bluuebunny/crossref_metadata_2025_split huggingface dataset:
Large changes in cytoplasmic biopolymer concentration with osmolality indicate that macromolecular crowding may regulate protein–DNA interactions and growth rate in osmotically stressed Escherichia coli K‐12
Authors: Cayley Scott , Record M. Thomas 
Published: August 2004

AbstractFrom determination of amounts and concentrations of biopolymers and solutes in the cytoplasm of Escherichia coli, we are obtaining information needed to assess the effect of macromolecular crowding on cytoplasmic properties and processes of osmotically stressed bacteria. We observe that growth rate, and the amount of cytoplasmic water decrease and cytoplasmic concentrations of biopolymers and K+, increase with increasing osmolality, even for cells grown in the presence of osmoprotectants like glycine betaine. We observe general correlations between the amount of cytoplasmic water, growth rate and cytoplasmic K+ concentration in osmotically stressed cells grown both with and without osmoprotectants. To explain these correlations, we propose that crowding increases with increasing growth osmolality, which in turn buffers the binding of proteins to nucleic acids against changes in cytoplasmic K+ concentration and (by affecting biopolymer diffusion rates and/or assembly equilibria) is a determinant of growth rate of osmotically stressed cells. Changes in biopolymer concentration and crowding may also explain the increase of the activity coefficient of cytoplasmic water with increasing osmolality of growth in E. coli. Copyright © 2004 John Wiley & Sons, Ltd.
Effect of molecular crowding on self‐association of phosphorylase kinase and its interaction with phosphorylase b and glycogen
Authors: Chebotareva Natalia A. , Andreeva Iraida E. , Makeeva Valentina F. , Livanova Natalia B. , Kurganov Boris I. 
Published: August 2004

AbstractSelf‐association of phosphorylase kinase (PhK) and its interaction with glycogen (M=5500 kDa) and phosphorylase b (Phb) has been studied using analytical ultracentrifugation and turbidimetry under the conditions of molecular crowding arising from the presence of high concentrations of osmolytes. In accordance with the predictions of the molecular crowding theory, trimethylamine N‐oxide (TMAO) and betaine greatly favor self‐association of PhK induced by Mg2+ and Ca2+ and PhK interaction with glycogen. In contrast, proline suppresses these processes, probably, due to its specific interaction with PhK. All osmolytes tested prevented the complex formation between PhK and its physiological substrate, Phb. The specific interactions of PhK and Phb with glycogen, in the living cell, presumably is a factor allowing the negative effect of crowding on the recognition of Phb by PhK to be overcome. Copyright © 2004 John Wiley & Sons, Ltd.
Crowding and the polymerization of sickle hemoglobin
Authors: Ferrone Frank A. , Rotter Maria A. 
Published: August 2004

AbstractUnder physiological conditions, sickle hemoglobin, a natural mutant of human hemoglobin A with a surface hydrophobic valine in place of a negatively charged glutamic acid, polymerizes at high volume occupancy. Equilibrium solubility of sickle hemoglobin entails activity coefficients that can approach 103 at high concentrations. Polymerization occurs by homogeneous and heterogeneous nucleation mechanisms, which are both profoundly sensitive to crowding; homogeneous nucleation rates for example are enhanced by 1010 when the initial concentration is augmented by 50% non‐polymerizing hemoglobin. A molecular description of the reaction therefore entails substantial corrections for molecular crowding which are all very accurately described by excluded volume corrections, treating hemoglobin as a hard sphere with volume consistent with the molecular structure of the molecule, and involving no further adjustable parameters. These effects and the descriptions that rationalize this behavior are described. Copyright © 2004 John Wiley & Sons, Ltd.
Crowding effects in binary mixtures of rod‐like and spherical particles
Authors: Lago S. , Cuetos A. , Martínez‐Haya B. , Rull L. F. 
Published: August 2004

AbstractCrowding effects relevant to the phase stability of binary mixtures of rod‐like and spherical particles are investigated by means of Monte Carlo simulations in the isobaric NPT ensemble. The two types of particles are represented, respectively, by freely rotating hard spherocylinders of a moderate aspect ratio (L / σ = 5) and hard spheres of the same diameter σ. Molar fractions of spheres ranging xHS = 0.00–0.37 are considered with the aim of characterizing the crowding effects on the liquid crystal phases of the hard spherocylinder fluid induced by the spherical component as depleting agent. We find that the addition of the spherical crowder is beneficial for the stabilization of the layers of the rod‐like particles characteristic of the smectic phase. On the contrary, the addition of spheres has a negative impact upon the stability of the nematic phase, where the rod‐like particles tend to align collectively parallel to each other. Interestingly, the spheres tend to arrange forming rod‐like clusters in the nematic phase and lamellar structures in the smectic phase, which is compensated by the entropy gained by the spherocylinder particles in each phase. The main results are in qualitative agreement with recent experimental and theoretical studies and serve to test the prediction of current equations of state for these types of binary mixtures. Copyright © 2004 John Wiley & Sons, Ltd.
Non‐ideal tracer sedimentation equilibrium: a powerful tool for the characterization of macromolecular interactions in crowded solutions
Authors: Rivas Germán , Minton Allen P. 
Published: August 2004

AbstractNon‐ideal tracer sedimentation equilibrium is a technique devised to quantify the effect of high concentrations of unrelated macromolecules on the self‐ or hetero‐associations of dilute macromolecules. Principles and experimental techniques are reviewed, and previous experimental work summarized. A new analysis of experimental data is presented that requires no a priori assumptions regarding the nature of weak repulsive interactions between solute species and the concentrated (crowding) species. Published in 2004 by John Wiley & Sons, Ltd.
Genomic channeling in bacterial cell division
Authors: Mingorance Jesús , Tamames Javier , Vicente Miguel 
Published: August 2004

AbstractThe bacterial dcw cluster is a group of genes involved in cell division and peptidoglycan synthesis. Comparison of the cluster across several bacterial genomes shows that its gene content and its gene order are conserved in distant bacterial lineages and, moreover, that, being most conserved in rod‐shaped bacteria, the degree of conservation relates to bacterial morphology. We propose a model in which the selective pressure to maintain the cluster arises from the need to efficiently coordinate the processes of elongation and septation in rod‐shaped bacteria. Gene order in the dcw cluster would be conserved as a result of mechanisms comprising: (i) a limited amout of peptidoglycan precursors required both for septation and elongation of the wall; (ii) co‐translational assembly of the protein complexes involved in cell division and in the synthesis of the peptidoglycan precursors; and (iii) alternation in the cellular localization of the assembled complexes to participate either in the synthesis of the septal peptidoglycan and division, or in the synthesis of the lateral wall. The name genomic channeling is proposed for this model as it involves a genomic arrangement that could facilitate the assembly of specific protein complexes and their subsequent conveyance to specific locations in the crowded cytoplasm and the envelope. Copyright © 2004 John Wiley & Sons, Ltd.
Changes produced in the aroma compounds and structural integrity of basil (Ocimum basilicum L) during drying
Authors: Díaz‐Maroto M Consuelo , Sánchez Palomo Eva , Castro Lucía , González Viñas MA , Pérez‐Coello M Soledad 
Published: August 2004

AbstractThe influence of drying on the aroma compounds, from a chemical and sensory standpoint, and on the structural integrity of basil (Ocimum basilicum L) was evaluated. The drying methods tested were oven drying at 45 °C, air drying at room temperature and freeze‐drying. The volatile compounds of fresh and dried basil were extracted and concentrated by simultaneous distillation/extraction and analysed by gas chromatography/mass spectrometry. In all, 27 volatile components were identified, linalool being the major component, followed by eugenol. The total quantity of volatiles of fresh basil decreased considerably during oven drying and freeze‐drying, whereas air drying of basil at room temperature brought about only small losses of volatile components. The cell damage produced on basil leaves during drying was evaluated by scanning electron microscopy. From a sensory standpoint, fresh basil was described as having a fresh, herbaceous and floral odour, while the dried samples had a mentholated, spicy, hay‐like and earthy odour. Copyright © 2004 Society of Chemical Industry
Reactions of CH3O2 radicals on solid surface
Authors: Manucharova L. A. , Tsarukyan S. V. , Vardanyan I. A. 
Published: August 2004

AbstractThe reaction probability of CH3O2 radicals with NO2, CH4, C3H6, and CH3CHO on the solid surface of KCl in flow at low pressure and temperature range of 297–353 K has been studied. The chosen conditions allowed excluding homogeneous interaction of radicals. The heterogeneous radical decay of peracetic acid served as a source of CH3O2 radicals.On the basis of ESR measurements of CH3O2 radicals with the above‐mentioned compounds, a heterogeneous reaction mechanism has been identified.The reactivity of NO2 was greatest for the compounds studied.The effective activation energy was evaluated to be 10.4 ± 0.8 kJ/mol for the reaction of RO2 radicals with NO2 and −21.3 ± 2.8 kJ/mol for methane. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 591–595, 2004
Stopped‐flow investigation of the reaction of hexabromoiridate(III) with bromine in aqueous solution
Authors: Hoag Craig M. , Hanrahan Robert J. 
Published: August 2004

AbstractThe reaction of hexabromoiridate(III) with bromine to form hexabromoiridate(IV) and bromide ion was studied using a Durrum stopped‐flow spectrophotometer. Special precautions were taken while studying this reaction. All of the experiments were carried out within 3 min after preparation of the hexabromoiridate solution throughout this investigation in order to limit the amount of conversion of hexabromoiridate(III) to aquapentabromoiridate(III) before reaction with bromine. Very dilute solutions were used because of the rapidity of the reaction. The rate constant for the reaction at 24 ± 1°C was determined to be (3.2 ± 0.4) × 103 L mol−1 s−1. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 623–626, 2004
Effect of Nucleating Agents on Crystallization and Melting Behavior and Mechanical Properties of Nucleated Syndiotactic Poly(propylene)
Authors: Supaphol Pitt , Charoenphol Paninlada , Junkasem Jirawut 
Published: August 2004

AbstractSummary: The effects of various nucleating agents [e.g. 1,3:2,4‐dibenzylidene sorbitol (DBS), 1,3:2,4‐di‐p‐methyldibenzilidene sorbitol (MDBS), 1,3:2,4‐di‐m,p‐methylbenzylidene sorbitol (DMDBS), kaolin, talcum, marl, titanium dioxide (TiO2) and silica (SiO2)] on non‐isothermal melt crystallization and the subsequent melting behavior and mechanical properties of nucleated syndiotactic poly(propylene) (sPP) in comparison with those of the neat sample were investigated. Analysis of the non‐isothermal melt‐crystallization exotherms revealed that the ability of these fillers to nucleate sPP could be ranked from the best to the worst as follows: DBS > talcum > MDBS > kaolin > SiO2 > DMDBS > marl > TiO2. The subsequent melting endotherms for most of the sPP compounds exhibited double melting peaks, while that for the marl‐filled sPP exhibited triple melting peaks. Wide‐angle X‐ray diffraction analysis showed that addition of these fillers did not affect the crystal modification of the sPP matrix. Mechanical property measurements revealed that both the tensile strength and the percentage of elongation at yield for the sPP compounds investigated were not much different from those of the neat sPP. After natural weathering for 1 month, the tensile strength at yield for the sPP compounds investigated increased, at the expense of the percentage of elongation at yield, but, after natural weathering for 3 months, both the tensile strength and the percentage of elongation at yield were found to decrease.Effects of various organic and inorganic nucleating agents on non‐isothermal melt‐crystallization of syndiotactic poly(propylene) (recorded at a cooling rate of 10 °C · min−1).magnified imageEffects of various organic and inorganic nucleating agents on non‐isothermal melt‐crystallization of syndiotactic poly(propylene) (recorded at a cooling rate of 10 °C · min−1).
Cover Picture: Macromol. Theory Simul. 7/2004
Authors: Amoskov Victor M. , Birshtein Tatiana M. , Darinskii Anatoly A. , Tupitsyna Alla I. 
Published: August 2004

Cover: The picture on the cover shows how a lateral force (flow) applied to a polymer brush induces its compression.Further details can be found in the Full Paper by V. M. Amoskov, T. M. Birshtein,* A. A. Darinskii, and A. I. Tupitsyna on page 629.
Impact of the motor complications of Parkinson's disease on the quality of life
Authors: Chapuis Stéphane , Ouchchane Lemlih , Metz Olivier , Gerbaud Laurent , Durif Franck 
Published: August 2004

AbstractThe impact of motor complications of Parkinson's disease (PD), especially levodopa‐induced dyskinesias, on quality of life (QL) was studied in 143 patients with PD. All were evaluated on the Hoehn and Yahr (H&Y) scale, and the Motor part of the Unified Parkinson's Disease Rating Scale (UPDRS). Motor complications were analyzed using the UPDRS Parts IVA and IVB and the Abnormal Involuntary Movement Scale. A specific Parkinson's disease quality of life questionnaire (39‐item version, PDQ‐39) was used. Motor complications significantly worsened the PDQ‐39 Summary Index (PDQ‐SI) of patients with PD. The dimensions of Mobility, Activities of Daily Living, Stigma, and Communication were the most strongly affected. “Peak dose” dyskinesia decreased Mobility, Emotional Well‐Being, and Cognition, whereas biphasic dyskinesia affected Mobility, Stigma, Communication, and Activities of Daily Living. Morning akinesia, end‐of‐dose fluctuations, and “unpredictable offs” decreased QL on the dimensions of Mobility, Activities of Daily Living, Stigma, and Communication. Nocturnal akinesia led to a deterioration of all dimensions of the PDQ‐39. Thus, motor complications and especially nocturnal akinesia and biphasic dyskinesias worsened the QL of PD patients. © 2004 Movement Disorder Society
Disturbed egocentric space representation in cervical dystonia
Authors: Müller Sandra V. , Gläser Peggy , Tröger Matthias , Dengler Reinhard , Johannes Sönke , Münte Thomas F. 
Published: August 2004

AbstractIn addition to visual spatial input, vestibular and proprioceptive signals are used in judging the egocentric space. We asked whether the abnormal head posture of patients with cervical dystonia (CD) is associated with distortions of their internal spatial reference frame. The perception of subjective straight‐ahead (SSA) was tested under various conditions in 28 CD patients and in matched controls. They were asked to direct a laser pointer to the position that they believed to be “straight ahead” relative to their bodies' orientation (body‐centered spatial perception). Body‐independent visual spatial perception was assessed with different neuropsychological tests. CD patients had a greater deviation of the subjective straight ahead, indicating body‐centered visual spatial perception, than controls. No effects were seen in body‐independent visual spatial perception. Patients with CD are impaired in body‐centered, egocentric spatial perception, but not in body‐independent, allocentric spatial perception. © 2004 Movement Disorder Society
Substituent effects on scalar J(13C, 13C) couplings in pyrimidines. An experimental and DFT study
Authors: de Kowalewski Dora G. , Díez Ernesto , Esteban Angel L. , Barone Verónica , Peralta Juan E. , Contreras Rubén H. 
Published: August 2004

AbstractOne‐ two‐ and three 13C, 13C (n = 1, 2, 3) scalar couplings, nJ(C,C) in a set of pyrimidine derivatives were studied both experimentally at natural abundance and theoretically by their DFT calculation of all four contributions. Trends of non‐contact terms are discussed and substituent effects are rationalized, comparing some of them with the corresponding values in benzene and pyridine. Although substituent effects on non‐contact terms are relatively important, the whole trend is dominated by the Fermi contact term. According to the current literature, substituent effects on 1J(C,C) couplings in benzene derivatives are dominated by the inductive effect, which, apparently, is also the case in nitrogen heteroaromatic compounds. However, some differences observed in this work for substituent effects on 1J(C,C) couplings in pyrimidine derivatives suggest that in the latter type of compounds substituent effects can be affected by the orientation of the ring nitrogen lone pairs. Copyright © 2004 John Wiley & Sons, Ltd.
Dependence of 1H NMR chemical shifts of geminal protons of glycosyloxy methylene (H2‐26) on the orientation of the 27‐methyl group of furostane‐type steroidal saponins
Authors: Agrawal Pawan K. 
Published: August 2004

AbstractAn approach based on the difference (Δab = δa − δb) between the 1H NMR chemical shifts (δa, δb) of the geminal protons of glycosyloxy methylene (H2‐26) (Δab = <0.48 for 25R; Δab = >0.57 for 25S) is proposed for ascertaining 25R/25S orientation of the 27‐methyl group of furostane‐type steroidal saponins. These studies suggested the 25R‐orientation of the 27‐Me group for the furostanol glycosides isolated by Wu et al. from Tribulus terrestris. Copyright © 2004 John Wiley & Sons, Ltd.
A study of the 17O carbonyl chemical shifts in substituted benzaldehydes
Authors: Li Lidong , Li Linsheng 
Published: August 2004

AbstractAn analysis of 17O carbonyl chemical shifts of 50 substituted benzaldehydes leads to an empirical equation, δcal(17O) = 564.0 + ΣΔo + ΣΔm + ΣΔp + C, for calculating 17O chemical shifts. This equation is based on a linear regression analysis using 11 substituent parameters and leads to good conformity with the expected data. Copyright © 2004 John Wiley & Sons, Ltd.
Heating caused by radiofrequency irradiation and sample rotation in 13C magic angle spinning NMR studies of lipid membranes
Authors: Dvinskikh Sergey V. , Castro Vasco , Sandström Dick 
Published: August 2004

AbstractApplication of rapid sample rotation and radiofrequency irradiation in magic angle spinning (MAS) NMR of lipid bilayers can significantly increase the sample temperature. In this work, we studied the extent of heating during the acquisition of 1H‐decoupled 13C MAS spectra of hydrated dimyristoylphosphatidylcholine (DMPC) in the Lα phase. First, we describe a simple procedure for determining the increase in temperature by observing the shift of the 1H water signal. The method is then used to identify and assess the various factors that contribute to the sample heating. The important factors discussed in this paper include: (i) the spinning speed, (ii) the variable‐temperature gas pressure, (iii) the rotor geometry, (iv) the power, duration and frequency of the radiofrequency irradiation and (v) the hydration level. A comparison of different heteronuclear decoupling schemes in terms of their ability to produce highly resolved 13C spectra of DMPC is also reported. Copyright © 2004 John Wiley & Sons, Ltd.
Theoretical studies on the aromaticity of selected hydroxypyrones and their cations and anions. Part 1—Aromaticity of heterocyclic pyran rings
Authors: Zborowski Krzysztof , Grybos Ryszard , Proniewicz Leonrad M. 
Published: August 2004

AbstractThe aromaticity of heterocyclic pyran rings in selected hydroxypyrones and their anions and cations was studied using three aromaticity indices, HOMA, I6 and NICS. These values were determined for theoretical geometries obtained at the HF, SVWN, B3LYP and B1LYP levels of calculations with the 6–311 + +G(d,p) basis set. The data obtained show that the aromaticity for the hydroxypyrones under investigation increases in the order: anion < neutral molecule < cation. Copyright © 2004 John Wiley & Sons, Ltd.
Kinetic isotope effects for non‐adiabatic proton transfer in benzophenone—N‐methylacridan contact radical ion pairs
Authors: Peters Kevin S. , Kim Ganghyeok 
Published: August 2004

AbstractThe dynamics of proton transfer within a variety of substituted benzophenones–N‐methylacridan contact radical ion pairs in benzene were examined. The correlation of the rate constants for proton transfer with the thermodynamic driving force reveals both normal and inverted regions for proton transfer in benzene. Employing the isotopically labeled compounds N‐methyl‐d3‐acridan and N‐methylacridan‐9,9‐d2, the kinetic deuterium isotope effects were examined. The isotope dependence for the transfer process was examined within the context of the Lee–Hynes model for non‐adiabatic proton transfer. The theoretical analysis of the experimental data suggests that the reaction path for proton–deuteron transfer involves tunneling. Conventional transition‐state theory with the inclusion of the Bell correction for tunneling in the region of the transition state cannot account for the observed kinetic behavior. Copyright © 2004 John Wiley & Sons, Ltd.
A new concept for isotope ratio monitoring liquid chromatography/mass spectrometry
Authors: Krummen Michael , Hilkert Andreas W. , Juchelka Dieter , Duhr Alexander , Schlüter Hans‐Jürgen , Pesch Reinhold 
Published: August 2004

AbstractA new interface for the on‐line coupling of a liquid chromatograph to a stable isotope ratio mass spectrometer has been developed and tested. The interface is usable for 13C/12C determination of organic compounds, allowing measurement of small changes in 13C abundance in individual analyte species. All of the carbon in each analyte is quantitatively converted into CO2 while the analyte is still dissolved in the aqueous liquid phase. This is accomplished by an oxidizing agent such as ammonium peroxodisulfate. The CO2 is separated from the liquid phase and transferred to the mass spectrometer. It is shown that the whole integrated process does not introduce isotope fractionation. The measured carbon isotope ratios are accurate and reproducible. The sensitivity of the complete system allows isotope ratio determination down to 400 ng of compound on‐column. By‐passing the high‐performance liquid chromatography (HPLC) separation allows bulk isotopic analysis with substantially lower sample amounts than those required by conventional elemental analyzers. The results of the first applications to amino acids, carbohydrates, and drugs, eluted from various types of HPLC columns, are presented. The wide range of chromatographic methods enables the analysis of compounds never before amenable to isotope ratio mass spectrometry techniques and may lead to the development of many new assays. Copyright © 2004 John Wiley & Sons, Ltd.