bluuebunny/crossref_metadata_2025 huggingface dataset:
Main‐chain viologen polymers with triflimide counterion exhibiting lyotropic liquid‐crystalline properties in polar organic solvents
Authors: Bhowmik Pradip K. , Han Haesook , Nedeltchev Ivan K.
Published: August 2002

The solution‐phase behavior of three main‐chain viologen polymers, which are composed of isomeric xylyl units and triflimide as a counterion, was studied in methanol, dimethylformamide, acetonitrile, and dimethyl sulfoxide as solvents microscopically under crossed polarizers. Each of them exhibited a lyotropic lamellar phase in both polar protic and aprotic solvents. Their C* for the formation of biphasic solutions (1–5 wt %) and concentrations (20–30 wt %) for the lyotropic solutions in methanol was much lower than those in polar aprotic solvents (20–71 and 60–81 wt %, respectively). Their high solubility, high C* for the formation of biphasic solutions, and high concentrations for the formation of lyotropic solutions in polar aprotic solvents were related to the significant reduction of strong ionic interactions between triflimide and 4,4′‐bipyridinium ions in each of these viologen polymers. They were the first examples of viologen polymers that exhibited a lyotropic phase in polar aprotic solvents. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2015–2024, 2002
Synthesis of poly(methyl methacrylate) in a pyridine solution by atom transfer radical polymerization
Authors: Luis de la Fuente José , Fernández‐García Marta , Fernández‐Sanz Marina , López Madruga Enrique
Published: August 2002

Pyridine was used as a solvent for the atom transfer radical polymerization (ATRP) of methyl methacrylate. The homopolymerizations were carried out with methyl 2‐halopropionate (MeXPr, where X was Cl or Br) as an initiator, copper halide (CuX) as a catalyst, and 2,2′‐bipyridine as a ligand from 80 to 120 °C. The mixed halogen system methyl 2‐bromopropionate/copper chloride was also used. For all the initiator systems used, the polymerization reaction showed linear first‐order rate plots, a linear increase in the number‐average molecular weight with conversion, and relatively low polydispersities. In addition, the dependence of the polymerization rate on the temperature is presented. These data are compared with those obtained in bulk, demonstrating the effectiveness of this solvent for this monomer in ATRP. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3443–3450, 2001
Effect of the length of the substituents on the phase structure and transition behavior of a series of laterally attached side‐chain liquid‐crystalline polynorbornenes
Authors: Kim Gue‐Hyun , Jin Shi , Pugh Coleen , Cheng Stephen Z. D.
Published: August 2002

A series of polynorbornenes (PNBEs) with 1,4‐bis[(3′‐fluoro‐4′‐n‐alkoxyphenyl)ethynyl]benzene mesogens (n = 1–12, where n is the number of methylene units in the substituents of the mesogens) laterally attached to polymer backbones through a one‐carbon spacer were previously synthesized by the ring‐opening metathesis polymerization of the corresponding norbornene‐based monomers. Differential scanning calorimetric results showed that the first‐order transition temperatures exhibit an odd–even alternation, especially when PNBEs have lower values of n. PNBE (n = 8), similar to the previously studied PNBEs (n = 9–12), shows a smectic C (SC) phase at room temperature (Kim, Pugh, and Cheng, Macromolecules, 33, 8983, 2000.) According to one‐ and two‐dimensional wide‐angle X‐ray scattering experiments, PNBEs (n = 2–7) exhibit a nematic (N) phase with SC fluctuations, whereas for PNBE (n = 1), only an N phase is observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 3029–3037, 2001
Thermoresponsive conductivity of poly(N‐isopropylacrylamide)/potassium chloride gel electrolytes
Authors: Chen Jinhua , Maekawa Yasunari , Yoshida Masaru , Tsubokawa Norio
Published: August 2002

A series of thermoresponsive polymer gel electrolytes (PGEs) based on poly(N‐isopropylacrylamide) in aqueous potassium chloride was synthesized by radiation‐induced polymerization and gelation using γ rays from a 60Co source. The electric conductivity and swelling properties of the PGE were determined as a function of temperature. It was found that the electric conductivity of the PGE depended strongly on the swelling ratio; most notably, it changed drastically near the volume phase‐transition temperature of the PGE. The temperature/conductivity profile of the PGE exhibits a maximum peak at a certain temperature that is defined as the maximum conductivity temperature (Tmax). The Tmax of all of the PGEs prepared by low‐dose irradiation agreed with the temperature, near the end of the volume phase transition, where the PGE was completely shrunken. Consequently, the conductivity of gels should provide a good method with which the totally shrunken temperature of the thermoresponsive gels can be monitored with good temperature precision. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 134–141, 2002
Dynamic mechanical analyses of Nafion®/organically modified silicate nanocomposites
Authors: Young S. K. , Mauritz K. A.
Published: August 2002

Nafion®/organically modified silicate (ORMOSIL) hybrids were generated via polymer in situ sol–gel copolymerizations of tetraethylorthosilicate (TEOS) with difunctional and trifunctional organoalkoxysilane monomers, and the dynamic mechanical relaxations and thermomechanical stability of the resultant composites were investigated. All ORMOSIL fillers restrict main‐chain and side‐chain mobility. The results suggest that sulfonic acid side chains become entrapped in silicate or ORMOSIL structures that evolve during the in situ sol–gel process. Some but not all of the ORMOSIL combinations display trends in the α or β relaxation temperature with respect to the TEOS comonomer ratio. All of the hybrids have greater high‐temperature thermomechanical stability than the unfilled acid form. There are definite composition trends in the vertical displacement of the storage‐modulus–temperature curves. For some of the semiorganic comonomers, there is a monotonic increase in storage modulus with decreasing comonomer content in the high‐temperature regime, which is understood in terms of a progressive immobilization of the long side chains by progressively more rigid ORMOSIL nanostructures. For other semiorganic comonomers, the high‐temperature plateau shifts upward to a maximum and then shifts downward with decreasing comonomer fraction. In addition to the chemical nature of the imparted nanophases, these molecular motions are expected to influence the transport properties of these novel heterogeneous membranes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1282–1295, 2001
Enthalpy distributions and densities of states in linear polymers
Authors: Poland Douglas
Published: August 2002

Using polypropylene as an example, we applied a method we have recently developed to calculate the probability distribution of enthalpy from the temperature dependence of the heat capacity. The method involves the use of local temperature expansions of the heat capacity to calculate a set of moments of the enthalpy distribution. Using the maximum‐entropy method, one can then construct the enthalpy distribution for the system. The method is completely model free. The enthalpy distribution so obtained is the analogue of the Maxwell–Boltzmann distribution of kinetic energies for a gas, and like that function, tells one the distribution of enthalpies that an average unit in the polymer chain can have, a quantity that is crucial to understanding the chemical and physical properties of a polymer. Given the enthalpy distribution, one can then calculate the Gibbs free energy and the density of states that correspond to a particular value of enthalpy, thus giving one an expanded thermodynamics of the system in addition to the usual average quantities. We illustrate the fact that the Gibbs free‐energy distribution for this system scales as a simple function of temperature and that the density‐of ‐states function yields a simple empirical partition function for the system giving both the average thermodynamics and the distribution functions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1513–1518, 2001
Help‐seeking behaviour for cancer symptoms: perceptions of patients and general practitioners
Authors: De Nooijer Jascha , Lechner Lilian , De Vries Hein
Published: August 2002

The aim of this study is to increase our understanding of the relationship between knowledge and interpretation of symptoms, fear and trust on the one hand, and the decision to consult a general practitioner (GP) for cancer symptoms on the other. Qualitative interviews were used to evaluate the various factors. Twenty‐three patients and ten GPs were interviewed. A number of factors were found to play different roles for different patients groups, i.e. patients that consult their doctor prematurely, at the right time, or those that delay. A lot of the findings can be tested using various concepts of socio‐psychological theory. Further research should provide an improved understanding of the way these models can be applied to help‐seeking behaviour. In terms of implications for health education, we conclude that each patient group has different needs and requires different information. Copyright © 2001 John Wiley & Sons, Ltd.
The oriented lakes of Tuktoyaktuk Peninsula, Western Arctic Coast, Canada: a GIS‐based analysis
Authors: Côté M. M. , Burn C. R.
Published: August 2002

The orientation, size and shape of 578 lakes on Tuktoyaktuk Peninsula were obtained from 1 : 250 000 Canadian National Topographic Survey map sheets, using ArcView geographic information system. These lakes are outside the glacial limits in a tundra plain with <15m relief. The lakes range from 20 to 1900 ha, and have mean orientation N07 °E, with standard error 1.6°. The maps show 145 former lake basins, with lakes inset in 130 of these. The mean orientations of the basins and inset lakes are not statistically different from each other or the general population. Several theories have been proposed for the origin of the oriented lakes, and one theory attributes the orientation to cross winds establishing currents that preferentially erode the ends of the lakes. Data from Tuktoyaktuk and Nicholson for 1970–95 indicate a consistent wind regime within the region, with prevailing winds from the east and west. Using data from Nicholson, a geometric model generates resultant lake orientations of N if all winds are considered, and N08 °E if winds above 30km h−1 are used. The coincidence of the modelled orientation and lake statistics supports the efficacy of cross wind‐induced effects in orienting the lakes. The similar orientation of existing lakes and former basins suggests that these processes have been effective for at least several centuries. Copyright © 2002 John Wiley & Sons, Ltd.
Bronchoscopically administered recombinant human DNase for lobar atelectasis in cystic fibrosis*
Authors: Slattery Dubhfeasa M. , Waltz David A. , Denham B. , O'Mahony M. , Greally P.
Published: August 2002

Lobar atelectasis is a common complication of cystic fibrosis. The majority of cases respond to intravenous antibiotics and chest physiotherapy. In a subgroup of patients, atelectasis is resistant to medical therapy, and its persistence in the pediatric population is associated with a poor prognosis.

Bronchoscopic instillation of human recombinant DNase expanded atelectatic lobes in three children resistant to at least 2 weeks of medical therapy. This method of administration of DNase has been successful in resistant cases of lobar atelectasis in patients with chronic obstructive pulmonary disease, quadriplegia, and status asthmaticus. Purulent cystic fibrosis sputum has a very high DNA content, and DNA has been shown to become more pourable in vitro when treated with rhDNase.

Bronchoscopic instillation of rhDNase should be considered in cases of persistent lobar atelectasis unresponsive to medical therapy. Pediatr Pulmonol. 2001; 31:383–388. © 2001 Wiley‐Liss, Inc.
Epidemiology of bronchial asthma and chronic rhinitis in schoolchildren of different ethnic origins from two neighboring towns in Israel
Authors: Kivity Shaye , Sade Kobi , Abu‐Arisha Fuad , Lerman Yehuda , Kivity Shmuel
Published: August 2002

Allergic diseases have increased significantly in developed countries for reasons yet to be determined. We studied the epidemiology of bronchial asthma (B.A.) and chronic rhinitis (Ch.R.) among Israeli school children from two neighboring towns, one Jewish (Zichron Yaakov, school population = 585) and the other Arab (Paradis, school population = 658). The children (age range 8–17 years, 567 males, 676 females) shared the same climate and had similar demographic characteristics. They received similar medical care and had the same rates of hospitalization and emergency room visits.

The Jewish children had a higher prevalence of B.A. (13.7% vs. 9.4%), Ch.R. (19.7% vs. 9.7%), and stuffy nose (31% vs. 14%) than their Arab counterparts. In addition to ethnicity, parental smoking habits were the major differentiating factor between the two groups: 20% of the mothers and 29% of the fathers from Zichron Yaakov and 2% of the mothers and 60% of the fathers from Paradis were smokers. Smoking fathers increased the rate of B.A. in both towns as well as emergency room visits, but not the rate of Ch.R. or stuffy nose. A familial history of B.A. was the main determinant for having childhood asthma or chronic rhinitis.

We conclude that in addition to family history and ethnicity, smoking among mothers was the major contributing factor for the higher prevalence of atopic diseases among Jewish schoolchildren compared to their Arab counterparts. Pediatr Pulmonol. 2001; 32:217–221. © 2001 Wiley‐Liss, Inc.
Vitamin D receptor gene polymorphism and prostate cancer risk
Authors: Gsur Andrea , Madersbacher Stephan , Haidinger Gerald , Schatzl Georg , Marberger Michael , Vutuc Christian , Micksche Michael
Published: August 2002

BACKGROUND

1,25‐dihydroxyvitamin D, the active form of vitamin D, exerts antiproliferative effect on prostatic cells, mediated through the vitamin D receptor. In a case‐control study, we examined whether the vitamin D receptor (VDR) gene polymorphism in exon 9 could affect prostate cancer susceptibility.

METHODS

One hundred ninety newly diagnosed prostate cancer patients and 190 age‐matched men with benign prostatic hyperplasia (BPH), in whom the presence of prostate cancer was excluded clinically or histologically, were recruited for this study. The VDR TaqI polymorphism was investigated by polymerase chain reaction (PCR) following restriction fragment length polymorphism using DNA from lymphocytes. Depending on the presence or absence of the TaqI restriction site at the third position of codon 352, patients were classified as TT, Tt, or tt.

RESULTS

The frequency of the tt genotype was not significantly different between prostate cancer patients (18%) and controls (12%; P = 0.07). The odds ratio (OR), calculated relative to individuals with the TT genotype was 1.76 (95% confidence limit (CL) = 0.90–3.45). After stratification for Gleason score and prostate specific antigen levels in a case–case comparison (n = 190), no significant associations with the VDR genotypes were detectable either.

CONCLUSIONS

In this case‐control study of Austrian Caucasians, no statistically significant association of the VDR TaqI polymorphism and prostate cancer risk was found. Prostate 51:30–34, 2002. © 2002 Wiley‐Liss, Inc.
Molecular staging of surgical margins after radical prostatectomy by detection of telomerase activity
Authors: Straub Bernd , Müller Markus , Krause Hans , Goessl Carsten , Schrader Mark , Heicappell Rüdiger , Miller Kurt
Published: August 2002

Background

The further course of prostate cancer (PC) after radical prostatectomy (RPX) is decisively influenced by the local tumor stage. Although it is thus far possible to assess the risk of local recurrence from the pathohistology, precise predictions cannot be made. A more precise evaluation would be desirable, mainly for early planning of adjuvant therapy. Other authors have shown that telomerase activity may be a marker for malignant potential. We assessed the detection of telomerase activity using the telomeric repeat amplification protocol (TRAP) in surgical margins compared to conventional histopathological examination.

Methods

Ninety‐two patients with local PC who underwent RPX were examined. After RPX biopsies were obtained from four defined areas of the prostatic fossa and processed by TRAP assay for telomerase activity using a standard protocol.

Results

In 5 of 48 patients (10.4%) with organ‐confined prostate carcinoma (pT2) telomerase activity could be detected. Seven of 47 patients (14.9%) with locally advanced PC (> pT2) had at least one positive specimen.

Conclusions

The results obtained in our study indicate that detection of telomerase activity by TRAP assay may be a suitable parameter for molecular staging of surgical margins, because of the high tumor‐specificity. Further follow‐up must clarify whether patients with positive molecular detection have an increased risk of local recurrence. Prostate 49:140–144, 2001. © 2001 Wiley‐Liss, Inc.
In silico two‐hybrid system for the selection of physically interacting protein pairs
Authors: Pazos Florencio , Valencia Alfonso
Published: August 2002

Deciphering the interaction links between proteins has become one of the main tasks of experimental and bioinformatic methodologies. Reconstruction of complex networks of interactions in simple cellular systems by integrating predicted interaction networks with available experimental data is becoming one of the most demanding needs in the postgenomic era. On the basis of the study of correlated mutations in multiple sequence alignments, we propose a new method (in silico two‐hybrid, i2h) that directly addresses the detection of physically interacting protein pairs and identifies the most likely sequence regions involved in the interactions. We have applied the system to several test sets, showing that it can discriminate between true and false interactions in a significant number of cases. We have also analyzed a large collection of E. coli protein pairs as a first step toward the virtual reconstruction of its complete interaction network. Proteins 2002;47:219–227. © 2002 Wiley‐Liss, Inc.
QSAR: Hydropathic analysis of inhibitors of the p53–mdm2 interaction
Authors: Galatin Peter S. , Abraham Donald J.
Published: August 2002

To date, a number of p53‐derived peptides have been evaluated in vitro for their ability to inhibit the carcinogenic p53–mdm2 interaction. Design of second‐generation nonpeptidic compounds requires the reduction of large peptide structures down to small molecules maintaining the proper spatial arrangement of key functional groups. Molecular modeling software exists that can predict and rank intermolecular interactions from the p53–mdm2 complex crystal structure. Such analyses can yield a pharmacophore model suitable as a search query for a 3D chemical database to generate new lead compounds. As preliminary validation of this methodology, the Hydropathic INTeractions (HINT) program has been used to generate noncovalent interaction measurements between reported peptide inhibitors and mdm2. Quantitative structure–activity relationships were developed expressing peptide activity as a linear combination of hydropathic descriptors. In general, HINT measurements accurately modeled the effects of even single‐atom alterations of the p53–peptide structure on activity, accounting for 70–90% of variation in experimental inhibition constants. These results surpassed those of a recently described molecular dynamics‐based approach and required significantly less computation time. In conclusion, the HINT program can be integrated into the drug design cycle for next‐generation p53–mdm2 complex inhibitors with confidence in its ability to simulate this noteworthy protein–protein interaction. Proteins 2001;45:169–175. © 2001 Wiley‐Liss, Inc.
Theoretical study of the conformation of the lipoamide arm in a mutant H protein
Authors: Roche Olivier , Field Martin J.
Published: August 2002

The lipoamide arm of the H protein plays a pivotal role in the catalytic cycle of the glycine decarboxylase complex (GDC) by being successively methylamine loaded (Hmet), reduced (Hred), and oxidized (Hox). In a previous study, we calculated free‐energy surfaces as a function of the lipoamide arm position of the three forms of the wild‐type protein and found close agreement with the available experimental data. Our simulations, together with crystallographic and NMR data, showed that the methylamine‐loaded arm is locked in a cavity by interaction with Ser12, Glu14, and Asp67. In this work, we investigate the behavior of the methylamine‐loaded form of a mutant H protein (HEA) where Glu14 has been replaced by Ala. We find that the arm can still be held in the cavity but that the energy barrier to release of the arm is halved from ∼40 kcal mol−1 for Hmet to ∼12 kcal mol−1 for HEA. To compensate for the loss of Glu14, the methylamine group shifts toward Ser66 in the mutant form. These results provide a structural basis for the equilibrium between the loaded and the unloaded forms of the arm observed by Gueguen et al. (Gueguen et al., J Biol Chem 1999;274:26344–26352) in HEA. Proteins 2001;45:237–240. © 2001 Wiley‐Liss, Inc.
Thermal decomposition and isomerization of cis‐permethrin and β‐cypermethrin in the solid phase
Authors: González Audino Paola , Licastro Susana A , Zerba Eduardo
Published: August 2002

The stability to heat of cis‐permethrin and β‐cypermethrin in the solid phase was studied and the decomposition products identified. Samples heated at 210 °C in an oven in the dark showed that, in the absence of potassium chlorate (the salt present in smoke‐generating formulations of these pyrethroids), cis‐permethrin was not isomerized, although in the presence of that salt, decomposition was greater and thermal isomerization occured. Other salts of the type KXO3 or NaXO3, with X being halogen or nitrogen, also led to a considerable thermal isomerization. Heating the insecticides in solution in the presence of potassium chlorate did not produce isomerization in any of the solvents assayed. Salt‐catalysed thermal cis–trans isomerization was also found for other pyrethroids derived from permethrinic or deltamethrinic acid but not for those derived from chrysanthemic acid. The main thermal degradation processes of cis‐permethrin and β‐cypermethrin decomposition when potassium chlorate was present were cyclopropane isomerization, ester cleavage and subsequent oxidation of the resulting products. Permethrinic acid, 3‐phenoxybenzyl chloride, alcohol, aldehyde and acid were identified in both cases, as well as 3‐phenoxybenzyl cyanide from β‐cypermethrin. A similar decomposition pattern occurred after combustion of pyrethroid fumigant formulations.

© 2001 Society of Chemical Industry
Linkage of genes for sodium channel and cytochrome P450 (CYP6B10) in Heliothis virescens
Authors: Park Sujin , Brown Thomas M
Published: August 2002

Genetic linkage of hscp (heliothis sodium channel protein) and CYP6B10 was discovered in Heliothis virescens. The hscp gene encodes the sodium channel target of pyrethroid insecticides and cytochrome P450 genes encode important enzymes involved in detoxication of various pesticides. Previously, two mechanisms, nerve insensitivity due to sodium channel and synergism by propynyl aryl ethers, were observed in pyrethroid‐resistant H virescens and were not separated by repeated back‐crossing. We hypothesized genetic linkage of target site insensitivity and monooxygenase‐mediated detoxication. Single nucleotide polymorphisms were discovered in IIS6 of hscp; Hpy of hscp and CYP6B10. Segregation of these and other markers was tested in backcrosses. We observed co‐segregation of hscp to CYP6B10, but both genes assorted independently of y, ye and sex. Genes y and ye assorted independently of each other. This was the first observation of linkage between genes controlling detoxication and sodium ion channel insensitivity in a species known to express high levels of pyrethroid resistance. Linkage was not likely because this species has 31 chromosomes; therefore, we will investigate the possibility of a resistance cassette. We expect similar linkage in other noctuid pests.

© 2001 Society of Chemical Industry
Semiochemical strategies for sea louse control: host location cues
Authors: Ingvarsdóttir Anna , Birkett Michael A , Duce Ian , Genna Richard L , Mordue William , Pickett John A , Wadhams Lester J , Mordue (Luntz) A Jennifer
Published: August 2002

The development of behavioural bioassays and electrophysiological recording techniques has enabled the role of semiochemicals to be investigated for the first time in Lepeophtheirus salmonis (Krøyer). Adult male sea lice L salmonis were activated by, and attracted to, salmon‐conditioned water (SCW) and SCW extract. Non‐host fish odours, turbot‐conditioned water (TCW) and turbot‐conditioned water extract (TCW extract), elicited activation but no attraction in the lice. Solid‐phase extraction techniques were developed to extract low molecular weight components of fish odours, and biological activity was shown to be confined to these. Electrophysiological activity from aesthetascs in the first antennae was found and neural responses to odours were recorded from the antennal nerves. Preliminary experiments on individual chemicals (isophorone, 1‐octen‐3‐ol) linked to salmon revealed behavioural activation and electrophysiological responses in adult male L salmonis. Isophorone was shown to be significantly attractive to sea lice when placed in a slow‐release system in a perfused tank of seawater in a choice situation. Proof of concept has been established for successfully extracting odour cues from seawater, analysing their biological activity and applying these to slow‐release technologies for field trapping of lice. Future work involving linked GC–MS techniques using behaviour, electrophysiological responses, and organolepsis will establish further host location cues specific to Atlantic salmon.

© 2002 Society of Chemical Industry
Discovery of potent and selective peptide agonists at the GRP‐preferring bombesin receptor (BB2)
Authors: Darker John G. , Brough Stephen J. , Heath Jennie , Smart Darren
Published: August 2002

Analogues of the nonselective bombesin receptor synthetic agonist H‐D‐Phe‐Gln‐Trp‐Ala‐Val‐βAla‐His‐Phe‐Nle‐NH2 were prepared and their biological activity assessed at the NMB‐preferring/bombesin receptor (NMB‐R; BB1), the GRP‐preferring/bombesin receptor (GRP‐R; BB2) and the orphan receptor bombesin receptor subtype‐3 (BRS‐3; BB3). Progressive N‐terminal deletions identified the minimum C‐terminal sequences required for maintaining a significant agonist effect, whilst an alanine scan, targeted changes in stereochemistry and other pertinent substitutions identified key side‐chain and stereochemical requirements for activation. Key structural elements required for functional potency at BB1 BB2 and BB3, and for selectivity between these receptor subtypes were established. Synthetic peptides were discovered, which were highly potent agonists at BB2 and extremely selective over both BB1 and BB3. Copyright © 2000 European Peptide Society and John Wiley & Sons, Ltd.
Screening of Brazilian plant extracts for antioxidant activity by the use of DPPH free radical method
Authors: Mensor Luciana L. , Menezes Fábio S. , Leitão Gilda G. , Reis Alexandre S. , Santos Tereza C. dos , Coube Cintia S. , Leitão Suzana G.
Published: August 2002

Brazilian plant extracts belonging to 16 species of 5 different families (71 extracts) were tested against the stable DPPH (2,2‐diphenyl‐1‐picryl‐hydrazyl‐hydrate) free‐radical. The ability to scavenge DPPH radical was measured in these experiments by the discoloration of the solution. Ginkgo biloba and rutin, commonly used as antioxidants for medical purposes, were used as standards. Based on our results, we can say that as a general rule the ethanol extracts of plants belonging to the Verbenaceae family showed lower EC50 values than the other plant extracts. Among the partitions, the more polar ones (ethyl acetate and n‐butanol) are those that generally have higher antioxidant activity (AA). Copyright © 2001 John Wiley & Sons, Ltd.
The antioxidant activity of the essential oils of Artemisia afra, Artemisia abyssinica and Juniperus procera
Authors: Burits M. , Asres K. , Bucar F.
Published: August 2002

The essential oils of Artemisia afra Jacq., Artemisia abyssinica Schultz‐Bip. and Juniperus procera Hoechst ex Endl. were examined for their potential radical scavenging activities. First a rapid evaluation of antioxidants was made using a TLC screening method. The abilities of the volatile oils to act as nonspecific donors for hydrogen atoms or electrons were checked in the diphenylpicrylhydrazyl assay. Oils from all three species showed positive results and were examined further. The oils of A. afra and J. procera were also effective hydroxyl radical scavenging agents when assessed in the deoxyribose degradation assay, whilst oils from A. abyssinica exhibited a paradoxical effect. In the in vitro assay for non‐enzymatic lipid peroxidation in liposomes, the oils of A. afra and J. procera also displayed antioxidant potential. It was not possible to measure the effect of A. abyssinica oil in this system because certain components, e.g. alk‐2‐enals, interfered with the assay. The compounds that contribute to the radical scavenging activities of A. afra and J. procera were identified and then assessed for their effects in the various test systems. Finally, the qualitative and quantitative compositions of the essential oils were studied by GC‐MS. Copyright © 2001 John Wiley & Sons, Ltd.
Experience with St John's Wort (Hypericum perforatum) in children under 12 years with symptoms of depression and psychovegetative disturbances
Authors: Hübner Wolf‐Dietrich , Kirste Tilman
Published: August 2002

The value of an extract of Hypericum perforatum (St John's wort) for children with mild to moderate depressive symptoms was investigated for the first time in a multi‐centre post‐marketing surveillance study. One hundred and one children under 12 years were treated for a minimum of 4 weeks with an extension to 6 weeks with parental consent and medical practitioner recommendation. the dosage used ranged from 300 to 1800 mg per day. Compliance, tolerability and efficacy were assessed every 2 weeks by physicians and parents. Based on the data available for analysis, the number of physicians rating effectiveness as ‘good’ or ‘excellent’ was 72% after 2 weeks, 97% after 4 weeks and 100% after 6 weeks. The ratings by parents were very similar. There was, however, an increasing amount of missing data at each assessment point with the final evaluation including only 76% of the initial sample. Tolerability was good and no adverse events were reported. The results of this study suggest that Hypericum is a potentially safe and effective treatment for children with symptoms of depression. Copyright © 2001 John Wiley & Sons, Ltd.
Effect of Cirsium pascuarense on blood glucose levels of normoglycaemic and alloxan‐diabetic mice
Authors: Perez G. R. M. , Ramirez L. M. E. , Vargas S. R.
Published: August 2002

Blood glucose levels of normal and alloxan‐treated diabetic mice were determined after i.p. administration of various doses of the hexane, chloroform and methanol extracts of Cirsium pascuarense. From the data obtained, it is concluded that the i.p. administration of 100, 150 and 200 mg/kg of hexane extract of this plant produced a significant hypoglycaemic effect in normal as well as in diabetic mice. In addition, the extracts altered glucose tolerance in alloxan induced diabetic rats. Chloroform and methanol extracts did not produce any significant change in blood glucose levels. Copyright © 2001 John Wiley & Sons, Ltd.
Information distance analysis of molecular electron densities
Authors: Nalewajski Roman F. , Świtka Elžbieta , Michalak Artur
Published: August 2002

The information‐theoretic basis of the Hirshfeld partitioning of the molecular electronic density into the densities of the “stockholder” atoms‐in‐molecules (AIM) is summarized. It is argued that these AIM densities minimize both the directed divergence (Kullback–Leibler) and divergence (Kullback) measures of the entropy deficiency between the AIM and their free atom analogs of the promolecule. The local equalization of the information distance densities of the Hirshfeld components, at the local value of the corresponding global entropy deficiency density, is outlined and several approximate relations are established between the alternative local measures of the missing information and the familiar function of a difference between the molecular and promolecule densities. Various global (of the system as a whole) and atomic measures of the entropy deficiency or the displacements relative to the isoelectronic promolecule, defined for densities or probabilities (shape functions) in both the local resolution and the Hirshfeld AIM discretization, are introduced and tested. This analysis is performed also for the valence electron (frozen‐core) approximation. Illustrative results for representative linear molecules, including diatomics, triatomics, and tetraatomics, are reported. They are interpreted as complementary characteristics of changes in the net AIM charge distribution and of the displacements in the information content of the electron distributions of bonded atoms. These numerical results confirm the overall similarity of the stockholder AIM to their free atom analogs and reflect the information displacements due to the AIM polarization and charge transfer in molecules. They also demonstrate the semiquantitative nature of the approximate relations established between the entropy deficiency densities and the related functions involving the density difference function. This development extends the range of interpretations based on the density difference diagrams into probing the associated information displacements in a molecule accompanying the formation of the chemical bonds. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002
Radical polymerization of diallylamine compounds: From quantum chemical modeling to controllable synthesis of high‐molecular‐weight polymers
Authors: Timofeeva L. M. , Vasilieva Y. A. , Kleshcheva N. A. , Gromova G. L. , Topchiev D. A.
Published: August 2002

We investigated the possibility to obtain high‐molecular‐weight (HMW) polymers from the monomers of the diallylamine (DAA) series using quantum chemical and experimental methods. Such monomers are known to polymerize into oligomeric products due to the reaction of the degradative chain transfer to the monomer. We studied potential energy profiles of the chain propagation and competing chain transfer reactions, viz., the free radical double bond addition and α‐hydrogen radical abstraction, respectively, for a number of polymerization processes. Calculations were carried in the framework of the polarized continuum solvent model utilizing the procedure based on the semiempirical MNDO‐PM3 background. It was found that the necessary condition for decreasing competitiveness of the chain transfer to the monomer is the availability of monomer molecules in only protonated form in the polymerizing system. Using these results, we developed the strategy for obtaining HMW polymers based on said monomers. We synthesized a monomer system (the equimolar salt of N,N‐diallyl‐N‐methylamine and trifluoroacetic acid) that fully corresponds to such requirements. Novel HMW polymers were then synthesized by radical polymerization of this salt at soft conditions. We established that chain termination is controlled by the bimolecular mechanism. We showed that the degradative chain transfer transforms into the effective chain transfer. The mechanisms of the observed phenomena are discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Possibilities of molecular magnetic metals and high Tc superconductors in field effect transistor configurations
Authors: Kawakami Takashi , Kitagawa Yasutaka , Matsuoka Fumitake , Yamashita Yoshifumi , Isobe Hiroshi , Nagao Hidemi , Yamaguchi Kizashi
Published: August 2002

Ab initio molecular orbital (MO) and density functional theory (DFT) calculations of neutral and anion radical states of anthracene are performed to elucidate their vibrational frequencies. They are used to calculate the transition temperatures of superconductivity of these species in the field effect transistor (FET) configuration on the basis of the electron–phonon coupling mechanism. Anderson and Kondo lattice models are also examined in relation to possible electronic phases of segregated columns of donors or acceptors with radical groups, and conducting polymers with radical groups in the FET configuration. The effective exchange interactions within conduction electrons and localized spins are calculated by theoretical methods. The electron or hole doping into molecular crystals and/or thin films of these systems in the FET configuration are studied in relation to possible magnetic states, Kondo and dense Kondo states, and superconducting states via spin fluctuations. The cooperative mechanism between the electron–phonon and spin fluctuation is also discussed to search the high Tc superconductor. Finally, the magnetic modifications of helical conducting polymers and DNA chains with chiral spin sources are discussed in relation to possibility of molecular solenoid, which may be generated in the FET configuration. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Solving the hydrodynamic formulation of quantum mechanics: A parallel MLS method
Authors: Brook R. Glenn , Oppenheimer Paul E. , Weatherford Charles A. , Banicescu Ioana , Zhu Jianping
Published: August 2002

This article documents the first implementation of a parallel algorithm for solving the governing equations of the hydrodynamic formulation of quantum mechanics. The algorithm employs a quantum trajectory method (QTM) based on the serial algorithm introduced by Wyatt and Lopreore. The OpenMP API is employed to parallelize the code across the quantum trajectories in a shared memory environment. An outline of the parallel algorithm is provided; the analytical solution for a moving free particle is used to verify the solution obtained by the parallel algorithm. Further validation against several of the results obtained by Wyatt and Lopreore is also provided. The parallel speedups and runtimes are presented, and several performance issues are noted. Finally, the results of a preliminary accuracy study examining a moving free particle are provided. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Role of initial orbital alignment in H++K(4p) collisions at low energies
Authors: Saha Bidhan C. , Kumar Anil
Published: August 2002

We report calculations of state‐selective electron capture by H+ from K(4p) in Σ and Π alignments, in the 0.01–1 keV/amu energy range. We use, in the impact parameter formalism, the semiclassical close‐coupling method with molecular‐state expansion embodying electronic translation factors. Molecular states and adiabatic states are obtained from standard one‐electron LCAO calculations using Slater‐type orbitals and pseudopotentials for the e−–K core interactions. In addition to the state‐selective capture cross sections, we also have calculated the K(5s), K(3d), and K(5p) excitation cross sections. We report the anisotropy parameters A(n) for n=2 and n=3 states of the formed H atom as well as A(ex) for populating the excited states of the K atom for the first time. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Evaluating the relative free energy of hydration of new thrombin inhibitor candidates using the finite difference thermodynamic integration (FDTI) method
Authors: Guimarães Cristiano Ruch Werneck , Bicca de Alencastro Ricardo
Published: August 2002

Thrombin is a serine protease involved in blood coagulation. Since thrombin inhibitors appear to be effective in the treatment and prevention of thrombotic and embolic disorders, considerable attention has been focused on the structure and interactions of the enzyme. In this work, we calculated the relative free energies of hydration of the new thrombin inhibitor candidates, p‐substituted derivatives of benzamidine, a well‐known noncovalent thrombin inhibitor. We used molecular dynamics and the finite difference thermodynamic integration (FDTI) algorithm within the Discover program of MSI. We have shown that the orthogonality problem that occurs in the calculation of intraperturbed‐group contributions to the free energy is treated adequately by the FDTI method. We have also shown that problems of singularity and convergence in free energy calculations can be properly solved using this method. To conclude, the calculated free energies of hydration gave the following order of solvation for the candidates: p‐(2‐oxo‐1‐propyl)benzamidine > p‐methylbenzamidine > p‐ethylbenzamidine > p‐(1‐propyl)benzamidine > benzamidine. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Identification of proteins from Escherichia coli using two‐dimensional semi‐preparative electrophoresis and mass spectrometry
Authors: Gustafsson Elisabet , Thorén Kajsa , Larsson Thomas , Davidsson Pia , Karlsson Karl‐Anders , Nilsson Carol L.
Published: August 2002

Escherichia coli is a gram‐negative bacterium that causes sepsis and infections of the nervous system, and the digestive and urinary tracts. The availability of the complete nucleotide sequence encoding the E. coli K‐12 genome has made this organism an excellent model for proteomic studies. Semi‐preparative two‐dimensional electrophoresis, including liquid phase isoelectric focusing (IEF), one‐dimensional sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and gel elution, have for the first time been used in combination with matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS), electrospray tandem mass spectrometry and database searching for rapid separation of proteins from a uropathogenic strain of E. coli. The identity of 30 proteins, including the membrane protein nmpC, was obtained using this approach. Copyright © 2001 John Wiley & Sons, Ltd.
Melanogenesis by tyrosinase action on 3,4‐dihydroxyphenylalanine (DOPA) in the presence of polyethylene glycol: a matrix‐assisted laser desorption/ionization mass spectrometric investigation
Authors: Bertazzo Antonella , Vogliardi Susanna , Favretto Donata , Costa Carlo V. L. , Allegri Graziella , Traldi Pietro
Published: August 2002

The enzymatic reaction between DOPA and tyrosinase, the enzyme considered to be responsible for melanogenesis, was carried out in the presence of polyethylene glycol (PEG). This choice was made in order to increase the solubility of melanins, since these polymers are highly insoluble. The reaction mixtures were sampled at different times, immediately ultrafiltered to remove the enzyme, lyophilized, and analyzed by matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. The results were very different from those obtained in the absence of PEG. Only a few oligomers of dihydroxyindole (DHI) and dihydroxyindole‐2‐carboxylic acid (DHICA) were detected in low abundances, whereas new species originating from reaction of PEG with species belonging to the Raper‐Mason pattern appeared. The results show that, in the presence of PEG, tyrosinase‐catalyzed oligomerization of DOPA exhibits kinetics slower than those observed in the absence of the polymer. However, melanogenesis still takes place in the presence of PEG, as indicated by the formation of black pigments and by the detection of DHI and DHICA oligomers, considered to be the first intermediates in melanin formation. Copyright © 2001 John Wiley & Sons, Ltd.
Improvement of in‐gel digestion protocol for peptide mass fingerprinting by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Katayama Hiroyuki , Nagasu Takeshi , Oda Yoshiya
Published: August 2002

High‐sensitivity, high‐throughput analysis of proteins for proteomics studies is usually performed by polyacrylamide gel electrophoresis in combination with mass spectrometry. However, the quality of the data obtained depends on the in‐gel digestion procedure employed. This work describes an improvement in the in‐gel digestion efficiency for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) analysis. A dramatic improvement in the coverage of tryptic peptides was observed when n‐octyl glucoside was added to the buffer. Whole cell extracted proteins from S. cerevisiae were separated by two‐dimensional gel electrophoresis and stained with silver. Protein spots were identified using our improved in‐gel digestion method and MALDI‐TOFMS. In addition, the mass spectra obtained by using the matrix α‐cyano‐4‐hydroxycinnamic acid (CHCA) were compared with those obtained using 2,5‐dihydroxybenzoic acid (DHB). The DHB matrix usually gave more peaks, which led to higher sequence coverage and, consequently, to higher confidence in protein identification. This improved in‐gel digestion protocol is simple and useful for protein identification by MALDI‐TOFMS. Copyright © 2001 John Wiley & Sons, Ltd.
Identification of a novel series of alkylitaconic acids in wood cultures of Ceriporiopsis subvermispora by gas chromatography/mass spectrometry
Authors: del Río José C. , Gutiérrez Ana , Martínez María J. , Martínez Ángel T.
Published: August 2002

A novel series of long‐chain unsaturated dicarboxylic acids consisting of a long aliphatic chain attached to the C‐3 position of itaconic acid has been identified by gas chromatography/mass spectrometry during in vitro decay of eucalypt wood by the white‐rot basidiomycete Ceriporiopsis subvermispora. The major compounds were identified as tetradecyl‐, 7‐hexadecenyl‐ and hexadecylitaconic acids by their mass fragmentation patterns. Other members of the same compound series, identified as dodecanyl‐, tridecanyl‐, tetradecenyl‐, pentadecanyl‐, octadecenyl‐ and octadecanylitaconic acids, were present in very minor amounts or traces. Whereas hexadecenylitaconic acid has already been reported in cultures of C. subvermispora, to our knowledge this is the first report of the presence of the other alkylitaconic acids in fungal cultures. These new alkylitaconic‐type metabolites may constitute a source for peroxidizable lipids involved in lignin degradation during wood decay by C. subvermispora and other white‐rot basidiomycetes. Copyright © 2001 John Wiley & Sons, Ltd.
Identification of the interface of a large protein–protein complex using H/D exchange and Fourier transform ion cyclotron resonance mass spectrometry
Authors: Yamada Naoyuki , Suzuki Ei‐ichiro , Hirayama Kazuo
Published: August 2002

An infrared multiphoton dissociation (IRMPD) spectrum, obtained by Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS), was used to dissociate and to identify fragment ions from recombinant human interleukin‐6 (IL‐6; 21 KDa). The entire sequence was assigned by a single IRMPD experiment, and the observed fragment ions reflected the IL‐6 secondary structure. This method was combined with H/D off‐exchange to identify IL‐6 and anti‐human IL‐6 mouse monoclonal antibody MH166 (150 kDa) binding sites in the IL‐6 molecule. To facilitate the data analysis, the protein complex formation and the hydrogen exchange were performed with an immobilized antibody. Quenching of the hydrogen exchange reaction and collection of the deuterated IL‐6 were performed by elution under acidic conditions to measure the mass spectrum directly. IL‐6 was dissociated by using IRMPD, and the interface of IL‐6 bound to anti‐IL‐6 antibody MH166 was determined to analyze the deuterium incorporation level of each fragment ion. Thus, two discontinuous regions, Leu 126‐Lys 131 and Asp 160‐Met 184, were identified as the antibody binding sites. These regions are adjacent to each other on the tertiary structures determined by NMR and X‐ray analyses. Copyright © 2002 John Wiley & Sons, Ltd.