bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microfluidic delivery of small molecules into mammalian cells based on hydrodynamic focusing
Authors: Wang Fen , Wang Hao , Wang Jun , Wang Hsiang‐Yu , Rummel Peter L. , Garimella Suresh V. , Lu Chang 
Published: December 2007

AbstractMicrofluidics‐based cell assays offer high levels of automation and integration, and allow multiple assays to be run in parallel, based on reduced sample volumes. These characteristics make them attractive for studies associated with drug discovery. Controlled delivery of drug molecules or other exogenous materials into cells is a critical issue that needs to be addressed before microfluidics can serve as a viable platform for drug screening and studies. In this study, we report the application of hydrodynamic focusing for controlled delivery of small molecules into cells immobilized on the substrate of a microfluidic device. We delivered calcein AM which was permeant to the cell membrane into cells, and monitored its enzymatic conversion into fluorescent calcein during and after the delivery. Different ratios of the sample flow to the side flow were tested to determine how the conditions of hydrodynamic focusing affected the delivery. A 3D numerical model was developed to help understand the fluid flow, molecular diffusion due to hydrodynamic focusing in the microfluidic channel. The results from the simulation indicated that the calcein AM concentration on the outer surface of a cell was determined by the conditions of hydrodynamic focusing. By comparing the results from the simulation with those from the experiment, we found that the calcein AM concentration on the cell outer surface correlated very well with the amount of the molecules delivered into the cell. This suggests that hydrodynamic focusing provides an effective way for potentially quantitative delivery of exogenous molecules into cells at the single cell or subcellular level. We expect that our technique will pave the way to high‐throughput drug screening and delivery on a microfluidic platform. Biotechnol. Bioeng. 2008;100: 150–158. © 2007 Wiley Periodicals, Inc.
Thermodynamic and kinetic characterization using process dynamics: Acidophilic ferrous iron oxidation by Leptospirillum ferrooxidans
Authors: Kleerebezem Robbert , van Loosdrecht Mark C.M. 
Published: December 2007

AbstractKinetic and stoichiometric properties of acidophilic aerobic ferrous iron oxidation by growing and non‐growing Leptospirillum ferrooxidans cultures were investigated. The use of a continuous stirred tank reactor operated at a variable dilution rate and equipped with on‐line measurement of the electron donor, acceptor and anabolic substrate uptake rate enabled detailed kinetic characterization from a single experiment. It was demonstrated that substrate conversion and microbial growth are tightly coupled processes in L. ferrooxidans, and uncoupling occurs only due to the minor impact of substrate conversion for growth‐independent maintenance purposes. The tight stoichiometric coupling implies bioenergetic uncoupling of the catabolism and anabolism because the Gibbs energy change for ferrous iron oxidation as a function of the actual growth rate of the culture ranges from −45 to −25 kJ mol‐FeII−1. Bioenergetic description of the process could only be achieved by introduction of a growth rate dependent Gibbs energy dissipation term. Removal of carbon dioxide from the influent gas stopped biomass growth, but the biomass specific respiration rate was unaffected or slightly stimulated. The uncoupling of the catabolism and anabolism is suggested to induce instantaneously an energy dissipation pathway. Also dosage of a low concentration propionic acid resulted in complete inhibition of the anabolism. Propionic acid served as an uncoupler of the membrane potential and all catabolic energy is required for the increased maintenance requirements. Recovery of the anabolism after reestablishment of the normal cultivation conditions was obtained only after 1–2 days. The results obtained provide additional constraints on cultivation of L. ferrooxidans for biotechnological application. Biotechnol. Bioeng. 2008;100: 49–60. © 2007 Wiley Periodicals, Inc.
Transcriptional regulation of changes in growth, cell cycle, and gene expression of Saccharomyces cerevisiae due to changes in buoyancy
Authors: Coleman Chasity B. , Allen Patricia L. , Valles James M. , Hammond Timothy G. 
Published: December 2007

AbstractTo understand the cellular effects of magnetic traps requires independent analysis of the effects of magnetic field, gravity, and buoyancy. In the current study, buoyancy is manipulated by addition of Ficoll, a viscous substance that can create gradients of buoyancy without significantly affecting osmolality. Specifically, we investigated whether Ficoll induces concentration dependent changes in cell growth, cell cycle, and gene expression in Saccharomyces cerevisiae, with special attention paid to the neutrally buoyant concentration of 35% Ficoll. Cell growth and cell cycle analysis were examined in three strains: wild‐type (WT) yeast and strains with deletions in transcription factors Msn4 (Msn4Δ) or Sfp1 (Sfp1Δ). Changes in growth were observed in all three strains with WT and Msn4Δ strains showing strong concentration dependence. In addition, these changes in growth were supported by changes in the cell cycle of all three strains. Gene expression changes were observed in seven GFP‐reporter strains including: SSA4, YIL052C, YST2, Msn4ΔSSA4, Sfp1ΔSSA4, Msn4ΔYIL052C, and Sfp1ΔYIL052C. Buoyancy forces had selective concentration dependent effects on gene expression of SSA4 and YIL052C with transcription factor dependence on Msn4. Additionally, SSA4 expression was dependent on Sfp1. YST2 gene expression was not dependent on changes in buoyancy force. This study shows that buoyancy has selective and concentration dependent effects on growth, cell cycle and gene expression, some of which are Msn4 and Sfp1 dependent. For the first time, SSA4 gene expression is shown to be dependent on Sfp1 and YIL052C gene expression is dependent on Msn4. Biotechnol. Bioeng. 2008;100: 334–343. © 2007 Wiley Periodicals, Inc.
Controlling the membrane fluidity of yeasts during coupled thermal and osmotic treatments
Authors: Simonin Hélène , Beney Laurent , Gervais Patrick 
Published: December 2007

AbstractYeasts are often exposed to variations in osmotic pressure in their natural environments or in their substrates when used in fermentation industries. Such changes may lead to cell death or activity loss. Previous work by our team has allowed us to relate the mortality of cells exposed to a combination of thermal and osmotic treatments to leakage of cellular components through an unstable membrane when lipid phase transition occurs. In this study, yeast viability was measured after numerous osmotic and thermal treatments. In addition, the fluidity of yeast membranes was assessed according to aw and temperature by means of 1,6‐diphenyl‐1,3,5‐hexatriene (DPH) anisotropy measurement. The results show that there is a negative correlation between the overall fluidity variation undergone by membranes during treatments and yeast survival. Using a diagram of membrane fluidity according to aw and temperature, we defined dehydration and rehydration methods that minimize fluidity fluctuations, permitting significantly increased yeast survival. Thus, such membrane fluidity diagram should be a potential tool for controlling membrane state during dehydration and rehydration and improve yeast survival. Overall fluidity measurements should now be completed by accurate structural analysis of membranes to better understand the plasma membrane changes occurring during dehydration and rehydration. Biotechnol. Bioeng. 2008;100: 325–333. © 2007 Wiley Periodicals, Inc.
An actively mixed mini‐bioreactor for protein production from suspended animal cells
Authors: Diao Jinpian , Young Lincoln , Zhou Peng , Shuler Michael Louis 
Published: December 2007

AbstractBiopharmaceutical production would benefit from rapid methods to optimize production of therapeutic proteins by screening host cell line/vector combination, culture media, and operational parameters such as timing of induction. Miniaturized bioreactors are an emerging research area aiming at improving the development speed. In this work, a 3 mm thick mini‐bioreactor including two 12 mm wide culture chambers connected by a 5 mm wide channel is described. Active mixing is achieved by pressure shuttling between the two chambers. Gas‐liquid phase exchange for oxygen and carbon dioxide is realized by molecular diffusion through 50 µm thick polymethylpentene membranes. With this unique design, a velocity difference between the middle area and the side areas at the interfaces of the culture chambers and the connecting channel is created, which enhances the mixing efficiency. The observed mixing time is on the order of 100 s. The combination of high permeability toward oxygen of polymethylpentene membranes and fluid movement during active pressure shuttling enables higher volumetric oxygen transfer coefficients, 5.7 ± 0.4–14.8 ± 0.6 h−1, to be obtained in the mini‐bioreactors than the values found in traditional 50 mL spinner flasks, 2.0–2.5 h−1. Meanwhile, the calculated volume averaged shear stress, in the range of 10−2–10−1 N/m2, is within the typical tolerable range of animal cells. To demonstrate the applicability of this mini‐bioreactor to culture suspended animal cells, the insect cell, Spodoptera frugiperda, is cultured in mini‐bioreactors operated under a KLa value of 14.8 ± 0.6 h−1 and compared to the same cells cultured in 50 mL spinner flasks operated under a KLa value of 2.2 h−1. Sf‐21 cells cultured in the mini‐bioreactors present comparable length of lag phases and growth rates to their counterparts cultured in 50 mL spinner flasks, but achieve a higher maximum cell density of 5.3 ± 0.9 × 106 cell/mL than the value of 3.4 ± 0.4 × 106 cell/mL obtained by cells cultured in 50 mL spinner flasks. Sf‐21 cells infected with SEAP‐baculovirus produce a maximum SEAP concentration of 11.3 ± 0.7 U/mL when cultured in the mini‐bioreactor. In contrast, infected Sf‐21 cells cultured in 50 mL spinner flasks produce a maximum SEAP concentration of 7.4 ± 0.9 U/mL and onset of production is delayed from 18 h in minibioreactor to 40 h in spinner flasks. Biotechnol. Bioeng. 2008;100: 72–81. © 2007 Wiley Periodicals, Inc.
Monovalent cations and their influence on activated sludge floc chemistry, structure, and physical characteristics
Authors: Kara F. , Gurakan G.C. , Sanin F.D. 
Published: December 2007

AbstractMultivalent cations have been known to be important components of activated sludge floc structure due to their bridging ability of the negatively charged sites on the biopolymer network. Recently in batch systems it was found that excess concentration of monovalent cations led to the deterioration in settleability, dewaterability of sludges and effluent quality of the system. In this study, effect of influent monovalent cations (potassium and sodium) on activated sludge floc structure was investigated in semi‐continuous reactors. Results revealed that the increase in concentration of both ions correlated to the general increase in total EPS concentration. The zeta potential values were affected by the cation type and dose in such a way that sludge from sodium reactors had always higher zeta potential values (higher negative charge) than the sludges from potassium reactors. Flocs from sodium reactors were more fragile and weak and the capillary suction time values of these sludges were higher compared to those from potassium reactors. The findings of this research conclude that the floc structure is significantly weakened with the increase of monovalent cations. Even though EPS is produced, it is unable to bind the floc components together. With this, the physical properties of sludge deteriorate for both cations. Biotechnol. Bioeng. 2008;100: 231–239. © 2007 Wiley Periodicals, Inc.
Improved production of recombinant human antithrombin III in Chinese hamster ovary cells by ATF4 overexpression
Authors: Ohya Tomoshi , Hayashi Tetsuji , Kiyama Eriko , Nishii Hiroko , Miki Hideo , Kobayashi Kaoru , Honda Kohsuke , Omasa Takeshi , Ohtake Hisao 
Published: December 2007

AbstractTo improve the production of recombinant human antithrombin III (AT‐III) in Chinese hamster ovary (CHO) cells, the genes encoding transcription factors, ATF4 (activating transcription factor 4) and XBP‐1s (the spliced form of X‐box binding protein 1), which were involved in the mammalian unfolded protein response (UPR), were cloned from CHO‐K1 cells. Overexpression of ATF4 significantly enhanced the production of recombinant AT‐III in CHO 13D‐35D cells. The specific rate of AT‐III production in the ATF4‐overexpressed CHO 13D‐35D cells reached approximately 23 pg/cell/day. After 144 h of incubation, the AT‐III concentration in the culture supernatant was twofold greater compared to that observed with parental CHO 13D‐35D cells. In contrast, ectopic expression of XBP‐1s failed to enhance the production of recombinant AT‐III in CHO 13D‐35D cells. RT‐PCR analysis revealed that high levels of XBP‐1s mRNA were present in the CHO cells, regardless of ectopic expression of XBP‐1s. Our results indicate that overexpression of the UPR transcription factor ATF4 is a promising means for improving the production of secreted protein pharmaceuticals in CHO cells. Biotechnol. Bioeng. 2008;100: 317–324. © 2007 Wiley Periodicals, Inc.
Medium factor optimization and fermentation kinetics for phenazine‐1‐carboxylic acid production by Pseudomonas sp. M18G
Authors: He Li , Xu Yu‐Quan , Zhang Xue‐Hong 
Published: December 2007

AbstractWe investigated the production of biofungicide phenazine‐1‐carboxlic (PCA) by Pseudomonas sp. M18G, a gacA‐deficient mutant of M18 for PCA high‐production. Glucose was chosen as the optimal carbon source and soy peptone as the nitrogen source. A Plackett–Burman design revealed that glucose, soy peptone and NaCl were the most significant factors in PCA fermentation. Response surface methodology (RSM) and artificial neural network (ANN) models involving the significant factors were developed using common data. The prediction accuracy of ANN was slightly higher compared to RSM. The genetic algorithm (GA) was used to search the optimal input space of the trained ANN model and find the corresponding PCA yield. The optimum composition was found to be: glucose 34.3 g L−1, soy peptone 43.2 g L−1, NaCl 5.7 g L−1, and the predictive maximum PCA yield reached 980.1 µg mL−1. The optimized medium allowed PCA yield to be increased from 673.3 to 966.7 µg mL−1 after verification experiment tests. Additionally, PCA fermentation kinetics was investigated. Kinetic models based on the modified Logistic and Luedeking–Piret equations were developed, providing a good description of temporal variations of biomass (X), product (P), and substrate (S) in PCA fermentation. Biotechnol. Bioeng. 2008;100: 250–259. © 2007 Wiley Periodicals, Inc.
Microbial Transformation of Spirolaxine, a Bioactive Undecaketide Fungal Metabolite from the Basidiomycete Sporotrichum laxum
Authors: Nasini Gianluca , Bava Adriana , Fronza Giovanni , Giannini Giuseppe 
Published: December 2007

AbstractIncubation of (+)‐spirolaxine (=(3R)‐5‐hydroxy‐7‐methoxy‐3‐{5‐[(2R,5R,7R)‐2‐methyl‐1,6‐dioxaspiro[4.5]dec‐7‐yl]pentyl}‐2‐benzofuran‐1(3H)‐one; 1a) with Bacillus megaterium afforded two new mono‐ and one new dihydroxylated metabolite(s), all OH groups being introduced on the non‐activated six‐membered ring. In contrast, exposure of 1a to Cunninghamella echinulata gave rise to hydroxylation on the five‐membered ring of the parent structure. The structures and absolute configurations of the new products 1b–e were deduced on the basis of MS and NMR data. The metabolite 1b was investigated, in comparison to 1a, for its cytotoxicity (sulforhodamin‐B test) and for its antiproliferative activity towards bovine microvascular endothelial cells (BMEC).
Transcription‐Inhibition and Antitumor Activities of N‐Alkylated Tetraazacyclododecanes
Authors: Xiong Xiao‐Qin , Liang Feng , Yang Li , Wang Xiao‐Lin , Zhou Xiang , Zheng Cong‐Yi , Cao Xiao‐Ping 
Published: December 2007

AbstractA series of alkyl‐substituted tetraazacyclododecane congeners were synthesized, and their antitumor activities towards human HeLa cells as well as their effect on the in vitro transcription with T7 RNA polymerase were investigated. A structure–activity‐relationship (SAR) study identified the most‐active congeners as those with medium alkyl‐chain lengths. Three compounds, 5–7, were found to exhibit significant biological activities, with IC50 values towards HeLa cells in the low‐micromolar range.
Synthesis of Oligonucleotides Carrying 5′‐5′ Linkages Using Copper‐Catalyzed Cycloaddition Reactions
Authors: Alvira Margarita , Eritja Ramon 
Published: December 2007

AbstractThere is considerable interest in coupling oligonucleotides to molecules and surfaces. Although amino‐ and thiol‐containing oligonucleotides are being successfully used for this purpose, cycloaddition reactions may offer greater advantages due to their higher chemoselectivity and speed. In this study, copper‐catalyzed 1,3‐dipolar cycloaddition reactions between oligonucleotides carrying azido and alkyne groups are examined. For this purpose, several protocols for the preparation of oligonucleotides carrying these two groups are described. The non‐templated chemical ligation of two oligonucleotides via copper‐catalyzed [3+2] cycloaddition is described. By solid‐phase methodology, oligonucleotides carrying 5′‐5′ linkages can be obtained in good yields.
Arguside A: A New Cytotoxic Triterpene Glycoside from the Sea Cucumber Bohadschia argusJaeger
Authors: Liu Bao‐Shu , Yi Yang‐Hua , Li Ling , Zhang Shi‐Long , Han Hua , Weng Yi‐Yi , Pan Min‐Xiang 
Published: December 2007

AbstractA new holostane‐based triterpene glycoside, arguside A (1), was isolated from the sea cucumber Bohadschia argus, collected in the South China Sea. The structure of the new compound was elucidated by spectroscopic and mass‐spectrometric analyses, in combination with chemical transformations. Compound 1 exhibited significant cytotoxicity against different human tumor cell lines, being more active towards HCT‐116 cells (IC50=0.14 μM) than 10‐hydroxycamptothecin (HCP) used as positive control.
Glucosides from the Roots of Capparis tenera
Authors: Su Dong‐Min , Wang Ying‐Hong , Yu Shi‐Shan , Yu De‐Quan , Hu You‐Cai , Tang Wen‐Zhao , Liu Geng‐Tao , Wang Wen‐Jie 
Published: December 2007

AbstractTwo new lignan glucosides, compounds 2 and 3, two new 1H‐indole‐alkaloid glucosides, 5 and 6, as well as two new phenolic glucosides, 7 and 10, were isolated from the roots of Capparis tenera, together with five known compounds. Their structures were characterized by chemical and spectroscopic methods. Most of these isolates were obtained for the first time from Capparidaceae. The antioxidant and anti‐inflammatory activities of the new compounds were investigated.
Redox Processes of Sulfur and Manganese in a Constructed Wetland
Authors: Šíma Jan , Diáková Kateřina , Holcová Veronika 
Published: December 2007

AbstractConstructed wetlands are very popular in terms of wastewater treatment today. Formation of redox potential gradients inside such a system strongly influences the wastewater‐treatment efficiency. Individual oxidation forms of sulfur, and dissolved and precipitated manganese forms were determined in the vegetation bed of the constructed wetland. The aim of the speciation analysis was to contribute to the characterization of its redox properties. Sulfur was mostly oxidized at the inflow. The concentration of sulfates at the inflow varied from 25 to 55 mg/l, while concentration of sulfides was always lower than 6.0 mg/l and mostly even lower than 1.0 mg/l. However, sulfates were reduced during the pretreatment and the wastewater flow through the vegetation bed. The concentration of total manganese varied from 0.2 to 0.8 mg/l. Approximately 60% of Mn was precipitated at the inflow. The content of precipitated Mn forms declined to ca. 40–50% at the inflow zone, this content was almost constant across the vegetation bed to the outflow when water was sampled from 60‐cm depth. However, the content of precipitated Mn forms increased to ca. 74% for samples from 20‐cm depth. With respect to the aeration of the system, manganese can be precipitated as MnO2 in these samples.
Tetralones and Flavonoids from Pyrola calliantha
Authors: Liu Lei , Li An‐Liang , Zhao Ming‐Bo , Tu Peng‐Fei 
Published: December 2007

AbstractTwo new tetralones, pyrolones A (1) and B (2), and a new flavonol glycoside, 2″‐O‐(4‐hydroxybenzoyl)hyperin (3), were isolated from Pyrola calliantha (whole plant), together with six structurally related compounds, including 2″‐O‐galloylhyperin (4), hyperin (5), formononetin (6), quercetin 3‐O‐α‐L‐arabinopyranoside (7), quercetin 3‐O‐α‐L‐arabinofuranoside (8), and kaempferol 3‐O‐β‐D‐galactopyranoside (9). The structures and absolute configurations of the new compounds were elucidated on the basis of spectroscopic (UV, ORD, CD, NMR) and mass‐spectrometric (HR‐ESI‐MS) analyses.
Decrypting the TEM Images for Deciphering the Microstructural Code of Complex Oxides
Authors: Hervieu Maryvonne , Martin Christine , Pérez Olivier , Retoux Richard , Malo Sylvie 
Published: December 2007

AbstractThe knowledge of the structure of the real solids is required for achieving the desired architectures in the research of new materials and/or optimizing the relationships between structure and properties. Understanding complex oxides needs accurate characterization at different length scales and the combined application of all solid‐state techniques. Deciphering the relationships between all this information provides codes that allow the identification of the different structural levels, their roles and the way they interact. These step‐by‐step routes are illustrated through two basic mechanisms of solid‐state chemistry: to determine the building units of one complex oxide in order to predict the existence of other arrangements on the one hand and to correlate complex ordering phenomena, such as those involving charges, orbitals and spins of manganese atoms in perovskite‐type manganites on the other hand.