bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple mRNA species are generated by alternate polyadenylation from the human calmodulin‐I gene
Authors: Senterre‐Lesenfants Sylviane , Alag Amala S. , Sobel Mark E.
Published: May 2005

Three distinct genes encode an identical calmodulin protein in mammalian cells. In addition, multiple mRNA transcripts, with approximate sizes of 1.6 kb and 4.4 kb, are visualized on Northern blots hybridized to calmodulin‐I cDNA probes. To elucidate the mechanism generating multiple calmodulin mRNAs, the complete sequence of the 4194 base human calmodulin‐I mRNA was determined from cDNA clones and 3′ rapid amplification of complementary ends (3′ RACE). The 5′ untranslated region of calmodulin‐I mRNA contains a GC‐rich domain containing multiple repeats of GGC interrupted by a GCA sequence, as well as a tandem repeat sequence of eight GCA triplets. The 3′ untranslated region of calmodulin‐I mRNA contains two canonical and one aberrant (ATTAAA) polyadenylation signal, consistent with the sizes of 1.6 kb and 4.4 kb mRNAs visualized on Northern blots, and a potential minor 4.2 kb mRNA detected by 3′ RACE. Hybridization experiments using specific probes upstream and downstream of the polyadenylation signals demonstrated that alternate use of polyadenylation signals is the molecular mechanism for multiple calmodulin‐I mRNA transcripts in human cells. Thirteen adenine rich elements with the motif AUUUA were detected in the 3′ untranslated region. Three such motifs are embedded in regions that are conserved with the rat 3′ untranslated region of calmodulin‐I mRNA. One of these is surrounded by an adenine‐uridine rich region that can form an 11‐base pair stem structure. We propose that sequences in the 3′ untranslated region of calmodulin‐I mRNA may play a role in the regulation of calmodulin expression.
Growth and maturation of primary‐cultured adipocytes from lean and ob/ob mice
Authors: Black Marsha A. , Bégin‐Heick Nicole
Published: May 2005

Stromal vascular cells from epididymal fat pads of lean and obese mice were cultured in a medium (α‐MEM) containing fetal bovine serum (FBS) and cell replication followed for 11 days. In both types of cells, confluence occurred at 4–5 days, after which virtual growth arrest occurred in lean‐mouse cells while replication continued, albeit at a slower rate in obese‐mouse cells. Little or no lipid accumulation or glycerol‐3‐phosphate dehydrogenase (GPDH) activity was observed under these conditions. When a differentiation mixture consisting of insulin, corticosterone and isobutylmethylxanthine was added to the serum‐containing α‐MEM, a proportion of the lean‐mouse cells accumulated triglycerides and GPDH activity increased significantly, indicating differentiation. By contrast, little or no differentiation occurred in obese‐mouse cells. When cells grown in serum‐containing α‐MEM were transferred to a serum‐free defined medium at confluence, extensive differentiation and maturation occurred in lean‐mouse cells but not in obese‐mouse cells. Similar experiments were conducted in cells isolated from the retroperitoneal fat pad. Although the growth pattern was similar to that of epididymal preadipocytes, the retroperitoneal lean‐ and obese‐mouse cells differentiated more readily than epididymal cells, as shown by the GPDH specific activity. These data suggest that cells from obese mice are resistant to differentiation under conditions that support extensive differentiation in lean‐mouse cells.
Citric acid extracts a specific set of proteins from isolated cell nuclei
Authors: Rosenberger Uwe , Shakibaei Mehdi , Weise Christoph , Franke Peter , Buchner Klaus
Published: May 2005

The treatment of isolated cell nuclei with citric acid was described as a method for separating inner and outer nuclear membrane. Using cell nuclei from bovine cerebral cortex, we can show that citric acid does not cause a separation of the two nuclear membranes, but extracts a specific set of proteins from the nuclei. The extraction of proteins is not just an effect of damaging the nuclear membrane or destructing the cytoskeleton, but rather a specific effect of citric acid treatment. One of the extracted proteins, chosen as a marker for the putative outer nuclear membrane fraction, has an apparent molecular weight of 145 kDa and is located in the nucleoplasm as shown by immunofluorescence microscopy. By sequencing tryptic peptides it was identified as RNA helicase A, an abundant nuclear protein assumed to participate in the processing of mRNA. © 1995 Wiley‐Liss, Inc.
Premature expression of cyclin B sensitizes human HT1080 cells to caffeine‐induced premature mitosis
Authors: Tam Sun W. , Belinsky Glenn S. , Schlegel Robert
Published: May 2005

Eukaryotic cells do not normally initiate mitosis when DNA replication is blocked. This cell cycle checkpoint can be bypassed in some cells, however, by treatment with caffeine and certain other chemicals. Although S‐phase arrested hamster cells undergo mitosis‐specific events such as premature chromosome condensation (PCC) and nuclear envelope disassembly when exposed to caffeine, human cells show little response under the same conditions. To further investigate the molecular basis of this cell type specificity, a panel of hamster/human whole cell hybrids was created. The frequency of caffeine‐induced PCC and the level of cyclin B‐associated H1 kinase activity in the various hybrids were directly correlated with the extent of cyclin B synthesis during S‐phase arrest. To determine whether expression of cyclin B alone could sensitize human cells to caffeine, cyclin B1 was transiently overexpressed in S‐phase arrested HT1080 cells. The transfected cell population displayed a 5‐fold increase in the frequency of caffeine‐induced PCC when compared with normal HT1080 cells, roughly equivalent to the frequency of cells expressing exogenous epitope‐tagged cyclin B1. In addition, immunofluorescent microscopy showed that individual cells overexpressing cyclin B1 during S phase arrest underwent PCC when exposed to caffeine. These results provide direct evidence that premature expression of cyclin B1 can make cells more vulnerable to chemically‐induced uncoupling of mitosis from the completion of DNA replication. © 1995 Wiley‐Liss, Inc.
Endoplasmic reticulum protein HSP47 binds specifically to the N‐Terminal globular domain of the amino‐propeptide of the procollagen I α1(I)‐chain
Authors: Hu Geng , Gura Trisha , Sabsay Boris , Sauk John , Dixit Saryu N. , Veis Arthur
Published: May 2005

Hsp47, an endoplasmic reticulum‐resident heat shock protein in fibroblasts has gelatin‐binding properties. It had been hypothesized that it functions as a chaperone regulating procollagen chain folding and/or assembly, but the mechanism of the hsp47‐procollagen I interaction was not clear. Hsp47 could bind to both denatured and native procollagen I. A series of competition studies were carried out in which various collagens and collagen domain peptides were incubated with35[S]‐methionine‐labeled murine 3T6 cell lysates prior to mixing with gelatin‐Sepharose 4B beads. The gelatin‐bound proteins were collected and analyzed by gel electrophoresis and autoradiography. Collagenase digested procollagen I had the same effect as denatured intact procollagen, indicating that the propeptides were the major interaction sites. The addition of intact pro α1 (l)‐N‐propeptide at 25 μg/ml compeletely inhibited hsp47 binding to the gelatin‐Sepharose. Even the pentapeptide VPTDE, residues 86–90 of the pro α1 (l)‐N‐propeptide, inhibits hsp47‐gelatin binding. These data implicating the pro α1 (l)‐N‐propeptide domain were confirmed by examination of polysome‐associated pro α chains. The nascent pro α1(l)‐chains with intact N‐propeptide regions could be precipitated by monoclonal hsp47 antibody 11D10, but could not be precipitated by monoclonal anti‐pro α1 (l)‐N‐propeptide antibody SP1.D8 unless dissociated from the hsp47. GST‐fusion protein constructs of residues 23–108 (NP1), 23–151 (NP2), and 23–178 (NP3) within the pro α1 (l)‐N‐propeptide were coupled to Sepharose 4B and used as affinity beads for collection of hsp47 from 3T6 cell lysates. NP1 and NP2 both showed strong specific binding for lysate hsp47. Finally, the interaction was studied in membrane‐free in vitro cotranslation systems in which the complete pro α1(l)‐ and pro α2(l)‐chain RNAs were translated alone and in mixtures with each other and with hsp47 RNA. There was no interaction evident between pro α2(l)‐chains and hsp47, whereas there was strong interaction between pro α1 (l)‐chains and nascent hsp47. SP1.D8 could not precipitate pro α1 (l)‐chains from the translation mix if nascent hsp47 was present. These data all suggest that if hsp47 has a “chaperone” role during procollagen chain processing and folding it performs this specific role via its preferential interaction with the proα1 (l) chain, and the pro α1 (l) amino‐propeptide region in particular. © 1995 Wiley‐Liss, Inc.
Arrest at the G2/M transition of the cell cycle by protein‐tyrosine phosphatase inhibition: Studies on a neuronal and a glial cell line
Authors: Faure Robert , Vincent Michel , Dufour Maurice , Shaver Alan , Posner Barry I.
Published: May 2005

The addition of the peroxovanadium (pV) derivatives potassium bisperoxo(1,10‐phenanthroline)oxovanadate(v) (bpV[phen]) or potassium bisperoxo(pyridine‐2‐carboxylato)oxovanadate(v) (bpV[pic]), both of which are potent inhibitors of protein tyrosine phosphatases (PTPs) [Posner et al. (1994): J Biol Chem 269:4596–4604], to the culture medium of neuroblastoma NB 41 and glioma C6 cells resulted in a marked decrease in their proliferation rates and a progressive accumulation at the G2/M transition of the cell cycle. The effect was dependent on dose, cell type, and the pV compound employed. Mean values of the RNA‐to‐DNA and RNA‐to‐protein ratios in NB cells treated for 48 h with increased doses of bpV[phen] showed that general synthetic functions were not altered, nor did we observe oxidative damage to DNA using a sensitive DNA‐nick detection assay. No changes in the expression and localization of vimentin, a component of the intermediate filament cytoskeleton, were observed by indirect immunofluorescence, showing that treatment did not disturb the cytoskeleton network. Measurements of BrdU incorporation into newly synthesized DNA showed that cells treated were not totally arrested. Furthermore, cells arrested at G2/M were able to reenter the cycle rapidly after the release of inhibition. This progressive accumulation at G2/M coincided with the detection of tyrosine‐phosphorylated p34cdc2 and a dramatic reduction in its kinase activity toward histone H1 by 48 h of culture. Both compounds were equally potent in inhibiting the catalytic activity of a yeast and the structurally distant mouse cdc25B in vitro, suggesting that the augmented tyrosine phosphorylation of p34cdc2 derived from the in vivo inhibition of cdc25. Their equal in vitro potency contrasted with the considerably greater potency of bpV[phen] in vivo, suggesting that factors regulating the intracellular access of these compounds to cdc25 might be critical in determining in vivo specificity. In conclusion the final consequence of long‐term exposure to potent and structurally defined PTP inhibitors on two highly proliferative nerve cell lines is to restrict cell growth. The corresponding hyperphosphorylation and reduced activity of p34cdc2 likely reflects the unusual sensitivity of cdc25 as an in vivo target for peroxovanadium compounds. © 1995 Wiley‐Liss, Inc.
Properties and regulation of 17β‐hydroxysteroid oxidoreductase of OVCAR‐3, CAOV‐3, and A431 cells: Effects of epidermal growth factor, estradiol, and progesterone
Authors: Blomquist Charles H. , Leung Benjamin S. , Zhang Ruoping , Zhu Youyang , Chang Patricia M.
Published: May 2005

Although there is a growing body of evidence that 17β‐hydroxysteroid oxidoteductase plays a role the regulation of steroid levels in epithelial tumors of the endometrium and breast, out knowledge of its role in other gynecologic tumors is limited. In this investigation, the 17β‐hydroxysteroid oxidoreductase activity of cell lines derived from two ovarian tumors (OVCAR‐3, CAOV‐3) and an epidermoid tumor of the vulva (A431) was assayed under conditions which differentiate between 17β‐hydroxysteriod oxidoreductase type 1, a cytosolic isoform highly specific for estradiol, and type 2, a membrane bound isoform reactive with both estradiol and testosterone. On the basic of estradiol/testosterone activity ratios, all three cell lines appear to have type 2‐like activity, with the specific activity of A431 markedly greater than that of the other cell lines. Estradiol, progesterone, or EGE, alone or in combination, were without effect on the enzymatic activity of OVCAR‐3 cells. EGE decreased the activity of CAOV‐3 cells slightly. In contrast, EGE stimulated A431 17β‐hydroxysteriod oxidoreductase activity 7–8‐fold over a 5‐day exposure. Estradiol or progesterone, singly or in combination, also did not effect the enzymatic activity of A431 cells. However, progesterone inhibited the increase in activity seen in the presence of EGE. With EGE, estradiol, and progesterone together, the increase in enzymatic activity was comparable to that with EGE alone. The effects of estradiol and progesterone appear to result from steroid actions following binding of EGE to low‐affinity receptors on A431 cells. © 1995 Wiley‐Liss, Inc.
U2 and U1 snRNA gene loci associate with coiled bodies
Authors: Smith Kelly P. , Carter Kenneth C. , Johnson Carol V. , Lawrence Jeanne Bentley
Published: May 2005

The coiled bodies are nuclear structures rich in a variety of nuclear and nucleolar components including snRNAs. We have investigated the possibility that coiled bodies may associate with snRNA genes and report here that there is a high degree of association between U2 and U1 genes with a subset of coiled bodies. As investigated in human HeLa cells grown in monolayer culture, about 75% of the nuclei had at least one U2 gene associated with a coiled body, and 45% had at least one U1 locus associated. In another suspension‐grown HeLa cell strain, 92% of cells showed association of one or more U2 genes with coiled bodies. In contrast to the U2 and U1 gene associations, a locus closely linked to the U2 gene cluster appeared associated with a coiled body only in 10% of cells. Associated snRNA gene signals were repeatedly positioned at the edge of the coiled body. Thus, this association was highly nonrandom and spatically precise. Our analysis revealed a much higher frequency of association for closely spaced “doublet” U2 gene signals, with over 80% of paired signals associated as opposed to 35% for single U2 signals. This finding, coupled with the fact that not all genes were associated in all cells, suggested the possibility of a cell‐cycle‐dependent, possibly S‐phase, association. However, an analysis of S‐ and non‐S‐phase cells using BrdU incorporation or cell synchronization did not indicate an increased level of association in S‐phase. These and other results suggested that a substantial fraction of paired U2 signals represented association of U2 genes on homologous chromosomes rather than only replicated DNA. Furthermore, triple lable analysis showed that in a significant fraction of cells U1 and U2 genes were both associated with the same coiled body. U1 and U2 genes were closely paired in approximately 20% of cells, over 60% of which were associated with a readily identifiable coiled body. This finding raises the possibility that multiple genes of a particular class may be in association with each coiled body. Thus, the coiled body may be a dynamic structure which transiently interacts with or is formed by one or more specific genetic loci, possibly carrying out some function related to their expression. © 1995 Wiley‐Liss, Inc.
Nuclear domain 10 (ND10) associated proteins are also present in nuclear bodies and redistribute to hundreds of nuclear sites after stress
Authors: Maul Gerd G. , Yu Eunsil , Ishov Alexander M. , Epstein Alan L.
Published: May 2005

The promyelocytic leukemia protien fused to the retinoic acid receptor in t(15;17) acute promyelocytic leukemia, the primary biliary cirrhosis autoantigen, Sp100, as well as the incompletely charterized protien NDP55, are co‐localized in specific immunohistochemically defined nuclear domains (ND10), which are potential equyivalents of ultrastructurally defined nuclear bodies. We investigated whether the distribution of these proteins depends on environmental conditions and whether ND10 correlate with nuclear bodies. Certain nuclear bodies and ND10 react in a similar bodies, which herpes simplex virus infection or heat shock modify both. Redistribution of ND10‐associated proteins to hundreds of small sites throughout the chromatin was inducible by stress in the form of heat shock and exposure to Cd++ ions. The change of distribution was rapid and independent of proteins synthesis, and thus not part of the classical heat shock response. The very rapid redistribution of these proteins after heat shock, together with the development of ND10 upon interferon actication, raises the possibility that ND10 represent storage sites of certain matrix proteins readily accessible throughout the chromatin in response to stress or other effectors that induce global nuclear changes. © 1995 Wiley‐Liss, Inc.
Prothrombin cleavage by human vascular smooth muscle cells: A potential alternative pathway to the coagulation cascade
Authors: Benzakour Omar , Kanthou Chryso , Lupu Florea , Dennehy Ulla , Goodwin Chris , Scully Michael F. , Kakkar Vijay V. , Cooper David N.
Published: May 2005

Thrombin is a potent mitogen for human vascular smooth muscle cells (HVSMC) and its enzymatic activity is required for this function. The present study demonstrates that prothrombin is also mitogenic for HVSMC due to the generation of enzymatically active thrombin which occurs upon incubation of prothrombin with the cells. Analysis by SDS‐PAGE, immunoblotting, and amino acid sequencing revealed that prothrombin incubated with HVSMC undergoes limited proteolysis. Prethrombin 1 was formed through cleavage at R155‐S156. Cleavage at R271‐T272 generated fragment 1.2 and prethrombin 2 whilst cleavage at R284‐T285 yielded truncated prothrombin 2 (prethrombin 2′). However, cleavage at R320‐I321 which, during prothrombin activation produces two‐chain α‐thrombin, was not detectable. Studies on HVSMC‐conditioned medium revealed that a similar pattern of prothrombin cleavage occurred by a cell‐secreted factor(s). Amidolytic activity analysis indicated that 1–3% catalytically active thrombin‐like activity was generated upon incubation of prothrombin with HVSMC‐conditioned medium. By treating conditioned medium with various classes of proteinase inhibitors or hirudin, it was determined that prothrombin is cleaved by a cell‐derived serine proteinase‐like factor(s) at R271‐S272 and by α‐thrombin at R155‐S156 and R284‐T285. Antibodies neutralising the activity of either urokinase, tissue plasminogen activator, or factor Xa failed to alter the prothrombin cleaving activity of conditioned medium. This activity which may catalyse an alternative pathway for the generation of thrombin, was eluted from a gel filtration column as a single peak with apparent molecular mass of 30–40 kDa. © 1995 Wiley‐Liss, Inc.
Retrovirally mediated wild‐type p53 restores S‐phase modulation without inducing WAF1 mRNA in breast carcinoma cells containing mutant p53
Authors: Runnebaum Ingo B. , Wang Shan , Kreienberg Rolf
Published: May 2005

The mechanism of negative growth regulation by the nuclear phosphoprotein p53 in breast cancer cells may rely on its role as a transcriptional activator of cell cycle‐related genes. We have tested this hypothesis using retrovirally transduced wild‐type (wt) p53 in breast cancer cell lines containing homozygously endogenous mutant (mt) p53. Restoring the expression of wt p53, the percentage of cells in S phase was reduced, G1/S transition was slowed, and progression through S was restrained. The fraction of cells with a flattened “Cdk‐minus” phenotype increased 5‐ to 10‐fold. High constitutive mRNA expression of the cyclin‐Cdk inhibitor WAF1 in MDAMB231 cells was not induced upon restored wt p53 expression suggesting a p53‐independent pathway in the regulation of WAF1 mRNA expression. Wt p53 acted trans‐dominantly in the presence of accumulating mt p53 and installed a modulation of G1/S transition and S phase progression independent of WAF1 expression. © 1995 Wiley‐Liss, Inc.
Recovery of gold by electroless precipitation from acid solutions using polyaniline
Authors: Ting Y. P. , Neoh K. G. , Kang E. T. , Tan K. L.
Published: May 2005

The oxidation of the leucoemeraldine (LM) and emeraldine (EM) states of polyaniline (PAN) and the subsequent reprotonation and reduction of the nigraniline (NA) and pernigraniline (PNA) in acid gold solution were utilized for the spontaneous and sustained reduction of gold. The rate of Au reduction is strongly dependent on the intrinsic oxidation state of the polymer and the polymer surface area. The rate also increases with decreasing pH of the chloroauric solution to about pH ∼ 1. X‐ray photoelectron spectroscopic (XPS) results indicate that only elemental gold or Au(0) accumulates on the polymer surface. The N1s core‐level spectra of the protonated and base form of EM films after Au reduction confirm that the intrinsic structure of the polymer remains intact. The process, however, is limited by the decreasing effective surface area of the polymer due to Au deposition. The results indicate that an LM film accumulated up to five times its own weight of Au (Au/monomer mole ratio > 2) before the recovery rate was significantly retarded.
Use of capillary suction apparatus for estimating the averaged specific resistance of filtration cake
Authors: Lee Duu‐Jong , Hsu Yuan‐Hway
Published: May 2005

A method for estimating the averaged specific resistance of filtration cake, which avoids the necessity of measuring the liquid invasion volume in capillary suction apparatus (CSA) experiments, is proposed. When insufficient slurry is used, the slurry will exhaust during an experiment and the curve of wet front radius versus time shows transition. The transition point shifts according to the slurry concentration, cake specific resistance and the CSA parameters. Based on the wet front radius and the capillary suction time (CST) of the transition point, the liquid saturation under the inner cylinder can be estimated and the averaged specific resistance of cake calculated without the liquid invasion volume data. The proposed method agrees well with vacuum filtration data.
Scale‐up of a cyclone bioreactor
Authors: Sheppard John D. , Marchessault Philippe , Whalen Thomas , Barrington Suzelle F.
Published: May 2005

The operation of a cyclone bioreactor differs from conventional stirred tanks since the agitation is accomplished by means of a pumped reciculation loop. Oxygen transfer can occur across the swirling gas—liquid interface in the cyclone or from bubbles entrained in the recirculation loop. A cyclone bioreactor was scaled‐up from a 1 dm3 bench top unit to a 75 dm3 Process Development Unit (PDU). A reduction in the aspect ratio was compensated for by extending the length of the recirculation loop and providing additional aeration. Performance of the two reactors for the production of microbial poly‐β‐hydroxybutyrate (PHB) was compared under various operation conditions. The culture used for PHB production was Alcaligenes eutrophus DSM 545, grown on a mineral salts medium limited by the supply of nitrogen. The levels of dissolved oxygen obtained in the PDU were strongly dependent on the location at which the air was introduced into the reactor. However, with aeration balanced between two injection points and a similar level of power input, 17 J s−1 dm−3, the PDU was able to provide at least as much oxygen transfer capability as the laboratory‐scale reactor. Under all conditions tested, the PHB accumulation by A. eutrophus was in excess of 80% of the biomass dry weight, although the yield on glucose was lower in the PDU than in the laboratory‐scale reactor.
Residence time distribution measurements in a pulsed baffled tube bundle
Authors: Ni Xiongwei
Published: May 2005

Experimental flow pattern and associated residence time distribution measurements are reported for a tube bundle where periodic baffles and fluid oscillation may be present. When there is no fluid oscillation, high Reynolds number flow conditions are required to give sharp residence time distributions. When baffles are present, fluid oscillation can give sharp residence time distributions for modest low net flow Reynolds numbers. These observations extend our previous results and also show the viability of the system, for example in use as a reactor or heat exchanger where a multi‐tube configuration might be required.
Immobilization of an endopectinlyase on γ‐alumina: Study of factors influencing the biocatalytic matrix stability
Authors: Dinnella Caterina , Lanzarini Gaetano , Stagni Andrea , Palleschi Claudio
Published: May 2005

Endopectinlyase (EC 4.2.2.10) from Aspergillus japonicus was immobilized on to γ‐alumina. Adsorption performed at pH 5·0 and a subsequent cross‐linking phase using 0·1% glutaraldehyde were the chosen immobilization conditions. The comparison between the main biochemical parameters of the immobilized and free form of the enzyme showed that the immobilization procedure used did not affect the enzyme biochemical properties. The interactions between the carrier and the enzyme are essentially secondary bonding. In fact they depend on the pH and on the presence of phosphate ions in the medium. A tentative chemical model of the biocatalytic matrix thus obtained is proposed.
A lysine sensor for process control
Authors: Siegler Klaus , Weber Bettina , Weber Ekkehard , Tonder Karin , Klingner Edith , Riechert Frank
Published: May 2005

A lysine sensor for process control of lysine fermentation was developed based on a Clark‐type electrode in combination with L‐lysine‐α‐oxidase. The enzyme, isolated from Trichoderma viride, was immobilized between a cellulose and a polypropylene foil using a polyurethane resin. Lysine determinations were carried out in a flow‐through system as anodic measurements when H2O2 was measured and as chathodic measurements when the consumption of O2 was followed. The sensitivity of the sensor toward other amino acids was determined.
Residence time distribution in a packed bed bioreactor containing porous glass particles: Influence of the presence of immobilized cells
Authors: De Backer Luc , Baron Gino
Published: May 2005

An experimental investigation of the liquid phase residence time distribution (RTD) in a packed bed bioreactor containing porous glass particles is presented. For Re < 1, intraparticle forced convection is negligible and only diffusion, characterized by an effective diffusion coefficient, must be considered to describe the mass transfer process between the extraparticle and the intraparticle fluid phase. For Re > 1, the mass transfer rate becomes dependent on the liquid flow rate, indicating the existence of intraparticle convection. A model including axially dispersed flow for the external fluid phase and an ‘apparent’ effective diffusivity that combines diffusion and convection, predicts experimental RTD data satisfactorily. Yeast cells immobilized inside the porous glass beads did not affect the mass transfer rate at low biomass loading. At high biomass loading (0·02 g yeast cells g−1 carrier), the mass transfer rate between the extraparticle and intraparticle fluid phase was significantly decreased. Comparison of the RTD data from experimets performed in the presence and absence of cells in the external fluid phase revealed that the mass transfer rate is influenced by the cells immobilized inside the porous particles and not by the cells present in the external fluid phase.
Thermal properties of silicate esters
Authors: Alagar Muthu K. , Manohar Amsavel , Manohar Paramasivam
Published: May 2005

Fourteen dimethyldialkoxysilanes are prepared by reacting dimethyldichlorosilane with corresponding alcohols in the liquid phase. Their physicochemical properties are determined by standard methods and their tentative empirical formulae are elucidated. The thermal conductivity values of dimethyldialkoxysilanes are determined using a two slab guarded hot plate apparatus over a temperature range of 30–190°C. The thermal conductivity values of dimethyldialkoxysilanes calculated from empirical equations are found to vary from ‐14% to +19%. Because thermal conductivity is an important parameter in heat transfer calculations, and to minimise the deviation of the values, new equations involving easily measurable ultrasonic parameters have been formulated. The proposed equations have been tested for the series of dimethyldialkoxysilanes, tetraalkoxysilanes and polydimethylsiloxanes. The thermal conductivity values computed from the proposed equations are comparable with experimental thermal conductivity values. Further, an equation involving the calculation of thermal conductivity values at varying temperatures is also proposed.
Optimum conditions for the reactivity of chromium (III) salts on collagen in the solvent tanning process
Authors: Silvestre F. , Rocrelle C. , Rigal L. , Gaset A.
Published: May 2005

The reactivity of trivalent chromium salts towards collagen, the main protein in animal skins, was investigated in organic solvents on lamb skins of controlled water content. The optimal conditions were determined by experiment modelling. Complete exhaustion of the tanning baths, and much higher chromium binding was observed with this system than with traditional processes carried out in aqueous media.
Recovery of tartaric and malic acids from dilute aqueous effluents by solvent extaction technique
Authors: Malmary Guy , Vezier Annick , Robert Arlette , Molinier Jacques , Mourgues Jean , Conte Thierry
Published: May 2005

Solvent extraction deserves consideration for the recovery of carboxylic acids from wastewater in order to clean up industrial effluents. Tartaric and malic acids are present in low concentration in the effluents of distilleries producing grape sugar. The separation of these acids from dilute aqueous solutions by the technique of dissociation–extraction employing respectively tributylphosphate dissolved in dodecane and triisooctylamine (tris‐(6‐methylheptyl)‐amine) dissolved in 1‐octanol as solvents was explored in this study. With a solvent ratio of 0·5 and a solvent containing 0·6 mole of triisooctylamine per dm3 of the triisooctylamine + 1‐octanol mixture, the best percentages of malic and tartaric acids recovered were respectively 92 mass% and 99 mass% relative to the quantities of these acids present in the initial aqueous solutions.
Mechanical control of foaming in tower reactors
Authors: Takesono Satoshi , Onodera Masayuki , Yamagiwa Kazuaki , Ohkawa Akira
Published: May 2005

Rotating‐disk mechanical foam‐breakers (MFRDs) were applied to the control of foaming in bubble column (BC) reactors containing complex solutions and biological media. The foaming behaviour of BCs and the foam‐breaking behaviour of MFRDs fitted to BCs were evaluated respectively from the changes in the liquid hold‐up in ascending foam, ϕb, and the required critical disk rotational speed, Nc, for foam‐breaking. The differences in ϕb and Nc, reflecting the difficulty or ease of foam‐breaking among the liquids, correlated well with differences in the foaming characteristic term, FCT, of respective liquids, which could be determined on the basis of the results measured in the experimental small foaming apparatus which were different from those measured in the gas‐bubbling apparatus employed in practice. The usefulness of the empirical correlations for the prediction of ϕb and Nc, which can be applied independently of the type and concentration of foaming liquid or their physical properties, was also demonstrated.
Production of cellulases from coconut coir pith in solid state fermentation
Authors: Muniswaran P. K. Ananda , Selvakumar Pitchaivelu , Charyulu N. C. L. Narasimha
Published: May 2005

Coconut coir pith, available in abundance especially in tropical countries, was studied as a substrate for the production of cellulase[1,4(1,3;1,4)‐β‐D‐glucan 4‐glucanohydrolase, EC 3.2.1.4] and β‐D‐glucosidase(β‐D‐glucoside glucohydrolase, EC 3.2.1.21) in solid state fermentation. The effects of fermentation time, nutrient level, substrate particle size and inoculum size have been examined for optimal production of these enzymes by the fungal strain Aspergillus niger NCIM 1005. The highest filter paper activity (FPA) of 4.11 IU g−1, carboxyl methyl cellulose (CMCase) activity of 15·55 IU g−1 and cellobiase activity of 9·31 IU g−1 were obtained after 7 to 8 days of fermentation. Reese and Mandel's mineral solution in the substrate to mineral solution ratio of 1:10 (w/v) supported high cellulase and cellobiase activities. An inoculum size of 20–50% (v/v) based on the volume of mineral medium and substrate average particle size of 375 μm were optimum for enzyme production.
Investigation of the stability and selectivity of phenylalanine transport across a supported liquid membrane
Authors: Campbell Moray J. , Walter Robert P. , Knowles Christopher J. , Singleton Ray
Published: May 2005

A supported liquid membrane system was investigated for the carrier mediated transport of phenylalanine to more fully understand the contradictory effects, described in the literature, of chloride ion concentration in the aqueous phases on the stability of the system. The role of the organic phase and its interaction with carrier and support material was considered. The carrier mediated transport was comparable to an enzyme mediated process. Kinetic studies were undertaken and the data interpreted in a manner appropriate to biological transport processes to consider the transport process at a molecular level. The system was shown to deviate from a direct 1: 1 exchange process between phenylalanine and chloride and had a high degree of selectivity with respect to phenylalanine.
Energetics of Pseudomonas cepacia G4 growth in a chemostat with phenol limitation
Authors: Solomon Bamidele O. , Posten Clemens , Harder Michael P. F. , Hecht Volker , Deckwer Wolf‐Dieter
Published: May 2005

Analysis of the growth of Pseudomonas cepacia G4 on phenol in continuous culture has been carried out. The data were checked for consistency using both available electron and carbon balances. Coupled with the covariate adjustment estimation technique, the best estimates for true biomass energetic yield, ηmax and maintenance, me, were obtained when the carbon dioxide measurements were excluded. However, upon making corrections to the gas measurements, the best estimates were the maximum likelihood estimates (MLE) based on the complete data. The method therefore allows discrimination to be made between data. Also, similar estimates were obtained using Pirt's model based on the Monod approach and a modified form based on substrate uptake rate being the limiting factor. For the aerobic growth of P. cepacia G4 on phenol, ηmax = 0·417 and me = 0·0513 h−1 were obtained when the CO2 data were excluded. When corrections were made to the gas measurements to take into account the dissolved CO2 and the effect of operating temperature, ηmax = 0·432 and me = 0·0684 h−1 were obtained. From the 95% confidence intervals, a maximum of about 38–47·5% of the energy contained in phenol is incorporated into the biomass while the balance (52·5–62%) is evolved as heat with only a little energy needed for the maintenance of the organism.
Kinetics of anaerobic digestion of soft drink wastewater in immobilized cell bioreactors
Authors: Borja R. , Banks C. J.
Published: May 2005

A kinetic study of the anaerobic digestion of soft drink wastewater was undertaken, using bioreactors containing various suspended supports (bentonite, zeolite, sepiolite, saponite and polyurethane foam), on to which the microorganisms effecting the purification were immobilized. Assuming the overall anaerobic digestion process conforms to first‐order kinetics, the specific rate constants, K0, derived from the reactors with saponite and sepiolite (magnesium silicates) were approximately twice those from bentonite and zeolite (aluminium silicates) and almost five times higher than in the control reactor (without support); the polyurethane support showed an intermediate behaviour. The methanogenic activity increased linearly with COD load, with saponite and sepiolite supports showing the highest values. The average yield coefficient of methane was 325 cm3 CH4 STP g−1 COD and the percentage elimination of COD was 77·8%; these values were not significantly altered by the type of support used.
Catalysis by intermetallic compounds II. The behaviour of the pseudobinary alloy systems CeRh3–x Pdx and ZrRh3–xPdx for buta‐1,3‐diene hydrogenation
Authors: Bahia Amrik , Harris I. Rex , King Charles E. , Winterbottom John M.
Published: May 2005

The hydrogenation of buta‐1,3‐diene in the temperature range 45–110°C at 1 bar (101·5 kPa) total pressure has been studied using the pseudo‐binary alloy systems MRh3–x Pdx (M = Ce, Zr; 0 ≤ x ≤ 3) as catalysts. Characterisation studies show that surface and bulk Rh/Pd ratios are very similar but the surfaces were enriched particularly in cerium, with strong indications of oxide formation. Similar conclusions can be drawn with respect to zirconium but to a smaller extent. Differencs in product distributions, particularly in butene distributions are discussed in terms of two mechanisms which can interpret differences between the Rh‐rich system and the Pd‐rich system in respect of cis/trans‐but‐2‐ene ratios.
Effect of glucose concentration on citric acid production by Yarrowia lipolytica
Authors: Moresi Mauro
Published: May 2005

Citric acid production by Yarrowia lipolytica ATCC 20346 was studied in a laboratory‐scale fermenter and schematically subdivided into three different phases, appropriately characterised by unstructed kinetic models. As the sugar level in the growth medium was increased from 40 to 108 g dm−3; a negative effect on the kinetic growth rate constant of the trophophase was obtained, where both the yield coefficients for glucose and nitrogen were found to be approximately constant. By using a production medium devoid of nitrogen, a citrate lag phase was observed whilst the yeast reduced its intracellular nitrogen fraction from 7–8% (w/w) to a new equilibrium value as low as 2·3–4·4%. Finally, the idiophase was found to be a non‐growth associated process, the citric acid formation rate being dependent on the cellular nitrogen concentration only. The yield factors for citric, isocitric and fumaric acids appeared to be independent of the initial concentration of glucose in the production medium (Sop). However, the yield factors for α‐ketoglutaric, malic, pyruvic and cis‐aconitic acids exhibited a negative correlation with respect to Sop, being virtually equal to zero for Sop values greater than 160–175 g dm−3. The strain in question was capable of equalling the best mutant strains of Aspergillus niger used industrially in citric acid productivity (ca. 1·05 g dm−3 h−1), but not in selectivity, since citric acid represented only 85·5% of total citric and isocitric acid and 83·7% of the total acid.
Activated carbon from sugar cane bagasse by carbonization in the presence of inorganic acids
Authors: Girgis Badie S. , Khalil Laila B. , Tawfik Tarek A. M.
Published: May 2005

Dried ground bagasse, impregnated with 50% inorganic acids and carbonized at 500°C, showed the sequence H3PO4 > H2SO4 > HCl > HNO3, with respect to the efficiency of activation. Treatment with phosphoric acid of various concentrations (30–50 wt%) was followed by carbonization at 300–500°C for 3 h. Pore structure parameters were determined from the low‐temperature adsorption of nitrogen, by applying the BET and αs methods. Activated carbons obtained at low temperatures are essentially microporous with a low degree of mesoporosity. At higher temperatures products of higher surface area and total pore volume with developed mesoporosity and low microporosity are formed. An increase in the period of carbonization leads to a small decrease in both surface area and pore volume. Activated carbons with surface areas > 1000 m2 g−1 and mean pore dimensions around 2·0 nm, suitable for various purposes, are thus obtained.
Preparation of substituted carbonyl compounds by catalytic dehydrogenation of substituted alcohols
Authors: Gulková Daniela , Kraus Miloš
Published: May 2005

Possibilities for the preparation of substituted ketones by catalytic dehydrogenation of corresponding secondary alcohols were explored using a ZnO–Cr2O3 catalyst at 370–400°C. It was found that addition of about 1 wt% of sodium to the catalyst increases the yield of the ketone because the competitive dehydration of the alcohol is suppressed. Further improvement of the process was achieved by adding 20 wt% of water to the alcohol feed, which inhibited catalyst deactivation. Preparative experiments were conducted and 1‐methoxy‐2‐propanone, 1‐methoxy‐2‐butanone, 1‐phenoxy‐2‐propanone and 2‐methoxy‐1‐cyclohexanone were obtained.
Fourier‐transform infrared assay of bile salt‐stimulated lipase activity in reversed micelles
Authors: O'Connor Charmian J. , Cleverly Douglas R.
Published: May 2005

A Fourier‐transform infrared (FT‐IR) spectroscopic method has been developed for assaying the bile salt‐stimulated human milk lipase (BSSL, EC3.1) catalyzed hydrolysis of triolein in AOT reversed micelles in iso‐octane. At 37°C in 50 mmol dm−3 AOT the molar absorbtivities for the carbonyl stretching frequencies for triolein (at 1751 cm−1) and oleic acid (at 1714 cm−1) were 1646 dm3 mol−1 cm−1 and 743 dm−3 mol−1 cm−1, respectively. The rate was linearly dependent upon the concentration of enzyme in the water pool up to 10 mg cm−3 and maximum activity was observed at a ratio (w0) of [H2O]:[AOT] = 16·7. Using these conditions, and in the presence of 10 mmol dm−3 sodium taurocholate (TC), the derived Michaelis–Menten parameters Vmax and Km were 57·5 μmol min−1 mg−1 and 5·53 mmol dm−3, respectively. These results are compared with those obtained in an oil‐in‐water microemulsion system and are discussed in terms of the relative partitioning of the enzyme and the substrate in the aqueous and oil phases and the interfacial concentration of the substrate in the two systems.
Narrowing of alkylphenol ethoxylate distribution
Authors: Barhoum R. , Szymanowski J. , Hreczuch W. , Meissner Egbert
Published: May 2005

The homologue distribution of alkylphenol ethoxylates can be narrowed by using the non‐standard catalyst proposed for alcohol ethoxylation. The reaction is carried out at 180–185°C in the presence of 0·3% catalyst in relation to the alkylphenol. The formation of increased amounts of dioxane and polyglycols is not observed.
Synergistic extraction of penicillin G with aliphatic alcohols and butyl acetate
Authors: Yang Zhi‐Fa , Yu Shu‐Qiu , Chen Jia‐Yong
Published: May 2005

A solvent mixture of 1‐hexanol and butyl acetate has been successfully used for the extraction of penicillin G. This solvent mixture may not only synergistically and effectively extract penicillin G, but also inhibit emulsion formation during the extraction of penicillin G from the filtrate of the fermentation broth. The equilibrium constants of the extraction, the molar ratios of 1‐hexanol and penicillin G in the extracted species and the synergistic extraction of penicillin G have been studied by chemical analysis and by monitoring the absorbency shift in the FT‐IR spectra of the functional groups in the solvents.
The separation of pectinlyase from β‐glucosidase in a commercial preparation
Authors: Martino Angela , Pifferi Pier G. , Spagna Giovanni
Published: May 2005

This paper describes a new, simple and inexpensive procedure for separating pectinlyase (PL, EC 4.2.2.3) from β‐glucosidase (β‐glu, EC 3.2.1.21), both of which have potential for use in the beverage processing industry. The method described here, which entails the treatment of crude preparations with bentonite (4% (w/v)) and the acidification of the resulting supernatant to pH 3·5, leads to the production of two enzymic solutions which contain PL and β‐glu, respectively. In both solutions the amount of brown pigment is considerably less than in the crude mixture, and partial purification from extraneous proteins is also achieved.
Heavy metals in the environment. Part IV: An investigation into the solubility of metal chlorides in HCl‐saturated solutions and the recycling of high‐aluminium zinc residues in the zinc chloride process
Authors: Chaudhary Abdul J. , Donaldson John D. , Grimes Susan M. , Boddington Stephen C.
Published: May 2005

An investigation into the solubility of aluminium and lead chlorides in HCl‐saturated zinc chloride solutions and the use of high‐aluminium zinc residues in the production of zinc chloride solution is reported. The process developed involves leaching of the high‐aluminium zinc residues with concentrated hydrochloric acid followed by HCl gas treatment to reduce the concentration of aluminium and lead from zinc chloride solutions. The solubility of aluminium and lead chlorides in HCl‐saturated solutions depends on the zinc chloride concentration. The optimum zinc chloride concentration for maximum reduction in the aluminium and lead levels is 30–55% and 53% (w/w) respectively. Under optimum conditions the aluminium and lead concentrations are reduced to less than 0·1 and 0·9 mg cm−3 respectively.
Applications of supercritical CO2 extraction to microalgae and plants
Authors: Mendes Rui L. , Coelho José P. , Fernandes Helena L. , Marrucho Isabel J. , Cabral Joaquim M. S. , Novais Júlio M. , Palavra Antóanio F.
Published: May 2005

A flow apparatus was constructed to carry out studies of supercritical fluid extraction in the temperature range 298·15–353·15 K and pressures up to 40 MPa. To test the apparatus, studies on the solubility of naphthalene in CO2 at 308·15, 313·15 and 318·15 K and pressures up to 35 MPa were carried out. These experimental data were correlated through the Peng–Robinson equation of state. Samples of the microalgae Botryococcus braunii and Chlorella vulgaris which produce diolefines C25–C31 and carotenoids, respectively, were submitted to supercritical CO2. The extraction yields for these compounds were studied and compared with those obtained using organic solvents. Supercritical CO2 was also used to produce extracts from rosemary leaves (Rosmarinus officinalis L.), which were compared with those obtained by hexane extraction.
Resistance of recombinant proteins to proteolysis during folding and in the folded state
Authors: Fountoulakis Michael
Published: May 2005

Protein purification often involves the use of denaturing agents for solubilization. During refolding, following removal of the denaturants, the proteins of interest are exposed to proteases present in the expression system. Here the resistance of selected recombinant proteins to three widely used proteolytic enzymes, trypsin (EC 3.4.21.4), proteinase K (EC 3.4.21.14) and endoproteinase Glu‐C (EC 3.4.21.19), was investigated during folding and in the folded state. Target proteins and protease mixtures were denatured in 8 mol dm−3 urea and the proteins were allowed to refold by removal of the urea by dialysis. The proteolytic products were analyzed by sodium dodecyl sulfate–polyacrylamide gels and the protein digestion during folding was compared with the digestion under similar conditions in physiological buffer. Depending on the folding state of the proteins, the proteases had different effects on the substates. During folding, certain recombinant proteins were more efficiently digested by trypsin and, in particular, by proteinase K in comparison with digestion in the folded state, while other protein substrates were more resistant to proteolytic degradation in a denatured or partially denatured state than their folded counterparts. Incubation of most substrate proteins with endoproteinase Glu‐C yielded kinetics of digestion that were essentially similar for both partially folded and unfolded substrates. The results reported may be useful for protection of sensitive proteins and in studies of protein folding mechanisms.