bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of diffusion coefficients and diffusion characteristics for chlorferon and diethylthiophosphate in Ca‐Alginate gel beads
Authors: Ha Jiyeon , Engler Cady R. , Lee Seung Jae 
Published: December 2007

AbstractDiffusion characteristics of chlorferon and diethylthiophosphate (DETP) in Ca‐alginate gel beads were studied to assist in designing and operating bioreactor systems. Diffusion coefficients for chlorferon and DETP in Ca‐alginate gel beads determined at conditions suitable for biodegradation studies were 2.70 × 10−11 m2/s and 4.28 × 10−11 m2/s, respectively. Diffusivities of chlorferon and DETP were influenced by several factors, including viscosity of the bulk solution, agitation speed, and the concentrations of diffusing substrate and immobilized cells. Diffusion coefficients increased with increasing agitation speed, probably due to poor mixing at low speed and some attrition of beads at high speeds. Diffusion coefficients also increased with decreasing substrate concentration. Increased cell concentration in the gel beads caused lower diffusivity. Theoretical models to predict diffusivities as a function of cell weight fraction overestimated the effective diffusivities for both chlorferon and DETP, but linear relations between effective diffusivity and cell weight fraction were derived from experimental data. Calcium‐alginate gel beads with radii of 1.65–1.70 mm used in this study were not subject to diffusional limitations: external mass transfer resistances were negligible based on Biot number calculations and effectiveness factors indicated that internal mass transfer resistance was negligible. Therefore, the degradation rates of chlorferon and DETP inside Ca‐alginate gel beads were reaction‐limited. Biotechnol. Bioeng. 2008;100: 698–706. © 2007 Wiley Periodicals, Inc.
Hypoxic fed‐batch cultivation of Pichia pastoris increases specific and volumetric productivity of recombinant proteins
Authors: Baumann Kristin , Maurer Michael , Dragosits Martin , Cos Oriol , Ferrer Pau , Mattanovich Diethard 
Published: December 2007

AbstractHigh cell density cultivation of Pichia pastoris has to cope with several technical limitations, most importantly the transfer of oxygen. By applying hypoxic conditions to chemostat cultivations of P. pastoris expressing an antibody Fab fragment under the GAP promoter, a 2.5‐fold increase of the specific productivity qP at low oxygen supply was observed. At the same time the biomass decreased and ethanol was produced, indicating a shift from oxidative to oxidofermentative conditions. Based on these results we designed a feedback control for enhanced productivity in fed batch processes, where the concentration of ethanol in the culture was kept constant at approximately 1.0% (vv−1) by a regulated addition of feed medium. This strategy was tested successfully with three different protein producing strains, leading to a three‐ to sixfold increase of the qP and threefold reduced fed batch times. Taken together the volumetric productivity QP increased 2.3‐fold. Biotechnol. Bioeng. 2008;100: 177–183. © 2007 Wiley Periodicals, Inc.
Creating a spectrum of fibrocartilages through different cell sources and biochemical stimuli
Authors: Hoben Gwendolyn M. , Athanasiou Kyriacos A. 
Published: December 2007

AbstractIn this study a scaffoldless approach was employed with two different cell sources and biochemical stimuli to engineer a spectrum of fibrocartilages representative of the different regions of the knee meniscus. Constructs composed of 100% fibrochondrocytes (FC) or a 50:50 co‐culture of fibrochondrocytes and chondrocytes (CC) were cultured in 10% fetal bovine serum medium or serum‐free “chondrogenic” medium, each ±10 ng/mL TGF‐β1 (+T). Constructs from these two cell groups and four culture conditions were cultured for 6 weeks. By varying the cell type and presence of the growth factor, GAG per dry weight of the constructs spanned that of native tissue, ranging 16–45% and 1–7% in the CC and FC groups, respectively. Collagen density was most dependent on cell type and was significantly lower than tissue values. The collagen I/II ratio could be manipulated by cell type and serum presence to span the native range, from 3.5 in the serum‐free CC group to over 1,000 in the FC groups treated with serum‐containing medium. Using the CC cell group in the presence of serum‐free medium dramatically increased the compressive stiffness to 128 ± 34 kPa, similar to native tissue. Similarly, serum‐free medium or TGF‐β1 treatment enhanced the tensile modulus by an order of magnitude, up to 3,000 kPa. Using two cell sources and manipulating biochemical stimuli, a range of fibrocartilaginous neotissues was engineered. Fibrocartilages such as the knee meniscus are characterized by heterogeneity in matrix and functional properties, and this work demonstrates a strategy for recreating these heterogeneous tissues. Biotechnol. Bioeng. 2008;100: 587–598. © 2007 Wiley Periodicals, Inc.
Synthesis and Antifungal Activity of Aromatic Bis‐γ‐lactones Analogous to Avenaciolide
Authors: Castelo‐Branco Pedro A. , Rubinger Mayura M. M. , Alves Leandro de C. , de Barros Pauline M. , Pereira Sinval G. , de Melo Vanessa J. , Pilo‐Veloso Dorila , Zambolim Laércio 
Published: December 2007

AbstractAvenaciolide is a bis‐γ‐lactone isolated from Aspergillus avenaceus and possesses antifungal activity. Here, we describe the total syntheses and characterization by elemental analyses, and IR and NMR spectroscopy of three new bis‐γ‐lactones analogous to avenaciolide, where the octyl group of the natural product was replaced by aromatic groups. The effects of the avenaciolide, the novel compounds, and their synthetic precursors on the mycelia development and conidia germination of Colletotrichum gloeosporioides were evaluated in vitro. The new compounds were as active as avenaciolide in the tested conditions, while the synthetic precursors were inactive. The preparation and characterization of 15 new synthetic intermediates are also described.
Acute Toxicity of the Water‐Soluble Fraction of Spent Lubricating Oil on the African Catfish Clarias gariepinus
Authors: Ogali Regina E. , Osuji Leo C. , Ayodele Olufemi 
Published: December 2007

AbstractStatic tests were employed to assess the acute toxicity of the water‐soluble fraction (WSF) of spent automotive lubricating oil (of mixed SAE grades) on Clarias gariepinus, a freshwater fish commonly cultured in Nigeria. Median lethal concentrations (LC50) of the WSF were found to decrease as a function of exposure time from 690±21 (after 24 h) to 513±58 mg/l (after 96 h). The characteristics of the WSF such as mean acidity (pH 6.6), turbidity (40 NTU), total dissolved solids (TDS; 40 mg/l) and significantly reduced (P<0.05) dissolved‐oxygen (DO) values (1.44 mg/l) were not compliant with existing standards set for discharged effluents. The solubility of the detected straight‐chain aliphatics ranked as C14>C16>C32>C18>C28; that of the simple aromatics was ortho‐xylene>para‐xylene; and that of the polyaromatic hydrocarbons (PAHs) was acenaphthylene>9H‐fluorene>naphthalene>anthracene>phenanthrene>chrysene>benzo[k]fluoranthene>benzo[a]pyrene>benzo[b]fluoranthene, most of which being serious carcinogens. These oil constituents and the overall physico‐chemical properties of the WSF are expected to act synergistically on the test organism (C. gariepinus), eliciting the quantal responses observed. The toxicity of the WSF points to the base constituent, oxidative degradation, and mechano‐chemical reactions associated with aged crankcase oils. These oils, therefore, should definitely no longer be disposed into water streams or landscape, not even at sub‐lethal concentrations, because of the inherent toxicity of their soluble fractions and the associated danger of bioaccumulation.
Evolution of ‘Ligand‐Diffusion Chreodes’ on Protein‐Surface Models: A Genetic‐Algorithm Study
Authors: Marashi Sayed‐Amir , Kargar Mehdi , Katanforoush Ali , Abolhassani Hassan , Sadeghi Mehdi 
Published: December 2007

AbstractLattice models have been previously used to model ligand diffusion on protein surfaces. Using such models, it has been shown that the presence of pathways (or ‘chreodes’) of consecutive residues with certain properties can decrease the number of steps required for the arrival of a ligand at the active site. In this work, we show that, based on a genetic algorithm, ligand‐diffusion pathways can evolve on a protein surface, when this surface is selected for shortening the travel length toward the active site. Biological implications of these results are discussed.
Two New Antibacterial Sesquiterpenoids from Centipeda minima
Authors: Liang Heng‐Xing , Bao Fu‐Kai , Dong Xiao‐Ping , Zhu Hua‐Jie , Lu Xiao‐Jie , Shi Ming , Lu Qing , Cheng Yong‐Xian 
Published: December 2007

AbstractTwo new guaiane‐type sesquiterpene lactones, compounds 1 and 2, along with three known guaianolide‐ or pseudoguaianolides, were isolated from Centipeda minima (whole plant). Their structures were identified by spectroscopic and mass‐spectrometric analyses. The configuration at C(5) of the guaiane framework of 1 was rationalized by quantum‐mechanical calculations (Table 2). All compounds were found to be active against eight different microbial pathogens (Table 3), with MIC values in the range of 6.25–100 μg/ml.
Qualitative and Quantitative HPLC/MS Determination of Proanthocyanidins in Areca Nut (Areca catechu)
Authors: Wu Qingli , Yang Yonghong , Simon James E. 
Published: December 2007

AbstractProanthocyanidins (PACs) in areca nut (Areca catechu L.) were analyzed by high‐performance liquid chromatography (HPLC) combined with electrospray‐ionization mass spectrometry (ESI‐MS) and compared to grape seed extract. Under optimized conditions, the separated PACs were individually analyzed and identified on the basis of their [M+H]+ peaks. The PAC distribution in areca nut was found to be very similar to that in grape seed, but lacking any gallate conjugates. Based on reverse‐phase HPLC separation, the PAC monomers (+)‐catechin (CA, 1) and (−)‐epicatechin (EC; 2) were successfully quantified by ESI‐MS in the selected‐ion‐monitoring (SIM) mode, (−)‐epigallocatechin (EGC; 3) being used as internal standard. Detailed quality and validation assays showed that the accuracy and repeatability (n=8) were within 10% for each analyte.
Solid‐Phase Total Synthesis and Antimicrobial Activities of Loloatins A–D
Authors: Ding Yan , Qin Chuanguang , Guo Zhihong , Niu Weining , Zhang Ruijie , Li Yang 
Published: December 2007

AbstractThe first total synthesis of the decapeptide antibiotics loloatins A–D (1–4), originally isolated from the marine bacterial isolate MK‐PNG‐276A, possibly in the genus Bacillus, was accomplished by solid‐phase peptide synthesis (SPPS), followed by ‘head‐to‐tail’ cyclization of the activated linear precursors, without protection of nucleophilic side‐chain functions, on a safety‐catch resin. The synthetic peptides were equally active as the natural products isolated from the bacterial source and found to possess similar bacterial selectivity as other members in the family of amphipathic antimicrobial cyclic decapeptides.
Studies on the Cytotoxicity of Miscellaneous Compounds from Eupatorium betonicaeforme (D.C.) Baker (Asteraceae)
Authors: Rocha Danilo D. , Dantas Ivana N. F. , Albuquerque Maria Rose Jane R. , Montenegro Raquel C. , Pessoa Cláudia , de Moraes Manoel Odorico , Pessoa Otília Deusdênia L. , Silveira Edilberto R. , Costa‐Lotufo Letícia V. 
Published: December 2007

AbstractA detailed study on the cytotoxic effects of five known constituents isolated from the flowers and roots of Eupatorium betonicaeforme is reported, including 2,2‐dimethyl‐6‐vinylchroman‐4‐one (1), 2‐senecioyl‐4‐vinylphenol (2), 6‐acetyl‐2,2‐dimethylchroman‐4‐one (3), (4E)‐8β‐angeloyloxy‐9β,10β‐dihydroxy‐1‐oxogermacra‐4,11(13)‐dien‐12,6α‐olide (4), and 3β‐hydroxyicosan‐1,5β‐olide (5). The sesquiterpene lactone 4 exhibited the highest cytotoxicity, with IC50 values ranging from 3.9 to 9.9 μM, showing some degree of cell selectivity. The antiproliferative activity of 4 was examined towards HL‐60 cells, and found to diminish cell viability in a dose‐dependent manner. Moreover, at all concentrations tested, there was a decrease in the number of cells capable of incorporating 5‐bromo‐2′‐deoxyuridine (BrdU), indicating disruption of DNA synthesis. The morphological changes induced by 4 were compatible with apoptotic cell death. This work, thus, corroborates the anticancer potential of Eupatorium secondary metabolites.
High Diversity of Ligularia dictyoneura in Chemical Composition and DNA Sequence
Authors: Nagano Hajime , Iwazaki Yukiko , Matsushima Mika , Sato Masahiko , Gong Xun , Shen Yuemao , Hirota Hiroshi , Kuroda Chiaki , Hanai Ryo 
Published: December 2007

AbstractThe chemical composition of root extracts of the title species collected at 20 different places in the Hengduan Mountains of China was examined. From these samples, a total of 17 eremophilane derivatives were isolated, three of which were new franoeremophilane derivatives: 3β‐acetoxy‐6β‐(angeloyloxy)furanoeremophilan‐10β‐ol, 1α‐acetoxyfuranoeremophilan‐15,6α‐olide, and 6β‐[2‐(hydroxymethyl)prop‐2‐enoyloxy]furanoeremophil‐1(10)‐ene. Based on the chemical composition, the samples could be classified into as many as seven types: one type containing non‐furanoeremophilane derivatives and the other six containing furanoeremophilane derivatives with different oxidation levels. Results of DNA sequencing of the atpB‐rbcL region and the internal transcribed spacers of the ribosomal RNA gene also indicated a high diversity in the species.
Microcalorimetric and Spectroscopic Investigation of the Antibacterial Properties of Cationic Ytterbium(III)–Porphyrin Complexes Lacking Charged Peripheral Groups
Authors: Hou An‐Xin , Xue Zhi , Liu Yi , Qu Song‐Sheng , Wong Wai‐Kwok 
Published: December 2007

AbstractThe antibacterial activities towards Escherichia coli of two cationic YbIII–monoporphyrin complexes, [YbIII(TMP)(H2O)3]Cl (1) and [YbIII(TTP)(H2O)3]Cl (2), were investigated at the cellular and sub‐cellular levels. The biological effects of the complexes on the growth of E. coli were evaluated by microcalorimetry and by analysis of the resulting metabolic thermogenic curves, from which IC50 values and metabolic parameters such as growth rate and generation time were derived. At the subcellular level, DNA‐binding experiments were performed by means of UV/VIS‐ and fluorescence‐titration experiments, as well as by near‐infrared (NIR) emission, which revealed that 1 and 2 strongly bind to herring‐sperm DNA (HS‐DNA), though by different binding modes.
Three Novel, Structurally Unique Spirocyclic Alkaloids from the Halotolerant B‐17 Fungal Strain of Aspergillus variecolor
Authors: Wang Wen‐Liang , Zhu Tian‐Jiao , Tao Hong‐Wen , Lu Zhen‐Yu , Fang Yu‐Chun , Gu Qian‐Qun , Zhu Wei‐Ming 
Published: December 2007

AbstractDuring our search for novel antitumor lead compounds from microorganisms living under extreme conditions, three novel alkaloids, variecolortides A–C (1–3), were isolated from the mycelia of the halotolerant fungal strain Aspergillus variecolor B‐17. The new compounds were found to share an unprecedented ‘spiro‐anthronopyranoid diketopiperazine’ structure, with a stable hemiaminal function, as corroborated by in‐depth NMR‐spectroscopic and mass‐spectrometric analyses, as well as by a single‐crystal X‐ray analysis of 1. All compounds were shown to exhibit weak cytotoxic and antioxidant activities.
4′′′‐Acetylvitexin‐2″‐O‐rhamnoside, Isoorientin, Orientin, and 8‐Methoxykaempferol‐3‐O‐glucoside as Markers for the Differentiation of Crataegus monogyna and Crataegus pentagyna from Crataegus laevigata (Rosaceae)
Authors: Prinz Sonja , Ringl Alexandra , Huefner Antje , Pemp Enne , Kopp Brigitte 
Published: December 2007

AbstractIn our chemotaxonomic investigation of pharmaceutically relevant Crataegus species, the qualitative and quantitative flavonoid fingerprint of Crataegus monogyna and C. pentagyna is presented. Six flavonoids were identified as vitexin‐2″‐O‐rhamnoside (1), vitexin (2), isovitexin (3), rutin (4), hyperoside (5), and isoquercitrin (6). Besides the verification of the main compounds isoorientin (7) and orientin (8) in C. pentagyna, further four flavonoids were isolated and identified as isoorientin‐2″‐O‐rhamnoside (9), orientin‐2″‐O‐rhamnoside (10), isovitexin‐2″‐O‐rhamnoside (11), and 8‐methoxykaempferol‐3‐O‐glucoside (12) by means of 1D‐ and 2D‐NMR, MS, and UV analyses. Compound 12 was isolated for the first time from C. pentagyna. In contrast to C. pentagyna, C. monogyna samples were predominated by 4′′′‐acetylvitexin‐2″‐O‐rhamnoside (13), which was missing in C. pentagyna. Hence, 13 represents an interesting compound for chemotaxonomy of C. monogyna, whereas the main flavonoids 7, 8, and 12 could be proposed as markers for C. pentagyna. The absence of 7, 8, 12, and 13 in C. laevigata offers an appropriate tool for additional differentiation from C. monogyna and C. pentagyna, and for sample identification and quality control of the three main Crataegus species used in European phytotherapy.
Intra‐ and Intermolecular Interactions Influence the Reactivity of RNA Oligonucleotides
Authors: Linjalahti Heidi , Mikkola Satu 
Published: December 2007

AbstractThe transesterification of RNA oligonucleotides was studied over a wide pH range. The rate constants obtained indicate that, under neutral conditions, oligonucleotides with an adenosine moiety as the 5′‐linked nucleoside can be up to 1000‐fold more reactive than the reference oligonucleotide, a 13‐mer oligo‐U (1). Experiments with the modified oligonucleotide with N6,N6‐dimethyladenosine (9) as the 5′‐linked nucleoside moiety suggest that the exocyclic amino group is involved in the reaction, influencing the reactivity of the neighboring phosphodiester bond. In addition to such intramolecular interactions, weak intermolecular interactions most probably contribute to the reactivity.
Two New Alkaloids from Brachystemma calycinum and Their Inhibitory Effects on Lymphocyte Proliferation
Authors: Lu Qing , Zhang Li , He Guo‐Rong , Liang Heng‐Xing , Du Guan‐Hua , Cheng Yong‐Xian 
Published: December 2007

AbstractTwo new alkaloids, brachystemidines F (1) and G (2), were isolated from the roots of Brachystemma calycinum. Their structures were established on the basis of detailed spectroscopic analyses, including extensive NMR and HR‐MS techniques. Compound 2, which exhibits an unusual N‐hydroxydiazenyl (HONN) moiety, is a potent immunosuppressive agent, as demonstrated by inhibition of mouse T‐ and B‐lymphocyte proliferation, with IC50 values of 6.33 and 5.60 μg/ml, resp.
New Chiral Lanthanide Amide Ate Complexes for the Catalysed Synthesis of Scalemic Nitrogen‐Containing Heterocycles
Authors: Aillaud Isabelle , Collin Jacqueline , Duhayon Carine , Guillot Régis , Lyubov Dmitrii , Schulz Emmanuelle , Trifonov Alexander 
Published: December 2007

AbstractNew chiral binaphthylamido yttrium and ytterbium ate complexes with lithium and potassium counterions have been synthesised and characterised. X‐ray structures have been obtained for [Li(thf)4][Ln{(R)‐C20H12(NC5H9)2}2] (Ln=Yb, Y) and [K(thf)5][Yb{(R)‐C20H12(NCH2CMe3)2}2] as isostructural complexes. The efficiency of these complexes for the enantioselective intramolecular hydroamination was examined. [Li(thf)4][Yb{(R)‐C20H12(NC5H9)2}2] afforded the highest enantiomeric excess (up to 87 %) for the synthesis of a spiropyrrolidine, while [Li(thf)4][Y{(R)‐C20H12(NC5H9)2}2] proved to be slightly more active. The role of the counter cation in the active catalytic species was evidenced by the comparison between lithium and potassium ate complexes. The most active catalyst of this series, [Li(thf)4][Yb{(R)‐C20H12(NCH2CMe3)2}2], was successfully used for the cyclisation of aminopentenes with internal double bonds.
Antiaromaticity and Reactivity of a Planar Cyclooctatetraene Fully Annelated with Bicyclo[2.1.1]hexane Units
Authors: Nishinaga Tohru , Uto Takayuki , Inoue Ryota , Matsuura Akira , Treitel Noach , Rabinovitz Mordecai , Komatsu Koichi 
Published: December 2007

AbstractA detailed investigation has been made into the antiaromaticity and chemical reactivity of a planar cyclooctatetraene (COT) molecule fully annelated with bicyclo[2.1.1]hexane units 2. In spite of its planar 8π‐electronic structure, theoretical calculations have indicated that the antiaromaticity of COT 2 is considerably decreased in comparison with a planar COT 16 with D4h symmetry. This behavior appears to be related to the wider HOMO–LUMO gap of 2 relative to 16, which is caused by the raised LUMO level as a result of the effective σ–π* orbital interaction between the strained bicyclic framework and the COT π system. The two‐electron reduction of 2 required the use of potassium mirror or a combination of lithium/corannulene in highly dried [D8]THF at −78 °C under vacuum. In contrast, the [4+2] cycloaddition of 2 with tetracyanoethylene (TCNE) proceeded quite smoothly owing to the high‐lying HOMO. Reaction of 2 with meta‐chloroperbenzoic acid gave all‐trans tetraepoxide 23 in the same way as the corresponding benzene derivative 3. While the Simons–Smith‐type cyclopropanation of benzene 3 gave tricyclopropanated derivative 21, the reaction of 2 only afforded isomers of dicyclopropanated derivatives 25 and 26. Yet, the reactivity of 2 is higher than the parent COT, which does not show any reactivity under the same conditions. On the basis of homodesmic reactions, it was concluded that release of strain is also an important factor for such relatively high reactivity in the epoxidation and cyclopropanation of bicycloannelated COT 2 as well as benzene 3.
Exploring the Relation between Amplification and Binding in Dynamic Combinatorial Libraries of Macrocyclic Synthetic Receptors in Water
Authors: Corbett Peter T. , Sanders Jeremy K. M. , Otto Sijbren 
Published: December 2007

AbstractHerein we describe an extensive study of the response of a set of closely related dynamic combinatorial libraries (DCLs) of macrocyclic receptors to the introduction of a focused range of guest molecules. We have determined the amplification of two sets of diastereomeric receptors induced by a series of neutral and cationic guests, including biologically relevant compounds such as acetylcholine and morphine. The host–guest binding affinities were investigated using isothermal titration calorimetry. The resulting dataset enabled a detailed analysis of the relationship between the amplification of selected receptors and host–guest Gibbs binding energies, giving insight into the factors affecting the design, simulation and interpretation of DCL experiments. In particular, two questions were addressed: Is amplification by a given guest selective for the best receptor? And does the best guest induce the largest amplification of a given receptor? Our experimental results and computer simulations showed that the relative levels of amplification of hosts by a guest are well‐correlated with their relative affinities, and simulations have confirmed previous observations that amplification can be selective for the best receptor when only modest amounts of guest are used. In contrast, the correlation between guest binding and the extent of amplification of a given receptor across a wide range of guests tends to be poorer, because every guest has its own unique set of affinities for competing receptors in the DCL. This implies that the results of screening a DCL for selective receptors by comparing the response of the mixture to two different guests should be interpreted with caution. DCLs are complex mixtures in which all compounds are connected through a set of equilibria. Obtaining quantitative information about all host–guest binding constants from such systems will require the explicit and simultaneous consideration of all of the main equilibria within a DCL.