bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating the potential refolding yield of recombinant proteins expressed as inclusion bodies
Authors: Ho Jason G. S. , Middelberg Anton P. J. 
Published: August 2004

AbstractRecombinant protein production in bacteria is efficient except that insoluble inclusion bodies form when some gene sequences are expressed. Such proteins must undergo renaturation, which is an inefficient process due to protein aggregation on dilution from concentrated denaturant. In this study, the protein–protein interactions of eight distinct inclusion‐body proteins are quantified, in different solution conditions, by measurement of protein second virial coefficients (SVCs). Protein solubility is shown to decrease as the SVC is reduced (i.e., as protein interactions become more attractive). Plots of SVC versus denaturant concentration demonstrate two clear groupings of proteins: a more aggregative group and a group having higher SVC and better solubility. A correlation of the measured SVC with protein molecular weight and hydropathicity, that is able to predict which group each of the eight proteins falls into, is presented. The inclusion of additives known to inhibit aggregation during renaturation improves solubility and increases the SVC of both protein groups. Furthermore, an estimate of maximum refolding yield (or solubility) using high‐performance liquid chromatography was obtained for each protein tested, under different environmental conditions, enabling a relationship between “yield” and SVC to be demonstrated. Combined, the results enable an approximate estimation of the maximum refolding yield that is attainable for each of the eight proteins examined, under a selected chemical environment. Although the correlations must be tested with a far larger set of protein sequences, this work represents a significant move beyond empirical approaches for optimizing renaturation conditions. The approach moves toward the ideal of predicting maximum refolding yield using simple bioinformatic metrics that can be estimated from the gene sequence. Such a capability could potentially “screen,” in silico, those sequences suitable for expression in bacteria from those that must be expressed in more complex hosts. © 2004 Wiley Periodicals, Inc.
Establishment of FUT8 knockout Chinese hamster ovary cells: An ideal host cell line for producing completely defucosylated antibodies with enhanced antibody‐dependent cellular cytotoxicity
Authors: Yamane‐Ohnuki Naoko , Kinoshita Satoko , Inoue‐Urakubo Miho , Kusunoki Machi , Iida Shigeru , Nakano Ryosuke , Wakitani Masako , Niwa Rinpei , Sakurada Mikiko , Uchida Kazuhisa , Shitara Kenya , Satoh Mitsuo 
Published: August 2004

AbstractTo generate industrially applicable new host cell lines for antibody production with optimizing antibody‐dependent cellular cytotoxicity (ADCC) we disrupted both FUT8 alleles in a Chinese hamster ovary (CHO)/DG44 cell line by sequential homologous recombination. FUT8 encodes an α‐1,6‐fucosyltransferase that catalyzes the transfer of fucose from GDP‐fucose to N‐acetylglucosamine (GlcNAc) in an α‐1,6 linkage. FUT8−/− cell lines have morphology and growth kinetics similar to those of the parent, and produce completely defucosylated recombinant antibodies. FUT8−/−‐produced chimeric anti‐CD20 IgG1 shows the same level of antigen‐binding activity and complement‐dependent cytotoxicity (CDC) as the FUT8+/+‐produced, comparable antibody, Rituxan. In contrast, FUT8−/−‐produced anti‐CD20 IgG1 strongly binds to human Fcγ‐receptor IIIa (FcγRIIIa) and dramatically enhances ADCC to approximately 100‐fold that of Rituxan. Our results demonstrate that FUT8−/− cells are ideal host cell lines to stably produce completely defucosylated high‐ADCC antibodies with fixed quality and efficacy for therapeutic use. © 2004 Wiley Periodicals, Inc.
Change of extracellular cAMP concentration is a sensitive reporter for bacterial fitness in high‐cell‐density cultures of Escherichia coli
Authors: Lin Hongying , Hoffmann Frank , Rozkov Aleksei , Enfors Sven‐Olof , Rinas Ursula , Neubauer Peter 
Published: August 2004

AbstractGuanosine‐3′,5′‐tetraphosphate (ppGpp) and σS, two regulators of the starvation response of Escherichia coli, have received increasing attention for monitoring cell physiological changes in production processes, although both are difficult to quantify. The kinetics of cAMP formation and degradation were not yet investigated in such processes, although the complex regulation of cAMP by synthesis, release, and degradation in connection with straightforward methods for analysis renders it a highly informative target. Therefore, we followed the cAMP concentration in various nonrecombinant and in four different recombinant glucose‐limited fed‐batch processes in different production scales. The intracellular cAMP concentration increases strongly at the end of the batch phase. Most cAMP is released to the cultivation medium. The rates of accumulation and degradation of extracellular cAMP are growth‐rate‐dependent and show a distinct maximum at a growth rate of about 0.35 h−1. At very low growth rates, below 0.05 h−1, extracellular cAMP is not produced but rather degraded, independent of whether this low growth rate is caused by glucose limitation or by the high metabolic load of recombinant protein production. In contrast to intracellular cAMP, which is highly unstable, analysis of extracellular cAMP is simpler and the kinetics of accumulation and degradation reflect well the physiological situation, including unlimited growth, limitation, and severe starvation of a production host. © 2004 Wiley Periodicals, Inc.
Real‐time update of calibration model for better monitoring of batch processes using spectroscopy
Authors: Kornmann Henri , Valentinotti Sergio , Marison Ian , Stockar Urs von 
Published: August 2004

AbstractIn order to reduce the large calibration matrix usually required for calibrating multiwavelength optical sensors, a simple algorithm based on the addition in process of new standards is proposed. A small calibration model, based on 14 standards, is periodically updated by spectra collected on‐line during fermentation operation. Concentrations related to these spectra are reconciled into best‐estimated values, by considering carbon and oxygen balances. Using this method, fructose, acetate, and gluconacetan were monitored during batch fermentations of Gluconacetobacter xylinus 12281 using mid‐infrared spectroscopy. It is shown that this algorithm compensates for noncalibrated events such as production or consumption of by‐products. The standard error of prediction (SEP) values were 0.99, 0.10, and 0.90 g/L for fructose, acetate, and gluconacetan, respectively. By contrast, without an updating of the calibration model, the SEP values were 2.46, 0.92, and 1.04 g/L for fructose, acetate, and gluconacetan, respectively. Using only 14 standards, it was therefore possible to approach the performance of an 88‐standard‐based calibration model having SEP values of 1.11, 0.37, and 0.79 g/L for fructose, acetate, and gluconacetan, respectively. Therefore, the proposed algorithm is a valuable approach to reduce the calibration time of multiwavelength optical sensors. © 2004 Wiley Periodicals, Inc.
Arabidopsisglycosyltransferases as biocatalysts in fermentation for regioselective synthesis of diverse quercetin glucosides
Authors: Lim Eng‐Kiat , Ashford David A. , Hou Bingkai , Jackson Rosamond G. , Bowles Dianna J. 
Published: August 2004

AbstractRegioselectivity of glycosyltransferases offers an important means to overcome the limitations of chemical synthesis of small molecule glycosides. In this study we explore a large multigene family of UDP‐glucose:glycosyltransferases ofArabidopsisfor their potential as novel biocatalysts for in vitro synthesis and whole‐cell catalysis. We used quercetin as a substrate for this study because the flavonol and its glycosides have important medicinal properties and the metabolite provides a complex structure for regioselective glucosylation. We analyzed the activity of 91 recombinant enzymes for in vitro activity toward quercetin and discovered 29 that are capable of glucosylating the substrate. We demonstrate the first enzymic synthesis of a range of glucosides in vitro, including the 3‐O‐, 7‐O‐, 3′‐O‐, and 4′‐O‐monoglucosides, 3,7‐di‐O‐glucoside, and 7,3′‐di‐O‐glucoside. We also show that the regioselectivity of glucosylation can be maintained when the enzymes are used as whole‐cell biocatalysts inEscherichia coli. © 2004 Wiley Periodicals, Inc.
Brønsted Acidic Ionic Liquids and Their Zwitterions: Synthesis, Characterization and pKa Determination
Authors: Fei Zhaofu , Zhao Dongbin , Geldbach Tilmann J. , Scopelliti Rosario , Dyson Paul J. 
Published: August 2004

AbstractImidazolium chlorides with one or two carboxylic acid substituent groups, 1‐methyl‐3‐alkylcarboxylic acid imidazolium chloride, [Me{(CH2)nCOOH}im]Cl (n=1, 3), and 1,3‐dialkylcarboxylic acid imidazolium chloride, [{(CH2)nCOOH}2im]Cl (n=1, 3), have been synthesized via their corresponding acid esters. Deprotonation of the carboxylic acid functionalized imidazolium chlorides with triethylamine affords the corresponding zwitterions [Me{(CH2)nCOO}im] (n=1, 3) and [{(CH2)nCOOH}{(CH2)nCOO}im] (n=1, 3). Subsequent reaction of the zwitterions with strong acids gives the new imidazolium salts [Me{(CH2)nCOOH}im]X (n=1, 3; X=BF4, CF3SO3) and [{(CH2)nCOOH}2im]X (n=1, 3; X=BF4, CF3SO3), which exhibit melting points as low as −61 °C. The solid‐state structures of two of the carboxylic acid functionalized imidazolium salts have been determined by single‐crystal X‐ray diffraction analysis. Extensive hydrogen bonding is present between the chloride and the imidazolium, with eight Cl⋅⋅⋅H interactions below 3 Å. The pKa values of all the salts, determined by potentiometric titration, lie between 1.33 and 4.59 at 25 °C.
Machinable Long PVP‐Stabilized Silver Nanowires
Authors: Jiang Peng , Li Shun‐Yu , Xie Si‐Shen , Gao Yan , Song Li 
Published: August 2004

AbstractPVP‐capped silver nanowires with a diameter range from 150 to 200 nm and a length range from 50 to 100 μm have been synthesized in large quantity by using a soft‐template liquid‐phase method. The so‐obtained longer and thicker metallic nanowires exhibit fivefold‐twinned structures bound by five {1 0 0} wall‐planes and two spearlike ends around five {1 1 1} facets. X‐ray photoelectron spectroscopy (XPS) investigations show that a strong interaction exists between the carboxyl oxygen atom (CO) of PVP and the Ag core interface. The PVP‐capped Ag nanowires can either self‐assemble into ordered raft structures or form a complicated network, depending on the dispersive solvent employed. In addition, the Ag nanowires can also be specifically bent into various angles, demonstrating their excellent mechanical stability.
Diverted Total Synthesis and Biological Evaluation of Gambierol Analogues: Elucidation of Crucial Structural Elements for Potent Toxicity
Authors: Fuwa Haruhiko , Kainuma Noriko , Tachibana Kazuo , Tsukano Chihiro , Satake Masayuki , Sasaki Makoto 
Published: August 2004

AbstractGambierol is a polycyclic ether toxin, which has been isolated from the marine dinoflagellate Gambierdiscus toxicus. A series of gambierol analogues have been prepared from an advanced intermediate of our total synthesis of gambierol and investigated for their toxicity against mice, thus providing the first systematic structure–activity relationships (SAR) of this polycyclic ether class of marine toxin. The SAR studies described herein clearly indicate that 1) the C28C29 double bond within the H ring and the unsaturated side chain are the crucial structural elements required for exerting potent biological activity and 2) the C1 and C6 hydroxy groups, the C30 methyl group, and the C37C38 double bond have little influence on the degree of neurotoxicity against mice.
Synergic Binding of Carbon Monoxide and Cyanide to the FeMo Cofactor of Nitrogenase: Relic Chemistry of an Ancient Enzyme?
Authors: Pickett Christopher J. , Vincent Kylie A. , Ibrahim Saad K. , Gormal Carol A. , Smith Barry E. , Fairhurst Shirley A. , Best Stephen P. 
Published: August 2004

AbstractThe first electrochemical and infra‐red data on the binding of cyanide to the isolated iron–molybdenum cofactor of nitrogenase, FeMoco, is described. It is shown that cyanide stabilises a hitherto unrecognised, low‐spin, EPR‐active (S=${{ 1/2 }}$), superoxidised form of FeMoco, and we provide the first evidence that carbon monoxide and cyanide bind synergically to the oxidised and semireduced states of the isolated cofactor, states which are unreactive to carbon monoxide alone.
New Amphiphilic Silicon(IV) Phthalocyanines as Efficient Photosensitizers for Photodynamic Therapy: Synthesis, Photophysical Properties, and in vitro Photodynamic Activities
Authors: Lo Pui‐Chi , Huang Jian‐Dong , Cheng Diana Y. Y. , Chan Elaine Y. M. , Fong Wing‐Ping , Ko Wing‐Hung , Ng Dennis K. P. 
Published: August 2004

AbstractA novel series of silicon(IV) phthalocyanines substituted axially with one or two 1,3‐bis(dimethylamino)‐2‐propoxy group(s) have been prepared by ligand substitution and alkoxy exchange reactions. Two dicationic and tetracationic phthalocyanines have also been prepared by methylation of two of these compounds. The nonionic phthalocyanines are essentially nonaggregated in common organic solvents and show a weak fluorescence emission, while the methylated derivatives are also nonaggregated, even in aqueous media, and exhibit a strong fluorescence emission. These new phthalocyanines, in particular the unsymmetrical and amphiphilic analogues, are highly potent against HepG2 human hepatocarcinoma cells and J774 mouse macrophage cells with IC50 values down to 0.02 μM. The photodynamic activities are related to the cellular uptake and the efficiency to generate singlet oxygen. A higher positive charge at the phthalocyanine hinders the uptake, reflected by the lower intracellular fluorescence intensity. Fluorescence microscopic studies have also revealed that the unsymmetrical phthalocyanine SiPc[C3H5(NMe2)2O](OMe) (4) has a high and selective affinity to the mitochondria of HepG2 cells.
Enantioselective Cyanosilylation of Ketones by a Catalytic Double‐Activation Method with an Aluminium Complex and an N‐Oxide
Authors: Chen Fu‐Xue , Zhou Hui , Liu Xiaohua , Qin Bo , Feng Xiaoming , Zhang Guolin , Jiang Yaozhong 
Published: August 2004

AbstractDouble‐activation catalysis promises high catalytic efficiency in the enantioselective cyanosilylation of ketones through the combined use of a Lewis acid and a Lewis base. Catalyst systems composed of a chiral salen–Al complex and an N‐oxide have high catalytic turnovers (200 for aromatic ketones, 1000 for aliphatic ones). With these catalysts, a wide range of aliphatic and aromatic ketones were converted under mild conditions into tertiary cyanohydrin O‐TMS ethers in excellent yields and with high enantioselectivities (94 % ee for aromatic ketones, 90 % ee for aliphatic ones). Preliminary mechanistic studies revealed that the salen–Al complex played the role of a Lewis acid to activate the ketone and the N‐oxide that of a Lewis base to activate TMSCN; that is, double activation.
Leukemia incidence following primary breast carcinoma treatment
Authors: Kaplan Henry G. , Malmgren Judith A. , Atwood Mary 
Published: August 2004

AbstractBACKGROUNDThe results of randomized clinical trials have suggested that after receiving radiotherapy and/or chemotherapy, patients with primary breast carcinoma have an increased risk of developing leukemia. In the current study, the authors set out to assess the reported association between breast carcinoma treatment and leukemia risk.METHODSA registry of all patients with breast carcinoma who were treated at a community‐based institution since 1989 (updated annually for recurrence and/or vital status) was linked to the National Cancer Institute Surveillance, Epidemiology, and End Results database to confirm complete ascertainment of leukemia cases occurring within this registry population. Incidence rates were calculated for women who were treated for primary Stage 0–III breast carcinoma and had a follow‐up duration of ≥ 24 months (n = 2866). Patients who did not undergo surgery (n = 5), patients for whom chemotherapy records were incomplete or who received nonstandard chemotherapy regimens (n = 69), patients who underwent stem cell transplantation (n = 83), and patients who were lost to follow‐up or who had unknown disease status at follow‐up (n = 81) were excluded from the analysis (total, n = 238).RESULTSAmong patients diagnosed with breast carcinoma between 1992 and 1999, the crude overall leukemia incidence rate was 0.28%, and the acute myelogenous leukemia (AML)/myelodysplastic syndrome (MDS) incidence rate was 0.11%. The average follow‐up duration was 5.46 years (minimum, 2 years). Eight incident cases of leukemia were documented (2 cases of AML, 1 case of acute lymphoblastic leukemia, 1 case of MDS/refractory anemia with excess blasts, 2 cases of chronic myelogenous leukemia, and 2 cases of chronic lymphocytic leukemia). National age‐adjusted overall leukemia incidence rates for the period 1996–1998 predict the occurrence of 9 cases (incidence rate, 0.31%) in the current cohort of women ages 21–94 years. The incidence of leukemia by treatment category was as follows: no surgery/no chemotherapy/no radiotherapy, 2 of 154 patients (1.30%); surgery/no chemotherapy/radiotherapy, 4 of 1403 patients (0.29%); surgery/chemotherapy/no radiotherapy, 0 of 352 patients (0%); and surgery/chemotherapy/radiotherapy, 2 of 957 patients (0.21%).CONCLUSIONSIn contrast to findings reported from previous randomized clinical trials, the authors did not find evidence of increased posttreatment leukemia incidence in association with the use of chemotherapy, including doxorubicin‐based regimens. Cancer 2004. © 2004 American Cancer Society.
The computation of deterministic bounds to multiplexed MPEG video traffic using z‐characterization
Authors: Poon Wai‐Chung , Lo Kwok‐Tung 
Published: August 2004

AbstractIn this paper, we propose a method called z‐characterization for computing the deterministic bounds of an aggregated MPEG stream at frame level. Traditional deterministic characterization methods like empirical envelope generally suffer from the drawback of high computation complexity. In our approach, the I, P and B sub‐traces of an MPEG trace will be characterized independently such that they possess their own empirical envelopes. By exploiting the periodic group‐of‐pictures (GOP) structure of MPEG video, the I, P and B sub‐envelopes can act as building blocks for computing the characterization of the aggregate stream in real‐time. Experimental results show that our proposed characterization closely bounds the empirical envelope in both homogenous and heterogeneous multiplexing scenarios. Copyright © 2004 John Wiley & Sons, Ltd.
Dinuclear CuII Complexes with a New Phenol‐Based Ligand Bearing Pyridine and Thiophene Substituents: Synthesis, Characterization and Interaction with Catechol Substrates
Authors: Koval Iryna A. , Huisman Mieke , Stassen Arno F. , Gamez Patrick , Roubeau Olivier , Belle Catherine , Pierre Jean‐Louis , Saint‐Aman Eric , Lüken Matthias , Krebs Bernt , Lutz Martin , Spek Anthony L. , Reedijk Jan 
Published: August 2004

AbstractThe reaction of the phenol‐based ligand 4‐methyl‐2,6‐bis{[(2‐methylpyridyl)(2‐methylthiophenyl)amino]methyl}phenol(Hpy2th2s), containing pyridine and thiophene substituents, with copper(II) chloride and bromide yields two new dinuclear complexes with the composition [Cu2(py2th2s)X3], where X = Cl or Br. In both complexes, the copper(II) ions are pentacoordinate and bridged by the deprotonated phenolate anion and by one halogen anion. Both complexes exhibit geometric asymmetry, as the coordination environment around one of the two copper ions is square‐pyramidal, whereas the geometry around the other can be best described as a distorted trigonal bipyramid. The complexes were characterized by means of X‐ray single‐crystal diffraction, ligand field and EPR spectroscopy, mass spectrometry, and electrochemically. Magnetic susceptibility measurements indicate an antiferromagnetic coupling between the two metal centers (2J ≈︁ −200 cm−1). The interaction of the complexes with model substrates 3,5‐di‐tert‐butylcatechol and tetrachlorocatechol is reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A New Synthetic Method and Solution Equilibria for the Chlorotitanate(IV) Anions − Evidence for the Existence of a New Species: [Ti2Cl11]3−
Authors: Robé Emmanuel , Daran Jean‐Claude , Vincendeau Sandrine , Poli Rinaldo 
Published: August 2004

AbstractTiCl3 is oxidized by SOCl2 in the presence of the appropriate amount of [NEt3Bz]Cl or [PPN]Cl [Bz = benzyl; PPN = bis(triphenylphosphanyl)iminium] to afford the corresponding salts of [Ti2Cl9]−, [Ti2Cl10]2− or [TiCl6]2−. The results of cyclic voltammetric and solution IR studies in the Ti−Cl stretching region are interpreted in terms of a rapid chloride‐redistribution equilibrium between [Ti2Cl10]2− on one side and a mixture of [Ti2Cl9]− and a previously unreported [Ti2Cl11]3− species on the other side. In the solid state, however, a compound with the [PPN]3[Ti2Cl11] stoichiometry exists as a mixture of [PPN]2[Ti2Cl10] and [PPN]2[TiCl6]. The PPN salt of [Ti2Cl9]− has been structurally characterized by X‐ray diffractometry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Mono(alkyne)cobalt Complexes and Electron‐Rich Alkynes − The Formation of an Alkyne‐Bridged Dinuclear Cobalt Complex by a One‐Pot Procedure
Authors: Werz Daniel B. , Gleiter Rolf , Rominger Frank 
Published: August 2004

Abstract[η2‐Bis(tert‐butylsulfonyl)acetylene](carbonyl)(η5‐trimethylsilylcyclopentadienyl)cobalt (2c) proved to be reactive towards bis(telluro)‐ and bis(seleno)‐substituted alkynes 3 and 4, respectively, to yield push‐pull‐substituted CpCo‐stabilized cyclobutadiene complexes. By utilizing the unsymmetrical diyne 6 and the symmetrical bis(thio)‐substituted triyne 7 it was shown that only the most electron‐rich triple bond was attacked by the electrophilic compound 2c. In the case of 7 a dinuclear CpCo‐stabilized cyclobutadiene complex 14 bridged by one acetylene moiety was obtained. All the reactions could be carried out at room temperature under rather mild conditions. X‐ray investigations of 8, 12, 14a, and 15 show almost equal C−C bond lengths in the cyclobutadiene moieties. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)