bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of water‐soluble perylenediimide‐functionalized polymer through esterification with poly(vinyl alcohol)
Authors: Salavagione Horacio J. , Martínez Gerardo , Gómez Rafael , Segura José L. 
Published: July 2010

AbstractA new material has been prepared by covalent attachment of a perylene derivative, N‐(carboxyphenyl)‐N′‐(8‐pentadecyl)perylene‐3,4:9,10‐bis(dicarboximide) (PDI‐COOH), to poly(vinyl alcohol) (PVA) by esterification. The perylenediimide (PDI)‐modified PVA polymers are soluble in water and dimethylsulfoxide (DMSO). This solubility is conferred to the insoluble perylene derivative by the water‐soluble polymer. The materials have been characterized by hydrogen‐nuclear magnetic resonance, Fourier transform infrared spectra, X‐ray diffraction, and X‐ray photoelectron spectroscopy confirming the covalent attachment of the PDI to the polymer chains. The significant changes in the crystalline parameters and the thermal stability observed for the polymer after the esterification also confirm the covalent linkage with PDI. In addition, the PDI‐modified PVA shows good fluorescence both in solution (quantum yield ∼0.2–0.25) and in solid suggesting that the PDI retains largely its photochemical and photophysical properties after immobilization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3613–3622, 2010
Well‐controlled amphiphilic block glycopolymers and their molecular recognition with lectins
Authors: León Orietta , Bordegé Vanesa , Muñoz‐Bonilla Alexandra , Sánchez‐Chaves Manuel , Fernández‐García Marta 
Published: July 2010

AbstractThe atom transfer radical polymerization of an unprotected glycomonomer, 2‐{[(D‐glucosamin‐2N‐yl)carbonyl]oxy}ethyl methacrylate (HEMAGl) is firstly reported. Controlled polymerizations were performed with the CuBr/N,N,N′,N′,N′‐pentamethyldiethylene triamine catalytic system with ethyl 2‐bromoisobutyrate and 1,2‐bis(bromoisobutyryloxy) ethane as mono and difunctional initiators in DMF solutions (80% w/w) at 40 and 50 °C, respectively. The polymerization of HEMAGl resulted in a controlled polymerization with linear kinetics, molecular weights which increase with conversion and narrow polydispersity indexes. Mono and difunctional PHEMAGl macroinitiators were used to synthesize the amphiphilic di and triblock glycopolymers with n‐butyl acrylate, verifying their living character. The self‐assembly of these glycopolymers in distilled water and in 0.1M NaCl solutions was studied by dynamic light scattering, showing the role of hydrogen bonds and the hydrophobic parts. In addition, their interaction with Concanavalin A lectin was examined, demonstrating the influence of molecular weight and copolymer composition. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3623–3631, 2010
9,9′‐spirobifluorene‐containing polycarbonates: Transparent polymers with high refractive index and low birefringence
Authors: Seto Ryota , Sato Takashi , Kojima Takahiro , Hosokawa Katsumoto , Koyama Yasuhito , Konishi Gen‐Ichi , Takata Toshikazu 
Published: July 2010

AbstractSyntheses of 2,2′‐bisalcoholic group‐substituted 9,9′‐spirobifluorene monomers 2 were performed by the reaction of 2,2′‐dihydroxy‐9,9′‐spirobifluorene 2a with haloalcohols. Polycarbonates consisting of 9,9′‐spirobifluorene skeleton in the main chain (PC 4) were synthesized by the polycondensation of 2,2′‐bisalcoholic monomers 2 and triphosgene or diphenyl carbonate. PC 4 showed good thermal stability: the 5% weight loss temperature was over 330 °C under both nitrogen and air atmospheres. The glass transition temperature was in a range of 16–269 °C estimated by differential scanning calorimetry, depending on the flexibility of the alkylene or oxyethylene chains of 2. PC 4 showed high solubility toward ordinary organic solvents such as CHCl3, benzene, and THF, making possible the preparation of the flexible thin films. Very high refractive index in a range of 1.62–1.66 at 589 nm was observed although PC 4 consists only of C, H, and O atoms, whereas very low degree of birefringence was confirmed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3658–3667, 2010
Solution properties of thermothickening copolymers bearing hydrocarbon end‐capped oxyethylene units
Authors: Zhang Xiaofei , Jiang Xiancai , Zhang Xi , Dai Hua 
Published: July 2010

AbstractNovel thermothickening copolymers composed of acrylamide and a macromer bearing hydrocarbon end‐capped oxyethylene units were synthesized. Influences of polymer concentration, salt content, shear rate, and temperature on the solution behavior were investigated. The polymer solution exhibited shear‐thickening behavior at low‐to‐moderate shear rates (<50 s−1), and the shear‐thickening behavior was dependent on polymer concentration, NaCl content, and temperature. With the increase of salinity, apparent viscosity of polymer solution increased dramatically (especially at low shear rates). At higher NaCl content (>20 wt %), polymer solutions became physical gel, and the apparent viscosity increased by several orders of magnitude. The polymer solutions exhibited excellent thermothickening behavior, even at the low concentration of 0.15 wt %. The results of rheological measurements showed that the storage and loss modulus were successfully fitted to a single Maxwell element at low temperature (<60 °C). © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1799–1808, 2010
Effect of the lithium cation on the sorption and electrical properties of amphiphilic block copolymers and their composites
Authors: da Silva M. M. S. , Rieumont J. , Nogueiras C. , Sánchez R. , de Oliveira H. P. 
Published: July 2010

AbstractThe use of lithium cation in composites of block copolymers [polyethylene‐b‐polyethylene oxide (PE‐b‐50%PEO and PE‐b‐80%PEO)] and their derivatives was tested as a modifier of the vapor sorption and impedance of these complexes. The block copolymer PE‐b‐80%PEO was modified by oxidation of its hydroxyl end group to both a carboxylic acid group (PE‐b‐80%PEO)CH2COOH and its sodium salt (PE‐b‐80%PEO)CH2COO− Na+ for the purpose of improving its compatibility and performance as a matrix for composites. These modified copolymers were characterized by FTIR, DSC, and mass spectrometry. The sorption of water of these copolymers and their composites with lithium nitrate was also compared, as well as the electrical properties of their composites were measured by electrical impedance spectroscopy. For the composites obtained with PE‐b‐80%PEO and lithium nitrate, it was found that lithium cation plays an important role increasing the sorption rate, which is maximized for the PE‐b‐80%PEO + (21% lithium nitrate) composite. For the copolymers (PE‐b‐80%PEO)CH2COOH and (PE‐b‐80%PEO)CH2COO− Na+ and their composites, the highest sorption rate was observed for salt in the following order: COO− Na+ > COOH > OH. The PE‐b‐80%PEO + (21% lithium nitrate) composite behaves as a solid polymeric ionic conductor fitting the Williams–Landel–Ferry equation. However, both (PE‐b‐80% PEO)CH2COOH and (PE‐b‐80%PEO)CH2COO− Na+ + (21% lithium nitrate) composites fitted the Variable Range Hopping equation, indicating a conductance trend with temperature governed by a thermally activated with energy of 0.482 and 0.524 eV and not by a relaxation process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1809–1817, 2010
Complexation of poly(acrylic acid) and poly(ethylene oxide) investigated by enhanced Rayleigh scattering method
Authors: Li Yunbo , Li Haixia , Chen Xudong , Zhu Fangming , Yang Jin , Zhu Yubin 
Published: July 2010

AbstractThe method of enhanced Rayleigh scattering spectroscopy (ERS) was developed to investigate the complexation of poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) in semidilute polymer solutions. Based on the Ornstein‐Zernike equation, the relationship between macromolecular static correlation length and ERS intensity was presented. Moreover, the ERS spectra were calculated by the moving window two‐dimensional (MW2D) correlation spectroscopy to get detailed information of the polymer complexation. The results indicated that the ERS spectroscopy characteristics of the polymer mixtures have similar trend, and the ERS intensity promptly increases as the macromolecular chains contract. The increase of ERS intensity showed that the degree of complexation between PAA and PEO increases when the pH value decreases. The complexation results from the collapse of macromolecular chains, which is induced by the PAA chains contracting and the enhanced association between PAA and PEO chains because of the hydrogen bond formation. In addition, the association resulting from the complexation of PAA and PEO in solution was demonstrated by the MW2D correlation spectroscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1847–1852, 2010
‘Admission into a helping plan’: a watershed between positive and negative experiences in breast cancer
Authors: Lilliehorn Sara , Hamberg Katarina , Kero Anneli , Salander Pär 
Published: July 2010

AbstractCancer patients are in an exposed situation that raises certain psychosocial needs in contact with health care. Previous studies have mainly investigated these needs by assessments on pre‐defined categories.Objective: The purpose of the present study is, from the patients' perspective, to identify breast cancer patients' psychosocial needs, and to synthesise them in a model reflecting the core of these needs.Methods: Seventy‐one patients treated with radiation therapy were consecutively included and repeatedly interviewed about their experiences of health care. ‘Critical incidents’ where identified from the interviews and analysed due to the similarities–differences technique in grounded theory.Results: Four categories of needs where detected: ‘access’, ‘information’, ‘treatment’ and ‘how approached’. These categories and their properties merged into a core category—‘admission into a helping plan’. These findings are well understood in terms of attachment theory. In times of immanent danger and stress people strive to find a ‘safe haven’ to attach to. Cancer patients' ‘safe haven’ can be described as ‘a helping plan’. It is not the result of a separate patient–caregiver relationship but is created by a pattern of individual experiences from all kind of contacts with the health‐care system as a whole.Conclusions: The presented model of patients needs as converging into ‘admission into a helping plan’ may serve as an easily comprehendible model for caregivers, guiding them to contribute to the patient's feeling of security and trust, and thus to the patient's own ‘hope work’. Copyright © 2009 John Wiley & Sons, Ltd.
Decision‐making preferences and information needs among Greek breast cancer patients
Authors: Almyroudi Augoustina , Degner Lesley F. , Paika Vassiliki , Pavlidis Nicholaos , Hyphantis Thomas 
Published: July 2010

AbstractObjectives: We aimed at assessing Greek breast cancer patients' preferences for participation in treatment decision making and their information needs.Methods: In a cross‐sectional study, 329 breast cancer patients were administered at the Control Preferences Scale, a card‐sort measurement designed to elicit preferences for participation in decision making. Information needs were assessed with Cassileth's Information Styles Questionnaire.Results: The majority of patients (71.1%) preferred to play a passive role in treatment decision making, with most of them wanting to delegate responsibility of the decision completely to their doctor (45.3%). A collaborative role was preferred by 24%, whereas only 4.6% chose an active role. Most women expressed a general desire for as much information as possible about their illness (62.6%), but a substantial proportion (37.4%) did not want detailed information; instead, they wished to avoid awareness of bad news. Women who desired less informational details and preferred a passive role requested less frequently a mammography (p<0.001) and/or Pap test (p<0.0005) prediagnostically.Conclusions: This study's findings showed that the proportion of patients who wanted to play a passive role in decision making is the highest reported compared to similar studies from other countries, indicating the impact of the dominating paternalistic model of the doctor–patient relationship in the Greek medical encounter. The association of desired information details and decision‐making preferences with screening for cancer procedures prediagnostically highlights the significance of providing the patients with the appropriate information and the choices available for their treatment. Copyright © 2010 John Wiley & Sons, Ltd.
Structural evidence suggests that antiactivator ExsD from Pseudomonas aeruginosa is a DNA binding protein
Authors: Bernhards Robert C. , Jing Xing , Vogelaar Nancy J. , Robinson Howard , Schubot Florian D. 
Published: July 2010

AbstractThe opportunistic pathogen P. aeruginosa utilizes a type III secretion system (T3SS) to support acute infections in predisposed individuals. In this bacterium, expression of all T3SS‐related genes is dependent on the AraC‐type transcriptional activator ExsA. Before host contact, the T3SS is inactive and ExsA is repressed by the antiactivator protein ExsD. The repression, thought to occur through direct interactions between the two proteins, is relieved upon opening of the type III secretion (T3S) channel when secretion chaperone ExsC sequesters ExsD. We have solved the crystal structure of Δ20ExsD, a protease‐resistant fragment of ExsD that lacks only the 20 amino terminal residues of the wild‐type protein at 2.6 Å. Surprisingly the structure revealed similarities between ExsD and the DNA binding domain of transcriptional repressor KorB. A model of an ExsD‐DNA complex constructed on the basis of this homology produced a realistic complex that is supported by the prevalence of conserved residues in the putative DNA binding site and the results of differential scanning fluorimetry studies. Our findings challenge the currently held model that ExsD solely acts through interactions with ExsA and raise new questions with respect to the underlying mechanism of ExsA regulation.
The osmolyte trimethylamine‐N‐oxide stabilizes the Fyn SH3 domain without altering the structure of its folding transition state
Authors: Lin Sung Lun , Zarrine‐Afsar Arash , Davidson Alan R. 
Published: July 2010

AbstractTrimethylamine‐N‐oxide (TMAO) is a naturally occurring osmolyte that stabilizes proteins against denaturation. Although the impact of TMAO on the folding thermodynamics of many proteins has been well characterized, far fewer studies have investigated its effects on protein folding kinetics. In particular, no previous studies have used Φ‐value analysis to determine whether TMAO may alter the structure of the folding transition state. Here we have measured the effects on folding kinetics of 16 different amino acid substitutions distributed across the structure of the Fyn SH3 domain both in the presence and absence of TMAO. The folding and unfolding rates in TMAO, on average, improved to equivalent degrees, with a twofold increase in the protein folding rate accompanied by a twofold decrease in the unfolding rate. Importantly, TMAO caused little alteration to the Φ‐values of the mutants tested, implying that this compound minimally perturbs the folding transition state structure. Furthermore, the solvent accessibility of the transition state was not altered as reflected in an absence of a TMAO‐induced change in the denaturant β factors. Through TMAO‐induced folding studies, a β factor of 0.5 was calculated for this compound, suggesting that the protein backbone, which is the target of action of TMAO, is 50% exposed in the transition state as compared to the native state. This finding is consistent with the equivalent effects of TMAO on the folding and unfolding rates. Through thermodynamic analysis of mutants, we also discovered that the stabilizing effect of TMAO is lessened with increasing temperature.
The kinemage: A tool for scientific communication
Authors: Richardson David C. , Richardson Jane S. 
Published: July 2010

AbstractA “kinemage” (kinetic image) is a scientific illustration presented as an interactive computer display. Operations on the displayed kinemage respond within a fraction of a second: the entire image can be rotated in real time, parts of the display can be turned on or off, points can be identified by selecting them, and the change between different forms can be animated. A kinemage is prepared and specified by the author(s) of a journal article, in order to better communicate ideas that depend on three‐dimensional information. The kinemages are distributed as plain text files of commented display lists and accompanying explanations. They are viewed and explored in an open‐ended way by the reader using a simple graphics program, such as the one described here (called MAGE), which presently runs on Macintosh computers. A utility (called PREKIN) helps authors prepare the kinemages. Kinemages are being implemented under the auspices of the Innovative Technology Fund.
Differences in hydrogen exchange behavior between the oxidized and reduced forms of Escherichia coli thioredoxin
Authors: Kaminsky S.M. , Richards F.M. 
Published: July 2010

AbstractAmide proton exchange of thioredoxin is used to monitor the structural effects of reduction of its single disulfide. An effective 3–5‐proton difference between the oxidized and reduced protein form is observed early in proton out‐exchange of the whole protein, which is independent of temperature in the range of 5–45 °C, indicating that redox‐sensitive changes are probably not due to low‐energy structural fluctuations. Medium resolution hydrogen exchange experiments have localized the redox‐sensitive amide protons to two parts of the sequence that are distant from each other in the three‐dimensional structure: the active‐site turn and the first β‐strand. The sum of the proton differences observed in the peptides from these regions is equal to that of the whole protein, indicating that all redox‐sensitive hydrogen exchange effects are observed in the peptide experiments. A model combining structural changes within the protein matrix with changes in the surface hydration properties is proposed as a mechanism for the communication between distant sites within the protein. Sound velocity and density measurements of reduced and oxidized thioredoxin are presented in the accompanying paper (Kaminsky, S.M. & Richards, F.M., 1992, Protein Sci. 1, 22–30).
Structure of a stabilizing disulfide bridge mutant that closes the active‐site cleft of T4 lysozyme
Authors: Jacobson R.H. , Matsumura M. , Faber H.R. , Matthews B.W. 
Published: July 2010

AbstractThe engineered disulfide bridge between residues 21 and 142 of phage T4 lysozyme spans the active‐site cleft and can be used as a switch to control the activity of the enzyme (Matsumura, M. & Matthews, B.W., 1989, Science 243, 792–794). In the oxidized form the disulfide increases the melting temperature of the protein by 11 °C at pH 2.The crystal structure of this mutant lysozyme has been determined in both the reduced and oxidized forms. In the reduced form, the crystal structure of the mutant is shown to be extremely similar to that of wild type. In the oxidized form, however, the formation of the disulfide bridge causes the α‐carbons of Cys 21 and Cys 142, on opposite sides of the active‐site cleft, to move toward each other by 2.5 Å. In association with this movement, the amino‐terminal domain of the protein undergoes a rigid‐body rotation of 5.1° relative to the carboxy‐terminal domain. This rotation occurs about an axis passing through the junction of the amino‐terminal and carboxy‐terminal domains and is also close to the axis that best fits the apparent thermal motion of the amino‐terminal domain seen previously in crystals of wild‐type lysozyme. Even though the engineered Cys 21‐Cys 142 disulfide links together the amino‐terminal and carboxy‐terminal domains of T4 lysozyme, it does not reduce the apparent mobility of the one domain relative to the other. The pronounced “hinge‐bending” mobility of the amino‐terminal domain that is suggested by the crystallographic thermal parameters of wild‐type lysozyme persists in the oxidized (and reduced) mutant structures. In the immediate vicinity of the introduced disulfide bridge the mutant structure is more mobile (or disordered) than wild type, so much so that the exact conformation of Cys 21 remains obscure. As with the previously described disulfide bridge between residues 9 and 164 of T4 lysozyme (Pjura, P.E., Matsumura, M., Wozniak, J.A., & Matthews, B.W., 1990, Biochemistry 29, 2592–2598), the engineered cross‐link substantially enhances the stability of the protein without making the folded structure more rigid.
Automated carboxy‐terminal sequence analysis of peptides
Authors: Bailey Jerome M. , Shenoy Narmada R. , Ronk Michael , Shively John E. 
Published: July 2010

AbstractProteins and peptides can be sequenced from the carboxy‐terminus with isothiocyanate reagents to produce amino acid thiohydantoin derivatives. Previous studies in our laboratory have focused on solution phase conditions for formation of the peptidylthiohydantoins with trimethylsilylisothiocyanate (TMS‐ITC) and for hydrolysis of these peptidylthiohydantoins into an amino acid thiohydantoin derivative and a new shortened peptide capable of continued degradation (Bailey, J.M. & Shively, J.E., 1990, Biochemistry 29, 3145–3156). The current study is a continuation of this work and describes the construction of an instrument for automated C‐terminal sequencing, the application of the thiocyanate chemistry to peptides covalently coupled to a novel polyethylene solid support (Shenoy, N.R., Bailey, J.M., & Shively, J.E., 1992, Protein Sci. 1, 58–67), the use of sodium trimethyl‐silanolate as a novel reagent for the specific cleavage of the derivatized C‐terminal amino acid, and the development of methodology to sequence through the difficult amino acid, aspartate. Automated programs are described for the C‐terminal sequencing of peptides covalently attached to carboxylic acid‐modified polyethylene. The chemistry involves activation with acetic anhydride, derivatization with TMS‐ITC, and cleavage of the derivatized C‐terminal amino acid with sodium trimethylsilanolate. The thiohydantoin amino acid is identified by on‐line high performance liquid chromatography using a Phenomenex Ultracarb 5 ODS(30) column and a triethylamine/phosphoric acid buffer system containing pentanesulfonic acid. The generality of our automated C‐terminal sequencing methodology was examined by sequencing model peptides containing all 20 of the common amino acids. All of the amino acids were found to sequence in high yield (90% or greater) except for asparagine and aspartate, which could be only partially removed, and proline, which was found not to be capable of derivatization. In spite of these current limitations, the methodology should be a valuable new tool for the C‐terminal sequence analysis of peptides.