chemical oxygen demand (COD) concentration and hydraulic retention time on the reactor performance. Simulation results thus obtained were carefully analyzed based on qualitative understanding of UASB process and were found to provide important insights into key variables that were responsible for influencing the working of the UASB reactor under varying input conditions. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 806–814, 2002; DOI 10.1002/bit.10168
Characterizing the adhesion of motile and nonmotile Escherichia coli to a glass surface using a parallel‐plate flow chamber
Authors: McClaine Jennifer W. , Ford Roseanne M. 
Published: September 2002

AbstractA parallel‐plate flow chamber was used to measure the attachment and detachment rates of Escherichia coli to a glass surface at various fluid velocities. The effect of flagella on adhesion was investigated by performing experiments with several E. coli strains: AW405 (motile); HCB136 (nonmotile mutant with paralyzed flagella); and HCB137 (nonmotile mutant without flagella). We compared the total attachment rates and the fraction of bacteria retained on the surface to determine how the presence and movement of the flagella influence transport to the surface and adhesion strength in this dynamic system. At the lower fluid velocities, there was no significant difference in the total attachment rates for the three bacterial strains; nonmotile strains settled at a rate that was of the same order of magnitude as the diffusion rate of the motile strain. At the highest fluid velocity, the effect of settling was minimized to better illustrate the importance of motility, and the attachment rates of both nonmotile strains were approximately five times slower than that of the motile bacteria. Thus, different processes controlled the attachment rate depending on the parameter regime in which the experiment was performed. The fractions of motile bacteria retained on the glass surface increased with increasing velocity, whereas the opposite trend was found for the nonmotile strains. This suggests that the rotation of the flagella enables cells to detach from the surface (at the lower fluid velocities) and strengthens adhesion (at higher fluid velocities), whereas nonmotile cells detach as a result of shear. There was no significant difference in the initial attachment rates of the two nonmotile species, which suggests that merely the presence of flagella was not important in this stage of biofilm development. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 179–189, 2002; DOI 10.1002/bit.10192
Electrochemical monitoring of cell behaviour in vitro: A new technology
Authors: Woolley D. E. , Tetlow L. C. , Adlam D. J. , Gearey D. , Eden R. D. 
Published: September 2002

AbstractThis article describes a novel electrochemical technique for the real‐time monitoring of changes in the behaviour of adherent human cells in vitro: i.e., a biosensor that combines a biological recognition mechanism with a physical transduction technique, described collectively as Oncoprobe. Confluent viable cells adherent to gold electrodes (sensors) modify the extracellular microenvironment at the cell:sensor interface to produce a change in the electrochemical potential compared to that measured in the absence of cells. The potential was measured as an open circuit potential (OCP) with respect to a saturated calomel reference in the bulk culture medium. Typical OCP values for confluent cultures of human breast carcinoma cells, 8701‐BC, approximated −100mV compared with cell‐free values of approximately −15mV. The OCP for 8701‐BC cells was modified in response to temperature changes over the range 32 to 40°C and also to treatments with phytohemagglutinin (PHA, 25 μg/mL), cycloheximide (30 μM) and interleukin‐1 β (IL‐1, 0.5 ng/mL) over 24 h. Cultures of synovial fibroblasts also responded to the same treatments with similar responses, producing negative shifts in the OCP signal with PHA and IL‐I, but a positive shift in OCP signal with cycloheximide, all relative to the untreated control cultures. From experimental data and theoretical considerations it is proposed that the cell‐derived signals are mixed electrode potentials reflecting a “conditioned,” more reducing environment at the cell:sensor interface. Only viable cells caused a negative shift in the OCP signal, this being lost when cells were rendered nonviable by formalin exposure. This technology appears unique in its ability to passively “listen in” on cell surface activities, suggesting numerous applications in the fields of drug discovery, chemotherapy, and cell behaviour © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 725–733, 2002; DOI 10.1002/bit.10217
Sol‐gel encapsulated enzyme arrays for high‐throughput screening of biocatalytic activity
Authors: Park Chan B. , Clark Douglas S. 
Published: September 2002

AbstractWe developed versatile low‐cost arrays of sol‐gel‐encapsulated enzymes (referred to as solzymes) suitable for repeated assays of bioactivity or enzyme inhibition. Sol‐gel microstructures containing active enzymes were stabilized on glass at moderate pH and room temperature without harsh calcination. A multi‐well bilayer of polydimethylsiloxane was used to support the solzyme array and contain the reaction medium. Each of the 147 microwells has a working volume of 5 μL and contains 50 μg of immobilized enzyme. The solzyme arrays maintained high activity through repeated applications and exhibited superior thermostability compared to soluble enzymes. Among the enzymes used were lipases, glucose oxidase, and horseradish peroxidase. Twenty different lipases and proteases were also used to prepare a hydrolase array, for which bromthymol blue served as a generic indicator of activity. The relative activities of the encapsulated hydrolases correlated closely with those of the soluble hydrolases, illustrating that sol‐gel encapsulation preserved the hierarchy of enzyme activity. The development of solzyme arrays paves the way to higher throughput screening of diverse proteins and enzymes, including those that are available only in trace amounts. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 229–235, 2002; DOI 10.1002/bit.10238
Simple and robust method for estimation of the split between the oxidative pentose phosphate pathway and the Embden‐Meyerhof‐Parnas pathway in microorganisms
Authors: Christensen Bjarke , Christiansen Torben , Gombert Andreas Karoly , Thykaer Jette , Nielsen Jens 
Published: September 2002

AbstractThe flux through the oxidative pentose phosphate (PP) pathway was estimated in Bacillus clausii, Saccharomyces cerevisiae, and Penicillium chrysogenum growing in chemostats with [1‐13C]glucose as the limiting substrate. The flux calculations were based on a simple algebraic expression that is valid irrespective of isotope rearrangements arising from reversibilities of the reactions in the PP pathway and the upper part of the Embden‐Meyerhof‐Parnas pathway. The algebraically calculated fluxes were validated by comparing the results with estimates obtained using a numerical method that includes the entire central carbon metabolism. Setting the glucose uptake rate to 100, the algebraic expression yielded estimates of the PP pathway flux in B. clausii, S. cerevisiae, and P. chrysogenum of 20, 42, and 75, respectively. These results are in accordance with the results from the numerical method. The information on the labeling patterns of glucose and the proteinogenic amino acids were obtained using gas chromatography / mass spectrometry, which is a very sensitive technique, and therefore only a small amount of biomass is needed for the analysis. Furthermore, the method developed in this study is fast and readily accessible, as the calculations are based on a simple algebraic expression. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 517–523, 2001.
Metabolic‐flux analysis of continuously cultured hybridoma cells using 13CO2 mass spectrometry in combination with 13C‐lactate nuclear magnetic resonance spectroscopy and metabolite balancing
Authors: Bonarius Hendrik P. J. , Özemre Ahmet , Timmerarends Bram , Skrabal Peter , Tramper Johannes , Schmid Georg , Heinzle Elmar 
Published: September 2002

AbstractProtein production of mammalian‐cell culture is limited due to accumulation of waste products such as lactate, CO2, and ammonia. In this study, the intracellular fluxes of hybridoma cells are measured to determine the amount by which various metabolic pathways contribute to the secretion of waste products derived from glucose. Continuously cultured hybridoma cells are grown in medium containing either 1‐13C‐, 2‐13C‐, or 6‐13C‐glucose. The uptake and production rates of amino acids, glucose, ammonia, O2, and CO2 as well as the cellular composition are measured. In addition, the 13C distribution of the lactate produced and alanine produced by the hybridomas is determined by 1H‐NMR spectroscopy, and the 13CO2/12CO2 ratio is measured by on‐line mass spectrometry. These data are used to calculate the intracellular fluxes of the glycolysis, the pentose phosphate pathway, the TCA cycle, and fluxes involved in amino acid metabolism. It is shown that: (i) approximately 20% of the glucose consumed is channeled through the pentose shunt; (ii) the glycolysis pathway contributes the most to lactate production, and most of the CO2 is produced by the TCA cycle; (iii) the pyruvate–carboxylase flux is negligibly small; and (iv) the malic‐enzyme flux is estimated to be 10% of the glucose uptake rate. Based on these flux data suggestions are made to engineer a more efficient glucose metabolism in mammalian cells. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 528–538, 2001.
Determination of molecular mass of acidic polysaccharides by capillary electrophoresis
Authors: Kinoshita Mitsuhiro , Shiraishi Hiroyuki , Muranushi Chiho , Mitsumori Naomichi , Ando Takao , Oda Yasuo , Kakehi Kazuaki 
Published: September 2002

AbstractWe developed a method for the determination of molecular mass of acidic polysaccharides based on their high‐resolution separation by capillary electrophoresis. Polymers of N‐acetylneuraminic acid (NeuAc) and polysulfated hyaluronic acid were separated into their molecular species up to 100 mono‐ and 20 disaccharide units, respectively. The relationship between the molecular mass of NeuAc‐polymer and their electrophoretic mobilities showed good linearity, and was applied to the determination of molecular masses of larger NeuAc species unresolved by capillary electrophoresis under the same conditions. In the first step, the standard curve for the determination of molecular mass was constructed from the relationship between electrophoretic mobility and molecular mass. Subsequently, the mobility was extrapolated to the standard curve, and the molecular mass was calculated. Five different preparations of NeuAc polymers having different molecular masses showed smaller values than those determined by conventional chromatographic techniques. Further, molecular mass determined by the present method correlated with number‐average molecular mass. The methodology presented here was applied to the determination of molecular mass of polysulfated hyaluronic acid. The data indicated that native hyaluronic acid was extensively degraded during sulfonation reaction. Copyright ­© 2002 John Wiley & Sons, Ltd.
Structure analysis of lipoglycans and lipoglycan‐derived carbohydrates by capillary electrophoresis and mass spectrometry
Authors: Lamari Fotini N. , Gioldassi Xanthee M. , Mitropoulou Theoni N. , Karamanos Nikos K. 
Published: September 2002

AbstractLipoglycans (lipopolysaccharides, lipoarabinomannans and glycolipids) are unique components of the cell membrane of all cells and the envelope of many bacteria. They play important roles in determining cell–environment interactions, which, however, are only partly understood due to incomplete description of their structural components, lipids and glycans. Capillary electrophoresis is an analytical technique of high separation efficiency and minimum sample requirements and has successfully been used for the analysis of several molecules of biological importance: proteins, nucleic acids and glycoconjugates. In the last years, a few applications of capillary electrophoresis to the analysis of lipoglycans have been reported. Analysis of lipoglycans involves the study of two parameters: intact molecules and carbohydrate parts. The conjunction of capillary electrophoresis and mass spectroscopy not only enhances the detection sensitivity, but also provides structural information on these structurally complex molecules. The interest in the field is rising and the results from the exact determination on the lipoglycan structure are expected to improve our understanding of the molecular mechanism of lipoglycan binding to proteins and cells of host organisms as well as their relationship to the virulence and pathogenesis of bacteria. In this report, an overview of the capillary electrophoresis methods used to analyze and characterize the intact lipoglycans as well as their carbohydrate parts is presented. Copyright © 2002 John Wiley & Sons, Ltd.
Ascertainment of D‐amino acids in germ‐free, gnotobiotic and normal laboratory rats
Authors: Brückner Hans , Schieber Andreas 
Published: September 2002

AbstractFree D‐amino acids were ascertained in the blood serum, urine and aqueous ethanolic extracts of feces of germ‐free laboratory rats and a rat made gnotobiotic (tetra‐associated) with species of Streptococcus, Lactobacillus and Clostridium. D‐Amino acids were also determined in the brains of two germ‐free rats. For comparison, D‐amino acids were also measured in the blood serum of normal rats and the blood plasma, urine and feces of normal white mice. D‐Enantiomers of most protein L‐amino acids were detected in all physiological samples of animals. Quantities of free D‐amino acids were determined as N(O)‐pentafluoropropionyl‐(2)‐propyl esters by enantioselective gas chromatography and mass spectrometry. Stereoisomers of the bacterial marker 2,6‐diaminopimelic acid, analyzed as N‐trifluoroacetyl‐(2)‐propyl esters, were detected in feces of the gnotobiotic but not of the germ‐free rat. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

common protein amino acids are abbreviated according to three‐letter nomenclature

Asx, Asp/Asn

Glx

Glu/Gln

Dap

2,6‐diaminopimelic acid

GC‐SIM‐MS

gas chromatographie/selected ion monitoring mass spectrometry

Orn

ornithin.
High performance liquid chromatography analysis of 9‐(2′,3′‐dideoxy‐2′β‐fluoro‐D‐threo‐penta furanosyl) adenine and its metabolite in human plasma using solid‐phase extraction on a polyfluorinated reversed stationary phase
Authors: Aboul‐Enein Hassan Y. , Abu‐Zaid Suhair 
Published: September 2002

AbstractA quick and sensitive reversed‐phase HPLC method has been developed for the analysis of 2′‐β ‐fluoro‐2′,3′‐dideoxy adenosine (F‐ddA), the acid‐stable anti‐AIDS drug, and its metabolite 2′‐fluoro‐2′,3′‐dideoxy inosine (F‐ddI) in human plasma using polyfluorinated stationary phase column (Fluo fix, 15 cm, 4.0 mm i.d., 5 µm particle size). The mobile phase consisted of ammonium phosphate buffer solution (10 mM) adjusted with phosphoric acid 85% to pH 6.8:dimethyl formamide (97:3, v/v). F‐ddA and F‐ddI were monitored by UV–visible detector at 258 and 247 nm, respectively. The recoveries of F‐ddA and F‐ddI from plasma using a C18 solid‐phase extraction cartridge were 99.2% and 99.7%, respectively. Copyright © 2001 John Wiley & Sons, Ltd.
Abbreviations used:

AIDS

acquired immunodeficiency syndrome

AZT

zidovudine

CNS

central nervous system

ddA

2′,3′‐dideoxy adenosine

ddC

2′,3′‐dideoxy cytidine

ddG

2′,3′‐dideoxy Guanosine

ddI

2′,3′‐dideoxy inosine

ddT

2′,3′‐dideoxy thymidine

FDA

food and drug administration

F‐ddA

2′‐fluoro‐2′,3′‐dideoxy adenosine

F‐ddI

2′‐fluoro‐2′,3′‐dideoxy inosine

HIV

human immunodeficiency virus

HPLC

high performance liquid chromatography.
Effect of selenium on N‐nitrosodiethylamine‐induced multistage hepatocarcinogenesis with reference to lipid peroxidation and enzymic antioxidants
Authors: Thirunavukkarasu C. , Sakthisekaran D. 
Published: September 2002

AbstractWe have studied the relationship between antioxidant and anticancer properties of selenium (Se) in multistage hepatocarcinogenesis induced by N‐nitrosodiethylamine (DEN). In this study we have observed an increased level of lipid peroxide (LPO) products and decreased antioxidant enzyme activities (superoxide dismutase and catalase) in hepatoma and surrounding liver tissues of cancer‐bearing animals. Selenium (Se) was supplemented either before initiation or during initiation and selection/promotion phases of hepatocarcinogenesis and was found to be effective in altering hepatic lipid peroxidation and antioxidant enzyme activities to a statistically significant level measured either in the hepatoma or in the surrounding liver tissues. These alterations inclined towards normal in a time‐dependent manner on selenium supplementation. Furthermore, increased levels of lipid peroxidation and decreased levels of antioxidants (superoxide dismutase and catalase) were also observed in distant organs of cancer‐bearing rats other than the tumour‐bearing site. These alterations are brought back to normal levels upon Se treatment. Our results confirm the fact that Se is particularly protective in limiting the action of DEN by its antioxidant property. Copyright © 2001 John Wiley & Sons, Ltd.
Effects of Se, Cu and Se + vitamin E deficiency on the activities of CuZnSOD, GSH‐Px, CAT and LPO levels in chicken erythrocytes
Authors: Bozkaya Lütfiye Arzu , Öztürk‐Ürek Raziye , Aydemir Tülin , Tarhan Leman 
Published: September 2002

AbstractAntioxidant enzymes and vitamins provide a defence against the damage of cells by reactive oxygen species in living systems. The effect of Cu, Se and vitamin E deficiencies on the antioxidant enzyme activities and lipid peroxide levels of chicken erythrocytes were investigated during 6 weeks of a depletion diet. CuZnSOD activity and the plasma Cu level of the Cu‐deficient group which was fed a diet containing 0.2 mg Cu kg−1 were reduced to 62 and 71% respectively. GSH‐Px activity of the Se‐deficient group was decreased by 46% but by 21% in the Cu‐deficient group. CAT activity values of Se‐ and Cu‐deficient groups were increased by 28 and 10% respectively. The maximum increase of LPO levels in erythrocyte membranes was observed as 32% for the Se+E‐deficient group. The LPO level of the Cu‐deficient group which had decreased CuZnSOD and GSH‐Px activity, was also observed to be significantly increased when compared with the controls (p < 0.05). Copyright © 2001 John Wiley & Sons, Ltd.