bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and thermal behavior of poly(ethylene oxide) poly(N‐substituted urethane)
Authors: Kweon Jung‐Ohk , Lee Yong‐Kuen , Noh Si‐Tae
Published: August 2002

Poly(N‐substituted urethane)s with an alkyl or ligo(ethylene oxide) monomethyl ether side chain were synthesized by the reaction operating in the following two‐step process: first, by metalation of the starting polymer with potassium tertiary butoxide (t‐BuOK) and then by treatment of the obtained urethane polyanion with tosylate in dimethyl sulfoxide. The thermal properties of poly(ethylene oxide) poly(N‐substituted urethane) (N‐sub PEOPU) were investigated in view of the N‐substitution degree and properties of the substituent. The chemical structures were characterized by Fourier transform infrared, 1H NMR, and 13C NMR spectroscopies. DSC and thermogravimetric analysis (TGA) were used to investigate the thermal properties of N‐sub PEOPUs. As the degree of N‐methylation increased, the glass‐transition temperature (Tg) of the N‐sub PEOPUs linearly decreased from 6 to −29 °C, and the weight‐loss temperature of 5% (T) from TGA in air increased from 278 to 360 °C. In the fully N‐substituted PEOPUs, the behavior of the thermal decomposition of the PEOPU that was processed in two stages was changed to one‐step decomposition in the temperature range of 360–440 °C. The Tg was shifted to a lower temperature with an increasing length of the substituent in N‐sub PEOPU. Improvement of the thermal stability by N‐substitution was more significant in N‐alkyl PEOPU than in N‐ethoxylate PEOPU. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4129–4138, 2001
Polyaddition of bis(seven‐membered cyclic carbonate) with diamines: A novel and efficient synthetic method for polyhydroxyurethanes
Authors: Tomita Hidetoshi , Sanda Fumio , Endo Takeshi
Published: August 2002

This article deals with the polyaddition of a novel bis(seven‐membered cyclic carbonate), 1,2‐bis[3‐(1,3‐dioxepan‐2‐one‐5‐yl)‐propylthio]ethane, with the diamines 4,9‐dioxa‐1,12‐dodecanediamine and p‐xylylenediamine. The polyaddition was carried out at 30–70 °C for 6–24 h in dimethyl sulfoxide to obtain the corresponding polyhydroxyurethanes with number‐average molecular weights of 10,900–35,700 in good yields. The reaction of a monofunctional seven‐membered cyclic carbonate, 5‐allyl‐1,3‐dioxepan‐2‐one (7CC), with monoamines was also carried out to examine the reactivity in comparison with that of six‐ and five‐membered cyclic carbonates. The reaction rate constants of 7CC with n‐hexylamine and benzylamine were estimated to be 48.5 and 11.0 L/mol · h, respectively, in dimethyl sulfoxide‐d6 (initial reagent concentration = 1 M) at 30 °C. The seven‐membered cyclic carbonate ring was 2.98 and 5.82 kcal/mol more strained than those of the six‐ and five‐membered cyclic carbonates, respectively, according to a semiempirical molecular orbital calculation with the PM3 Hamiltonian. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4091–4100, 2001
Highly biodegradable copolymers composed of chiral depsipeptide and L‐lactide units with favorable physical properties
Authors: Shirahama Hiroyuki , Tanaka Akira , Yasuda Hajime
Published: August 2002

Syntheses of copolymers composed of optically active depsipeptides (3,6‐dimethyl‐2,5‐morphorinedione) and L‐lactide—poly(L‐3,L‐6‐dimethyl‐2,5‐morphorinedione‐co‐L‐lactide), poly(L‐3,DL‐6‐dimethyl‐2,5‐morphorinedione‐co‐L‐lactide), and poly(L‐3,D‐6‐dimethyl‐2,5‐morphorinedione‐co‐L‐lactide)—were examined in an effort to improve the biodegradability and physical properties of homopoly(L‐lactide). In degradation tests, the copolymers composed of 3,6‐dimethyl‐2,5‐morphorinedione and lactide in the ratios 10/90 to 13/87 exhibited high biodegradability toward proteinase K, whereas a homopolymer, poly(L‐lactide), exhibited very poor biodegradability (only 50% after 200 h). These polymers composed of 3,6‐dimethyl‐2,5‐morphorinedione/L‐lactide in 11/89 to 13/87 ratios also degrades rapidly after being in compost for 30 days. The resulting copolymers, however, showed relatively low elongation properties. Therefore, ternary copolymerizations of L‐3,DL‐6‐dimethyl‐2,5‐morphorinedione, ϵ‐caprolactone, and L‐lactide were explored in an effort to improve their mechanical properties, especially the elongation, and sufficient results were obtained with an approximate ratio of 3/11/86. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 302–316, 2002
Solid polymer electrolytes III: Preparation, characterization, and ionic conductivity of new gelled polymer electrolytes based on segmented, perfluoropolyether‐modified polyurethane
Authors: Chen Chi‐Chang , Liang Wuu‐Jyh , Kuo Ping‐Lin
Published: August 2002

New segmented polyurethanes with perfluoropolyether (PFPE) and poly(ethylene oxide) blocks were synthesized from a fluorinated macrodiol mixed with poly(ethylene glycol) (PEG) in different ratios as a soft segment, 2,4‐toluene diisocyanate as a hard segment, and ethylene glycol as a chain extender. Fourier transform infrared, NMR, and thermal analysis [differential scanning calorimetry and thermogravimetric analysis (TGA)] were used to characterize the structures of these copolymers. The copolymer films were immersed in a liquid electrolyte (1 M LiClO4/propylene carbonate) to form gel‐type electrolytes. The ionic conductivities of these polymer electrolytes were investigated through changes in the copolymer composition and content of the liquid electrolyte. The relative molar ratio of PFPE and PEG in the copolymer played an important role in the conductivity and the capacity to retain the liquid electrolyte solution. The copolymer with a 50/50 PFPE/PEG ratio, having the lowest decomposition temperature shown by TGA, exhibited the highest ionic conductivity and lowest activation energy for ion transportation. The conductivities of these systems were about 10−3 S cm−1 at room temperature and 10−2 S cm−1 at 70 °C; the films immersed in the liquid electrolyte with an increase of 70 wt % were homogenous with good mechanical properties. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 486–495, 2002; DOI 10.1002/pola.10119
Staff‐type dendrimer: End functionalization of the dendronized siloxane polymer Me3SiO(MeSiHO)nSiMe3
Authors: Kim Chungkyun , Kwark Kyongran
Published: August 2002

A staff‐type dendritic carbosilane was synthesized with the siloxane polymer Me3SiO[MeSi(H)O]nSiMe3 as the core. Through hydrosilation and alcoholysis, the polymeric core grew to the second generation, which contained three, six, and nine allyloxy end groups on each siloxane unit backbone, respectively. The reaction of the monofunctionalized second‐parent generation, which had three SiCl groups on the peripheral layer of the unit backbone, with allylalcohol, cholesterol, 8‐hydroxyquinoline, 5‐(2‐hydroxyl)‐4‐methylthiazole, 4‐pyridinepropanol, and 4‐pyridinealdoxime in the presence of 1,1,2,2‐tetramethyethylenediamine, produced end‐functionalized, staff‐type dendrimers. The characterization of the dendritic polymers was carried out with NMR spectroscopy and gel permeation chromatography as well as elemental analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 976–982, 2002
Synthesis and characterization of temperature‐ and pH‐sensitive hydrogels based on poly(2‐ethyl‐2‐oxazoline) and poly(D,L‐lactide)
Authors: Wang Chau‐Hui , Hsiue Ging‐Ho
Published: August 2002

A novel series of temperature‐ and pH‐sensitive hydrogels based on poly(2‐ethyl‐2‐oxazoline) and three‐arm poly(D,L‐lactide) were synthesized via photocopolymerization. For the creation of polymeric networks, two types of macromers terminated with methacrylate groups were prepared: poly(2‐ethyl‐2‐oxazoline) dimethacrylate and three‐arm poly(D,L‐lactide) trimethacrylate. The chemical structures were analyzed with 1H NMR and Fourier transform infrared techniques. The thermal behaviors, morphologies, and swelling properties were measured for the characterization of the polymeric networks. All the poly(2‐ethyl‐2‐oxazoline)/three‐arm poly(D,L‐lactide)hydrogels provided high water retention capacity and exhibited reversible swelling–shrinking behavior in response to temperature and pH variations. The hydrogels with higher poly(2‐ethyl‐2‐oxazoline) dimethacrylate contents were more effective in raising the swelling ratio and temperature and pH sensitivity. However, higher contents of three‐arm poly(D,L‐lactide) trimethacrylate produced larger particles and pore sizes in the hydrogels. This study effectively proves that this unique combination of water swellability and biodegradability provides hydrogels with a much wider range of applications in biomedical fields. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1112–1121, 2002
Syntheses and characterizations of thermally degradable epoxy resins. III
Authors: Li Haiying , Wang Lejun , Jacob Karl , Wong C. P.
Published: August 2002

In flip‐chip technology, the development of reworkable underfill materials has been one of the keys to the recovery of highly integrated and expensive board assembly designs through the replacement of defective chips. This article reports the syntheses, formulations, and characterizations of two new diepoxides, one containing secondary ester linkages and the other containing tertiary ester linkages, that are thermally degradable below 300 °C. The secondary and tertiary ester diepoxides were synthesized in three and two steps, respectively. Both compounds were characterized with NMR and Fourier transform infrared spectroscopy and formulated into underfill materials with an anhydride as the hardener and an imidazole as the catalyst. A dual‐epoxy system was also formulated containing the tertiary ester diepoxide and a conventional aliphatic diepoxide, 3,4‐epoxy cyclohexyl methyl‐3,4‐epoxycyclohexyl carboxylate (ERL‐4221E), with the same hardener and catalyst. The curing kinetics of the formulas were studied with differential scanning calorimetry (DSC). Thermal properties of cured samples were characterized with DSC, thermogravimetric analysis, and thermomechanical analysis. The dual‐epoxy system showed a viscosity of 18.7 and 0.87 P at 25 and 100 °C, respectively. The cured secondary, tertiary, and dual‐epoxy formulas showed decomposition temperatures around 265, 190, and 220 °C, glass‐transition temperatures around 120–140, 110–157, and 140–157 °C, and coefficients of thermal expansion of 70, 72, and 64 ppm/°C below their glass‐transition temperatures, respectively. The shear strength of the cured dual‐epoxy system decreased quickly with aging at 230 °C. The reworkability test showed that the removal of a chip underfilled with this material from the board was quite easy, and the residue on the board could be thoroughly removed with a mechanical brush without obvious damage to the solder mask. In summary, the synthesized tertiary epoxide can be used as a reworkable underfill for flip‐chip applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1796–1807, 2002
Copolymerization of dodecyl‐4‐vinyl benzoate and dodecyl acrylate by conventional, atom transfer, and nitroxide‐mediated free‐radical polymerization
Authors: Bisht H. S. , Ray S. S. , Pandey D. , Sharma C. D. , Chatterjee A. K.
Published: August 2002

n‐Dodecyl acrylate (DA) and dodecyl‐4‐vinyl benzoate (DVB) were copolymerized by conventional free‐radical polymerization (CFRP); atom transfer radical polymerization (ATRP), and nitroxide‐mediated living free‐radical polymerization (NMLFRP) with benzoyl peroxide, 1‐phenyl ethyl chloride/cuprous chloride/2,2′‐bipyridine, and benzoyl peroxide/2,2,6,6‐tetramethylpiperidinyl‐1‐oxy initiator systems, respectively. In CFRP and NMLFRP, toluene and xylene were used as solvents, whereas ATRP was performed in bulk. Mayo–Lewis, Kelen–Tüdös, and Fineman–Ross methods were used for the determination of the monomer reactivity ratios (r1 and r2). They all gave nearly the same values of r1 and r2. The reactivity ratios of the two monomers in CFRP, ATRP, and NMLFRP were 0.17 ≤ r1 ≤ 0.4 (DA) and 1.0 ≤ r2 ≤ 1.24 (DVB). The side‐chain crystallinity of the copolymers decreased with an increasing DVB molar fraction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1818–1830, 2002
Synthesis of polyquinoline ether and its optical sensor property in the presence of metal cations
Authors: Seung Lee Taek , Yang Changduk , Kim Jong Lae , Lee Jin‐Kyun , Park Won Ho , Won Youjip
Published: August 2002

Semirigid polyquinoline with a flexible ether linkage was prepared via Friedländer quinoline synthesis, of which monomer was obtained through a five‐step synthesis. We investigated the polymer as a fluorescent sensor toward ferric ion that used a quinoline unit as a fluoroionophore group. The polymer solution in dimethylformamide/tetrahydrofuran showed the hyperchromic shift of the absorption maximum upon addition of metal ions exhibiting that the effect was clearly manifested upon exposure to ferric ion. A fluorescence quenching was observed in the presence of ferric ion corresponding to an interaction of the ferric cation to the polyquinoline ether, which results in a photoinduced electron‐transfer quenching pathway showing a Stern–Volmer constant (KSV) of 7.17 × 103 (M−1). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1831–1837, 2002
Hydrogen effects in propylene polymerization reactions with titanium‐based Ziegler–Natta catalysts. II. Mechanism of the chain‐transfer reaction
Authors: Kissin Yury V. , Rishina Laura A. , Vizen Elizabeth I.
Published: August 2002

Hydrogen is a very effective chain‐transfer agent in propylene polymerization reactions with Ti‐based Ziegler–Natta catalysts. However, measurements of the hydrogen concentration effect on the molecular weight of polypropylene prepared with a supported TiCl4/dibutyl phthalate/MgCl2 catalyst show a peculiar effect: hydrogen efficiency in the chain transfer significantly decreases with concentration, and at very high concentrations, hydrogen no longer affects the molecular weight of polypropylene. A detailed analysis of kinetic features of chain‐transfer reactions for different types of active centers in the catalyst suggests that chain transfer with hydrogen is not merely the hydrogenolysis reaction of the TiC bond in an active center but proceeds with the participation of a coordinated propylene molecule. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1899–1911, 2002
Unique dual function of La(C5Me5)[CH(SiMe3)2]2(THF) for polymerizations of both nonpolar and polar monomers
Authors: Tanaka Kohji , Furo Masahito , Ihara Eiji , Yasuda Hajime
Published: August 2002

A half‐metallocene‐type complex, La(C5Me5)[CH(SiMe3)2]2tetrahydrofuran (THF) 1, showed the dual function of performing the controlled polymerizations of nonpolar monomers such as ethylene and styrene as well as polar monomers like methyl methacrylate, hexyl isocyanate, and acrylonitrile in high yields. On the other hand, the metallocene‐type rare‐earth metal complexes, [(C5H4SiMe3)2Y(μ‐Me)]2 2 and (C5Me5)2YMe(THF) 3, showed relatively low catalytic activity. The structure of complex 2 was characterized by X‐ray analysis. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1382–1390, 2001
Stereocontrol during the free‐radical polymerization of methacrylates with Lewis acids
Authors: Isobe Yutaka , Nakano Tamaki , Okamoto Yoshio
Published: August 2002

The free‐radical polymerizations of methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, and 2‐methoxyethyl methacrylate were carried out in the presence of various Lewis acids. The MMA polymerization in the presence of scandium trifluoromethanesulfonate [Sc(OTf)3] in toluene or CHCl3 produced a polymer with a higher isotacticity and heterotacticity than that produced in the absence of Sc(OTf)3. Similar effects were observed during the polymerization of the other monomers. ScCl3, Yb(OTf)3, Er(OTf)3, HfCl4, HfBr4, and In(OTf)3 also increased the isotacticity and heterotacticity of the polymers. The effects of the Lewis acids were greater in a solvent with a lower polarity and were negligible in tetrahydrofuran and N,N‐dimethylformamide. Sc(OTf)3 was also found to accelerate the polymerization of MMA. On the basis of an NMR analysis of a mixture of Sc(OTf)3, MMA, and poly(methyl methacrylate), the monomer–Sc(OTf)3 interaction seems to be involved in the stereochemical mechanism of the polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1463–1471, 2001
Preparation of antimicrobial sodium alginate with chito‐oligosaccharide side chains
Authors: Song Jae Wook , Ghim Han Do , Choi Jin Hyun , Ko Sohk‐Won , Lyoo Won Seok
Published: August 2002

To provide sodium alginate (SA) with an antimicrobial property, we introduced chito‐oligosaccharide (COS) via chemical bonding in a two‐step procedure. We reacted COS with N‐methylol acrylamide (NMA) with N‐methylol groups to prepare acrylamidomethyl chito‐oligosaccharide (COS–NMA). SA with COS side chains (SA–COS) was produced through a subsequent reaction of SA with COS–NMA. The chemical structure of SA–COS was confirmed by IR spectroscopy and 1H NMR spectroscopy. With a two‐step method, we successfully prevented insoluble‐complex formation due to electrostatic attraction between chitosan and alginate. SA–COS showed excellent antimicrobial activity, with the growth of microorganisms completely suppressed by a small amount of COS (1.8 wt %). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1810–1816, 2001
The effect of rise in mean annual temperature on the stability of rock slopes containing ice‐filled discontinuities
Authors: Davies Michael C. R. , Hamza Omar , Harris Charles
Published: August 2002

Direct shear box tests have revealed that the stiffness and strength of an ice‐filled joint are a function of both normal stress and temperature. Comparison of these data with the results of similar experiments conducted on unfrozen joints indicates that at low temperatures and normal stresses the strength of an ice‐filled joint can be significantly higher than that of an unfrozen joint. However, in the absence of sufficient closure pressure, the strength of an ice‐filled joint can be significantly less than that of an unfrozen joint. This implies that if the stability of a slope is maintained by ice‐filled joints, its factor of safety will reduce with temperature rise. This hypothesis suggests that a jointed rock slope that is stable when there is no ice in the joints and is also stable when ice in the joints is at low temperatures will become unstable as the ice warms. Results from the model tests have confirmed this hypothesis. Copyright © 2001 John Wiley & Sons, Ltd.

Des tests de cisaillement directs ont révélés que la rigidité et la résistance d'un joint rempli de glace est fonction à la fois de la contrainte normale et de la température (Davies et al., 2000). La comparaison de ces données avec les résultats d'expériences semblables conduites sur des joints non gelés indique qu'à basse température et pour des contraintes normales identiques, la résistance d'un joint rempli de glace peut être plus élevée d'une manière significative que celle d'un joint non gelé. Toutefois, en l'absence d'une pression de fermeture suffisante, la résistance d'un tel joint rempli de glace peut être significativement moindre que celle d'une fissure non gelée. Ceci implique que si la stabilité de la pente est maintenue par des joints remplis de glace, son facteur de sécurité sera réduit avec l'augmentation de la température. Cette hypothèse suggère qu'une pente de roches fissurées qui est stable quand il n'y a pas de glace dans les joints et est aussi stable quand la glace dans les joints est à basse température, deviendra instable quand la glace s'échauffe. Des résultats obtenus par des tests ont confirmé ce résultat. Copyright © 2001 John Wiley & Sons, Ltd.
The thermal regime of soils in the north of Western Siberia
Authors: Pavlov A. V. , Moskalenko N. G.
Published: August 2002

The results of long‐term stationary observations upon the thermal regime of soils in natural and anthropogenically‐disturbed tundra and northern taiga landscapes in the north of Western Siberia are discussed. Quantitative assessments of the heating effect of snow cover and the cooling effect of surface organic layer on soil temperatures in both winter and summer seasons are given. Spatial and temporal variations in the depth of seasonal thaw and soil temperatures in the tundra and taiga zones are outlined. Data on changes in soil temperature regimes following disturbance of surface organic layers are presented. Contemporary tendencies in permafrost degradation induced by climatic warming, changes in the snow cover depth, and anthropogenic impacts are shown. Copyright © 2002 John Wiley & Sons, Ltd.
Functional residual capacity and passive compliance measurements after antenatal steroid therapy in preterm infants
Authors: McEvoy Cindy , Bowling Susan , Williamson Kathleen , Stewart Marion , Durand Manuel
Published: August 2002

Studies in preterm animal models have shown that antenatal corticosteroids enhance lung maturation by improving a variety of physiologic variables, including lung volumes. Changes in lung volume of preterm infants treated with a full course of antenatal steroids have not been investigated. We hypothesized that a full course of antenatal steroids would significantly increase functional residual capacity (FRC) in treated vs. untreated preterm infants. The objective of our study was to compare FRC and respiratory mechanics in steroid treated vs. untreated preterm infants. FRC and passive respiratory mechanics were prospectively studied within 36 hr of life in 20 infants (25–34 weeks of gestation) who had received a full course of antenatal steroids and in 20 matched untreated preterm infants. FRC was measured with the nitrogen washout method, and respiratory mechanics with the single‐breath occlusion technique.

Preterm infants who received steroids (n = 20; mean birth weight = 1,230 g; gestational age = 28.8 weeks) had a significantly higher FRC (29.5 vs. 19.3 mL/kg; P < 0.001) than untreated infants (n = 20; birth weight = 1,202 g; gestational age = 28.5 weeks). Passive respiratory system compliance was also increased in treated vs. untreated infants (P < 0.05).

In conclusion, FRC and passive respiratory system compliance were significantly improved in preterm infants (25–34 weeks gestation) treated with a full course of antenatal steroids, compared to matched untreated infants. Although this study was not randomized, it confirms that antenatal steroids have important effects on pulmonary function that may contribute to a decreased risk of respiratory distress syndrome in treated preterm infants. Pediatr Pulmonol. 2001; 31:425–430. © 2001 Wiley‐Liss, Inc.
Sex differences in response to steroids in preterm sheep lungs are not explained by glucocorticoid receptor number or binding affinity*
Authors: Kovar Jana , Waddell Brendan J. , Sly Peter D. , Willet Karen E.
Published: August 2002

We recently reported that prenatal glucocorticoid therapy is less effective at promoting an improvement in lung function in male than in female sheep. This observation, and the higher incidence of respiratory distress syndrome in human males, suggests that the male fetal lung may be less responsive to glucocorticoids than is the female fetal lung. Since glucocorticoids are known to exert their effects via specific cytoplasmic glucocorticoid receptors (GR), we hypothesized that there may be sexual dimorphism in either the number or binding affinity of lung GR. To test the hypothesis, binding of dexamethasone (a synthetic glucocorticoid, 0.5–40 nM) by cytosolic fractions of male (n = 16) and female (n = 16) fetal sheep lung was measured at 125 days gestation (term = 148 days).

Scatchard analysis of dexamethasone binding showed that the total number of GR (Bmax) did not significantly differ between male (346 ± 42 fmol/mg protein) and female (277 ± 23 fmol/mg protein) fetuses. The measured binding affinity (Kd) in male fetal lungs (6.85 ± 0.43 nM) was not significantly different from that in females (8.46 ± 1.02 nM).

In conclusion, this study suggests that sex differences in fetal sheep lung responses to glucocorticoid therapy are not due to differences in the number or binding affinity of lung GR. Pediatr Pulmonol. 2001; 32:8–13. © 2001 Wiley‐Liss, Inc.
Singular value decomposition analysis of protein sequence alignment score data
Authors: Fogolari F. , Tessari S. , Molinari H.
Published: August 2002

One of the standard tools for the analysis of data arranged in matrix form is singular value decomposition (SVD). Few applications to genomic data have been reported to date mainly for the analysis of gene expression microarray data. We review SVD properties, examine mathematical terms and assumptions implicit in the SVD formalism, and show that SVD can be applied to the analysis of matrices representing pairwise alignment scores between large sets of protein sequences. In particular, we illustrate SVD capabilities for data dimension reduction and for clustering protein sequences. A comparison is performed between SVD‐generated clusters of proteins and annotation reported in the SWISS‐PROT Database for a set of protein sequences forming the calycin superfamily, entailing all entries corresponding to the lipocalin, cytosolic fatty acid‐binding protein, and avidin–streptavidin Prosite patterns. Proteins 2002;46:161–170. © 2001 Wiley‐Liss, Inc.
Pressure effect on denaturant‐induced unfolding of hen egg white lysozyme
Authors: Sasahara Kenji , Sakurai Masao , Nitta Katsutoshi
Published: August 2002

The influence of hydrostatic pressure (≤100 MPa) on denaturant‐induced unfolding of hen egg white lysozyme was investigated by means of ultraviolet spectroscopy at various temperatures. Assuming a two‐state transition model, the dependence of Gibbs free‐energy change of unfolding on the denaturant concentration was calculated. Under applied hydrostatic pressure, these data were interpreted as suggesting that a two‐state model is not applicable in a restricted temperature range; the dominant effect of hydrostatic pressure is to affect the cooperativity in protein unfolding due to a chemical equilibrium shift in the direction of the reduction in the system volume. The deviation from the two‐state transition model appears to be rationalized by assuming that applied pressure induces an intermediate conformation between the native and unfolded states of the protein. The implication of the thermodynamic stability of protein under pressure was discussed. Proteins 2001;44:180–187. © 2001 Wiley‐Liss, Inc.
The crystal structure of chorismate lyase shows a new fold and a tightly retained product
Authors: Gallagher D. Travis , Mayhew Martin , Holden Marcia J. , Howard Andrew , Kim Kyung‐Jin , Vilker Vincent L.
Published: August 2002

The enzyme chorismate lyase (CL) catalyzes the removal of pyruvate from chorismate to produce 4‐hydroxy benzoate (4HB) for the ubiquinone pathway. In Escherichia coli, CL is monomeric, with 164 residues. We have determined the structure of the CL product complex by crystallographic heavy‐atom methods and report the structure at 1.4‐Å resolution for a fully active double Cys‐to‐Ser mutant and at 2.0‐Å resolution for the wild‐type. The fold involves a 6‐stranded antiparallel β‐sheet with no spanning helices and novel connectivity. The product is bound internally, adjacent to the sheet, with its polar groups coordinated by two main‐chain amides and by the buried side‐chains of Arg 76 and Glu 155. The 4HB is completely sequestered from solvent in a largely hydrophobic environment behind two helix–turn–helix loops. The extensive product binding that is observed is consistent with biochemical measurements of slow product release and 10‐fold stronger binding of product than substrate. Substrate binding and kinetically rate‐limiting product release apparently require the rearrangement of these active‐site‐covering loops. Implications for the biological function of the high product binding are considered in light of the unique cellular role of 4HB, which is produced by cytoplasmic CL but is used by the membrane‐bound enzyme 4HB octaprenyltransferase. Proteins 2001;44:304–311. © 2001 Wiley‐Liss, Inc.
Insecticidal properties of essential plant oils against the mosquito Culex pipiens molestus (Diptera: Culicidae)
Authors: Traboulsi Abdallah F , Taoubi K , El‐Haj Samih , Bessiere J M , Rammal Salma
Published: August 2002

The insecticidal activities of essential oil extracts from leaves and flowers of aromatic plants against fourth‐instar larvae of the mosquito Culex pipiens molestus Forskal were determined. Extracts of Myrtus communis L were found to be the most toxic, followed by those of Origanum syriacum L, Mentha microcorphylla Koch, Pistacia lentiscus L and Lavandula stoechas L with LC50 values of 16, 36, 39, 70 and 89 mg litre−1, respectively. Over 20 major components were identified in extracts from each plant species. Eight pure components (1,8‐cineole, menthone, linalool, terpineol, carvacrol, thymol, (1S)‐(−)‐α‐pinene and (1R)‐(+)‐α‐pinene) were tested against the larvae. Thymol, carvacrol, (1R)‐(+)‐α‐pinene and (1S)‐(−)‐α‐pinene were the most toxic (LC50 = 36–49 mg litre−1), while menthone, 1,8‐cineole, linalool and terpineol (LC50 = 156–194 mg litre−1) were less toxic.

© 2002 Society of Chemical Industry
Pesticide soil sorption parameters: theory, measurement, uses, limitations and reliability
Authors: Wauchope R Don , Yeh Simon , Linders Jan B H J , Kloskowski Regina , Tanaka Keiji , Rubin Baruch , Katayama Arata , Kördel Werner , Gerstl Zev , Lane Michael , Unsworth John B
Published: August 2002

The soil sorption coefficient Kd and the soil organic carbon sorption coefficient KOC of pesticides are basic parameters used by environmental scientists and regulatory agencies worldwide in describing the environmental fate and behavior of pesticides. They are a measure of the strength of sorption of pesticides to soils and other geosorbent surfaces at the water/solid interface, and are thus directly related to both environmental mobility and persistence. KOC is regarded as a ‘universal’ parameter related to the hydrophobicity of the pesticide molecule, which applies to a given pesticide in all soils. This assumption is known to be inexact, but it is used in this way in modeling and estimating risk for pesticide leaching and runoff. In this report we examine the theory, uses, measurement or estimation, limitations and reliability of these parameters and provide some ‘rules of thumb’ for the use of these parameters in describing the behavior and fate of pesticides in the environment, especially in analysis by modeling.

© 2002 Society of Chemical Industry
A review of plant species used to treat conjunctivitis
Authors: Sharma Poonam , Singh Gian
Published: August 2002

Conjunctivitis is a major occular external infection in tropical countries. Although not a very serious disease, it gives much discomfort and sometimes leads to partial blindness or blindness due to corneal involvement. Conjunctivitis has been known to occur in epidemic proportions in different parts of the world, mainly African and Asian regions. The indigenous cure of conjunctivitis using herbal products has been popular for centuries. This paper is an attempt to compile information on plants mentioned as a cure for conjunctivitis during ethnobotanical surveys between 1933 and 2000. Plants mentioned as a cure in various systems of medicine, namely Siddha and Ayurveda, are also included. Copyright © 2002 John Wiley & Sons, Ltd.
Impact of certain flavonoids on lipid profiles—­potential action of Garcinia cambogia flavonoids
Authors: Koshy Asha Sarah , Vijayalakshmi N. R.
Published: August 2002

Flavonoids from Cocos nucifera, Myristica fragrance, Saraka asoka and Garcinia cambogia exerted hypolipidaemic activity in rats. Lipid lowering activity was maximum in rats administered flavonoids (10 mg/kg BW/day) from Garcinia cambogia. A dose response study revealed biphasic activity. Higher doses were less effective in reducing lipid levels in serum and tissues, although devoid of toxic effects. Copyright © 2001 John Wiley & Sons, Ltd.
The protective effect of HD‐03 in CCl4‐induced hepatic encephalopathy in rats
Authors: Mitra S. K. , Venkataranganna M. V. , Gopumadhavan S. , Anturlikar S. D. , Seshadri S. J. , Venkatesha Udupa U.
Published: August 2002

The liver is a major parenchymal organ involved in many functional activities in the body. Hepatic encephalopathy is a syndrome characterized by increased blood ammonia level and is one of the major complications of cirrhosis. In the present study the protective effect of HD‐03, a poly‐herbal formulation, was evaluated against CCl4‐induced hepatic encephalopathy in rats. Hepatic encephalopathy was induced in Wistar rats by administration of CCl4 at a dose of 1 mL/kg orally in liquid paraffin (1:1) twice a week for 90 days. The liver enzymes (SGPT and SGOT) and blood ammonia levels were significantly (p < 0.001) higher in the CCl4‐intoxicated group compared with the untreated control group. Administration of HD‐03 at a dose of 750 mg/kg orally as an aqueous suspension significantly prevented the elevation of SGPT, SGOT and blood ammonia levels. Histomorphometric evaluation of liver and brain showed a protective effect of the HD‐03 treatment, thus correlating with the changes in biochemical profiles. The protective effect of HD‐03 against CCl4‐induced encephalopathy may be due to the improved hepatocellular function, which in turn helps in regulating the metabolism of ammonia. However, further studies are required to measure the activity of enzymes involved in the urea cycle and brain aromatic amino acids in order to elucidate the exact mechanism of action of HD‐03. Copyright © 2001 John Wiley & Sons, Ltd.
Antioxidant activity of extracts from plants growing in Sardinia
Authors: Dessí M. Assunta , Deiana Monica , Rosa Antonella , Piredda Martina , Cottiglia Filippo , Bonsignore Leonardo , Deidda Delia , Pompei Raffaello , Corongiu Francesco P.
Published: August 2002

The present work was carried out to study the effect of some plant methanol extracts and essential oils on lipid peroxidation in simple in vitro systems. The tested extracts were obtained from four plants, commonly known in the Mediterranean area, indigenous to Sardinia: Artemisia arborescens L., Calycotome villosa L., Daphne gnidium L. or naturalized in the island, Eucalyptus globulus Labill. The activity of the extracts was investigated during both autoxidation and iron or EDTA‐mediated oxidation of linoleic acid at 37 °C in the absence of solvent, and compared with that of BHT, α‐tocopherol and EDTA. During linoleic acid autoxidation all the extracts were active, showing an antioxidant activity in the order: BHT >α‐ tocopherol >Daphne gnidium (methanol extract) >Eucalyptus globulus (essential oil) >Calycotome villosa (essential oil) >Artemisia arborescens (essential oil and methanol extract) >Calycotome villosa (methanol extract). None showed any prooxidant activity. During the iron‐catalysed oxidation of linoleic acid the oils were not active, while all the methanol extracts showed some efficiency in preventing the oxidation process. All the extracts were also tested on cell cultures to investigate their cytotoxic activity or their ability to inhibit the growth of some pathogenic microorganisms. Copyright © 2001 John Wiley & Sons, Ltd.
Effect of the antiulcer polysaccharide fraction from Bupleurum falcatum L. on the healing of gastric ulcer induced by acetic acid in rats
Authors: Matsumoto T. , Sun X. B. , Hanawa T. , Kodaira H. , Ishii K. , Yamada H.
Published: August 2002

An antiulcer polysaccharide fraction (BR‐2) from Bupleurum falcatum L. was examined for its effect on the healing of chronic ulcers induced by acetic acid in rats. When BR‐2 was administered orally to the rats, it was shown to be effective in the healing of acetic acid‐induced chronic ulcer. This result suggests that the use of herbal prescriptions containing B. falcatum L. may prove useful for the treatment of peptic ulcers. Copyright © 2002 John Wiley & Sons, Ltd.
Low‐cost response surface methods from simulation optimization
Authors: Allen Theodore T. , Yu Liyang
Published: August 2002

We propose ‘low‐cost response surface methods’ (LCRSMs) that typically require half the experimental runs of standard response surface methods based on central composite and Box Behnken designs, but yield comparable or lower modeling errors under realistic assumptions. In addition, the LCRSMs have substantially lower modeling errors and greater expected savings compared with alternatives with comparable numbers of runs, including small composite designs and computer‐generated designs based on popular criteria such as D‐optimality. The LCRSM procedures appear to be the first experimental design methods derived as the solution to a simulation optimization problem. Together with modern computers, simulation optimization offers unprecedented opportunities for applying clear, realistic multicriterion objectives and assumptions to produce useful experimental design methods. We compare the proposed LCRSMs with alternatives based on six criteria. We conclude that the proposed methods offer attractive alternatives when the experimenter is considering dropping factors to use standard response surface methods or would like to perform relatively few runs and stop with a second‐order model. Copyright © 2002 John Wiley & Sons, Ltd.
Cassette‐accelerated rapid rat screen: a systematic procedure for the dosing and liquid chromatography/atmospheric pressure ionization tandem mass spectrometric analysis of new chemical entities as part of new drug discovery
Authors: Korfmacher Walter A. , Cox Kathleen A. , Ng Kwokei J. , Veals John , Hsieh Yunsheng , Wainhaus Sam , Broske Lisa , Prelusky Dan , Nomeir Amin , White Ronald E.
Published: August 2002

This report addresses the continuing need for increased throughput in the evaluation of new chemical entities (NCEs) in terms of their pharmacokinetic (PK) parameters by describing an alternative procedure for increasing the throughput of the in vivo screening of NCEs in the oral rat PK model. The new approach is called ‘cassette‐accelerated rapid rat screen’ (CARRS). In this assay, NCEs are dosed individually (n = 2 rats/compound) in batches of six compounds per set. The assay makes use of a semi‐automated protein precipitation procedure for sample preparation in a 96‐well plate format. The liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/API‐MS/MS) assay is also streamlined by analyzing the samples as ‘cassettes of six’. Using this new approach, a threefold increase in throughput was achieved over the previously reported ‘rapid rat screen’. Copyright © 2001 John Wiley & Sons, Ltd.
Monitoring the production yields of vincristine and vinblastine in Catharanthus roseus from somatic embryogenesis. Semiquantitative determination by flow‐injection electrospray ionization mass spectrometry
Authors: Favretto Donata , Piovan Anna , Filippini Raffaella , Caniato Rosamaria
Published: August 2002

A semiquantitative determination of two bis‐indole antitumor alkaloids, vincristine and vinblastine, has been performed by flow‐injection electrospray ionization mass spectrometric analysis of the extracts of Catharanthus roseus. Leaves and flowers of two different phenotypes (pink flower and white flower) obtained from somatic embryogenesis were thus examined and compared with the field‐grown mother plant. Different amounts of vincristine and vinblastine were detected depending on the examined samples. Copyright © 2001 John Wiley & Sons, Ltd.
A highly automated 96‐well solid phase extraction and liquid chromatography/tandem mass spectrometry method for the determination of fentanyl in human plasma
Authors: Shou Wilson Z. , Jiang Xiangyu , Beato Brian D. , Naidong Weng
Published: August 2002

A high‐throughput bioanalytical method based on automated sample transfer, automated solid phase extraction, and fast liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, has been developed for the determination of the analgesic fentanyl in human plasma. Samples were transferred into 96‐well plates using an automated sample handling system. Automated solid phase extraction (SPE) was carried out using a 96‐channel programmable liquid‐handling workstation using a mixed‐mode sorbent. The extracted samples were then dried down, reconstituted and injected onto a silica column using an aqueous/organic mobile phase with tandem mass spectrometric detection. The method has been validated over the concentration range 0.05–100 ng/mL fentanyl in human plasma, based on a 0.25‐mL sample size. The assay is sensitive, specific and robust. More than 2000 samples have been analyzed using this method. The automation of the sample preparation steps not only increased the analysis throughput, but also facilitated the transfer of the method between different bioanalytical laboratories of the same organization. Copyright© 2001 John Wiley & Sons, Ltd.
Qualitative and quantitative determination of poloxamer surfactants by mass spectrometry
Authors: Takáts Z. , Vékey K. , Hegedüs L.
Published: August 2002

Poloxamers are polyethylene‐polypropylene glycol linear co‐polymers. A simple matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) method has been developed for the determination of the average molecular weight of poloxamers. The molecular mass of five standard poloxamers determined by MALDI closely corresponds to that specified by the manufacturers, and no mass distribution effects were observed. Quantitation of distributions based on the molecular mass envelope using electrospray (ES) ionization was unsuccessful. To overcome this problem, quantitation was based on fragment ions (m/z 45 and 59) which gave reproducible signals using a very high orifice voltage (∼200 eV). Poloxamer concentrations were determined accurately with a good linear response using the standard addition method. We believe that the use of very small fragment ions for quantitation of polymers may become a widely applicable general technique. Copyright © 2001 John Wiley & Sons, Ltd.
Determination of gatifloxacin in human plasma by liquid chromatography/electrospray tandem mass spectrometry
Authors: Vishwanathan Karthick , Bartlett Michael G. , Stewart James T.
Published: August 2002

Gatifloxacin is an advanced‐generation, 8‐methoxyfluoroquinolone that is active against a broad spectrum of pathogens, including antiobiotic resistant Streptococcus pneumoniae. Development of a rapid, sensitive and selective method for the determination of gatifloxacin in human plasma is essential for understanding the pharmacokinetics of the drug when administered orally or intravenously. Solid phase extraction (SPE) using Oasis® HLB was used to extract gatifloxacin and the internal standard ciprofloxacin from plasma. A method based on liquid chromatography/electrospray tandem mass spectrometry (LC/ESI‐MS/MS) was developed and validated to quantitate gatifloxacin in human plasma. The precursor and major product ions of the analyte were monitored on a triple quadrupole mass spectrometer with positive ion electrospray ionization (ESI) in the multiple reaction monitoring (MRM) mode. Mechanisms for the formation of collision‐induced dissociation products of gatifloxacin are proposed. Linear calibration curves were generated from 10–1000 ng/mL with coefficients of determination greater than 0.99. The interday and intraday precision (%RSD) was less than 6.0% and accuracy (%error) was less than 5.4% for gatifloxacin. The limit of detection (LOD) for the method was 500 pg/mL based on a signal‐to‐noise ratio of 3. Copyright © 2001 John Wiley & Sons, Ltd.
Preparation of starch and other carbon fractions from higher plant leaves for stable carbon isotope analysis
Authors: Wanek Wolfgang , Heintel Sonja , Richter Andreas
Published: August 2002

The measurement of the carbon isotope composition of starch and cellulose still relies on chemical isolation of these water‐insoluble plant constituents and subsequent elemental analysis by isotope ratio mass spectrometry (EA/IRMS) of the purified fractions, while δ13C values of low‐molecular‐weight organic compounds are now routinely measured by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Here we report a simple and reliable method for processing milligram quantities of dried plant material for the analysis of the carbon isotope composition of lipids, soluble sugars, starch and cellulose from the same sample. We evaluated three different starch preparation methods, namely (1) enzymatic hydrolysis by α‐amylase, (2) solubilization by dimethyl sulfoxide (DMSO) followed by precipitation with ethanol, and (3) partial hydrolysis by HCl followed by precipitation of the resulting dextrins by ethanol. Starch recovery for three commercially available native starches (from potato, rice and wheat) varied from 48 to 81% for the techniques based on precipitation, whereas the enzymatic technique exhibited yields between 99 and 105%. In addition, the DMSO and HCl techniques introduced a significant 13C fractionation of up to 1.9‰, while the carbon isotope composition of native starches analyzed after enzymatic digestion did not show any significant difference from that of untreated samples. The enzymatic starch preparation method was then incorporated into a protocol for determinination of δ13C signatures of lipids, soluble carbohydrates, starch and crude cellulose. The procedure is based on methanol/chloroform/water extraction of dried and ground leaf material. After recovery of the chloroform phase (lipid fraction), the methanol/water phase was deionized by ion exchange (soluble carbohydrate fraction) and the pellet treated with heat‐stable α‐amylase (starch fraction). The remaining insoluble material was subjected to solvolysis by diglyme (cellulose fraction). The method was shown to be applicable to foliar tissues of a variety of different plant species (spruce, erect brome, maize and soybean). Copyright © 2001 John Wiley & Sons, Ltd.
Method development for measuring trace levels of penicillins in aqueous environmental samples
Authors: Bruno Federica , Curini Roberta , Corcia Antonio Di , Nazzari Manuela , Samperi Roberto
Published: August 2002

A method based on liquid chromatography/mass spectrometry with an electrospray ion source and a single quadrupole instrument (LC/ES‐MS) has been developed for determining trace levels of eight widely used penicillins in aqueous environmental samples. Analyte extraction was performed from 4 L tap water, 2 L groundwater, 1 L river water, 0.2 L treated sewage and 0.1 L raw sewage, by using a Carbograph 4 cartridge. During removal of the solvent, penicillins were purposely allowed to convert into their penicilloyl methyl esters. This ‘in situ’ derivatization step resulted in a dramatic enhancement of the response of the ES‐MS system for non‐amphoteric penicillins. Analyte recoveries were better than 80% irrespective of the type of aqueous sample, with the exception of amoxicillin (76%) and ampicillin (77%) in tap water. At the level of 50 ng/L of each analyte in ground water, the within‐day precision was in the range 6–10%. Calibration curves were linear for injected amounts up to 800 ng, with R2 in the range 0.9952–0.9995. When injecting large equivalent volumes of the aqueous samples, the electrospray matrix effect altered in‐source collision‐induced dissociation (CID) spectra of the analytes by severely weakening signals for fragment ions, as compared to spectra of reference standards. Remedies to obviate this anomalous unwelcome effect are suggested. On the basis of a signal‐to‐noise ratio of 10, limits of quantification were estimated to range between 2 (cloxacillin) and 24 ng/L (amoxicillin) in river water. Copyright © 2001 John Wiley & Sons, Ltd.