bluuebunny/crossref_metadata_2025_split huggingface dataset:
A mathematical model for metal affinity protein partitioning
Authors: Suh Sung‐Sup , Arnold Frances H. 
Published: May 2005

AbstractA mathematical model of metal affinity partitioning has been derived and used to describe protein partitioning in Cu (II)PEG/dextran systems. A working model has been extended to account for inhibition, which for metal affinity extraction is the inhibition of protein‐metal binding by hydrogen ion. PEG/dextran partitioning experiments were performed on four proteins, tuna heart cytochrome c,Candida kruseicytochrome c, horse myoglobin, and sperm whale myoglobin. The partition coefficients for these proteins are increased by the addition of Cu (II)PEG‐IDA, due to the affinity between the chelated copper atom and metal‐coordinating histidine residues on the protein surface. The results of experiments to determine the effects of the number of binding sites on the protein, the copper concentration, and pH on partitioning are all well‐described by the mathematical model. The pKavalue of the metal binding site was determined to be 6.5, which is in the range of pKavalues commonly observed for surface histidines. The average association constant for the binding of Cu (II)PEG‐IDA to accessible histidines was found to be 4.5 × 103. This value is comparable to stability constants measured by conventional potentiometry techniques for analogous small complexes.
Solvent selection for biocatalysis in mainly organic systems: Predictions of effects on equilibrium position
Authors: Halling Peter J. 
Published: May 2005

AbstractPredictions may be made for the influence of solvent choice on the equilibrium position of biocatalyzed reactions, based on data for the liquid–liquid distribution of the reactants. The most reliable predictions are probably for dilute systems, based on partition coefficients or correlations derived from them. The effective equilibrium constant for esterification reactions is predicted to alter by more than four orders of magnitude on changing between different water‐immiscible solvents. The equilibrium constant correlates well with the solubility of water in the solvent, and is most favorable for synthesis in the least polar solvents (aliphatic hydrocarbons). Similar effects seem to apply for other reactions, including oxidation of alcohols and hydrolysis of chlorides. Predictions can be made for nondilute systems using the UNIFAC system of group contributions, but the reliability of these is more questionable.
Dynamic on‐line optimization of a bioreactor
Authors: Petersen James N. , Whyatt Greg A. 
Published: May 2005

AbstractAn algorithm was developed which uses recursive least squares to identify a dynamic, discrete time model of a poorly defined system and uses both the dynamic and static portions of the identified model for on‐line optimization. To test this new algorithm, a model of an continuous biochemical reactor was used as the “process.” The objective, here, was to maximize ethanol production from the reactor by manipulating the feed rate to the reactor. The new algorithm, which uses dynamic information, was found to be superior to previously published algorithms which use only the steady‐state portion of the identified model.
A macromodel for outdoor algal mass production
Authors: Guterman H. , Vonshak A. , Ben‐Yaakov S. 
Published: May 2005

AbstractA model describing growth of an outdoor algal (Spir‐ulina platensis)culture was developed. The model can simulate biomass production, pH, growth rate, oxygen evolution, and CO2 fixation rate. It was calibrated and validated against experimental data obtained by a novel automatic data logger/controller instrumentation which can number most vital parameters of the culture including on line estimation of oxygen production rate (OPR). The importance of understanding light distribution through the pond and its effects on the photosynthesis and respiration processes are emphasized. A maximum yield of about 38g day−1 m−2 under optimal conditions is predicted. The present model can also be a useful tool for optimization of algal mass production sites.
Biosurfactant yields and nutrient consumption of Pseudomonas fluorescens 378 studied in a microcomputer controlled multifermentation system
Authors: Persson A. , Molin G. , Andersson N. , Sjöholm J. 
Published: May 2005

AbstractProduction of biosurfactant AP‐6 and consumption of carbon (succinic acid) and nitrogen (ammonium ions) by Pseudomonas fluorescens 378 were studied under different growth conditions. The study was performed in a microcomputer controlled multibatch fermentation system which enabled simultaneous running of 10 fermentors. The fermentors were mantled glass vessels, temperature controlled by circulated water, and mixing was arranged by magnetic stirrers. They were connected to the computer system (pH measurement and control) via signal conditioning cards. The microcomputer had a 128 kbytes RAM, two 800‐kbyte floppy disc drives, a graphic terminal, and expansion cards. Biosurfactant production was independent of the carbon‐to‐nitrogen ratio and the phosphorus content in the medium. Omitting the Fe(III) supplement to the medium increased the product yield by 120%. Changes in oxygen transfer rate and pH in the iron deficient cultures did not have any effect on the product yield. Iron deficiency increased the cell consumption of carbon source. Consumption of carbon source in relation to nitrogen uptake (carbon/nitrogen quotient) increased with increasing quotient in the growth medium. The uptake of carbon and nitrogen changed in the intervals of 1.2–1.5 g/g biomass and 0.09–0.16 g/g biomass, respectively. The consumption of carbon increased from 1.5 g/g biomass to 2.0 g/g biomass when the medium concentration of phosphorus was decreased from 0.18 to 0.027 g/L.
Enzymatic synthesis of alkyds
Authors: Geresh Shimona , Giiboa Yigal 
Published: May 2005

AbstractLipases were used as catalysts in the synthesis of “all‐trans” polyester oligomers in organic solvents. Esters of fumaric acid and 1,4‐butane diol served as the substrates in the enzyme‐catalyzed polytransesterification. No isomerization of the double bond was found under the mild conditions of enzymatic catalysis used by us, as opposed to the extensive isomerization found during chemical polycondensation. The alkoxy leaving group of the ester fumarate was found to be responsible for the rate of transesterification. Low (Mw ≃ 600–800) and high (Mw = 1250) molecular weight alkyds were synthesized depending on whether tetrahedrofuran or acetonitrile, respectively, was used as the solvent.
Dynamic model development for a continuous culture of Saccharomyces cerevisiae
Authors: O'Neil D. G. , Lyberatos G. 
Published: May 2005

AbstractThe problem of dynamically modeling a chemostat is addressed. Using the results of continuous culture experiments for the growth of a strain of Saccharomyces cerevisiae on a glucose‐limited medium, a general approach to developing dynamic models is discussed. The approach to develop and verify the model involves three different types of experiments: steady‐state, dynamic step response, and feedback identification.
Adsorption of cellulase from Trichoderma reesei on cellulose and lignacious residue in wood pretreated by dilute sulfuric acid with explosive decompression
Authors: Ooshima Hiroshi , Burns Douglas S. , Converse Alvin O. 
Published: May 2005

AbstractThe adsorption of cellulase on cellulose and a lignacious residue was examined by using cellulase from Trichoderma reesei, hardwood pretreated by dilute sulfuric acid under high pressure, and a lignacious residue prepared by a complete enzymatic hydrolysis of the pretreated wood. A significant amount of cellulase was found to adsorb on the lignacious residue during the hydrolysis of the pretreated wood. Hence, the adsorption of enzyme on the lignacious residue as well as cellulose must be taken into account in the development of the hydrolysis kinetics. It was found that the adsorption of enzyme on cellulose and on the lignacious residue could be represented by Langmuir type isotherms. The data show that the pretreatment at a higher temperature results in more enzyme adsorption on the cellulose fraction and less on the lignacious residue fraction. The relationship between the hydrolysis rate and the amount of enzyme adsorbed is discussed.
A stochastic model to simulate the growth of anchorage dependent cells on flat surfaces
Authors: Lim J. H. R. , Davies G. A. 
Published: May 2005

AbstractA stochastic model is proposed to simulate the growth of anchorage dependent cells on a flat surface. The model, based on representing the cell shapes on the surface as external irregular polygons with the nuclei distributed as a set of Poisson points (producing a modified Voronoi tessellation of 2 space) and incorporating a distribution function to describe cell division of the perimeter cells of the colony, provides data not only on population dynamics but also on the patterns produced by clusters of cells in the colony. These patterns produced by the model are qualitatively similar to observations reported for some cell cultures. The periods of induction, rapid growth, and decreasing growth asymptoting to zero as confluence is reached are predicted by the model. Quantitative comparison with published experimental data for this is good. The specific growth rate computed for the period of rapid growth predicted by the model is dependent on the distribution function describing the cell division time. As the standard deviation of this increases, the specific growth rate decreases as with a consequent increase in time to achieve confluence. The removal of cells from the colony by shear forces or death is considered in the model. As the probability for removal increases, the cell density at confluence and specific growth rate decrease. The clusters of cells, patterns, in the colony are very sensitive to cell removal. By analyzing these patterns in experiments, an estimate of cell removal can be made. The areas covered by cells on a substrate are fractal patterns. The fractal dimension is always greater than 1 and is a function of the removal probability.
Continuous production of prourokinase in feed harvest and perfusion cultures
Authors: Wagner A. , Marc A. , Engasser J. M. , Villermaux S. , Einsele A. 
Published: May 2005

AbstractThe production of prourokinase (PUK) by a human kidney tumor cell line is studied in long term cultures. Cells are grown on microcarriers which are retained inside the reactor by sedimentation or with a spin filter. Two modes of operation are compared: feed harvest at an average medium exchange rate of 0.3 d−1 and continuous perfusion at a higher dilution rate of 1.5 d−1. In the two systems a stable production of PUK has been maintained for more than 400 h. Kinetics of cellular growth, nutrient consumption, and metabolite and PUK excretion are similar. After an initial rapid growth period, one observes a 10‐fold reduction in all the cellular metabolic activities during the stationary phase. Continuous perfusion yields a higher cell density (7 × 106 cells·mL−1) than feed harvest (3 × 106 cells·mL−1), which results in a twofold increase in the reactor productivity. But higher final enzyme activities, about 250 ru·mL−1, are obtained in the feed harvest recovered medium than in the perfusion medium, 100–150 ru·mL−1. The cumulative medium consumption per mass of product is the same in the repeated batch and in the continuous operation mode.
Effects of cell density and glucose and glutamine levels on the respiration rates of hybridoma cells
Authors: Wohlpart Dave , Kirwan Donald , Gainer John 
Published: May 2005

AbstractThe effects of cell density as well as the concentration levels of glucose and glutamine on the specific respiration rate of a hybridoma cell line were investigated. The experimental oxygen consumption rate was found to be constant over a wide range of dissolved oxygen levels if the suspension medium contained glutamine. In glutamine‐free medium, however, the rate of oxygen consumption decreased slowly with time.In a stationary flask batch culture, the specific respiration rate decreased from about 7 to 2.9 μmol/min per 109 cells as the cell density increased exponentially from 1 × 105 to 1.2 × 106/mL. To isolate the effect of cell density, cells were re suspended in fresh culture medium so that nutrient concentrations were the same for all experiments. The specific respiration rate decreased with increasing cell density in the same manner as in the stationary flask culture, falling from 8 to 4 μmol/min per 109 cells as the cell density increased from 105 to 106 cells/mL, then declining to 2 μmol/min per 109 cells when the cell density reached 107 cells/mL.Cells suspended in Hanks balanced sale solution (HBSS) were used to elucidate the effect of glucose and glutamine levels on respiration. The addition of glucose in concentrations of 0.25, 0.50, and 0.75 g/L had no observable effect on the specific oxygen uptake rate; however, a glucose concentration of 1 g/L reduced the uptake rate by 22%. Glutamine in a concentration of 0.30 g/L increased the specific respiration rate in HBSS containing 0 and 1 g/L glucose by approximately 13%.
Enzymatic production of hydrogen peroxide and acetaldehyde in a pressure reactor
Authors: Nelles L. P. , Arnold J. A. , Willman D. S. 
Published: May 2005

AbstractAlcohol oxidase, an enzyme which exhibits relatively weak substrate specificity among short chain alcohols, forms the corresponding aldehyde and hydrogen peroxide as coproduct. The ability of alcohol oxidase from Pichia pastoris yeast to convert ethanol to acetaldehyde and hydrogen peroxide was examined in an oxygen pressure reactor under conditions, such that oxygen availability was sufficient to permit rapid catalysis. Hydrogen peroxide levels of ∼1.8/M (6% w/w) were attained in 2–3 h with 2.8 μM enzyme, corresponding to a productivity of ∼30 g peroxide/g enzyme. Optimal conditions (within equipment limitations) were 900 psi oxygen, 2.6M ethanol, at 4 °C. Similar levels of products were reached in the reactor using enzyme immobilized covalently on controlled pore glass and noncovalently on an anion exchange support. Recycle of covalently immobilized enzyme was not possible as a result of enzyme inactivation after a single run. Limited recycle of noncovalently immobilized enzyme was accomplished with substantial decreases in levels of product attainable on each cycle.
Hydrophobic interaction chromatography of autoproteolysis products of human seminal plasma
Authors: Mazzini M. N. , Di Giacomo M. A. , Cerezo A. S. 
Published: May 2005

AbstractHydrophobic interaction chromatography was employed for the fractionation of the glycopeptide mixture obtained after autoproteolysis and delipidization treatment of normal human seminal plasma samples. This sequence of procedures led to the elimination of highly hydrophobic components and to the concentration of the carbohydrate‐rich fractions. A partial separation between the O‐ and N‐glycosidic‐linked oligopeptides was also achieved after the chromatographic step.
HPLC determination of polyamines in the femtomole range
Authors: Yun Zhong , Zhang Ren‐en 
Published: May 2005

AbstractA new method for the chromatographic determination of polyamines is presented. The procedure consists of the reaction of 9‐fluorenylmethyl chloroformate (FMOC‐Cl) with polyamines at 50 ± 1°C for 10 min, followed by stepwise elution chromatography. The reaction is simple and the derivatives are stable. All the polyamine‐FMOC derivatives can be separated within 13 min. The linearity of this method is satisfactory in the range of 0.5–100 pmol. The detection limits for putrescine, cadaverine, spermidine and spermine are 83.3 fmol, 109 fmol, 25.5 fmol and 22.7 fmol respectively.
A rapid method for the determination of benzylpenicillin in serum by reversed‐phase HPLC
Authors: Soto‐Otero R. , Mendez‐Alvarez E. , Sierra‐Paredes G. , Galan‐Valiente J. , Aguilar‐Veiga E. , Sierra‐Marcuño G. 
Published: May 2005

AbstractA simple procedure for the determination of benzylpenicillin in serum is described. The assay involves the extraction of the drug and the internal standard (phenoxymethylpenicillinic acid) from the sample into dichloromethane, using tetrabutylammonium hydrogen sulfate neutralized with NaOH and buffered with citrate as an ion‐pairing reagent. RP–HPLC was performed on a Spherisorb 5 ODS column, eluting the drugs isocratically with 14% acetonitrile in 10 mM ammonium acetate buffer. Monitoring was by UV detection at 208 nm. Our results show that the method is accurate and reproducible, permitting quantification of serum levels of benzylpenicillin without interference from other drugs commonly used in therapy. Analytical recovery was greater than 79.2%.
A high performance liquid chromatographic post‐column fluorescent ion pair extraction system: Application to physostigmine and its metabolite eseroline in human serum
Authors: Quinn Karen D. , Stewart James T. 
Published: May 2005

AbstractA high performance liquid chromatographic post‐column fluorescent ion pair extraction system was developed for the analysis of quaternary ammonium and amine drugs in serum. A new fluorescent ion pair reagent, sodium α‐(3,4‐dimethoxyphenyl) cinnamonitrile‐2′‐sulfonate (DPS), was synthesized and characterized. The post‐column extraction system consisted of a three‐dimensional knitted teflon mixing coil and a membrane phase separator which was modified from an original literature design. Physostigmine and its metabolite eseroline were used as model cations. A solid phase extraction procedure using octadecylsilane columns was developed to extract the compounds and neostigmine bromide (internal standard) from human serum. The compounds were chromatographed on a diol column using a 80:20 aqueous phosphate buffer pH 4 absolute methanol mobile phase at a flow rate of 1 mL/min. Methylene chloride was used as the on‐line extraction solvent for the DPS ion pairs formed. Fluorescence of the extracted ion pairs was measured using an excitation of 243 nm and an emission cut‐off filter at 418 nm. Linearity was in the 2–100 ng/mL and 5–100 ng/mL ranges for physostigmine and eseroline, respectively. Detection limits based on a signal‐to‐noise ratio of 2, were 2 and 5 ng/mL, respectively. Precision of the method was found to be in the 1.5–3% range and percentage error in the 1.5–7% range for both compounds.
Liquid chromatographic analysis of mexiletine in serum, with alternate application to tocainide, procainamide, and N‐acetylprocainamide
Authors: vasBinder Eric , Annesley Thomas 
Published: May 2005

AbstractA simple and precise high performance liquid chromatographic method for the determination of mexiletine in human serum or plasma is described. Following addition of N‐propionylprocainamide as internal standard the specimens are extracted, under basic conditions, into methylene chloride. After removal of the aqueous layer the drug is back‐extracted into dilute acid, which is then injected directly for analysis. The extraction efficiency is 79% for both mexiletine and internal standard, and the assay is linear to 4 mg/L (twice upper therapeutic concentration). Inter‐run coefficients of variation are 3.0% or less. The relative retention time of mexiletine to internal standard averages 1.3. An adaptation of this method is described for an alternate application to the analysis of tocainide, procainamide and N‐acetylprocainamide.
A high performance liquid chromatographic procedure for the simultaneous determination of norfloxacin and furprofen in rat plasma
Authors: Carlucci Giuseppe , Mazzeo Pietro , Palumbo Giancarlo 
Published: May 2005

AbstractA rapid and simple high performance liquid chromatographic analytical method is described for the simultaneous determination of norfloxacin and furprofen in rat plasma. Following dichloromethane extraction, the solution was chromatographed in a Vydac anion exchange column using a mobile phase of 0.05 M phosphate buffer (pH=7.0):acetonitrile (80:20, v/v) at a flow‐rate of 1.8 mL/min. The drugs were detected by UV absorption at 278 nm. The total chromatographic analysis time was 10 min. The response was linear, 0.1‐5.0 μg/mL for norfloxacin and 0.1‐3.0 μg/mL for furprofen, respectively. This method is useful for pharmacokinetic studies of these compounds and will facilitate detailed investigations into the interactions between quinolones and furprofen.
Development of a chemiluminescence detection system using bis[4‐nitro‐2‐(3,6,9‐trioxadecyloxycarbonyl)phenyl] oxalate for the sensitive determination of the fluorescent compounds separated with an acidic mobile phase
Authors: Sugiura Masaki , Kanda Susumu , Imai Kazuhiro 
Published: May 2005

AbstractA rotating flow mixing device having three directional inlets was developed for a high performance liquid chromatographic peroxyoxalate chemiluminescence detection system for the sensitive detection of fluorescent compounds separated with acidic mobile phases, such as those containing trifluoroacetic acid. The diameters of the three inlets were 0.3, 0.3 and 0.5 mm i.d., for an acidic column eluate, chemiluminogenic reagents (bis[4‐nitro‐2‐(3,6,9‐trioxadecyloxycarbonyl)phenyl] oxalate and hydrogen peroxide) and imidazole solution (for neutralization and as a catalyst), respectively. The three mixed solutions flowed out through an outlet (0.5 mm i.d.) at the centre of the top of the vessel. The reaction conditions to give the appropriate signal‐to‐noise ratio (S/N) were investigated using dipyridamole (an antiplatelet aggregation drug) as a typical fluorescent compound. The system was applied to the detection of dipyridamole and dansylated amino acids with a mobile phase containing trifluoroacetic acid. The detection limits for dipyridamole and each dansylated amino acid were 10 amol and sub‐fmol (S/N=2), respectively.
Sensitive determination of enantiomers of amino acids derivatized with the fluorogenic reagent, 4‐fluoro‐7‐nitro‐2,1,3‐benzoxadiazole, separated on a pirkle‐type column, sumichiral OA 2500(S)
Authors: Imai Kazuhiro , Fukushima Takeshi , Uzu Sonoko 
Published: May 2005

AbstractSome L‐ and D‐amino acids (Phe or Leu) were derivatized with a fluorogenic reagent, 4‐fluoro‐7‐nitro‐2,1,3‐benzoxadiazole (NBD‐F) and separated on a Pirkle‐type column, Sumichiral OA 2500(S) [(S)‐1‐naphthylglycyl‐3,5‐dinitrophenylamide silica gel] with a mobile phase of 20 mM ammonium acetate in methanol. The fluorometric detection was made at 530 nm with excitation at 470 nm. No racemization of the enantiomers occurred during the derivatization reaction. The separation factors (α) for NBD‐L‐Phe and NBD‐D‐Phe, and NBD‐L‐Leu and NBD‐D‐Leu, were 1.27 and 1.17, respectively. The detection limits were in the range of ca. 30 fmol.