bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure‐property relationship of L‐tyrosine‐based polyurethanes for biomaterial applications
Authors: Sarkar Debanjan , Yang Jui‐Chen , Lopina Stephanie T. 
Published: February 2008

AbstractThe structure‐property relationship of L‐tyrosine‐based polyurethanes was demonstrated by using different polyols and diisocyanates. L‐tyrosine‐based chain extender, desaminotyrosyl tyrosine hexyl ester (DTH), was used to synthesize a series of polyurethanes. Polyethylene glycol (PEG) or poly caprolactone diol (PCL) was used as the soft segment and hexamethylene diisocyanate (HDI) or dicyclohexylmethane 4,4′‐diisocyanate (HMDI) was used with DTH as the hard segment. The polyurethanes were characterized to investigate the effect of structure on different polyurethane properties. From FTIR and DSC, these polyurethanes exhibit a wide range of morphology from phase‐mixed to phase‐separated structure. The decreasing molecular weight of the PEG soft segment leads to relatively more phase mixed morphology whereas for PCL‐based polyurethanes the extent of phase mixing is less with decreasing PCL molecular weight. Results show that PCL‐based polyurethanes are mechanically stronger than PEG‐based polyurethanes but PCL‐based polyurethanes degrade slower and absorb less water compared with PEG‐based polyurethanes. The HMDI‐based polyurethanes are less crystalline and comparatively more hydrophobic than HDI‐based polyurethanes. The characterization results show that the polyurethane properties are directly related to the structure and can be varied easily for a different set of properties that are pertinent for biomaterial applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Determination of the onset of shear thinning of polydimethylsiloxane
Authors: Hadjistamov Dimiter 
Published: February 2008

AbstractThe shear stress and the first normal stress difference were simultaneously measured in shear flow start‐up experiments and a subsequent stress relaxation. The measured polydimethylsiloxane show shear thinning flow behavior with a first Newtonian region up to the shear rate at the onset of shear thinning. We found that the shear stress and the first normal stress difference have an equal shear rate at the onset of shear thinning. The shear stress at the onset of shear thinning does not depend on the molecular weight of the polymer and on temperature. Similar to the viscosity master curve, it is possible to create a normal stress master curve, outgoing from the first normal stress coefficient. The shear rate at the onset of shear thinning is estimated from the viscosity master curve and the shear rate at the onset of normal stress thinning from the normal stress master curve. The shear stress and the first normal stress difference have similar transient behavior with start‐up stress curves without maximum in stress growth experiments with shear rates from the first Newtonian region. The shear flow start‐up experiment with the shear rate at the onset of shear thinning leads to the first indication of an overshoot of the start‐up curve. The shear flow start‐up experiments with shear rates from the shear thinning region show start‐up curves with a maximum for the shear stress and for the first normal stress difference. It was found that the shear rate at the onset of shear thinning and the shear rate at the onset of normal stress thinning, determined by the shear flow start‐up measurements, are equal to the values obtained from the master curves. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Impedance spectroscopy of N‐substituted oligo‐oxyethylene polypyrrole films
Authors: Cihaner Atilla , Önal Ahmet M. 
Published: February 2008

AbstractThe electrochemical properties of neutral (dedoped) and oxidized (doped) poly(1,11‐bis(1,1‐pyrrole)‐3,6,9‐trioxaundecane) (poly‐I) film electrodes were investigated using cyclic voltammetry and electrochemical impedance spectroscopy (EIS) techniques. Poly‐I was deposited on glassy carbon electrode (GCE) from acetonitrile solution containing 5.0 × 10−3M 1,11‐bis(1,1‐pyrrole)‐3,6,9‐trioxaundecane (I) and 0.1M LiClO4 supporting electrolyte. Doped poly‐I exhibits a single semicircle in its complex‐capacitance plots, indicating a single dominant ion transport process, together with high capacitance values. These features make this polymer film a candidate for an energy storage material. Also, poly‐I can be a candidate as a sensory material for the detection of Ag+ based on impedance parameters. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Curing behavior and properties of the cured resin based on bismaleimide, bisoxazoline, and oleic acid ternary copolymer
Authors: Li Youqing , Li Shengfang , Tang Heqing 
Published: February 2008

AbstractThe curing behavior and properties of bismaleimide (BMI), bisoxazoline (1,3‐PBO), and oleic acid ternary copolymers are investigated. It is found that the cure temperature of BMI/1,3‐PBO or BMI/1,3‐PBO/oleic acid could be lowered, compared with that of BMI. The reason lies in the copolymerization reaction between BMI, 1,3‐PBO, and oleic acid. SEM results confirm that 1,3‐PBO and oleic acid could toughen BMI system because of the formation of ester–amide bonds and the long fat chain of oleic acid. The cured resins from BMI/1,3‐PBO or BMI/1,3‐PBO/oleic acid have superior heat resistance and water resistance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Development of new heterobicationic monomethine dyes as effective photoinitiator of free radical polymerization in visible‐light region
Authors: Kabatc Janina , Kaczorowska Mirosława , Jędrzejewska Beata , Pączkowski Jerzy 
Published: February 2008

AbstractThe dye initiators consisting of N‐[3‐(p‐alkylpyridine)propyl]‐2‐[N‐(3‐bromopropyl)quinoline]‐2‐methylenebenzotiazolium diiodides as chromophores and n‐butyltriphenylborate anion as electron donor were prepared to achieve an efficient photoinitiator of free radical polymerization in a visible‐light region. The relative photoinitiating efficiencies of novel photoinitiators of vinyl monomers polymerization were evaluated. The results obtained clearly documented that the bicationic photoinitiators exhibit a marked increase in the photoinitiation ability compared to the initiators consisting of a single charged hemicyanine dye. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Impact of heterodimerization on intracellular localization of the ecdysteroid receptor (EcR)
Authors: Nieva Claudia , Spindler‐Barth Margarethe , Spindler Klaus‐Dieter 
Published: February 2008

AbstractInitially, nuclear import of the ecdysteroid receptor (EcR) in vertebrate cells (CHO‐K1 and COS‐7) does not afford a heterodimerization partner. Later on, EcR is retained in the nucleus only in the presence of a heterodimerization partner. Ultraspiracle (Usp) is more efficient compared to its vertebrate orthologue RXR and leads to an exclusively nuclear localization of EcR even in the absence of ligand. The DNA binding domain of the heterodimerization partner is important for retainment of EcR in the nucleus as shown by Usp4 (UspR130C), which has lost its DNA binding capability. The C‐terminal end of Usp (UspΔ205‐508) encompassing the C‐terminal part of the D‐domain and the E‐ and F‐domains are essential for retainment of EcR in the nucleus. Nuclear localization is further influenced by cell‐specific factors, since hormone and heterodimerization stabilizes the EcR protein in a cell‐specific way. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley‐Liss, Inc.
Synthesis and Monoamine Oxidase Inhibitory Activities of 1‐Thiocarbamoyl‐3,5‐diphenyl‐4,5‐dihydro‐1H‐pyrazole Derivatives
Authors: Palaska Erhan , Aydin Firat , Uçar Gülberk , Erol Dilek 
Published: February 2008

AbstractTen new 1‐thiocarbamoyl‐3‐(phenyl and/or 4‐substituted phenyl)‐5‐(3,4‐dimethoxyphenyl and/or 2‐chloro‐3,4‐dimethoxyphenyl)‐4,5‐dihydro‐1H‐pyrazole derivatives were synthesized by reacting 1,3‐diphenylpropen‐1‐ones and thiosemicarbazide. The chemical structures of the compounds were verified by means of their IR, 1H‐NMR, ESI‐MS spectroscopic data and elementary analyses. All the compounds were investigated for their ability to selectively inhibit monoamine oxidase (MAO) by in‐vitro tests. Monoamine oxidase was isolated and purified from the mitochondrial extracts of rat‐liver homogenates and human platelets. Monoamine oxidase inhibitory activities of the compounds were compared with pargyline and clorgyline. Most of the compounds inhibited the total activity of rat liver homogenates. The monoamine oxidase‐A inhibitory effects of 1‐thiocarbamoyl‐3‐(4‐methoxyphenyl)‐5‐(3,4‐dimethoxyphenyl)‐4,5‐dihydro‐1H‐pyrazole and 1‐thiocarbamoyl‐3‐(4‐methoxyphenyl)‐5‐(2‐chloro‐3,4‐dimethoxyphenyl)‐4,5‐dihydro‐1H‐pyrazole were detected as potent as clorgyline. Selective and irreversible inhibition of rat liver monoamine oxidase‐A by synthesized compounds have promising features for designing the new selective monoamine oxidase A inhibitors as potent and reliable anti‐depressants in the future.
Finding and using journal‐article components: Impacts of disaggregation on teaching and research practice
Authors: Sandusky Robert J. , Tenopir Carol 
Published: February 2008

AbstractThis article reports the results of a study into the use of discrete journal‐article components, particularly tables and figures extracted from published scientific journal articles, and their application to teaching and research. Sixty participants were introduced to and asked to perform searches in a journal‐article component prototype that presents individual tables and figures as the items returned in the search results set. Multiple methods, including questionnaires, observations, and structured diaries, were used to collect data. The results are analyzed in the context of previous studies on the use of scientific journal articles and in terms of research on scientists' use of specific journal‐article components to find information, assess its relevance, read, interpret, and disaggregate the information found, and reaggregate components into new forms of information. Results indicate that scientists believe searching for journal‐article components has value in terms of (a) higher precision result sets, (b) better match between the granularity of the prototype's index and the granularity of the information sought for particular tasks, and (c) fit between journal‐article component searching and the established teaching and research practices of scientists.
Identification of novel small molecule enhancers of protein production by cultured mammalian cells
Authors: Allen Martin J. , Boyce James P. , Trentalange Michael T. , Treiber David L. , Rasmussen Brian , Tillotson Benjamin , Davis Raymond , Reddy Pranhitha 
Published: February 2008

AbstractSmall molecule additives to cell culture media (e.g., sodium butyrate) that are capable of enhancing the expression of recombinant proteins have significant utility in the production and manufacture of therapeutic polypeptides. To identify novel small molecule enhancers (SMEs) of recombinant protein expression in Chinese Hamster Ovary (CHO) cells, we screened two separate small molecule libraries for compounds capable of enhancing the expression of either a fluorescent reporter protein or a monoclonal antibody. Several compounds that increased recombinant protein expression were identified, and these compounds fell into three broad classes: (1) aromatic carboxylic acids, (2) hydroxamic acids, and (3) acetamides. We examined the impact of SME addition to CHO cell cultures expressing different classes of recombinant proteins including monoclonal antibodies (MAbs). For CHO cell pools or clones grown in production shake‐flasks or bioreactors, recombinant protein titers up to 60% higher than control cultures were observed. Analysis of mRNA levels suggest that transcriptional activation plays a role in the expression enhancement seen for some SMEs, but other mechanisms may be involved for at least one compound. Finally, we tested many of the identified SMEs for their ability to increase MAb production by a hybridoma cell line. Hexanohydroxamic acid increased shake‐flask MAb production by 40% relative to a control. Taken together, these data demonstrate the potential utility of the compounds in the production of therapeutically relevant proteins from diverse cell‐based production systems. Biotechnol. Bioeng. 2008;100: 1193–1204. © 2008 Wiley Periodicals, Inc.
Supracondylar process of the humerus: Study on 375 Caucasian subjects in Cologne, Germany
Authors: Natsis Konstantinos 
Published: February 2008

AbstractThis study documents the prevalence of the supracondylar process of the humerus in the Caucasian subjects in a German dissecting room along with its morphology, height, and site by using an electronic digimatic caliper. Seven hundred and fifty dried humeri from 375 Causcasian cadavers were examined at the Department of Anatomy in the University of Cologne, Germany. The supracondylar process was found in 10 out of the 750 (1.3%) dried humeri from 10 individuals (2.7%). In five of these 10 bones, the supracondylar process was in the form of a tubercle. In the others it was a spine of average height 9.5 mm (range, 7.7–12.3 mm). The average distance of the supracondylar process from the medial epicondyle was 59.8 mm, ranging between 40.5 and 79.0 mm. The supracondylar process was more common on the left humerus (90%) and in male subjects (60%) (both P < 0.01). None of the processes we observed was bilateral. Literature review indicated that the supracondylar process appears in 0.4–2% of Caucasians and in 0.2–2.8% of their humeri. Clin. Anat. 21:138–141, 2008. © 2008 Wiley‐Liss, Inc.
A cross‐national examination of consumer perceived risk in the context of non‐deceptive counterfeit brands
Authors: Veloutsou Cleopatra , Bian Xuemei 
Published: February 2008

Abstract

This study investigates the relationships between six identified dimensions of perceived risk and the overall risk, and also their explanatory power to the overall risk when purchasing counterfeit brands in two different contexts. Using a self‐administered instrument, a total of 525 responses were collected, 230 from the UK and 295 from China. The results support the hypothesised significant interrelationship between the dimensions of perceived risk in both contexts. However there are some differences. The models have a different exploratory power, with the one based on the British sample being stronger, while a somewhat different combination of the risk dimensions seems to predict the overall risk in each context. The psychological risk is the only dimension of risk that with no doubt contributes to the formation of the overall risk in both contexts. Although one could argue that when purchasing counterfeits social risk could be an issue, the evidence reported in this study does not support the view.
Copyright © 2008 John Wiley & Sons, Ltd.
Single‐Step Electron Transfer on the Nanometer Scale: Ultra‐Fast Charge Shift in Strongly Coupled Zinc Porphyrin–Gold Porphyrin Dyads
Authors: Fortage Jérôme , Boixel Julien , Blart Errol , Hammarström Leif , Becker Hans Christian , Odobel Fabrice 
Published: February 2008

AbstractThe synthesis, electrochemical properties, and photoinduced electron transfer processes of a series of three novel zinc(II)–gold(III) bisporphyrin dyads (ZnPSAuP+) are described. The systems studied consist of two trisaryl porphyrins connected directly in the meso position via an alkyne unit to tert‐(phenylenethynylene) or penta(phenylenethynylene) spacers. In these dyads, the estimated center to center interporphyrin separation distance varies from 32 to 45 Å. The absorption, emission, and electrochemical data indicate that there are strong electronic interactions between the linked elements, thanks to the direct attachment of the spacer on the porphyrin ring through the alkyne unit. At room temperature in toluene, light excitation of the zinc porphyrin results in almost quantitative formation of the charge shifted state .+ZnPSAuP., whose lifetime is in the order of hundreds of picoseconds. In this solvent, the charge‐separated state decays to the ground state through the intermediate population of the zinc porphyrin triplet excited state. Excitation of the gold porphyrin leads instead to rapid energy transfer to the triplet ZnP. In dichloromethane the charge shift reactions are even faster, with time constants down to 2 ps, and may be induced also by excitation of the gold porphyrin. In this latter solvent, the longest charge‐shifted lifetime (τ=2.3 ns) was obtained with the penta‐(phenylenethynylene) spacer. The charge shift reactions are discussed in terms of bridge‐mediated super‐exchange mechanisms as electron or hole transfer. These new bis‐porphyrin arrays, with strong electronic coupling, represent interesting molecular systems in which extremely fast and efficient long‐range photoinduced charge shift occurs over a long distance. The rate constants are two to three orders of magnitude larger than for corresponding ZnPAuP+ dyads linked via meso‐phenyl groups to oligo‐phenyleneethynylene spacers. This study demonstrates the critical impact of the attachment position of the spacer on the porphyrin on the electron transfer rate, and this strategy can represent a useful approach to develop molecular photonic devices for long‐range charge separations.
Synthesis and Characterisation of Helical β‐Peptide Architectures that Contain (S)‐β3‐HDOPA(Crown Ether) Derivatives
Authors: Dutot Laurence , Gaucher Anne , Elkassimi Khadidja , Drapeau Jeremy , Wakselman Michel , Mazaleyrat Jean‐Paul , Peggion Cristina , Formaggio Fernando , Toniolo Claudio 
Published: February 2008

AbstractA new set of β‐amino acids that carry various crown ether receptors on their side chains of the general formula (S)‐β3‐HDOPA(crown ether) (HDOPA: homo‐3,4‐dihydroxyphenylalanine; (crown ether): [15]crown‐5 ([15‐C‐5]), [18]crown‐6 ([18‐C‐6]), [21]crown‐7 ([21‐C‐7]), 1,2‐Benzo‐[24]crown‐8 ([Benzo‐24‐C‐8]) and (R)‐Binol‐[20]crown‐6 ([(R)‐Binol‐20‐C‐6])) was prepared. Peptides that are based on these new crowned β‐amino acids combined with (1S,2S)‐ACHC (2‐aminocyclohexanecarboxylic acid), which is known to be a potent 314‐helix inducer, to the hexamer level, with two crowned residues at the i and i+3 positions of the main‐chain, were synthesized in solution by stepwise coupling using Boc‐Nα‐protection (Boc: tert‐butoxycarbonyl) and the EDC/HOAt C‐activation method. Their conformational analysis was performed by using FTIR absorption, NMR and CD spectroscopy techniques. Our results are in full agreement with a 314‐helix conformation.
Homochiral Laminar Europium Metal–Organic Framework with Unprecedented Giant Dielectric Anisotropy
Authors: Qu Zhi‐Rong , Ye Qiong , Zhao Hong , Fu Da‐Wei , Ye Heng‐Yun , Xiong Ren‐Gen , Akutagawa Tomoyuki , Nakamura Takayoshi 
Published: February 2008

AbstractHydrothermal (deuteratothermal) reaction of L‐ethyl lactate (Lig‐Et) with Eu(ClO4)3⋅6 H2O gives colorless block crystals of [Eu(Lig)2(X2O)2][ClO4] (1, X=H; 2, X=D) both of which possess a two‐dimensional laminar homochiral framework. Single‐crystal dielectric measurements reveal that 1 and 2 display a giant dielectric anisotropy approximately exceeding 100 and large isotopic effect with about 54 % enhancement along the a axis. Their ferroelectric features further confirm this respect. Crystal parameters: 1, C6H14ClO12Eu, Mr=465.58, monoclinic, C2, a=8.6786(6), b=8.3965(6), c=10.2153(7) Å, β=92.040(1)°, V=743.92(9) Å3, Z=2, ρcalcd=2.079 Mg m−3, R1=0.0508, wR2=0.1239, μ=4.448 mm−1, S=1.043; Flack=0.04(5). 2: C6H10D4ClO12Eu, Mr=469.61, monoclinic, C2, a=8.689(2), b=8.410(2), c=10.224(3) Å, β=92.057(4)°, V=746.7(3) Å3, Z=2, ρcalcd=2.089 Mg m−3, R1=0.0465, wR2=0.1150, μ=4.432 mm−1, S=1.058; Flack=0.02(5).
Discrimination in Metal‐Ion Binding to RNA Dinucleotides with a Non‐Bridging Oxygen or Sulfur in the Phosphate Diester Link
Authors: Knobloch Bernd , Nawrot Barbara , Okruszek Andrzej , Sigel Roland K. O. 
Published: February 2008

AbstractReplacement of a non‐bridging oxygen in the phosphate diester bond by a sulfur has become quite popular in nucleic acid research and is often used as a probe, for example, in ribozymes, where the normally essential Mg2+ is partly replaced by a thiophilic metal ion to reactivate the system. Despite these widely applied rescue experiments no detailed studies exist quantifying the affinity of metal ions to such terminal sulfur atoms. Therefore, we performed potentiometric pH titrations to determine the binding properties of pUp(S)U3− towards Mg2+, Mn2+, Zn2+, Cd2+, and Pb2+, and compared these data with those previously obtained for the corresponding pUpU3− complexes. The primary binding site in both dinucleotides is the terminal phosphate group. Theoretically, also the formation of 10‐membered chelates involving the terminal oxygen or sulfur atoms of the (thio)phosphate bridge is possible with both ligands. The results show that Mg2+ and Mn2+ exist as open (op) isomers binding to both dinucleotides only at the terminal phosphate group. Whereas Cd(pUpU)− only exists as Cd(pUpU)${{{- \hfill \atop {\rm op}\hfill}}}$, Cd(pUp(S)U)− is present to about 64 % as the S‐coordinated macrochelate, Cd(pUp(S)U)${{{- \hfill \atop {\rm cl}/{\rm PS}\hfill}}}$. Zn2+ forms with pUp(S)U3− three isomeric species, that is, Zn(pUp(S)U)${{{- \hfill \atop {\rm op}\hfill}}}$, Zn(pUp(S)U)${{{- \hfill \atop {\rm cl}/{\rm PO}\hfill}}}$, and Zn(pUp(S)U)${{{- \hfill \atop {\rm cl}/{\rm PS}\hfill}}}$, which occur to about 33, 12 (O‐bound), and 55 %, respectively. Pb2+ forms the 10‐membered chelate with both nucleotides involving only the terminal oxygen atoms of the (thio)phosphate bridge, that is, no indication of S binding was discovered in this case. Hence, Zn2+ and Cd2+ show pronounced thiophilic properties, whereas Mg2+, Mn2+, and Pb2+ coordinate to the oxygen, macrochelate formation being of relevance with Pb2+ only.
Concise Total Synthesis of the Thiazolyl Peptide Antibiotic GE2270 A
Authors: Delgado Oscar , Müller H. Martin , Bach Thorsten 
Published: February 2008

AbstractThe potent antibiotic thiazolylpeptide GE2270 A was synthesized starting from N‐tert‐butyloxycarbonyl protected valine in a longest linear sequence of 20 steps and with an overall yield of 4.8 %. Key strategy was the assembly of the 2,3,6‐trisubstituted pyridine core by consecutive cross‐coupling reactions starting from 2,6‐dibromo‐3‐iodopyridine. The complete Southern fragment was installed by Negishi cross‐coupling of 3‐zincated 2,6‐dibromopyridine at the terminal 2‐iodothiazole of a trithiazole (87 %). The substituent at C‐6 representing the Northern part of the molecule was introduced in form of the truncated tert‐butyl 2‐bromothiazole‐4‐carboxylate after metalation to a zinc reagent by another Negishi cross‐coupling (48 %). Decisive step of the whole sequence was the macrocyclization to a 29‐membered macrolactam, which was conducted as an intramolecular Stille cross‐coupling occurring at C‐2 of the pyridine core and providing the desired product in 75 % yield. The required stannane was obtained by amide bond formation (87 %) between a complex dithiazole fragment representing the Eastern part of GE2270 A and a 3,6‐disubstituted 2‐bromopyridine. Final steps included attachment of a serine‐proline amide dipeptide to the Northern part of the molecule (65 %), formation of the oxazoline ring and silyl ether deprotection (55 % overall).