bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly (acrylic acid) chitosan interpolymer complexes for stomach controlled antibiotic delivery
Authors: de la Torre Paloma M. , Torrado Guillermo , Torrado Santiago 
Published: October 2004

AbstractThe aim of this study was to develop a stomach‐specific drug delivery system to increase the efficacy of amoxicillin against Helicobacter pylori. Polyacrylic acid (PAA), chitosan (CS), and amoxicillin (A) were employed to obtain polyionic complexes. The design of the hydrogel delivery system was based on the swellable approach; with a floating feature to prolong the Gastric Residence Time (GRT). The polyionic complex (PAA:CS:A 2.5:5:2) showed a sustained drug release profile in enzyme‐free simulated gastric fluid (SGF) and pH 4.0. A pH independent swelling‐eroding pattern with adequate maximum swelling ratios of 17.76 and 13.42 was obtained at in SGF and pH 4.0, respectively, with similar eroding profiles in both pH media. This network carrier provides an amoxicillin protective effect towards the hydrolytic degradation in SGF. The in vivo study was performed on healthy volunteers, using the [13C] octanoic acid breath test. The proposed hydrogel showed a prolonged GRT of up to 3 h. The preliminary results from this study suggest that amoxicillin polyionic complexes have potential for improving local antibiotic therapy against H. pylori. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 72B: 191–197, 2005
Ribonucleotide activation by enzyme ribonucleotide reductase: Understanding the role of the enzyme
Authors: Cerqueira Nuno M. F. S. A. , Fernandes Pedro Alexandrino , Eriksson Leif A. , Ramos Maria João 
Published: October 2004

AbstractThis article focuses on the first step of the catalytic mechanism for the reduction of ribonucleotides catalyzed by the enzyme Ribonucleotide Reductase (RNR). This corresponds to the activation of the substrate. In this work a large model of the active site region involving 130 atoms was used instead of the minimal gas phase models used in previous works. The ONIOM method was employed to deal with such a large system. The results gave additional information, which previous small models could not provide, allowing a much clearer evaluation of the role of the enzyme in this step. Enzyme–substrate interaction energies, specific transition state stabilization, and substrate steric strain energies were obtained. It was concluded that the transition state is stabilized in 4.0 kcal/mol by specific enzyme–substrate interactions. However, this stabilization is cancelled by the cost in conformational energy for the enzyme to adopt the transition state geometry; the overall result is that the enzyme machinery does not lead to a rate enhancement in this step. It was also found that the substrate binds to the active site with almost no steric strain, emphasizing the complementarity and specificity of the RNR active site for nucleotide binding. The main role of the enzyme at the very beginning of the catalytic cycle was concluded to be to impose stereospecifity upon substrate activation and to protect the enzyme radical from the solvent, rather than to be an reaction rate enhancement. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 2031–2037, 2004
Implementation and testing of stable, fast implicit solvation in molecular dynamics using the smooth‐permittivity finite difference Poisson–Boltzmann method
Authors: Prabhu Ninad V. , Zhu Peijuan , Sharp Kim A. 
Published: October 2004

AbstractA fast stable finite difference Poisson–Boltzmann (FDPB) model for implicit solvation in molecular dynamics simulations was developed using the smooth permittivity FDPB method implemented in the OpenEye ZAP libraries. This was interfaced with two widely used molecular dynamics packages, AMBER and CHARMM. Using the CHARMM‐ZAP software combination, the implicit solvent model was tested on eight proteins differing in size, structure, and cofactors: calmodulin, horseradish peroxidase (with and without substrate analogue bound), lipid carrier protein, flavodoxin, ubiquitin, cytochrome c, and a de novo designed 3‐helix bundle. The stability and accuracy of the implicit solvent simulations was assessed by examining root‐mean‐squared deviations from crystal structure. This measure was compared with that of a standard explicit water solvent model. In addition we compared experimental and calculated NMR order parameters to obtain a residue level assessment of the accuracy of MD‐ZAP for simulating dynamic quantities. Overall, the agreement of the implicit solvent model with experiment was as good as that of explicit water simulations. The implicit solvent method was up to eight times faster than the explicit water simulations, and approximately four times slower than a vacuum simulation (i.e., with no solvent treatment). © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 2049–2064, 2004
Amniotic membrane transplantation in ocular surface disorders
Authors: Tosi Gian Marco , Massaro‐Giordano Mina , Caporossi Aldo , Toti Paolo 
Published: October 2004

AbstractChronic ocular surface disorders, which can result in severe functional impairment, have been viewed for decades as untreatable diseases. In 1995, the reintroduction of amniotic membrane transplantation (AMT), either alone or associated with limbal stem cell transplantation, has offered new hope of using tissue and cell therapy strategies to repair ocular surface disorders. Amniotic membrane (AM) has been found to exert its effects by acting as a substrate for the growth of ocular surface epithelia, by suppressing inflammation and scarring and by serving as an anti‐microbial barrier. Moreover, AM has recently been used as a substrate for ex vivo expansion of corneal epithelial cells for ocular surface reconstruction. Notwithstanding the substantial agreement among Authors regarding its clinical efficacy, there are still many uncertainties regarding the fate of grafted AM and consequently the mechanisms through which it exerts its long‐term effects. Further studies including controlled clinical trials with numerous cases are required to understand which ocular surface conditions are certain to benefit from AM transplantation and how its mechanical properties interact with the mediators produced to favor ocular surface reconstruction. © 2004 Wiley‐Liss, Inc.
Nitric oxide specifically reduces the permeability of Cx37‐containing gap junctions to small molecules
Authors: Kameritsch Petra , Khandoga Natascha , Nagel Wolfram , Hundhausen Christina , Lidington Darcy , Pohl Ulrich 
Published: October 2004

AbstractGap junction intercellular communication (GJIC) plays a significant role in the vascular system. Regulation of GJIC is a dynamic process, with alterations in connexin (Cx) protein expression and post‐translational modification as contributing mechanisms. We hypothesized that the endothelial autacoid nitric oxide (NO) would reduce dye coupling in human umbilical vein endothelial cells (HUVECs). In our subsequent experiments, we sought to isolate the specific Cx isoform(s) targeted by NO or NO‐activated signaling pathways. Since HUVEC cells variably express three Cx (Cx37, Cx40, and Cx43), this latter aim required the use of transfected HeLa cells (HeLaCx37, HeLaCx43), which do not express Cx proteins in their wild type form. Dye coupling was measured by injecting fluorescent dye (e.g., Alexa Fluor 488) into a single cell and determining the number of stained adjacent cells. Application of the NO donor SNAP (2 μM, 20 min) reduced dye coupling in HUVEC by 30%. In HeLa cells, SNAP did not reduce dye transfer of cells expressing Cx43, but decreased the dye transfer from Cx37‐expressing cells to Cx43‐expressing cells by 76%. The effect of SNAP on dye coupling was not mediated via cGMP. In contrast to its effect on dye coupling, SNAP had no effect on electrical coupling, measured by a double patch clamp in whole cell mode. Our results demonstrate that NO inhibits the intercellular transfer of small molecules by a specific influence on Cx37, suggesting a potential role of NO in controlling certain aspects of vascular GJIC. © 2004 Wiley‐Liss, Inc.
Photo‐oxidation of cyanide in aqueous solution by the UV/H2O2 process
Authors: Malhotra Sarla , Pandit M , Kapoor JC , Tyagi DK 
Published: October 2004

AbstractPhoto‐oxidation of cyanide was studied in aqueous solution using a low‐pressure ultra‐violet (UV) lamp along with H2O2 as an oxidant. It was observed that by UV alone, cyanide degradation was slow but when H2O2 was used with UV, the degradation rate became faster and complete degradation occurred in 40 min. The rate of degradation increased as the lamp wattage was increased. It was also observed that cyanide oxidation is dependent on initial H2O2 concentration and the optimum dose of H2O2 was found to be 35.3 mmol dm−3. Photo‐oxidation reactions were carried out at alkaline pH values (10–11) as at acidic pH values, cyanide ions form highly toxic HCN gas which is volatile and difficult to oxidise. By the UV/H2O2 process, using a 25 W low‐pressure UV lamp and at alkaline pH of 10.5 with an H2O2 dose of 35.3 mmol dm−3, cyanide (100 mg dm−3) was completely degraded in 40 min when air was bubbled through the reactor, but when pure oxygen was bubbled the time reduced to 25 min. The cyanide degradation reaction pathway has been established. It was found that cyanide was first oxidised to cyanate and later the cyanate was oxidised to carbon dioxide and nitrogen. The kinetics of cyanide oxidation were found to be pseudo‐first order and the rate constant estimated to be 9.9 × 10−2min−1 at 40 °C. The power required for complete degradation of 1 kg of cyanide was found to be 167 kWh (kilowatt hour). Copyright © 2004 Society of Chemical Industry
Kraft lignin degradation products for tanning and dyeing of leather
Authors: Suparno Ono , Covington Anthony D , Evans Christine S 
Published: October 2004

AbstractKraft lignin degradation by a biomimetic system was investigated, using hemin as a catalyst and hydrogen peroxide as an oxidising agent, which mimics the catalytic mechanism of lignin peroxidase (LiP) to produce phenolic compounds. The degradation products were identified using spectroscopy and gas chromatography–mass spectrometry (GC–MS): 2‐methoxyphenol, 4‐hydroxybenzaldehyde, vanillin and vanillic acid were produced and their formaldehyde polymerisation products used for tanning hide powders. The denaturation (shrinkage) temperature of hide powder was raised to 80 °C through hydrogen‐bonding interactions between the polymers and the collagenic hide powder. For dyeing of hide powder, the lignin degradation products were reacted with laccase (a polyphenol oxidase): 2‐methoxyphenol gave the darkest colour. These products have potential to be used as raw materials for tanning and dyeing of animal skins. Therefore, value can be added to this industrial byproduct and reduce its environmental impact. Copyright © 2004 Society of Chemical Industry
Comparative evaluation of full‐scale UASB reactors treating alcohol distillery wastewaters in terms of performance and methanogenic activity
Authors: Ince Orhan , Kolukirik Mustafa , Oz Nilgun Ayman , Ince Bahar Kasapgil 
Published: October 2004

AbstractIn this study, two full‐scale upflow anaerobic sludge blanket (UASB) reactors, namely TUASB and CUASB, at the wastewater treatment plants of the Tekirdaǧ Alcohol (Raki) and Canakkale Alcohol (Cognac) distilleries were investigated in terms of performance, acetoclastic methanogenic capacity and microbial composition. The results were compared with a previously studied other UASB reactor (IUASB) at the wastewater treatment plant of the Istanbul Alcohol (Raki) Distillery from which the two reactors (TUASB and CUASB) were seeded. The IUASB reactor performed well achieving COD removal efficiencies of no lower than 85% at organic logding rates (OLRs) in the range of 6–11 kg COD m−3 day−1 between 1996 and 2001. During the last one year of operation, between 2000 and 2001, performance of the CUASB reactor in terms of COD removal efficiency was 70–80% at OLRs in a range of 1–4.5 kg COD m−3 day−1 whereas it was 60–80% at OLRs in a range of 2.5–8.5 kg COD m−3 day−1 in the TUASB reactor. At the end of year 2000, specific methanogenic activity (SMA) tests were carried out to determine potential loading capacity and optimum operating conditions of the IUASB, CUASB and TUASB reactors. The potential methane production (PMP) rates of the CUASB, IUASB and TUASB reactors were measured as 230 cm3 CH4 gVSS−1 day−1, 350 cm3 CH4 gVSS−1 day−1 and 376 cm3 CH4 gVSS−1 day−1 respectively. When the PMP rates were compared with actual methane production (AMP) rates obtained from the three UASB reactors, AMP/PMP ratios were evaluated to be 0.18, 0.12 and 0.13 for CUASB, TUASB and IUASB reactors respectively. This showed that the CUASB, TUASB and IUASB reactors were using only 18%, 12% and 13% of their potential acetoclastic methanogenic capacity respectively. These results can be interpreted that the three UASB reactors were underloaded compared with their potential acetoclastic methanogenic capacities. It was, therefore, recommended that the three UASB reactors should be loaded at higher organic loading rates or sludge withdrawn in order to maintain an AMP/PMP ratio of 0.6–0.7, which can ensure desired reactor performance with safer operation. Results of epifluoresence microscopic examinations showed that the percentage of total autofluorescent methanogens was approximately 30% of the total population in sludges from the TUASB and IUASB reactors whereas it was 20% in sludge from the CUASB reactor. The two UASB reactors treating raki distillery wastewaters contained sludges having a higher percentage of autofluorescent methanogenic population and higher acetoclastic methanogenic activity. Copyright © 2004 Society of Chemical Industry
Ozonation of CI Reactive Black 5 using rotating packed bed and stirred tank reactor
Authors: Chen Yi‐Hung , Chang Ching‐Yuan , Su Wei‐Ling , Chiu Chun‐Yu , Yu Yue‐Hwa , Chiang Pen‐Chi , Chang Chiung‐Fen , Shie Je‐Lueng , Chiou Chyow‐San , Chiang Sally IM 
Published: October 2004

AbstractThis study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry
D‐Lactic acid production from waste cardboard
Authors: Yáñez Remedios , Alonso José Luis , Parajó Juan Carlos 
Published: October 2004

AbstractThe effects caused by alkaline treatment on the susceptibility of waste cardboard to enzymatic hydrolysis have been studied. Optimised conditions leading to extensive saccharification of both cellulose (870 g kg−1 conversion) and hemicelluloses (845 g kg−1 conversion) were identified. Samples treated under selected operational conditions were employed for producing D‐lactic acid by simultaneous saccharification and fermentation (SSF) in media containing cellulases, β‐glucosidase and Lactobacillus coryniformis ssp torquens cells. SSF fed‐batch experiments led to D‐lactic acid concentrations up to 23.4 g dm−3 at a product yield of 514 g lactic acid kg−1 of potential glucose and a volumetric productivity of 0.48 g dm−3 h−1. Copyright © 2004 Society of Chemical Industry
Influence of cosurfactant in microemulsion systems for color removal from textile wastewater
Authors: Beltrame Leocadia Terezinha Cordeiro , de Castro Dantas Tereza Neuma , Dantas Neto Afonso Avelino , de Barros Neto Eduardo Lins , Silva Lima Felipe Fialho 
Published: October 2004

AbstractMicroemulsion systems have proved very efficient in color removal from textile wastewater using n‐butyl alcohol as cosurfactant. The cosurfactant has a very important role in microemulsified systems, as it is responsible for their stability, mainly in systems formed by ionic surfactants. Although very efficient, n‐butyl alcohol is partially soluble in water, which would permit its passage to the effluent. In this work, isoamyl and octyl alcohols, due to their lower solubility in water, were used as cosurfactants to evaluate their influence in color removal. The colorimetry system used was the CIE L*a*b* (CIELAB) color space and CIE L*a*b* color difference (ΔE*ab). The wastewater used in this study was the reactive exhausted dye liquor from a dye house (first discharge) containing Procion Yellow H‐E4R (CI Reactive Yellow 84), Procion Blue H‐ERD (CI Reactive Blue 160) and Procion Red H‐E3B (CI Reactive Red 120). The obtained results were modeled using an experimental planning (the Scheffé net) and evaluated through isoresponse diagrams by correlation graphs between experimental values and those obtained by the models with an error lower than 4%. All the optimized systems were very efficient and more than 94% of the dyes contained in the effluent were removed. The microemulsion load capacity was determined using a synthetic solution containing, the same dyes present in the reactive exhausted dyebath, but 200 times concentrated, and the dyes extraction was more than 99.6%. By comparing n‐butyl, isoamyl and octyl alcohols, it was observed that the system using isoamyl alcohol presented slightly better color removal and much higher load capacity than the n‐butyl and octyl alcohols. Copyright © 2004 Society of Chemical Industry
Comparison of chitins produced by chemical and bioprocessing methods
Authors: Beaney Paul , Lizardi‐Mendoza Jaime , Healy Michael 
Published: October 2004

AbstractLactic acid fermentation was used to extract chitin from prawn shell (Nephrops norvegicus) at two different scales of operation. The fermentation products were characterized and compared with chitin extracted from the same source by a chemical method. Chitosans produced from the obtained chitins were evaluated in terms of their intrinsic viscosity, molecular weight and degree of acetylation (DA). The fermentation removed 690 g kg−1 and 770 g kg−1 of inorganic matter, 490 and 440 g kg−1 of protein and 540 and 770 g kg−1 of lipids from the shells at laboratory and pilot plant scales, respectively. However, the functional properties such as the DA of the chitin, the molecular weight and the DA of the chitosans were similar to those obtained for the chemically‐obtained chitin and its chitosan. Despite the incomplete extraction of chitin this biological process could be useful to produce chitin and chitosan in a more environment‐friendly approach. Copyright © 2004 Society of Chemical Industry
Obtaining 1‐heptene from 1‐heptyne semihydrogenation with an anchored rhodium complex on different supports as catalyst
Authors: Quiroga Mónica , Liprandi Domingo , L'Argentière Pablo , Cagnola Edgardo 
Published: October 2004

AbstractThe complex [RhCl(NH2(CH2)12CH3)3] was tested for the semihydrogenation of 1‐heptyne in homogeneous and heterogeneous conditions. γ‐Al2O3and two different commercial activated carbons (RX‐3 EXTRA and GF‐45) were used as supports. The results were, then, compared with those previously reported for the [PdCl2(NH2(CH2)12CH3)2] complex supported or unsupported, and with the results obtained with the classic Lindlar catalyst. The complex was characterised by FTIR and elemental analysis. The pure species and the supported one were also characterised by X‐ray photoelectron spectroscopy. Results determined by the latter technique suggest that the active species is the complex itself, which is stable under the reaction conditions. The supported rhodium tetra‐coordinated complex shows higher activity and selectivity than the same complex unsupported, and also than the classic Lindlar catalyst. Moreover, among the rhodium‐supported complexes the one immobilised on RX‐3 EXTRA has a better performance than that heterogenised on GF‐45, and this one has a better activity and selectivity than the γ‐Al2O3anchored complex. Our results also show that under the same operational conditions (temperature, hydrogen pressure and metal/substrate weight ratio) the rhodium complex, unsupported or supported, has a better performance than the corresponding palladium complex. Copyright © 2004 Society of Chemical Industry
Immunohistochemistry of neuronal nitric oxide synthase and protein nitration in the striatum of the aged rat
Authors: del Moral María Luisa , Esteban Francisco José , Hernández Raquel , Blanco Santos , Molina Francisco Javier , Martínez‐Lara Esther , Siles Eva , Viedma Gloria , Ruiz Alharilla , Pedrosa Juan Angel , Peinado María Angeles 
Published: October 2004

AbstractTo ascertain the possible implications of the nitric oxide (NO•) producing system in striatal senescence, and by using immunohistochemistry and image‐processing approaches, we describe the presence of the enzyme nitric oxide synthase (NOS), the NADPH‐diaphorase (NADPH‐d) histochemical marker, and nitrotyrosine‐derived complexes (N‐Tyr) in the striatum of adult and aged rats. The results showed neuronal NOS immunoreactive (nNOS‐IR) aspiny medium‐sized neurons and nervous fibres in both age groups, with no variation in the percentage of immunoreactive area but a significant decrease in the intensity and in the number of somata with age, which were not related to the observed increase with age of the striatal bundles of the white matter. In addition, NADPH‐d activity was detected in neurons with morphology similar to that of the nNOS‐IR cells; a decrease in the percentage of area per field and in the number of cells, but an increase in the intensity of staining for the NADPH‐d histochemical marker, were detected with age. The number of neuronal NADPH‐d somata was higher than for the nNOS‐IR ones in both age groups. Moreover, N‐Tyr‐IR complexes were observed in cells (neurons and glia) and fibres, with a significant increase in the percentage of the area of immunoreaction, related to the increase of white matter, but a decrease in intensity for the aged group. On the other hand, we did not detect the inducible isoform (iNOS) either in adult or in aged rats. Taken together, these results support the contention that NADPH‐d staining is not such an unambiguous marker for nNOS, and that increased protein nitration may participate in striatal aging. Microsc. Res. Tech. 64:304–311, 2004. © 2004 Wiley‐Liss, Inc.