bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen supply controls the onset of pristinamycins production by Streptomyces pristinaespiralis in shaking flasks
Authors: Mehmood N. , Olmos E. , Goergen J‐L. , Blanchard F. , Ullisch D. , Klöckner W. , Büchs J. , Delaunay S. 
Published: April 2011

AbstractAntibiotics are secondary metabolites, generally produced during stationary phase of growth under different nutritional and hydrodynamic stresses. However, the exact mechanisms of the induction of antibiotics production are still not clearly established. In a previous study, the induction of pristinamycins production by Streptomyces pristinaespiralis as well as product concentrations were correlated with power dissipation per unit of volume (P/V) in shaking flasks. In this study, detailed kinetics of growth, substrate consumption, oxygen transfer rate and pristinamycins production under varying P/V conditions have been obtained and analyzed. Our results showed that higher P/V resulted in a higher concentration of biomass and promoted an earlier nutrient limitation and ultimately an earlier induction of pristinamycins production. The maximal specific growth rate, specific oxygen consumption rate and specific consumption rate of glutamate increased with P/V while influence was less marked with specific consumption rate of glucose, arginine, ammonium ions and phosphate. When oxygen uptake rate (OUR) was limited by free‐surface oxygen transfer, pristinamycins production was not detected despite the occurrence of nitrogen and/or phosphate sources limitation. The threshold value for OUR observed was around 25 mmol L−1 h−1. This suggested that a limitation in nitrogen and/or phosphate alone was not sufficient to induce pristinamycins production by S. pristinaespiralis pr11. To induce this production, the oxygen transfer had to be non‐limiting. Biotechnol. Bioeng. 2011;108:2151–2161. © 2011 Wiley Periodicals, Inc.
Saturation of transgene protein synthesis from mRNA in cells producing a large number of transgene mRNA
Authors: Takahashi Yuki , Nishikawa Makiya , Takiguchi Naomi , Suehara Tetsuya , Takakura Yoshinobu 
Published: April 2011

AbstractExperimental results have suggested that transgene expression can be saturated when large amounts of plasmid vectors are delivered into cells. To investigate this saturation kinetic behavior, cells were transfected with monitoring and competing plasmids using cationic liposomes. Even although an identical amount of a monitoring plasmid expressing firefly luciferase (FL) was used for transfection, transgene expression from the plasmid was greatly affected by the level of transgene expression from competing plasmids expressing renilla luciferase (RL). Similar results were obtained by exchanging the monitoring and competing plasmids. The competing plasmid‐dependent reduction in transgene expression from the monitoring plasmid was also observed in mouse liver after hydrodynamic injection of plasmids. On the other hand, the mRNA and protein expression level of glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), an endogenous gene, in the liver hardly changed even when transgene expression process is saturated. The expression of FL from a monitoring plasmid was significantly restored by siRNA‐mediated degradation of RL mRNA that was expressed from a competing plasmid. These results suggest that the efficiency of protein synthesis from plasmid vectors is reduced when a large amount of mRNA is transcribed with no significant changes in endogenous gene expression. Biotechnol. Bioeng. 2011;108: 2380–2389. © 2011 Wiley Periodicals, Inc.
Kinetic modeling of light limitation and sulfur deprivation effects in the induction of hydrogen production with Chlamydomonas reinhardtii. Part II: Definition of model‐based protocols and experimental validation
Authors: Degrenne B. , Pruvost J. , Titica M. , Takache H. , Legrand J. 
Published: April 2011

AbstractPhotosynthetic hydrogen production under light by the green microalga Chlamydomonas reinhardtii was investigated in a torus‐shaped PBR in sulfur‐deprived conditions. Culture conditions, represented by the dry biomass concentration of the inoculum, sulfate concentration, and incident photon flux density (PFD), were optimized based on a previously published model (Fouchard et al., 2009. Biotechnol Bioeng 102:232–245). This allowed a strictly autotrophic production, whereas the sulfur‐deprived protocol is usually applied in photoheterotrophic conditions. Experimental results combined with additional information from kinetic simulations emphasize effects of sulfur deprivation and light attenuation in the PBR in inducing anoxia and hydrogen production. A broad range of PFD was tested (up to 500 µmol photons m−2 s−1). Maximum hydrogen productivities were 1.0 ± 0.2 mL H2/h/L (or 25 ± 5 mL H2/m2 h) and 3.1 mL ± 0.4 H2/h L (or 77.5 ± 10 mL H2/m2 h), at 110 and 500 µmol photons m−2 s−1, respectively. These values approached a maximum specific productivity of approximately 1.9 mL ± 0.4 H2/h/g of biomass dry weight, clearly indicative of a limitation in cell capacity to produce hydrogen. The efficiency of the process and further optimizations are discussed. Biotechnol. Bioeng. 2011;108: 2288–2299. © 2011 Wiley Periodicals, Inc.
A new direction for anticoagulants: Inhibiting fibrin assembly with PEGylated fibrin knob mimics
Authors: Stabenfeldt Sarah E. , Aboujamous Nader M. , Soon Allyson S.C. , Barker Thomas H. 
Published: April 2011

AbstractCurrent anticoagulants target coagulation factors upstream from fibrin assembly and polymerization (i.e., formation of fibrin clot). While effective, this approach requires constant patient monitoring since pharmacokinetics and pharmacodynamics vary from patient to patient. To address these limitations, we developed an alternative anticoagulant that effectively inhibits fibrin polymerization. Specifically, we investigated PEGylated fibrin knob “A” peptides, evaluating the effect of both polyethylene glycol (PEG) chain length (0, 2, 5, and 10–30 kDa) and knob peptide sequence (GPRPAAC, GPRPFPAC, and GPRPPERC) on inhibiting fibrin polymerization (i.e., clot formation). Thrombin‐initiated clotting assays with purified fibrinogen were performed to compare clot formation with each peptide–PEG conjugate. Results indicated a biphasic effect of PEG chain length, whereby, active‐PEG conjugates demonstrated increasingly enhanced inhibition of fibrin polymerization from 0 to 5 kDa PEG. However, the anticoagulant activity diminished to control levels for PEG chains above 5 kDa. Ultimately, we observed a 10‐fold enhancement of anticoagulant activity with active peptides PEGylated with 5 kDa PEG compared to non‐PEGylated knob peptides. The sequence of the active peptide significantly influenced the anticoagulant properties only at the highest 1:100 molar ratio where GPRPFPAC‐5 kDa PEG and GPRPPERC‐5 kDa PEG demonstrated significantly lower percent clottable protein than GPRPAAC‐5 kDa PEG. Moreover, human plasma treated with the active 5 kDa PEG conjugate exhibited delayed prothrombin time to within the therapeutic range specified for oral anticoagulants. Collectively, this study demonstrated the utility of PEGylated fibrin knob peptides as potential anticoagulant therapeutics. Biotechnol. Bioeng. 2011;108: 2424–2433. © 2011 Wiley Periodicals, Inc.
Influence of steam pretreatment severity on post‐treatments used to enhance the enzymatic hydrolysis of pretreated softwoods at low enzyme loadings
Authors: Kumar Linoj , Chandra Richard , Saddler Jack 
Published: April 2011

AbstractIt is recognized that some form of post‐treatment will usually be required if reasonable hydrolysis yields (>60%) of steam pretreated softwood are to be achieved when using low enzyme loadings (5 FPU/g cellulose). In the work reported here we modified/removed lignin from steam pretreated softwood while investigating the influence that the severity of pretreatment might have on the effectiveness of subsequent post‐treatments. Although treatment at a lower severity could provide better overall hemicellulose recovery, post‐treatment was not as effective on the cellulosic component. Pretreatment at medium severity resulted in the best compromise, providing reasonable recovery of the water soluble hemicellulose sugars and the use of post‐treatment conditions that significantly increased the enzymatic hydrolysis of the water insoluble cellulosic component. Post‐treatment with alkaline hydrogen peroxide or neutral sulfonation resulted in 62% cellulose hydrolysis at an enzyme loading of 5 FPU/g cellulose, which was four times greater than was obtained when the cellulosic fraction was not post‐treated. When the enzyme loading was increased to 15 FPU/g cellulose, the post‐treated cellulosic fraction was almost completely hydrolyzed to glucose. Despite the higher lignin content (44%) of the sulfonated substrate, similar hydrolysis yields to those achieved after alkaline peroxide post‐treatment (14% lignin content) indicated that, in addition to lignin removal, lignin modification also plays an important role in influencing the effectiveness of hydrolysis when low enzyme loadings are used. Biotechnol. Bioeng. 2011;108: 2300–2311. © 2011 Wiley Periodicals, Inc.
Engineered Bacterial Mimics of Human Drug Metabolizing Enzyme CYP2C9
Authors: Rentmeister Andrea , Brown Tristan R. , Snow Christopher D. , Carbone Martina N. , Arnold Frances H. 
Published: April 2011

AbstractSimple and universal methods for the preparation of human drug metabolites are required to produce quantities sufficient for their characterization and toxicity testing. Synthetic chemistry lacks general catalysts for selective oxidation of unactivated CH bonds, a transformation that plays a key role in metabolism; bioconversions using P450 enzymes have emerged as a powerful alternative. Variants of P450BM3 from Bacillus megaterium act on diverse substrates, including drugs. Acidic substrates, such as the compounds metabolized by CYP2C9, which is one of three main hepatic human P450s, are not accepted by P450BM3 variants engineered to date. Herein, we report bacterial mimics of CYP2C9, which are active on two widely administered drugs, naproxen and ibuprofen, that are CYP2C9 substrates in vivo. These P450BM3 variants can also act on desmethylnaproxen, the human metabolite of naproxen, and convert it to the 1,4‐naphthoquinone derivative. We analyzed the crystal structure of the heme domain of an early intermediate in the directed‐evolution experiment. The active site mutation, L75R, which initially conferred activity on charged substrates, dramatically increased structural flexibility in the B′‐helix. This increased flexibility, which was accompanied by a dramatic decrease in enzyme stability, may contribute to the variant’s ability to accept a broader range of substrates.
Mechanism and Site Requirements of Thiophene Hydrodesulfurization Catalyzed by Supported Pt Clusters
Authors: Wang Huamin , Iglesia Enrique 
Published: April 2011

AbstractKinetic, isotopic, and chemical analysis methods are used to examine the identity and kinetic relevance of elementary steps and the effects of Pt cluster size on thiophene hydrodesulfurization (HDS) turnover rates. Quasi‐equilibrated H2 and H2S heterolytic dissociation steps lead to sulfur chemical potentials given by the prevalent H2S/H2 ratio and to cluster surfaces with a metallic bulk, but near‐saturation sulfur coverages, during steady‐state catalysis. Sulfur‐vacancies on such surfaces are required for η1(S) or η4 thiophene adsorption modes and for H2 and H2S dissociation steps. H‐assisted CS bond cleavage of η1(S) thiophene and H‐addition to η4 thiophene limits rates of direct desulfurization and hydrogenation sulfur removal pathways, respectively. These steps, their kinetic relevance, and the prevalent sulfur‐saturated surfaces resemble those on Ru clusters; they are also consistent with the observed kinetic effects of reactants and products on rates, with the rapid isotopic exchange in H2/D2/H2S mixtures during HDS catalysis, and with measured H2/D2 kinetic isotope effects. Small Pt clusters exhibit lower turnover rates, stronger inhibition by H2S, and a greater preference for desulfurization pathways than those of large clusters. These effects reflect the prevalence of coordinatively unsaturated corner and edge sites on small clusters, which bind sulfur atoms more strongly and lead to lower densities of vacancies and to a preference for η1(S)‐bound thiophene species. Sulfur binding energies and their concomitant effects on the number of available vacancies also account for the higher turnover rates measured on Pt clusters compared with Ru clusters of similar size. These data and their mechanistic interpretation suggest that the concepts and steps proposed here apply generally to hydrogenation and direct desulfurization of organosulfur compounds. Taken together with similar observed effects of oxygen binding strength, metal identity, and cluster size for oxidation reactions of NO, hydrocarbons, and oxygenates, which also require vacancies in their respective kinetically relevant steps, these data also indicate that low reactivity of small clusters may reflect in most instances their coordinative unsaturation and the concomitant kinetic and thermodynamic preference for low vacancy concentrations on nearly saturated surfaces.
Neutral Tellurium Rings in the Coordination Polymers [Ru(Te9)](InCl4)2, [Ru(Te8)]Cl2, and [Rh(Te6)]Cl3
Authors: Günther Anja , Isaeva Anna , Baranov Alexey I. , Ruck Michael 
Published: April 2011

AbstractShiny black, air‐insensitive crystals of tellurium‐rich one‐dimensional coordination polymers were synthesized by melting a mixture of the elements with TeCl4. The compounds [Ru(Te9)](InCl4)2and [Ru(Te8)]Cl2crystallize in the monoclinic space group typeC2/c, whereas [Rh(Te6)]Cl3adopts the trigonal space group typeRc. In the crystal structures, linear, positively charged [Mm+(Ten±0)] (M=Ru,m=2; Rh,m=3) chains run parallel to thecaxes. Each of the uncharged Tenmolecules (n=6, 8, 9) coordinates two transition‐metal atoms as a bridging bis‐tridentate ligand. Because the coordinating tellurium atoms act as electron‐pair donors, the 18‐electron rule is fulfilled for the octahedrally coordinated transition‐metal cations. Based on DFT calculations, the quantum theory of atoms in molecules (QTAIM) and the electron localizability indicator (ELI) provide insight into the principles of the polar donor bonding in these complexes. Comparison with optimized ring geometries reveals substantial tension in the coordinating tellurium molecules.
ChemInform Abstract: Low‐Symmetry Uranyl Pyrophosphate Cage Clusters.
Authors: Ling Jie , Qiu Jie , Szymanowski Jennifer E. S. , Burns Peter C. 
Published: April 2011

AbstractNa64Li26 [(UO2)45(O2)44 (P2O7)23]·3H2O is obtained by self‐assembly from a solution containing UO2(NO3)2, LiOH, H2O2, Na2P2O7, and (COOH)2 (air, 24 h).
ChemInform Abstract: Practical Access to Highly Enantioenriched Quaternary Carbon Michael Adducts Using Simple Organocatalysts.
Authors: Nugent Thomas C. , Shoaib Mohammad , Shoaib Amna 
Published: April 2011

AbstractMichael addition of α‐branched aldehydes towards nitroolefins is efficiently catalyzed by an organocatalyst consisting of O‐tert‐butylthreonine as amino acid, sulfamide as hydrogen bond donor and DMAP as base.
ChemInform Abstract: Hydrogen Bond Induced Enantioselectivity in Mn(salen)‐Catalyzed Sulfoxidation Reactions.
Authors: Voss Felix , Herdtweck Eberhardt , Bach Thorsten 
Published: April 2011

AbstractA novel MnCl(salen)‐derived complex is synthesized and applied as chiral catalyst in enantioselective sulfoxidation reactions.
ChemInform Abstract: In situ Generation of Palladium Nanoparticles: Reusable, Ligand‐Free Heck Reaction in PEG‐400 Assisted by Focused Microwave Irradiation.
Authors: Du Zhengyin , Zhou Wanwei , Bai Lin , Wang Fen , Wang Jin‐Xian 
Published: April 2011

AbstractPolyethylene glycol 400 is found to reduce Pd(II) to Pd(0) and acts as stabilizer for the Pd‐nanoparticles.
ChemInform Abstract: A General and Selective Iron‐Catalyzed Aminocarbonylation of Alkynes: Synthesis of Acryl‐ and Cinnamides.
Authors: Driller Katrin Marie , Prateeptongkum Saisuree , Jackstell Ralf , Beller Matthias 
Published: April 2011

AbstractUnder an optimized CO pressure and use of a diazabutadiene as ligand, the chemoselective monocarbonylation of a variety of aromatic or aliphatic terminal alkynes in the presence of primary or secondary amines is achieved, to give in all cases (E)‐configurated α,β‐unsaturated amides.
ChemInform Abstract: Catalytic Asymmetric Synthesis of γ‐Substituted Vinyl Sulfones.
Authors: Lopez Rosa , Zalacain Maitane , Palomo Claudio 
Published: April 2011

AbstractThe conjugate addition of β‐nitroethylsulfones as bench‐storable readily available new formal β‐sulfonyl vinyl anions offers the advantages of a simple one‐pot procedure without the need for intermediate isolation, the use of an organocatalyst in substoichiometric quantities, very high chemical efficiency and great substrate tolerance.
ChemInform Abstract: Pd/PR3‐Catalyzed Cross‐Coupling of Aromatic Carboxylic Acids with Electron‐Deficient Polyfluoroarenes via Combination of Decarboxylation with sp2 C—H Cleavage.
Authors: Zhao Huaiqing , Wei Ye , Xu Jing , Kan Jian , Su Weiping , Hong Maochun 
Published: April 2011

AbstractUnfortunately, aromatic carboxylic acids without ortho‐ substituents do not yield the desired coupling products.
ChemInform Abstract: Solid‐Supported Palladium Nano and Microparticles: An Efficient Heterogeneous Catalyst for Ligand‐Free Suzuki—Miyaura Cross Coupling Reaction.
Authors: Das Pralay , Sharma Dharminder , Shil Arun K. , Kumari Avnesh 
Published: April 2011

AbstractThe catalyst can be reused up to 7 runs without significant loss of activity and it is stable enough under moist conditions.
ChemInform Abstract: Vinyldisiloxanes: Their Synthesis, Cross‐Coupling and Applications.
Authors: Sore Hannah F. , Boehner Christine M. , Laraia Luca , Logoteta Patrizia , Prestinari Cora , Scott Matthew , Williams Katharine , Galloway Warren R. J. D. , Spring David R. 
Published: April 2011

AbstractAliphatic and aromatic vinyldisiloxanes are applied in the fluoride‐free cross‐coupling reactions with aryl iodides to afford the (E)‐products mostly exclusively.
ChemInform Abstract: Synthesis of Symmetrical Diarylalkyne from Palladium‐Catalyzed Decarboxylative Couplings of Propiolic Acid and Aryl Bromides under Water.
Authors: Park Kyungho , Bae Goun , Park Ahbyeol , Kim Yong , Choe Jaehoon , Song Kwang Ho , Lee Sunwoo 
Published: April 2011

AbstractThe reaction proceeds in the presence of a phase transfer surfactant and is efficiently catalyzed by two different systems.
ChemInform Abstract: Fe3O4 Nanoparticle‐Supported Copper(I) Pybox Catalyst: Magnetically Recoverable Catalyst for Enantioselective Direct‐Addition of Terminal Alkynes to Imines.
Authors: Zeng Tieqiang , Yang Luo , Hudson Reuben , Song Gonghua , Moores Audrey R. , Li Chao‐Jun 
Published: April 2011

AbstractThe catalyst exhibits excellent reactivity to afford the propargyl amines with high yields and enantioselectivities.
ChemInform Abstract: Ytterbium Triflate Catalyzed Synthesis of β‐Functionalized Indole Derivatives.
Authors: Epifano Francesco , Genovese Salvatore , Rosati Ornelio , Tagliapietra Silvia , Pelucchini Caroline , Curini Massimo 
Published: April 2011

AbstractUltrasound‐assisted condensation of indole, aldehydes, and dimethyl malonate represents the first example of the Yonemitsu three‐component reaction catalyzed by a Lewis acid without the need of other promoters such as amines.
ChemInform Abstract: Synthesis of 1,2,4‐Trisubstituted‐1,2,5,6‐tetrahydropyridines.
Authors: Chang Meng‐Yang , Lee Ming‐Fang , Lee Nien‐Chia , Huang Yu‐Ping , Lin Chung‐Han 
Published: April 2011

AbstractA synthesis of title compounds (V) is achieved via NBS‐mediated alkoxybromination, DBU‐promoted formation of an enamine and reaction with Tms‐substituted C‐nucleophiles.
ChemInform Abstract: Per(poly)fluoroalkanesulfinamides Assisted Diastereoselective Three‐Component Inverse‐Electron‐Demand Aza Diels—Alder Reaction.
Authors: Li Peng , Liu Li‐Juan , Liu Jin‐Tao 
Published: April 2011

AbstractThree‐component inverse‐electron‐demand aza‐Diels—Alder reaction of polyfluoroalkanesulfinamide (III) with enones (I) and enol ether (II) provides access to a range of tetrahydropyridine derivatives with high endo‐ and facial selectivities (up to < 100:1).
ChemInform Abstract: Condensed Isoquinolines. Part 36. Cyclization of N‐Alkyl‐3‐(2‐benzoylbenzyl)azolium Salts. A Novel Method of Preparing Azolo[b]isoquinolines.
Authors: Potikha L. M. , Sypchenko V. V. , Kovtunenko V. A. 
Published: April 2011

AbstractThe preparation of azoloisoquinolinium bromides (IV) and (VIII) is based on the alkylation of N‐alkyl‐1,3‐diazoles, e.g. (II), or 1,3‐thiazole derivative (VI) using benzophenone derivatives (I) as novel equivalents of 1,4‐dielectrophile synthons, followed by cyclization of the quaternary azolium salts (III) and (VII) in the presence of a base.
ChemInform Abstract: One‐Pot Construction of Aza‐ or Oxa‐Bridged Benzocycloheptanes from Readily Available 2,3‐Allenyl Malonates or 2,3‐Allenols and o‐Iodobenzaldehyde or Imine.
Authors: Li Qiankun , Jiang Xinpeng , Fu Chunling , Ma Shengming 
Published: April 2011

AbstractA variety of biologically relevant racemic aza‐bridged and racemic and optically pure oxa‐bridged benzocycloheptane derivatives is prepared.
ChemInform Abstract: 3‐[Benzimidazo‐ and 3‐Benzothiadiazoleimidazo‐(1,2‐c)quinazolin‐5‐yl]‐2H‐chromene‐2‐ones as Potent Antimicrobial Agents.
Authors: Kuarm B. Suresh , Reddy Y. Thirupathi , Madhav J. Venu , Crooks Peter A. , Rajitha B. 
Published: April 2011

AbstractThe antimicrobial activities of the title compounds (III) and (V) are evaluated.
ChemInform Abstract: Synthesis of 4‐(Trifluoromethyl)pyrido[4,3‐d]pyrimidine Derivatives.
Authors: Vasil'ev L. S. , Baranin S. V. , Ignatenko A. V. , Nelyubina Yu. V. , Dorokhov V. A. 
Published: April 2011

AbstractThe title compounds, whose known derivatives possess a wide range of biological activity, are synthesized for the first time.
ChemInform Abstract: Construction of Mononitrogen Heterocycles with a Combined System of 1‐Azaspiro[4.n]alkene and 3‐Benzazocine Fragments Through the Intramolecular Eight‐Membered Heck Cyclization.
Authors: Kuznetsov N. Yu. , Khrustalev V. N. , Bubnov Yu. N. 
Published: April 2011

AbstractA new type of cyclization reaction in the presence of the Herrmann—Beller palladacycle is presented.
ChemInform Abstract: Synthesis and Photochromic Properties of Novel Nonsymmetric Dihetarylethenes Based on Benzindole and Thiophene.
Authors: Metelitsa A. V. , Rybalkin V. P. , Makarova N. I. , Levchenko P. V. , Kozyrev V. S. , Shepelenko E. N. , Popova L. L. , Bren' V. A. , Minkin V. I. 
Published: April 2011

AbstractUnlike the title of furandione (I), benzindole derivatives (II) exhibit photochromic and fluorescence properties in solutions.
ChemInform Abstract: Rhodium‐Catalyzed Asymmetric Addition of Arylboronic Acids to γ‐Phthalimido‐substituted‐α,β‐unsaturated Carboxylic Acid Esters: An Approach to γ‐Amino Acids.
Authors: Han Fuzhong , Chen Jun , Zhang Xiangyang , Liu Jibing , Cun Linfeng , Zhu Jin , Deng Jingen , Liao Jian 
Published: April 2011

AbstractThe mild process affords the desired products generally with excellent enantioselectivity.
ChemInform Abstract: Hyrtioseragamines A and B, New Alkaloids from the Sponge Hyrtios Species.
Authors: Takahashi Yohei , Iinuma Yoshiro , Kubota Takaaki , Tsuda Masashi , Sekiguchi Mitsuhiro , Mikami Yuzuru , Fromont Jane , Kobayashi Jun'ichi 
Published: April 2011

AbstractThe title compounds are the first natural products possessing a furopyrazine moiety.
ChemInform Abstract: Two New Paeciloxocins from a Mangrove Endophytic Fungus Paecilomyces sp.
Authors: Wen Lu , Chen Gang , She Zhigang , Yan Chunyan , Cai Juanni , Mu Lei 
Published: April 2011

AbstractIsolation and structure elucidation of two new compounds, paeciloxocins A (Ia) and B (Ib), are described.