bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of the pH Profile for Asymmetric Bioreduction of Ethyl 4‐Chloro‐3‐oxobutyrate on the Basis of a Data‐Driven Method
Authors: Chen Junghui , Wang Kuan‐Po , Houng Jer‐Yiing , Lee Shiou‐Ling 
Published: December 2002

AbstractThe goal of this paper was to design the optimal time‐varying operating pH profile in the asymmetric reduction of ethyl 4‐chloro‐3‐oxobutyrate by baker's yeast. Ethyl ( S)‐4‐chloro‐3‐hydroxybutyrate was produced to reach two important quality indices: reaction yield and product optical purity. The method integrated an orthogonal function approximation and an orthogonal array. The technique used a set of orthonormal functions as the basis for representing the possible profile. The optimal profile could be obtained if the orthogonal coefficients were properly adjusted. The orthogonal array was used to design and analyze the effect of each orthogonal coefficient in order to reach the optimal objective (quality) function. The performance based on the proposed strategy was significantly improved by over 10% compared with the traditional fixed pH or uncontrolled pH values during the reaction. The proposed method can be applied to the required dynamic profile in the bioreactor process to effectively improve the product quality, given good design directions and the advantage of the traditional statistical approach.
Electronic Speckle Pattern Interferometry: A Tool for Determining Diffusion and Partition Coefficients for Proteins in Gels
Authors: Karlsson David , Zacchi Guido , Axelsson Anders 
Published: December 2002

AbstractThe aim of this study was to demonstrate electronic speckle pattern interferometry (ESPI) as a powerful tool in determining diffusion coefficients and partition coefficients for proteins in gels. ESPI employs a CCD camera instead of a holographic plate as in conventional holographic interferometry. This gives the advantage of being able to choose the reference state freely. If a hologram at the reference state is taken and compared to a hologram during the diffusion process, an interferometric picture can be generated that describes the refraction index gradients and thus the concentration gradients in the gel as well as in the liquid. MATLAB is then used to fit Fick's law to the experimental data to obtain the diffusion coefficients in gel and liquid. The partition coefficient is obtained from the same experiment from the flux condition at the interface between gel and liquid. This makes the comparison between the different diffusants more reliable than when the measurements are performed in separate experiments. The diffusion and partitioning coefficients of lysozyme, BSA, and IgG in 4% agarose gel at pH 5.6 and in 0.1 M NaCl have been determined. In the gel the diffusion coefficients were 11.2 ± 1.6, 4.8 ± 0.6, and 3.0 ± 0.3 m2/s for lysozyme, BSA, and IgG, respectively. The partition coefficients were determined to be 0.65 ± 0.04, 0.44 ± 0.06, and 0.51 ± 0.04 for lysozyme, BSA, and IgG, respectively. The current study shows that ESPI is easy to use and gives diffusion coefficients and partition coefficients for proteins with sufficient accuracy from the same experiment.
Optimization of Allium sativum Solvent Extraction for the Inhibition of in Vitro Growth of Helicobacter Pylori
Authors: Cañizares Pablo , Gracia Ignacio , Gómez Luis A. , de Argila Carlos Martín , de Rafael Luis , García Antonio 
Published: December 2002

AbstractHelicobacter pylori (Hp) is the bacterium responsible for serious gastric diseases such as ulcers and cancer. The work described here involved the study of the inhibitory power of Allium sativum extracts against the in vitro growth of Hp(Hp ivg). We used purple garlic of the “Las Pedroñeras” variety for this study. The effects of two different extraction methods (Soxhlet, stirred tank extractor) and four solvents with different characteristics (water, acetone, ethanol, and hexane) were investigated in terms of the efficiency of the extraction process. Satisfactory results were obtained in most cases in the activity tests, indicating that different extracts gave rise to good inhibitory activity against Hp ivg. The extracts that showed the highest bacteriostatic activities were selected to evaluate the influence of the most important operation variables on the extraction yield: stirring speed, operation time, garlic conditioning, and garlic storage time. The best results were obtained using ethanol and acetone as solvents in a stirred tank. The inhibitory powers of these extracts were compared to those shown by some commercial antibiotics used in the medical treatment of Hp infections. The results of this study show that garlic extracts produce levels of inhibition similar to those of the commercial materials. These extracts were also tested against other common bacteria, and equally satisfactory results were obtained. The research described here represents an important starting point in the fight against and/or prevention of peptic ulcers, as well as other pathologies associated with Hp infections such us gastric cancer. The extracted material can be used by direct application and involves a simple and economical extraction procedure that avoids isolation or purification techniques.
Enhancement of Enzyme Activity in Supercritical Carbon Dioxide via Changes in Acid‐Base Conditions
Authors: Harper Neil , Barreiros Susana 
Published: December 2002

AbstractEnzyme performance is often impaired in supercritical carbon dioxide. We were able to enhance enzyme activity in this medium via changes in acid‐base conditions by using ion‐exchange materials (solid H+/Na+ buffer pairs and a zeolite), which were selected on the basis of the response of an organosoluble acid‐base indicator. The concentration of ion‐exchange materials had an important effect on the catalytic activity of subtilisin Carlsberg cross‐linked enzyme crystals (CLECs), and this was related to the protonation and hydration states of the enzyme. The buffer Na2CO3/NaHCO3 gave the highest enhancement in enzyme activity (by a factor of 54), probably as a result of its high basicity and capacity to counteract the deleterious effect of carbonic acid to a greater extent than the other materials tested.
Characterization of an Inducible Promoter System in Catharanthus roseus Hairy Roots
Authors: Hughes Erik H. , Hong Seung‐Beom , Shanks Jacqueline V. , San Ka‐Yiu , Gibson Susan I. 
Published: December 2002

AbstractTransgenic hairy root cultures of Catharanthus roseus were established with a glucocorticoid‐inducible promoter controlling the expression of green fluorescent protein (GFP), and GFP expression was characterized. The inducible system shows a tightly controlled, reversible, and dosage‐dependent response to the glucocorticoid dexamethasone in C. roseus hairy roots. Full induction was noted after 12–18 h in the mature regions of the root tips and after 6 h in the meristem tissue. Upon removal of the inducing agent, GFP expression declined to undetectable levels in the mature tissues after 24 h and in the meristem after 48 h. Although no dosage‐dependent response was noted in the meristem region, such a response was apparent in the mature region of the tip and verified by quantitative GFP analysis. The inducible promoter system allowed quantitative control of GFP expression between 0.01 and 10 μM dexamethasone with saturation occurring at higher levels. Using GFP as a model system allowed demonstration of the ability to control temporal and quantitative gene expression with the glucocorticoid‐inducible promoter in transgenic C. roseus hairy roots.
Alterations in Taxol Production in Plant Cell Culture via Manipulation of the Phenylalanine Ammonia Lyase Pathway
Authors: Brincat Michelle C. , Gibson Donna M. , Shuler Michael L. 
Published: December 2002

AbstractOne approach to increasing secondary metabolite production in plant cell culture is to manipulate metabolic pathways to utilize more resources toward production of one desired compound or class of compounds, such as diverting carbon flux from competing secondary pathways. Since phenylalanine provides both the phenylisoserine side chain and the benzoyl moiety at C‐2 of Taxol, we speculated that blockage of the phenylpropanoid pathway might divert phenylalanine into Taxol biosynthesis. We used specific enzyme inhibitors to target the first enzyme in the phenylpropanoid pathway, phenylalanine ammonia lyase (PAL), the critical control point for conversion of l‐phenylalanine to trans‐cinnamic acid. Cinnamic acid acted quickly in reducing PAL activity by 40–50%, without affecting total protein levels, but it generally inhibited the taxane pathway, reducing Taxol by 90% of control levels. Of the taxanes produced, 13‐acetyl‐9‐dihydro‐baccatin III and 9‐dihydrobaccatin III doubled as a percentage of total taxanes in C93AD and CO93P cells treated with 0.20 and 0.25 mM cinnamic acid, when all other taxanes were lowered. The PAL inhibitor α‐aminooxyacetic acid (AOA) almost entirely shut down Taxol production at both 0.5 and 1.5 mM, whereas l‐α‐aminooxy‐β‐phenylpropionic acid (AOPP) had the opposite effect, slightly enhancing Taxol production at 1 μM but having no effect at 10 μM. The discrepancy in the effectiveness of AOA and AOPP and the lack of effect with addition of phenylalanine or benzoic acid derivatives further indicates that the impact of cinnamic acid on Taxol is related not to its effect on PAL but rather to a specific effect on the taxane pathway. On the basis of these results, a less direct route for inhibiting the phenylpropanoid pathway may be required to avoid unwanted side effects and potentially enhance Taxol production.
Metabolic Control Analysis of Eucaryotic Pyruvate Dehydrogenase Multienzyme Complex
Authors: Modak Jayant , Deckwer Wolf‐Dieter , Zeng An‐Ping 
Published: December 2002

AbstractMetabolic control analysis (MCA) of pyruvate dehydrogenase multienzyme (PDH) complex of eucaryotic cells has been carried out using both in vitro and in vivo mechanistic models. Flux control coefficients (FCC) for the sensitivity of pyruvate decarboxylation rate to activities of various PDH complex reactions are determined. FCCs are shown to be strong functions of both pyruvate levels and various components of PDH complex. With the in vitro model, FCCs are shown to be sensitive to only the E1 component of the PDH complex at low pyruvate concentrations. At high pyruvate concentrations, the control is shared by all of the components, with E1 having a negative influence while the other three components, E2, X, and K, exert a positive control over the pyruvate decarboxylation rate. An unusual behavior of deactivation of the E1 component leading to higher net PDH activity is shown to be linked to the combined effect of protein X acylation and E1 deactivation. The steady‐state analysis of the in vivo model reveals multiple steady state behavior of pyruvate metabolism with two stable and one unstable steady‐states branches. FCCs also display multiplicity, showing completely different control distribution exerted by pyruvate and PDH components on three branches. At low pyruvate concentrations, pyruvate supply dominates the decarboxylation rate and PDH components do not exert any significant control. Reverse control distribution is observed at high pyruvate concentration. The effect of dilution due to cell growth on pyruvate metabolism is investigated in detail. While pyruvate dilution effects are shown to be negligible under all conditions, significant PDH complex dilution effects are observed under certain conditions. Comparison of in vitro and in vivo models shows that PDH components exert different degrees of control outside and inside the cells. At high pyruvate levels, PDH components are shown to exert a higher degree of control when reactions are taking place inside the cells as compared to the in vitro situation.
Complete Conversion of d,l‐5‐Monosubstituted Hydantoins with a Low Velocity of Chemical Racemization into d‐Amino Acids Using Whole Cells of Recombinant Escherichia coli
Authors: Martinez‐Rodriguez Sergio , Javier Las Heras‐Vazquez Francisco , María Clemente‐Jimenez Josefa , Mingorance‐Cazorla Lydia , Rodriguez‐Vico Felipe 
Published: December 2002

AbstractA reaction system was developed for the production of d‐amino acids from d,l‐5‐monosubstituted hydantoins with a very slow rate of spontaneous racemization. For this purpose the d‐hydantoinase and d‐carbamoylase from Agrobacterium radiobacter NRRL B11291 were cloned in separate plasmids and expressed in Escherichia coli. The third enzyme, hydantoin racemase, was cloned from Agrobacterium tumefaciens C58. The hydantoin racemase amino acid sequence was significantly similar to those previously described. A reaction system consisting of recombinant Escherichia coli whole cell biocatalysts containing separately expressed d‐hydantoinase, d‐carbamoylase, and hydantoin recemase showed high substrate specificity and was effective toward both aliphatic and aromatic d,l‐5‐monosubstituted hydantoins. After optimizing reaction conditions (pH 8 and 50 °C), 100% conversion of d,l‐5‐(2‐methylthioethyl)‐hydantoin (15 mM) into d‐methionine was obtained in 30 min.
Laminar‐Flow‐Based Separations at the Microscale
Authors: Oakey John , Allely Josh , Marr David W. M. 
Published: December 2002

AbstractThe natural separation maintained by microfluidic flows is employed as the basis of a particle/cell sorting device. This method of separating particulate suspensions exploits the inherent laminar nature of microscale fluid dynamics and incorporates applied fields and image cytometry to enable sorting based upon any visually identifiable difference between colloid‐sized cells or particles. This technique may be used to easily isolate, separate, sort, or enrich virtually any suspension of microscale biological or colloidal particles within a microfluidic system. The entire footprint of the device described here is less than 0.01 mm2, allowing it to be readily incorporated within highly integrated micro total analysis systems (μTAS).
Integrated Process for the Enzymatic Synthesis of the Octapeptide PhAcCCK‐8
Authors: Fité Mercè , Clapés Pere , López‐Santín Josep , Benaiges M. Dolors , Caminal Glòria 
Published: December 2002

AbstractA process for the enzymatic synthesis of PhAcCCK‐8 is presented. The CCK‐8 (CCK26‐33) peptide fragment is the minimum sequence with biological activity of the cholecystokinin hormone. A synthetic convergent strategy has been developed starting from amino acid derivatives as raw materials, employing proteases as biocatalysts for each peptide coupling. The enzymes have been immobilized by deposition onto solid supports in order to be employed in organic media at low water activity. N‐Terminal protecting groups such as PhAc, which can be introduced and removed enzymatically, have been employed. The synthesis process has been set up at preparative level with focus in the integration of reaction and separation steps with an overall yield of 15%.
High Initial Activity but Low Storage Stability Observed for Several Preparations of Subtilisin Carslberg Suspended in Organic Solvents
Authors: Martínez Susimar González , Alvira Edgardo , Cordero Liz Vergara , Ferrer Amaris , Montañés‐Clemente Ileana , Barletta Gabriel 
Published: December 2002

AbstractColyophilization with methyl‐β‐cyclodextrin activates subtilisin Carlsberg by more than 200‐fold in organic solvents, though this is a short‐lived effect. About 93% of the enzyme's high initial activity observed in THF (at 45 °C) decreases exponentially with a t1/2 of 1.8 h, until it reaches a residual activity (of 7%) that remains constant throughout the 4 days duration of the experiment. A further study of this enzyme reveals a general trend: the initial activities of the lyophilized powder and the cross‐linked enzyme crystals are also greatly reduced upon incubation in this solvent, although these preparations retain 50% of their activity after about 20 h of incubation. All of the preparations studied retained some residual activity (which persisted throughout the duration of the experiments) after the initial exponential decay. The data here presented suggest that the mode of enzyme preparation is an important issue to consider when planning lengthy reactions.
Strawberry Pectin Methylesterase (PME): Purification, Characterization, Thermal and High‐Pressure Inactivation
Authors: Ly‐Nguyen Binh , Van Loey Ann M. , Fachin Diana , Verlent Isabel , Duvetter Thomas , Vu Son T. , Smout Chantal , Hendrickx Marc E. 
Published: December 2002

AbstractPectin methylesterase (PME) was extracted from strawberries ( Fragaria ananassa, cv Elsanta) and purified by affinity chromatography on a CNBr‐Sepharose 4B‐PME‐inhibitor column. A single protein and PME activity peak was obtained. A biochemical characterization in terms of molecular mass, pI, and kinetic parameters of strawberry PME was performed. In a second step, the thermal and high‐pressure stability of the enzyme was studied. Isothermal and combined isothermal‐isobaric inactivation of purified strawberry PME could be described by a fractional‐conversion model. Purified strawberry PME is much more stable toward high‐pressure treatments in comparison to those from oranges and bananas.
Renaturation and Interaction of Ribonuclease A with AOT Surfactant in Reverse Micelles
Authors: Chen Wen‐Yih , Lee Ya‐Wen , Lin Shin‐Chun , Ho Ching‐Wen 
Published: December 2002

AbstractThis study extended works on effects of solute on the percolation of reverse micelles to the effects of interactions between protein and surfactants on protein refolding by reverse micelles. The changes in percolation behavior were identified and attributed to the position of solutes in the core aqueous phase and the interaction between the solute and the surfactants. The percolation behavior of reverse micelles with solutes was related to protein renaturation and the reverse micelle. This study aims to highlight the involvement of the interface and the interaction of the protein with the surfactant during protein refolding. Ribonuclease A and AOT reverse micelles together constitute a model system considered here. The systemic parameters of the reverse micelle, water content ( Wo) and pH value, were applied to modify the interaction between the denatured protein molecules and the surfactant interface. The interactions and the locations of the protein molecules were determined from changes in percolation temperature measured by conductivity. The percolation and protein activity show that a stronger interaction of the protein molecules with surfactant corresponds to superior recovery of protein activity. The investigation concludes that the refolding of protein by reverse micelles is not only facilitated by the isolation of reverse micelles but also by the interaction due to the interface of the reverse micelle.
Regulation of In Situ Skeletal Muscle Arteriolar Tone: Interactions Between Two Parameters
Authors: FRISBEE JEFFERSON C. 
Published: December 2002

ABSTRACTObjective: The growing understanding of the complexity of mechanisms regulating arteriolar tone demands that a systematic determination of how these processes interact to alter diameter be undertaken. This study examined how five mediators of skeletal muscle distal arteriolar tone [adenosine concentration, oxygen content, α‐adrenergic activation (norepinephrine), intravascular pressure and wall shear rate], taken two parameters at a time, interact to regulate vessel diameter.Methods: The reactivity of distal arterioles of in situ rat cremaster muscle after alterations in each of the above mediators was assessed. In addition, arteriolar responses to all two‐parameter combinations were evaluated to determine the effect of altered environment on vascular reactivity to stimuli.Results: Arteriolar dilation to adenosine was unaltered by changes in other parameters. In contrast, wall shear rate‐induced arteriolar dilation was impaired by 60–88% after increases in the other parameters. Myogenic reactivity was reduced by 28% with elevated O2 and by 65% with norepinephrine (because of vessel closure) and was impaired by 89% with elevated adenosine. O2‐induced arteriolar reactivity was impaired by 56% with increased adenosine and by 44% with increased norepinephrine concentration but was largely unaffected by elevated intravascular pressure. Adrenergic reactivity was attenuated with elevated intravascular pressure (by 69%) and O2 (by 54%) because of vessel closure but was unaltered with elevated adenosine.Conclusions: These data suggest that (1) individual mediators contributing to the regulation of arteriolar tone exist within a hierarchy of importance and (2) mechanisms regulating arteriolar tone can be impacted by unidentified alterations in other processes. Ongoing investigation into interactions between multiple processes regulating arteriolar tone will allow for a more integrated understanding of how microvessels regulate their diameter.
Guidelines for the Prevention of Intravascular Catheter–Related Infections
Authors: O'Grady Naomi P. , Alexander Mary , Dellinger E. Patchen , Gerberding Julie L. , Heard Stephen O. , Maki Dennis G. , Masur Henry , McCormick Rita D. , Mermel Leonard A. , Pearson Michele L. , Raad Issam I. , Randolph Adrienne , Weinstein Robert A. 
Published: December 2002

AbstractThese guidelines have been developed for practitioners who insert catheters and for persons responsible for surveillance and control of infections in hospital, outpatient, and home health-care settings. This report was prepared by a working group comprising members from professional organizations representing the disciplines of critical care medicine, infectious diseases, health-care infection control, surgery, anesthesiology, interventional radiology, pulmonary medicine, pediatric medicine, and nursing. The working group was led by the Society of Critical Care Medicine (SCCM), in collaboration with the Infectious Disease Society of America (IDSA), Society for Healthcare Epidemiology of America (SHEA), Surgical Infection Society (SIS), American College of Chest Physicians (ACCP), American Thoracic Society (ATS), American Society of Critical Care Anesthesiologists (ASCCA), Association for Professionals in Infection Control and Epidemiology (APIC), Infusion Nurses Society (INS), Oncology Nursing Society (ONS), Society of Cardiovascular and Interventional Radiology (SCVIR), American Academy of Pediatrics (AAP), and the Healthcare Infection Control Practices Advisory Committee (HICPAC) of the Centers for Disease Control and Prevention (CDC) and is intended to replace the Guideline for Prevention of Intravascular Device–Related Infections published in 1996. These guidelines are intended to provide evidence-based recommendations for preventing catheter-related infections. Major areas of emphasis include 1) educating and training health-care providers who insert and maintain catheters; 2) using maximal sterile barrier precautions during central venous catheter insertion; 3) using a 2% chlorhexidine preparation for skin antisepsis; 4) avoiding routine replacement of central venous catheters as a strategy to prevent infection; and 5) using antiseptic/antibiotic impregnated short-term central venous catheters if the rate of infection is high despite adherence to other strategies (i.e., education and training, maximal sterile barrier precautions, and 2% chlorhexidine for skin antisepsis). These guidelines also identify performance indicators that can be used locally by health-care institutions or organizations to monitor their success in implementing these evidence-based recommendations.