bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crosslinking reaction of poly(vinyl alcohol) with poly(acrylic acid) (PAA) by heat treatment: Effect of neutralization of PAA
Authors: Kumeta K. , Nagashima I. , S. Matsui  , K. Mizoguchi  
Published: September 2003

AbstractThe crosslinking reaction of poly(vinyl alcohol) (PVA) by esterification using poly(acrylic acid) (PAA) as a crosslinking reagent was investigated to obtain highly insoluble PVA materials. Blend films of PVA and PAA (PVA/PAA = 8/2) were prepared to examine the effect of degree of neutralization (DN) in PAA and heat‐treatment conditions on the degree of crosslinking reaction. The degree of crosslinking reaction varied significantly when the DN of PAA changed. The optimum DN for the crosslinking reaction was in the range of 5 to 10 mol %. In the case of unneutralized PAA, the degree of crosslinking reaction was at most 15 mol % by heat treatment for 20 min at 200°C. Applying partially neutralized PAA (DN = 10 mol %) raised the degree to about 40 mol % under the same heat‐treatment conditions. FTIR analysis revealed that the hydroxyl group of PVA in the film blended with unneutralized PAA was degraded to a greater degree than that with partially neutralized PAA as a result of heat treatment. It was found that heat treatment at a low pH condition enhances the degradation of the hydroxyl group of PVA, resulting in a decrease of the number of crosslinking sites by esterification. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2420–2427, 2003
Phase behavior of N‐isopropylacrylamide/acrylic acid copolymer hydrogels prepared with ultrasound
Authors: Seida Yoshimi , Takeshita Kenji , Nakano Yoshio 
Published: September 2003

AbstractN‐Isopropylacrylamide/acrylic acid copolymer hydrogels were synthesized with ultrasound. The thermoresponsive phase behaviors of gels synthesized with ultrasound (US gels) were investigated and compared with those of gels synthesized in the absence of ultrasound (FR gels). The US gels showed thermoresponsive swelling behavior with a large hysteresis over a wide range of temperatures around its phase‐transition temperature. The hysteresis became larger with an increasing copolymerized acrylic acid content. The US gels were also characterized from the viewpoint of chemical, hydration, and macroscopic physical structures. Little difference was observed in the chemical and hydration structures of the FR gels and US gels. The macroscopic physical structure of the US gels was, however, distinct from that of the FR gels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2449–2452, 2003
Influence of untreated and novel electron‐beam‐modified surface‐coated silica filler on the thermorheological properties of ethylene–octene copolymer
Authors: Ray Sudip , Bhowmick Anil K. , Swayajith S. 
Published: September 2003

AbstractWe developed surface‐modified silica fillers by coating these with an acrylate monomer, trimethylolpropane triacrylate, or a silane coupling agent, triethoxyvinyl silane, followed by electron‐beam irradiation at room temperature. These were incorporated in an ethylene–octene copolymer rubber. Thermorheological studies of the unvulcanized ethylene–octene copolymer and its untreated and modified silica‐filled composites were done with a shear dynamic oscillating rheometer. Modification of the silica filler, especially via the silanization process followed by electron beam treatment, significantly reduced filler–filler networking as revealed from the log–log plots of storage modulus and complex shear viscosity, and its real component. The rheological complexity of the compositions was analyzed from a double logarithmic plot of the storage modulus and loss modulus. The results obtained from the master curves constructed on the basis of the time–temperature superposition principle and the activation energy calculated from the Arrhenius equation for the flow of above these compounds further supported these findings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2453–2459, 2003
Molecular cloning and characterization of a cDNA encoding cytochrome c oxidase subunit Va from the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae)
Authors: Ayala Jorge , Dowdy Alan K. , Beeman Richard W. , Zhu Kun Yan 
Published: September 2003

AbstractA cDNA encoding subunit Va of cytochrome c oxidase (EC 1.9.3.1) was cloned and characterized from a lesser grain borer (Rhyzopertha dominica) cDNA library. The complete cDNA consists of 693‐bp and contains an open reading frame of 450‐bp that encodes 150 amino acid residues. The sequence includes a 28‐bp putative N‐terminal and a 122‐bp putative mature protein. The estimated molecular weight and pI for the predicted mature protein are 13,962 and 4.60, respectively. The cDNA‐deduced amino acid sequence of the mature protein shows 73% identity to that of a corresponding subunit of African malaria mosquito (Anopheles gambiae) and 59% identity to that of the fruit fly (Drosophila melanogaster). In addition, 31% of all amino acid residues are conserved among six different animal species. Evolutionary distance analysis suggests that cytochrome c oxidase subunit Va from R. dominica is most similar to the corresponding subunit from the malaria mosquito. Northern analysis revealed a single 4.9‐kb transcript that is much larger than that found in mammalian species. Arch. Insect Biochem. Physiol. 54:47–54, 2003. © 2003 Wiley‐Liss, Inc.
A continuous spectrophotometric assay for the determination of diamondback moth esterase activity
Authors: He Xiaodun 
Published: September 2003

AbstractConventional methods to determine esterase activity from insects are composed of a three‐step process where the enzyme is allowed to hydrolyze a 1‐naphthyl acetate substrate, that reaction is quenched by a SDS detergent, and then a Fast Blue B dye complex is formed with 1‐naphthol, the product of 1‐naphthyl acetate hydrolysis. These methods measure dye‐product complex rather than the product, 1‐naphthol. A new assay is presented that continuously monitors the formation of 1‐naphthol with the hydrolysis of an esterase substrate. The esterase activity was determined as the slope of the linear regression change in absorbance over time at 320 nm. The continuous assay provides a simple, rapid, and sensitive method for measuring esterases extracted from a single diamondback moth in 1–10 min. The detection limit of the assay is approximately 0.6 μM 1‐naphthol. The 1‐naphthol product from the esterase reaction was confirmed by HPLC analysis. According to the assay, the Km and Vmax values of the esterase were 28 ± 2 μM and 6.0 ± 0.1 μM/min, respectively, at 37°C for 1‐naphthyl acetate. The Ki value was 9 ± 2 μM using azadirachtin, an insecticide from neem tree, Azadirachta indica (A.Juss). Azadirachtin was a reversible competitive inhibitor of the esterase activity. Arch Insect Biochem Physiol 54:68–76, 2003. Published 2003 Wiley‐Liss, Inc.
The ken and barbie gene encoding a putative transcription factor with a BTB domain and three zinc finger motifs functions in terminalia development of Drosophila
Authors: Lukacsovich Tamas , Yuge Kazuya , Awano Wakae , Asztalos Zoltan , Kondo Shunzo , Juni Naoto , Yamamoto Daisuke 
Published: September 2003

AbstractMutations in the ken and barbie locus are accompanied by the malformation of terminalia in adult Drosophila. Male and female genitalia often remain inside the body, and the same portions of genitalia and analia are missing in a fraction of homozygous flies. Rotated and/or duplicated terminalia are also observed. Terminalia phenotypes are enhanced by mutations in the gap gene tailless, the homeobox gene caudal, and the decapentaplegic gene that encodes a TGFβ‐like morphogen. The ken and barbie gene encodes a protein with three CCHH‐type zinc finger motifs that are conserved in several transcription factors such as Krüppel and BCL‐6. All defects in ken and barbie mutants are fully rescued by the expression of a wild‐type genomic construct, which establishes the causality between phenotypes and the gene. Arch. Insect Biochem. Physiol. 54:77–94, 2003. © 2003 Wiley‐Liss, Inc.
Cloning of a putative Bombyx mori TFIIB‐related factor (BRF)
Authors: Martinez M. Juanita , Sprague Karen U. 
Published: September 2003

AbstractTo identify the protein domains responsible for its conserved and specialized functions, putative TFIIB‐Related Factor (BRF) from the silkworm (Bombyx mori) was compared with BRFs from other organisms. The Bombyx BRF coding region was assembled from three separate and overlapping cDNA fragments. Fragments encoding the middle portion and the 3′ end were discovered in the Bombyx mori Genome Project “Silkbase” collection through sequence homology with human BRF1, and the fragment encoding the N‐terminus was isolated in our laboratory using the 5′ RACE method. Southern analysis showed that silkworm BRF is encoded by a single‐copy gene. Bombyx BRF contains the following domains that have been noted in all other BRFs, and that are likely, therefore, to provide highly conserved functions: a zinc finger domain, an imperfect repeat, three “BRF Homology” domains, and an acidic domain at the C‐terminus. As expected from the evolutionary relationships among insects and mammals, Bombyx BRF is more similar overall to Drosophila BRF (55% identical) than to human BRF1 (42% identical). Detailed examination of individual domains reveals a remarkable exception, however. Domain II of Bombyx BRF is more similar to its human counterpart than to Drosophila Domain II. This result indicates that Domain II has undergone unusual divergence in Drosophila, and suggests a structural basis for Drosophila BRF's unique pattern of interaction with other transcription factors. Arch. Insect Biochem. Physiol. 54:55–67, 2003. © 2003 Wiley‐Liss, Inc.
Pharmacokinetics and pharmacodynamics of azosemide
Authors: Suh Ok K. , Kim So H. , Lee Myung G. 
Published: September 2003

AbstractAzosemide is used in the treatment of oedematous states and hypertension. The exact mechanism of action is not fully understood, but it mainly acts on both the medullary and cortical segments of the thick ascending limb of the loop of Henle. Delayed tolerance was demonstrated in humans by homeostatic mechanisms (principally an increase in aldosterone secretion and perhaps also an increase in the reabsorption of solute in the proximal tubule). After oral administration to healthy humans in the fasting state, the plasma concentration of azosemide reached its peak at 3–4 h with an absorption lag time of approximately 1 h and a terminal half‐life of 2–3 h. The estimated extent of absolute oral bioavailability in humans was approximately 20.4%. After oral administration of the same dose of azosemide and furosemide, the diuretic effect was similar between the two drugs, but after intravenous administration, the effect of azosemide was 5.5–8 times greater than that in furosemide. This could be due to the considerable first‐pass effect of azosemide. The protein binding to 4% human serum albumin was greater than 95% at azosemide concentrations ranging from 10 to 100 μg/ml using an equilibrium dialysis technique. The poor affinity of human tissues to azosemide was supported by the relatively small value of the apparent post‐pseudodistribution volume of distribution (Vdβ), 0.262 l/kg. Eleven metabolites (including degraded products) of azosemide including M1, glucuronide conjugates of both M1 and azosemide, thiophenemethanol, thiophencarboxylic acid and its glycine conjugate were obtained in rats. Only azosemide and its glucuronide were detected in humans. In humans, total body clearance, renal clearance and terminal half‐life of azosemide were 112 ml/min, 41.6 ml/min and 2.03 h, respectively. Azosemide is actively secreted in the renal proximal tubule possibly via nonspecific organic acid secretory pathway in humans. Thus, the amount of azosemide that reaches its site of action could be significantly modified by changes in the capacity of this transport system. This capacity, in turn, could be predictably changed in disease states, resulting in decreased delivery of the diuretic to the transport site, as well as in the presence of other organic acids such as nonsteroidal anti‐inflammatory drugs which could compete for active transport of azosemide. The urinary excretion rate of azosemide could be correlated well to its diuretic effects since the receptors are located in the loop of Henle. The diuretic effects of azosemide were dependent on the rate and composition of fluid replacement in rabbits; therefore, this factor should be considered in the evaluation of bioequivalence assessment. Copyright © 2003 John Wiley & Sons, Ltd.
Convergence in peptide folding simulation: Multiple trajectories of a potential AIDS pharmacophore
Authors: Mihailescu Dan , Reed Jennifer , Smith Jeremy C. 
Published: September 2003

AbstractTo examine the conformational properties in aqueous solution of a 15‐residue peptide that is a potential pharmacophore for AIDS vaccine development, molecular dynamics simulations were performed in water starting from structures determined experimentally in three different organic solvents. Convergence characteristics of the simulation are examined in Cartesian and conformational spaces. In addition, novel analysis tools are employed including a multidimensional scaling method to represent the distance between trajectory frames. As these methods are based on a variety of physical parameters, they provide a useful cross‐check on the structural convergence. Theoretical two‐dimensional (2D) 1H‐NMR spectra are also generated. These are superficially quite different in appearance, demonstrating that backbone similarities difficult to identify by visual inspection of 2D NMR data can be revealed using the methods described here. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 121–133, 2003
Molecular dynamics studies of alanine racemase: A structural model for drug design
Authors: Mustata Gabriela Iurcu , Soares Thereza A. , Briggs James M. 
Published: September 2003

AbstractAlanine racemase (AlaR) is a bacterial enzyme that catalyzes the interconversion of L‐ and D‐alanine, which is an essential constituent of the peptidoglycan layer of the bacterial cell wall and requires pyridoxal 5′–phosphate (PLP) as a cofactor. The enzyme is universal to bacteria, including mycobacteria, making it an attractive target for drug design. To investigate the effects of flexibility on the binding modes of the substrate and an inhibitor and to analyze how the active site is affected by the presence of the substrate versus inhibitor, a molecular dynamics simulation on the full AlaR dimer from Bacillus stearothermophilus (pdb code: 1SFT) with a D‐alanine molecule in one active site and the noncovalent inhibitor, propionate, in the second site has been carried out. Within the time scale of the simulation, we show that the active site becomes more stabilized in the presence of substrate versus inhibitor. The results of this simulation are in agreement with the proposed mechanism of alanine racemase reaction in which the substrate carboxyl group directly participates in the catalysis by acting cooperatively with Tyr 265′ and Lys 39. A structural water molecule in contact with both substrate and inhibitor (i.e., in both active sites) and bridging residues in both active sites was identified. It shows a remarkably low mobility and does not exchange with bulk water. This water molecule can be taken into account for the design of specific AlaR inhibitors by either utilizing it as a bridging group or displacing it with an inhibitor atom. The results presented here provide insights into the dynamics of the alanine racemase in the presence of substrate/inhibitor, which will be used for the rational design of novel inhibitors. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 186–200, 2003
Interaction of angiotensin II with the C‐terminal 300–320 fragment of the rat angiotensin II receptor AT1a monitored by NMR
Authors: D'Amelio Nicola , Gaggelli Elena , Gaggelli Nicola , Lozzi Luisa , Neri Paolo , Valensin Daniela , Valensin Gianni 
Published: September 2003

AbstractInteraction between angiotensin II (Ang II) and the fragment peptide 300–320 (fCT300–320) of the rat angiotensin II receptor AT1a was demonstrated by relaxation measurements, NOE effects, chemical shift variations, and CD measurements. The correlation times modulating dipolar interactions for the bound and free forms of Ang II were estimated by the ratio of the nonselective and single‐selective longitudinal relaxation rates. The intermolecular NOEs observed in NOESY spectra between HN protons of 9LysfCT and 6Hisang, 10PhefCT and 8Pheang, HN proton of 3TyrfCT and Hα of 4Tyrang, 5PhefCTHδ and Hα of 4Tyrang indicated that Ang II aromatic residues are directly involved in the interaction, as also verified by relaxation data. Some fCT300–320 backbone features were inferred by the CSI method and CD experiments revealing that the presence of Ang II enhances the existential probability of helical conformations in the fCT fragment. Restrained molecular dynamics using the simulated annealing protocol was performed with intermolecular NOEs as constraints, imposing an α‐helix backbone structure to fCT300–320 fragment. In the built model, one strongly preferred interaction was found that allows intermolecular stacking between aromatic rings and forces the peptide to wrap around the 6Leu side chain of the receptor fragment. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 134–144, 2003
Molecular weight effects on the glass transition of gelatin/cosolute mixtures
Authors: Kasapis Stefan , Al‐Marhoobi Insaf M. , Mitchell John R. 
Published: September 2003

AbstractThe structural properties of four gelatin fractions in mixture with sucrose and glucose syrup have been investigated extensively using small deformation dynamic oscillation. The total level of solids was 80%, the number average molecular weight of the protein ranged from 29.2 to 68 kD, and the temperatures were between 60 and −60°C. Remarkably, the nature of the time and temperature dependence on the viscoelastic functions of all samples could be reduced to master curves using horizontal shift factors. The construction of master curves indicates a common mechanism of structure formation, which, in accordance with the synthetic polymer literature, comprises the rubbery zone, glass transition region, and glassy state. Application of Ferry's free‐volume formalism and Rouse theory suggests that there is no change in the thermodynamic state of materials during vitrification, with changes in molecular weight simply introducing shifts in the time scale and temperature range of contributions to viscoelasticity. The thermorheological simplicity allowed development of the concept of “rheological” Tg. This was defined as the point between free‐volume phenomena of the polymeric backbone occurring in the glass transition region and an energetic barrier to rotation required for local chain rearrangements in the glassy state. Mechanical relaxation and retardation distribution functions were calculated, thus obtaining values for the effective friction coefficient per monomer unit of the protein. It appears that the local friction coefficient is governed by a linear relationship between fractional free volume and the decreasing molecular weight of the protein, which introduces additional voids due to molecular ends. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 169–185, 2003
Link, twist, energy, and the stability of DNA minicircles
Authors: Hoffman Kathleen A. , Manning Robert S. , Maddocks John H. 
Published: September 2003

AbstractWe describe how the stability properties of DNA minicircles can be directly read from plots of various biologically intuitive quantities along families of equilibrium configurations. Our conclusions follow from extensions of the mathematical theory of distinguished bifurcation diagrams9, 21 that are applied within the specific context of an elastic rod model of minicircles. Families of equilibria arise as a twisting angle α is varied. This angle is intimately related to the continuously varying linking number Lk for nicked DNA configurations that is defined as the sum of Twist and Writhe. We present several examples of such distinguished bifurcation diagrams involving plots of the energy E, linking number Lk, and a twist moment m3, along families of cyclized equilibria of both intrinsically straight and intrinsically curved DNA fragments. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 145–157, 2003
Structure of an elastin‐mimetic polypeptide by solid‐state NMR chemical shift analysis
Authors: Hong M. , Isailovic D. , McMillan R.A. , Conticello V.P. 
Published: September 2003

AbstractThe conformation of an elastin‐mimetic recombinant protein, [(VPGVG)4(VPGKG)]39, is investigated using solid‐state NMR spectroscopy. The protein is extensively labeled with 13C and 15N, and two‐dimensional 13C‐13C and 15N‐13C correlation experiments were carried out to resolve and assign the isotropic chemical shifts of the various sites. The Pro 15N, 13Cα, and 13Cβ isotropic shifts, and the Gly‐3 Cα isotropic and anisotropic chemical shifts support the predominance of type‐II β‐turn structure at the Pro‐Gly pair but reject a type‐I β‐turn. The Val‐1 preceding Pro adopts mostly β‐sheet torsion angles, while the Val‐4 chemical shifts are intermediate between those of helix and sheet. The protein exhibits a significant conformational distribution, shown by the broad line widths of the 15N and 13C spectra. The average chemical shifts of the solid protein are similar to the values in solution, suggesting that the low‐hydration polypeptide maintains the same conformation as in solution. The ability to measure these conformational restraints by solid‐state NMR opens the possibility of determining the detailed structure of this class of fibrous proteins through torsion angles and distances. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 158–168, 2003
Hyaluronate tetrasaccharide‐ CU(II) interaction: A NMR study
Authors: D'Auria Gabriella , Flores Germana , Falcigno Lucia , Oliva Romina , Vacatello Manuela , Michela Corsaro Maria , Parrilli Michelangelo , Paolillo Livio 
Published: September 2003

AbstractThe coordination of Cu(II) to a hyaluronate tetrasaccharide (HAt) was investigated in aqueous solution by 13C and 1H relaxation measurements at two magnetic fields, 9 and 14 T. The HAt interaction with the metal ion was monitored following the nuclear paramagnetic relaxation enhancements R1p and R2p produced by the copper addition. The data analysis shows that the paramagnetic effect is differently experienced by the nuclei in different monosaccharide residues. A molecular model for the complex HAt‐Cu(II) was built taking into account the experimental data. The model shows the presence of two binding sites, both involving the carboxylate groups of the two glucuronic acid units. The first site, that best simulates the HA binding site, is located on the ligand core, while the second one is located on the terminal glucuronic acid residue. Both binding sites involve, in addition to the carboxylate groups, the O4 oxygens of the glucuronic acid residues. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 260–269, 2003