bluuebunny/crossref_metadata_2025 huggingface dataset:
Melt fracture behavior of polypropylene‐type resins with narrow molecular weight distribution. II. Suppression of sharkskin by addition of adhesive resins
Authors: Fujiyama Mitsuyoshi , Inata Hitoshi
Published: August 2002

Standing on a hypothesis that the sharkskin of a polymer with a narrow molecular weight distribution at extrusion processing originates from a stick‐slip of the polymer at the die wall, the suppression of the sharkskin was tried by means of suppressing the slip by the addition of adhesives. To polypropylene (PP)‐type resins with narrow molecular weight distributions such as a PP‐type thermoplastic elastomer, PER and a controlled rheology PP were added small amounts of adhesives such as maleated PP, maleated PER, reactive polyolefin oligomers, ethylene/ethylacrylate/maleic anhydride (MAH) copolymer, ethylene/vinyl acetate copolymer, and styrene/MAH copolymer, and their melt fracture behaviors at capillary extrusion were observed. It was found that the sharkskin of the PP‐type resins with narrow molecular weight distributions was suppressed by the addition of the adhesive resins with good adhesion to metal. The suppressive effect of the sharkskin was generally the more remarkable by the higher loading of the adhesives with the higher MAH content. This is the direction of increasing adhesion. From this fact, it was assumed that the sharkskin of the PP‐type resins with narrow molecular weight distribution does not originate from a periodic growth and relaxation of tensile stress at the extrudate surface but from a stick‐slip at the die wall. Based on this mechanism, it may be said that the sharkskin can be suppressed by both ways of directions of promoting and suppressing the slip at the die wall. The former way is the previously known method, and the latter way is the method proposed in the present study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2120–2127, 2002
Surface modification of poly(vinyl chloride) for antithrombogenicity study
Authors: Xie Yunchuan , Yang Qingfang
Published: August 2002

A process was established to conduct heparinization on the surface of poly(vinyl chloride) for antithrombogenicity utilization. A bifunctional monomer, glycidyl methacrylate (GMA), was grafted onto the surface of PVC by gas‐phase photografting polymerization without degassing first; then heparin was immobilized onto the poly(glycidyl methacrylate) segments. The branch structure of GMA and heparin were characterized by Fourier transfer infrared (FTIR) spectroscopy and electron spectroscopy (ESCA). It was confirmed that the bifunctional monomer GMA and heparin were grafted successfully onto the surface of PVC. The antithrombogenicity of the samples was tested both in vitro and in vivo, respectively. Results indicated that the blood compatibility of those products was improved greatly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1013–1018, 2002
Thermal behavior and morphology of polyamide 6 based multicomponent blends
Authors: Jafari S. H. , Pötschke P. , Stephan M. , Pompe G. , Warth H. , Alberts H.
Published: August 2002

The thermal behavior and morphology of multicomponent blends based on PA6, polyamide 6 (PA6)/styrene–acrylonitirle copolymer (SAN), PA6/acrylonitrile–butadiene–styrene terpolymer (ABS), and their compatibilized blends with styrene–acrylonitrile–maleic anhydride copolymer (SANMA) were studied using DSC and SEM. The blends were prepared in a twin‐screw extruder under similar processing conditions, keeping the PA6 content fixed at 50 wt %. It was found that, in all the blends, the second component had a nucleating effect and improved the overall degree and rate of crystallization of PA6, whereas addition of a compatibilizer slightly diminished these effects and resulted in significant changes in the blend morphology. The nucleating effect and consequent changes in the crystallization behavior was attributed to the presence of SAN, which is a common component in all the blends. The Tg of PA6 in the blends with a cocontinuous morphology, due to the connectivity between the phases, is higher than in the blends with a disperse‐type morphology. The compatibilized blends have a lower crystallization rate and nucleation ability with a cocontinuous morphology, whereas the uncompatibilized blends have a higher crystallization rate with a higher nucleation ability and a disperse and/or a coarse cocontinuous morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2753–2759, 2002
Dielectric investigation of some normal alcohols and diols dispersed in some polymeric matrices
Authors: Abd‐El‐Messieh S. L. , Mohamed M. G. , Mazrouaa A. M. , Soliman A.
Published: August 2002

A series of diols and normal alcohols were dispersed in some polymeric matrices, namely, polystyrene (PS), polyethylene (PE), and poly(methyl methacrylate) (PMMA). The dielectric properties of these systems were investigated in the frequency range of 102–105 Hz at a room temperature of 25°C. The experimental data were analyzed according to the Fröhlich equation into two relaxation processes: The first relaxation in the lower‐frequency range could be attributed to the Maxwell–Wagner effect as a result of the difference in permittivities and conductivities of the investigated systems. The second relaxation in the higher‐frequency range could be attributed to an intramolecular motion involving the rotation of various segments of the chain about the CC bond accompanied by movement of the main dipoles for either diols or alcohols. The presence of the phenyl ring in the PS matrix may hinder such rotation when compared with the other matrices. The dielectric properties were also investigated for PMMA blended with either PS or PE at different ratios before and after the addition of small quantities of ethanediol. The interaction that might be expected between PMMA and PS in the blend may affect the rotation of the ethanediol chain in the blend matrix. The dielectric data as well as the data obtained from the calculated heat of mixing show that the investigated blends are incompatible. The addition of ethanediol to such blends gives the possibility that a large number of dipoles can be impregnated into the blend matrix and the problem of phase separation could be solved.© 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 271–281, 2002
Effect of different polymers on the efficiency of water‐borne methyl amine adduct as corrosion inhibitor for surface coatings
Authors: Badran Badran M. , Mohammed Heba A. , Aglan Heshmat A.
Published: August 2002

Styrene/acrylic emulsion copolymer and water‐based short oil urethane alkyd resin were used as binders to prepare water‐based, environmentally friendly paints by using 0.5% emulsified methylamine adduct as corrosion inhibitor. The choice of the two above‐mentioned binders was based on the fact that styrene/acrylic emulsion copolymer is a nonconvertible binder, whereas short oil urethane alkyd resin is a convertible binder. The physical, chemical, mechanical, and corrosion properties of the paint films were evaluated and compared with a commercially known anticorrosive water‐based paint. It was found that the prepared paints have unique desirable properties such as the following: they do not contain anticorrosive pigments (which contain heavy metals in their main chemical structure); they are solvent‐free; and they can be produced to match any color. Corrosion tests on the films of the formulated paints revealed that the short oil urethane alkyd resin is superior to the styrene/acrylic copolymer. Moreover, the corrosion inhibition properties of the paint films prepared from both binders are comparable with the commercially available paints containing anticorrosive pigments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 879–885, 2002
Effect of GMA on monodisperse epoxy‐functionalized polymer microsphere particles by dispersion copolymerization of styrene with glycidyl methacrylate
Authors: Lee Sung‐Soo , Park Kang‐Yeol , Kim Ju‐Young , Suh Kyung‐Do
Published: August 2002

Monodisperse poly[styrene‐co‐glycidyl methacrylate (GMA)] microparticles were synthesized by dispersion copolymerization in a water–ethanol medium. The effects of various polymerization parameters on the particle size and size distribution of the dispersion copolymerization were investigated. The dispersion of polymer particles decreased when the GMA was added if the polystyrene homopolymer particles were polydispersed. The GMA acted as a comonomer as well as a costabilizer in the dispersion copolymerization of styrene with GMA. The solvency of the monomer increased with the concentration of GMA in the polymerization medium because GMA has a greater hydrophilicity than styrene, resulting in a large particle size and a slow polymerization rate. From an HCl–dioxane analysis of the poly(styrene‐co‐GMA) microparticles, great amounts of epoxy groups were detected after the completion of dispersion copolymerization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1206–1212, 2001
Biodegradable polylactide/poly(ethylene glycol)/polylactide triblock copolymer micelles as anticancer drug carriers
Authors: Liu Li , Li Chenxi , Li Xuechen , Yuan Zhi , An Yingli , He Binglin
Published: August 2002

Adriamycin (ADR) was selected as a model drug to evaluate the potential applications of polylactide/poly(ethylene glycol)/polylactide (PLA/PEG/PLA) micelles as drug carriers in parenteral delivery systems. The PLA/PEG/PLA triblock copolymer micelles were characterized by dynamic light scattering and transmission electron microscopy. It was found that the micelle size increased with the increasing of the PLA chain length. The average size of ADR‐loaded micelles was 143.2 nm. The histogram analysis showed that the ADR‐loaded micelles possessed a narrow unimodal size distribution. The ADR loading contents of the micelles and ADR entrapment efficiency were dependent on the PLA chain length and PEG chain length in the copolymer. They increased with the increase of the PLA chain length, but the PEG chain length was identical and decreased with the increase of the PEG chain length; the length of the PLA block was similar. The initial amount of ADR also influenced the drug contents and entrapment efficiency (i.e., the more the initial amount added, the more the drug contents and the higher encapsulation efficiency). The drug release experiments indicated that the ADR‐loaded micelles possessed sustained release characteristics. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1976–1982, 2001
A study on HDPE/sulfonated EPDM‐treated CaCO3 blends
Authors: Li Huilin , Zheng Mingjia , Xu Xi
Published: August 2002

In this article, sulfonated ethylene‐propylene‐diene monomer terpolymer (H–SEPDM) was used to treat CaCO3 particles. CaCO3 particles are encapsulated by H–SEPDM through the reaction of sulfonic acid group (SO3H) in H–SEPDM with CaCO3 to improve the interface adhesion of CaCO3 with HDPE. In case the treated CaCO3 is blended with HDPE, a brittle–ductile transition occurs. The impact strength of the blend rises sharply at 25–30 wt % CaCO3, and amounts to more than 700 J/m, four times as high as that of HDPE at 30 wt % CaCO3, without much loss of its yield strength and modulus. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2140–2144, 2001
FTIR studies of the curing reactions of palm oil alkyd–melamine enamels
Authors: Gan Seng‐Neon , Tan Boon‐Yeow
Published: August 2002

Three alkyds of high hydroxyl numbers with oil lengths of 21, 30, and 41 were prepared from crude palm oil. The excess hydroxyl groups provided good compatibility with melamine resins, and also served as sites for crosslinking reactions. They were made into baking enamels by blending with 20% of a commercial melamine resin. All of them could be cured at temperatures below 200°C although thermodecomposition might occur above 290°C. The dry‐hard time of these enamels cured at temperatures between 140–180°C ranged from 10 to 180 min. Fourier transform infrared spectroscopy could be used to follow the major curing reactions. The absorbance of OH and NCH2OCH3 groups showed significant reduction. The changes in the absorbance of these peaks with time and temperature were investigated. The predominant reaction was identified as the formation of methylene ether linkages. However, the self‐condensation reactions of the amino resin and ester linkages did not occur to any noticeable extent. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2309–2315, 2001
Synthesis of tung oil–diacrylate copolymers via the Diels‐Alder reaction and properties of films from the copolymers
Authors: Trumbo D. L. , Mote B. E.
Published: August 2002

Copolymers were synthesized from tung oil and 1,6 hexanediol diacrylate or 1,4‐butanediol diacrylate via the Diels‐Alder reaction. The copolymers were completely soluble in common laboratory solvents, and had very broad molecular weight distributions. The residual double bonds in the copolymers were used to cure films by oxidative means. The films had good solvent resistance, good gloss, and a reasonable hardness–flexibility balance. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2369–2375, 2001
Preparation and characterization of nanofiltration composite membranes using polyacrylonitrile (PAN). II. Preparation and characterization of polyamide composite membranes
Authors: Oh Nam‐Wun , Jegal Jonggeon , Lee Kew‐Ho
Published: August 2002

Polyamide (PA) composite membranes in which PA active layers were interconnected with support layers via the formation of ionic bonds were prepared by the interfacial polymerization of piperazine (PIP) with trimesoyl chloride (TMC) on the surfaces of microporous polyacrylonitrile (PAN) supports containing carboxylic acid groups. Formation of the ionic bonds through an acid‐base reaction between NH group of PIP and COOH of the support was studied using FTIR‐ATR spectroscopy. Variation of the surface morphologies of the composite membranes that was induced by the presence of the ionic bonds was observed with a FESEM and an AFM. Permeation tests with various feed solutions such as PEG 600, Na2SO4, MgSO4, MgCl2, and NaCl solutions were carried out to see how the characteristics of the PAN supports affected on the flux and rejection of the corresponding PA composite membranes. Chemical stabilities of the composite membranes with the ionic bonds were studied and compared with that of a conventional PA composite membrane, using alcohol solutions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2729–2736, 2001
Characterization of poly(L‐lactic acid) fibers produced by melt spinning
Authors: Yuan Xiaoyan , Mak Arthur F. T. , Kwok K. W. , Yung Brian K. O. , Yao Kangde
Published: August 2002

Biodegradable poly(L‐lactic acid) (PLLA) fibers were processed by a two‐step melt‐spinning method (melt extrusion and hot draw) from PLLA with three different viscosity‐average molecular weights (494,600, 304,700, and 262,800). Before spinning, the polymer flakes were first milled into powders and dried under vacuum. Viscosity‐average molecular weight of PLLA following the fabrication process was monitored. Tensile properties of as‐spun and hot‐drawn fibers were investigated. Morphology of the PLLA fibers was viewed under a scanning electron microscope. Crystallinity of these fibers was assessed by thermogram analysis of differential scanning calorimetry. Results showed that the extent of decrease in the viscosity‐average molecular weight of PLLA dropped sharply by 13.1–19.5% during pulverization and by 39.0–69.0% during melt‐extrusion. The hot‐draw process in this study had a little effect on the viscosity‐average molecular weight of PLLA. Smoother fibers could be obtained for the die temperature at least 230°C for raw materials with higher crystallinity (more than 75%) and at least 220°C for raw materials with lower crystallinity (about 60%). The as‐spun fibers showed crystallinity of 16.5–22.8% and the value increased to 50.3–63.7% after hot draw. Tensile moduli of the as‐spun fibers were in the range of 1.2–2.4 GPa, which were raised to 3.6–5.4 GPa after hot draw. The final PLLA fibers with 110–160 μm diameters showed tensile strengths of 300–600 MPa. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 251–260, 2001
Miscibility and crystallization behavior of the solution‐blended sulfonated poly(phenylene oxide)/ poly(styrene‐co‐4‐vinyl pyridine) blend
Authors: Pan Yan , Fu Weiwen , Xue Feng , Luo Yuanfang , Gu Ju
Published: August 2002

The miscibility and crystallization behavior of the solution‐blended lightly sulfonated poly(phenylene oxide) (SPPO)/poly(styrene‐co‐4‐vinylpyridine) (PSVP) blend were investigated by conventional and modulated differential scanning calorimetry (MDSC). It was found that the original blend film is actually composed of a crystalline SPPO phase and a noncrystalline compatible SPPO–PSVP phase. The original phase‐segregated structure will evolve to a noncrystalline homogenous structure by subsequent high temperature annealing. The resulting good miscibility was attributed to two aspects: one is that the SPPO crystalline structure could be destroyed as annealing temperature is high enough; the other is that the acid–base interaction between the sulfonic group of SPPO and the pyridine ring of PSVP could promote mixing of different components effectively. And such acid–base interaction was demonstrated by 1C NMR spectra. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2843–2848, 2001
Preparation of epoxidized rubber using a reactive processing technique. I. Synthesis and characterization of epoxidized polybutadiene rubber
Authors: Zhang Ying , Chen Xin‐Zhong , Zhang Yong , Zhang Yin‐Xi
Published: August 2002

The epoxidation of high cis‐butadiene rubbers (BR) with monoperoxy phthalic acid was successfully performed in reactive processing equipment of the HAKKE mixer at room temperature. The effects of such reaction conditions as the concentration of peroxy acid and reaction time on the epoxidation level and the efficiency of monoperoxy phthalic acid were investigated. The structure of epoxidized BR was characterized by 1H NMR and Fourier transform infrared spectrometer. Differential scanning calorimeter analysis revealed that the glass transition temperature of epoxidized BR had a progressive increase with epoxidation level. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2987–2992, 2001
Analysis of the phase partitioning of additives in rubber‐modified plastics
Authors: Smith Patrick B. , Buzanowski Walter C. , Gunderson Judy J. , Priddy Duane B. , Pfenninger Lance
Published: August 2002

The phase partitioning of additives in polymer blends has a large impact on the performance of the blend. Therefore, it is necessary to be able to quantify the level of the additives in each phase. A 1H–NMR method is presented to determine the partitioning of additives between the rubber and rigid phases of a high‐impact polystyrene (HIPS) material. In one case, a HIPS material was modified with 2,6‐di‐tert‐butyl‐4‐methyl‐phenol (Ionol, CAS# 128‐37‐OMF) as a stabilizer for both phases. HIPS materials with varying levels of Ionol were melt‐blended by extrusion and the total level of additives was determined analytically for these standard materials. The 1H–NMR method was used to determine the level of Ionol in the poly(butadiene) rubber phase. The Ionol was found to preferentially partition into the rubber phase with a partition coefficient of about 2. A second example of the same concept, instead utilizing 13C–NMR, involved the analysis of the partition coefficient for both Tinuvin P and Tinuvin 770 (CAS# 2440‐22‐4 and 52829‐07‐9), partitioning between the rigid and rubber phases of an ethylene–propylene–diene‐modified (EPDM) toughened styrene–ran–acrylonitrile (SAN) copolymer. The partition coefficient was determined to be 0.5 for Tinuvin P and 1.3 for Tinuvin 770. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1963–1970, 2001
Succinoylation of wheat straw hemicelluloses with a low degree of substitution in aqueous systems
Authors: Sun Runcang , Sun X. F. , Bing X.
Published: August 2002

The reaction of wheat straw hemicelluloses with succinic anhydride in aqueous alkaline systems was studied. The products showed a rather low degree of substitution, ranging from 0.017 to 0.21. The effects of reaction times of 0.5–16 h, temperatures of 25–45°C, and molar ratios of succinic anhydride to anhydroxylose units in hemicelluloses of 1:5–1:1 on the succinoylation yield and degree of substitution were examined. With the reaction kept within a pH range of 8.5–9.0, a temperature range of 25–28°C, a reaction duration of 1–2 h, and a 1:1 molar ratio of succinic anhydride to hemicelluloses were preferred. The structure of the resulting polymers was determined with Fourier transform infrared and1H‐ and13C‐NMR spectroscopy, which indicated monoester substitution. The thermal stability of the esterified polymer increased with chemical modification. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 757–766, 2002
Effect of styrene‐butadiene‐styrene addition on polystyrene/high‐density polyethylene blends
Authors: Taşdemi̇r Münir , Yildirim Hüseyin
Published: August 2002

In order to prepare an ideal mixture, the physical and chemical properties of the constituent polymers must be known in detail. Thus, selection of the polymers that will constitute the mixture and a thorough study of the mixing methods and the economic factors become important. A rigid plastic is toughened by dispersing a small amount of rubbery material (generally 5–20%) in the rigid plastic matrix. Such a mixture of plastics is characterized by its impact resistance. Among thermoplastics toughened in this way are polystyrene (PS), poly(vinyl chloride), poly(methyl methacrylate), polypropylene, polycarbonate, and nylons, and recently thermoset resins such as epoxies, unsaturated polyester resins, and polyamids. In this study PS and high‐density polyethylene polymers were mixed in various ratios. In order to increase the compatibility of the mixtures, 5, 7.5, and 10% SBS copolymer was also added. The mixing operation was conducted by using a twin‐screw extruder. The morphology and the compatibility of the mixtures were examined by using SEM and DSC techniques. Furthermore, the elastic modulus, yield and tensile strengths, percent elongation, Izod impact resistance, hardness, and melt flow index values of the polymer alloys of various ratios were determined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2967–2975, 2002; DOI 10.1002/app.2325
Impact of hydropattern disturbance on crayfish population dynamics in the seasonal wetlands of Everglades National Park, USA
Authors: Acosta Charles A. , Perry Sue A.
Published: August 2002

1. The natural hydropattern in the seasonally‐flooded marl prairie wetlands of Everglades National Park has been severely disrupted by human water control activities, seriously impacting higher trophic organisms, e.g. wading birds, that depend on these wetlands. Less is known about the impacts on key aquatic fauna, such as crayfish Procambarus alleni, or how these populations might respond to proposed habitat restoration strategies.

2. Under severe environmental stress, populations of burrowing crayfish are predicted to have skewed size structure, low reproductive success, low survival, and widespread dispersal. As predicted for populations in stressed habitats, crayfish density was low, small dispersing adults were dominant, juvenile abundance was low, and survival was low in habitats where the hydroperiod (duration of flooding) was short and groundwater level was lowest.

3. Crayfish dispersed during flooding, but during the drydown, they burrowed rather than sought deeper water. This dispersal strategy may be adaptive for surviving in seasonal wetlands, but this had severe consequences on survival in disturbed habitats with shortened hydroperiods. Survival in burrows during the dry season was high in the longer‐hydroperiod habitats but was zero in the short‐hydroperiod habitat where the groundwater level fell more than 1 m.

4. Long‐hydroperiod marl prairie may function as sources, whereas short‐hydroperiod habitats act as population sinks. Our study suggests that the threshold conditions for preventing mass mortality of crayfish in these wetlands are hydroperiods >7 months and groundwater levels <0.5 m below the surface during the dry season.

5. Historical (pre‐drainage) hydroperiods appear to be restricted to the longest hydroperiod areas of the marl prairie. This indicates that much of the marl prairie wetlands now function as population sinks for crayfish and other invertebrates. The historical hydropatterns need to be re‐established throughout the marl prairie wetlands to achieve the restoration goal of increasing productivity in the aquatic faunal community.

Copyright © 2001 John Wiley & Sons, Ltd.
Functional morphology of venous structures associated with the male and female reproductive systems in Florida manatees (Trichechus manatus latirostris)†
Authors: Rommel Sentiel A. , Pabst D. Ann , McLellan William A.
Published: August 2002

The reproductive organs of Florida manatees (Trichechus manatus latirostris) are surrounded by thermogenic locomotory muscles and insulating fat. Manatees are reported to maintain core body temperatures of 35.6°–36.4° C, temperatures known to interfere with production and maturation of viable sperm in terrestrial mammals. We describe two novel venous plexuses associated with the manatee epididymis. Each epididymis is located in a hypogastric fossa at the caudolateral extremity of the abdominal cavity. Each hypogastric fossa is lined by an inguinal venous plexus that receives cooled blood from a superficial thoracocaudal plexus. We conclude that male manatees may prevent hyperthermic insult to their reproductive tissues by feeding cooled superficial blood to venous plexuses deep within their bodies. Female manatees also possess hypogastric fossae and venous structures similar to those found in male manatees. The ovaries, uterine tubes, and distal tips of the uterine horns are located in the hypogastric fossae. We suggest that the thermovascular structures we describe also prevent hypothermic insult to female manatee reproductive tissues. The venous structures in manatees are functionally similar to structures associated with reproductive thermoregulation in cetaceans and phocid seals. Thus, these thermovascular structures appear to be convergent morphological adaptations that occur in three clades of diving mammals with independent evolutionary histories. Anat Rec 264:339–347, 2001. Published 2001 Wiley‐Liss, Inc.
Bone density of the human talus does not increase with the cartilage degeneration score
Authors: Muehleman C. , Berzins A. , Koepp H. , Eger W. , Cole A.A. , Kuettner K.E. , Sumner D.R.
Published: August 2002

Osteoarthritis (OA) is a common, disabling condition of synovial joints that can eventually lead to reduced, or lost, mobility. It is characterized by both articular cartilage degeneration and subchondral bone changes. However, a cause‐and‐effect relationship between the two tissues remains controversial. Increased subchondral bone density has been associated with early degenerative changes in the cartilage of knee, hip, and finger joints—joints in which progressive changes to OA are common. In contrast, the ankle joint is known to exhibit early cartilage changes, but is not prone to the development of OA. In the present study, it was found that cartilage degeneration on the talus is not associated with an increase in bone density, as assessed through peripheral quantitative computed tomography (pQCT). Anat Rec 266:81–86, 2002. © 2002 Wiley‐Liss, Inc.
Immunolocalization of vacuolar‐type H+‐ATPase, cathepsin K, matrix metalloproteinase‐9, and receptor activator of NFkB ligand in odontoclasts during physiological root resorption of human deciduous teeth
Authors: Oshiro Takahiro , Shibasaki Yoshinobu , Martin T. John , Sasaki Takahisa
Published: August 2002

To investigate the cellular mechanisms of physiological root resorption in human deciduous teeth, the authors examined the immunocytochemical localization of vacuolar‐type H+‐ATPase, a lysosomal cysteine proteinase, cathepsin K, matrix metalloproteinase‐9 (MMP‐9), and receptor activator of NFKB ligand (RANKL) in odontoclasts. H+‐ATPase, cathepsin K, and MMP‐9 are the most important enzymes for decalcification of apatite crystals and degradation of type‐I collagen. In addition, RANKL is one of the key regulatory molecules in osteoclast formation and functions. Odontoclasts developed extensive ruffled borders and clear zones apposed to the resorbing root dentine surfaces. On immunoelectron microscopy, the expression of vacuolar‐type H+‐ATPase was detected along the limiting membranes of pale vacuoles and the ruffled border membranes of odontoclasts. Cathepsin K in odontoclasts was localized within pale vacuoles, lysosomes, the extracellular canals of ruffled borders, and the underlying resorbing dentine surfaces. MMP‐9 localization in odontoclasts was similar to those of cathepsin K. RANKL was detected in both mononuclear stromal cells and odontoclasts located on resorbing dentine surfaces. These results suggest that (1) odontoclasts are directly involved in decalcification of apatite crystals by active extrusion of proton ions mediated by H+‐ATPase and (2) extracellular degradation of dentine type‐I collagen by both cathepsin K and MMP‐9, and (3) odontoclast differentiation and activity are regulated, at least in part, by RANKL, possibly produced by mononuclear stromal cells and odontoclasts themselves in the resorbing tissues. Thus, the cellular mechanisms of physiological root resorption appear to be quite similar to those of osteoclastic bone resorption. Anat Rec 264:305–311, 2001. © 2001 Wiley‐Liss, Inc.
The X—a sexy chromosome
Authors: Graves Jennifer A. Marshall , Delbridge Margaret L.
Published: August 2002

There is new and convincing evidence(1) that the mammalian X chromosome, as well as the Y chromosome, contains an atypically high proportion of genes involved in sex and reproduction (SRR genes). Here we consider alternative explanations for this concentration. One possibility is that a particularly well‐endowed autosome was “chosen” for a career as a sex chromosome. Alternatively, the high concentration of SRR genes may have resulted from the accumulation of these genes on the X after the degradation of the Y, either by transposition of autosomal SRR genes to a “selfish X”, or by acquisition of SRR functions by widely expressed genes on the X. We suggest experiments to distinguish these possibilities, and speculate on the implications of gathering evidence that genes with other functions, too, are not distributed uniformly over the genome. BioEssays 23:1091–1094, 2001. © 2001 John Wiley & Sons, Inc.
Gleanings of a chemiosmotic eye
Authors: Harold Franklin M.
Published: August 2002

In 1961, an inventive Englishman, named Peter Mitchell, proposed a radically novel hypothesis to explain how energy is conserved during respiration and photosynthesis, and applied to the generation of ATP and other kinds of functional work. The chemiosmotic hypothesis sparked an intense controversy that lasted for 15 years. Today, Mitchell's conception of proton currents and their role in phosphorylation and active transport is generally accepted, and has ramified into many corners of cellular physiology. His most profound contribution may have been to introduce spatial direction into biochemistry, and thereby transform our perception of the relationship between molecules and cells. BioEssays 23:848–855, 2001. © 2001 John Wiley & Sons, Inc.
The association between a negatively charged ligand and the electronegative binding pocket of its receptor
Authors: Huang Hung‐Chung , Briggs James M.
Published: August 2002

Many examples exist of charged amino acids that play a role in attracting or holding a charged ligand toward or inside an oppositely charged binding pocket of the protein. For example, the enzymes superoxide dismutase, triose‐phosphate isomerase, and acetylcholinesterase can steer ligands toward their oppositely charged binding pockets or gorges. Interestingly, in our Brownian dynamics simulations of a phosphate‐binding protein, we discovered that negatively charged phosphate (HPO) could make its way into the negatively charged binding pocket. In fact, the phosphate‐binding protein exhibits counterintuitive kinetics of association. That is, one would expect that the rate of association would increase on increases to the ionic strength since the interaction between the ligand, with a charge of −2, and the electronegative binding pocket would be repulsive and greater screening should reduce this repulsion and increase the rate of association. However, the opposite is seen—i.e., the rate of association decreases on increases in the ionic strength. We used Brownian dynamics techniques to compute the diffusion limited association rate constants between the negatively charged phosphate ligand and several open forms of PBP (wild‐type and several mutants based on an x‐ray structure of open‐form PBP, mutant T141D). With the appropriate choices of reaction criteria and molecular parameters, the ligand was able to diffuse into the binding pocket. A number of residues influence binding of the ligand within the pocket via hydrogen bonds or salt bridges. Arg135 partially neutralizes the charges on the HPO ligand in the binding pocket, allowing it to enter. It is also found that the positive electrostatic patches above and below the binding entrance of PBP contribute the major attractive forces that direct the ligand toward the surface of the protein near the binding site. © 2002 Wiley Periodicals, Inc. Biopolymers 63: 247–260, 2002; DOI 10.1002/bip.10050
High resolution NMR analysis of the seven transmembrane domains of a heptahelical receptor in organic‐aqueous medium
Authors: Arshava Boris , Taran Irina , Xie Haibo , Becker Jeffrey M. , Naider Fred
Published: August 2002

The NMR properties of seven peptides representing the transmembrane domains of the α‐factor receptor from Saccharomyces cerevisiae were examined in trifluoroethanol/water (4:1) at 10 to 55°C. The parameters extracted indicated all peptides were helical in this membrane mimetic solvent. Using chemical shift indices as the criterion, helicity varied from 64 to 83%. The helical residues in the peptides corresponded to the region predicted to cross the hydrocarbon interior of the bilayer. A study of a truncated 25‐residue peptide corresponding to domain 2 gave evidence that the helix extended all the way to the N‐terminus of this peptide, indicating that sequence and not chain end effects are very important in helix termination for our model peptides. Both nuclear Overhauser effect spectroscopy (NOESY) connectivities and chemical shift indices revealed significant perturbations around prolyl residues in the helices formed by transmembrane domains 6 and 7. Molecular models of the transmembrane domains indicate that helices for domains 6 and 7 are severely kinked at these prolyl residues. The helix perturbation around proline 258 in transmembrane domain 6 correlates with mutations that cause phenotypic changes in this receptor. © 2002 Wiley Periodicals, Inc. Biopolymers 64: 161–176, 2002
Enzymatic coupling of phenol vapors onto chitosan
Authors: Wu Li‐Qun , Chen Tianhong , Wallace Kimberlee K. , Vazquez‐Duhalt Rafael , Payne Gregory F.
Published: August 2002

Phenols are important industrial chemicals, and because they can be volatile, also appear as air pollutants. We examined the potential of tyrosinase to react with the volatile phenol p‐cresol. Three lines of evidence support the conclusion that volatile phenols react with tyrosinase and are coupled (i.e., chemisorbed) onto chitosan films. First, phenol‐trapping studies indicated that p‐cresol can be removed from vapors if the vapors are contacted with tyrosinase‐coated chitosan films. Second, the ultraviolet absorbance of tyrosinase‐coated chitosan films changes dramatically when they are contacted with cresol‐containing vapors, whereas control films are unaffected by contacting with cresol vapors. Third, pressure measurements indicate that tyrosinase‐coated chitosan films only react with cresol vapors if the oxygen cosubstrate is present. Additional studies demonstrate the potential of tyrosinase‐coated chitosan films/membranes for the detection and removal of phenol vapors. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 325–332, 2001.
Transformation of phosphorus and relevant intracellular compounds by a phosphorus‐accumulating enrichment culture in the presence of both the electron acceptor and electron donor
Authors: Ahn Johwan , Daidou Tomotaka , Tsuneda Satoshi , Hirata Akira
Published: August 2002

This study was conducted to obtain a better insight into the metabolic behavior of denitrifying phosphate‐accumulating organisms relative to the transformations of relevant intracellular compounds as well as phosphorus and nitrate for enhanced biological phosphorus removal under different combinations of electron acceptor (oxygen or nitrate) and electron donor (acetate). Under anoxic conditions, the amount of polyhydroxybutyrate (PHB) produced per acetate taken up considerably increased with the increasing amount of nitrate reduced whereas the amounts of nitrate reduced and phosphorus released per acetate taken up remained almost constant. However, glycogen utilization occurred during PHB production and then was again observed in response to the initial supplementation of acetate after glycogen accumulation was transiently observed during anoxic phosphorus uptake using nitrate as an electron acceptor. On the other hand, under subsequent aerobic conditions, the additional supplementation of acetate again caused aerobic phosphorus release and PHB production, which showed that PHB production was associated with polyphosphate cleavage regardless of electron acceptor conditions. In contrast to anoxic conditions, glycogen accumulation was observed during PHB production. Based on these observations, the preliminary model for the metabolic behavior of denitrifying phosphate‐accumulating organisms was proposed and could well account for the complex transformations of PHB and glycogen together with phosphorus release in the presence of acetate under different electron acceptors. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 79: 83–93, 2002.
On‐column deracemization of an atropisomeric biphenyl by quinine‐based stationary phase and determination of rotational energy barrier by enantioselective stopped‐flow HPLC and CEC
Authors: Tobler Ernst , Lämmerhofer Michael , Mancini Giovanna , Lindner Wolfgang
Published: August 2002

The reversible enantiomerization of axially chiral 2′‐dodecyloxy‐6‐nitrobiphenyl‐2‐carboxylic acid was studied in the presence of a brush type chiral stationary phase based on O‐(tert‐butylcarbamoyl) quinine as chiral selector unit by stopped‐flow high‐performance liquid chromatography (sfHPLC) and capillary electrochromatography (sfCEC). After initial separation of the enantiomers in the first section of the column, the flow was stopped and the resolved species allowed to enantiomerize on‐column. From this conversion, which could be determined from the enantiomeric ratios at different enantiomerization times, kinetic rate constants were calculated. By sfHPLC at a constant temperature of 15°C, kinetic rate constants in the presence of the CSP were found to be 4.1 × 10−5s−1and 2.2 × 10−5s−1for the (−) and (+)‐enantiomers, respectively, corresponding to half‐lives of 279 and 530 min. Thus, apparent activation energies of enantiomerization were calculated to be 93.0 and 94.6 kJ mol−1for the (−) and (+)‐enantiomers. On the macroscopic level, the apparent difference of rotational energy barriers and kinetic rate constants for both enantiomers is reflected as deracemization. For example, starting from a racemic mixture, an enantiomeric excess (ee) of 14% was seen in the stopped‐flow HPLC experiment described after an enantiomerization time of 220 min at 15°C, and a maximal ee of 17% can be approximated after infinite enantiomerization time. There is good agreement between HPLC and CEC results as well as their experimental errors, confirming that the new sfCEC technique may be a valuable and convenient tool to study interconversion processes. Chirality 13:641–647, 2001. © 2001 Wiley‐Liss, Inc.
Enantiodiscrimination of chiral α‐aminophosphonic acids by mass spectrometry
Authors: Paladini A. , Calcagni C. , Di Palma T. , Speranza M. , Laganà A. , Fago G. , Filippi A. , Satta M. , Giardini Guidoni A.
Published: August 2002

Diastereomeric clusters between first‐group metal ions (M+) and chiral α‐aminophosphonic acids (A and B) have been readily generated in the gas phase by electrospray ionization (ESI) and their fragmentation investigated by mass spectrometry. The complexes studied had the general formula [MASB2]+ and [MARB2]+, where M = H, Li, Na, or K, AS and AR are the two enantiomers of a given acid A, and B is a reference α‐aminophosphonic acid of defined configuration. Collision‐induced decomposition (CID) of [MASB2]+ and [MARB2]+ leads to fragmentation patterns characterized by [MAB]+/[MB2] abundance ratios which depend on the configuration of ligand A. These different spectral features were correlated to the different stability of the diastereomeric [MASB2]+ and [MARB2]+ complexes in the gas phase. The results have been discussed in the light of MM2 Molecular Mechanics Force Field calculations. Chirality 13:707–711, 2001. © 2001 Wiley‐Liss, Inc.
Enantioseparation properties of (1→6)‐α‐D‐glucopyranan and (1→6)‐α‐D‐mannopyranan tris(phenylcarbamate)s as chiral stationary phases in HPLC
Authors: Kusuno Atsushi , Mori Manami , Satoh Toshifumi , Miura Masakatsu , Kaga Harumi , Kakuchi Toyoji
Published: August 2002

Synthetic polysaccharides, (1→6)‐α‐D‐glucopyranan (3a) and (1→6)‐α‐D‐mannopyranan (3b), were prepared by the cationic ring‐opening polymerization of 1,6‐anhydro‐2,3,4‐tri‐O‐allyl‐β‐D‐glucopyranose (1a) and 1,6‐anhydro‐2,3,4‐O‐6‐allyl‐β‐D‐mannopyranose (1b), followed by the cleavage of the allyl ether linkage of 2,3,4‐tri‐O‐allyl‐(1→6)‐α‐D‐glucopyranan (2a) and 2,3,4‐tri‐O‐allyl‐(1→6)‐α‐D‐mannopyranan (2b), respectively. 2,3,4‐Tris‐O‐(3,5‐dimethylphenylcarbamoyl)‐ and 2,3,4‐tris‐O‐(3,5‐dichlorophenylcarbamoyl)‐(1→6)‐α‐D‐glucopyranan (CSP‐1 and CSP‐2, respectively) and 2,3,4‐tris‐O‐(3,5‐dimethylphenylcarbamoyl)‐ and 2,3,4‐tris‐O‐(3,5‐dichlorophenylcarbamoyl)‐(1→6)‐α‐D‐mannopyranan (CSP‐3 and CSP‐4, respectively) were prepared by the reaction of 3 with the corresponding 3,5‐disubstituted phenylisocyanates and the chiral recognition abilities of CSP‐1–4 as chiral stationary phases (CSPs) in high‐performance liquid chromatography (HPLC) were evaluated. Racemic compounds such as trans‐cyclopropanedicarboxylic acid dianilide (9), 1,2,2,2‐tetraphenylethanol (10), flavanone (11), Tröger's base (12), benzoin (13), and cobalt(III) tris(acetylacetonate) (14) were efficiently resolved using CSP‐1–4. For comparison among CSPs, the chiral recognition properties of the (1→6)‐α‐D‐glucopyranan CSPs were different from that of the (1→6)‐α‐D‐mannopyranan CSPs, and CSP‐4 exhibited the highest chiral recognition ability among the CSPs. The resolution factors of 12 and 14 were 0.42 and 0.56 for CSP‐1, 0.32 and 2.16 for CSP‐2, 1.80 and 0.84 for CSP‐3, and 2.31 and 8.26 for CSP‐4, respectively. Chirality 14:498–502, 2002. © 2002 Wiley‐Liss, Inc.
Post‐karyokinesis centrosome movement leaves a trail of unanswered questions
Authors: Ou Young Y. , Rattner Jerome B.
Published: August 2002

The centrosome is a complex structure composed of a large number of proteins (pericentriolar material, PCM) usually organized around a pair of centrioles (or a centriole duplex). This structure is capable of nucleating and organizing microtubules, duplication, and motility. In general, episodes of dramatic centrosome movement correlate with periods of cellular reorganization and nowhere is cellular reorganization more apparent, or more important, than in the periods before and after cell division. It is now clear that centrosome movement occurs not only prior to cell division but also at its completion, in concert with cytokinesis. The focus of this review is the newly emerging picture of centrosome activity during the post‐karyokinesis period and the role that this activity might play in the transition of cells from mitosis to interphase. Cell Motil. Cytoskeleton 51:123–132, 2002. © 2002 Wiley‐Liss, Inc.
Simultaneous quantification of cell motility and protein‐membrane‐association using active contours
Authors: Dormann Dirk , Libotte Thorsten , Weijer Cornelis J. , Bretschneider Till
Published: August 2002

We present a new method for the quantification of dynamic changes in fluorescence intensities at the cell membrane of moving cells. It is based on an active contour method for cell‐edge detection, which allows tracking of changes in cell shape and position. Fluorescence intensities at specific cortical subregions can be followed in space and time and correlated with cell motility. The translocation of two GFP tagged proteins (CRAC and GRP1) from the cytosol to the membrane in response to stimulation with the chemoattractant cAMP during chemotaxis of Dictyostelium cells and studies of the spatio‐temporal dynamics of this process exemplify the method: We show that the translocation can be correlated with motility parameters and that quantitative differences in the rate of association and dissociation from the membrane can be observed for the two PH domain containing proteins. The analysis of periodic CRAC translocation to the leading edge of a cell responding to natural cAMP waves in a mound demonstrates the power of this approach. It is not only capable of tracking the outline of cells within aggregates in front of a noisy background, but furthermore allows the construction of spatio‐temporal polar plots, capturing the dynamics of the protein distribution at the cell membrane within the cells' moving co‐ordinate system. Compilation of data by means of normalised polar plots is suggested as a future tool, which promises the so‐far impossible practicability of extensive statistical studies and automated comparison of complex spatio‐temporal protein distribution patterns. Cell Motil. Cytoskeleton 52:221–230, 2002. © 2002 Wiley‐Liss, Inc.
Thermal activation of single kinesin molecules with temperature pulse microscopy
Authors: Kawaguchi Kenji , Ishiwata Shin'ichi
Published: August 2002

Conventional kinesin is a processive motor protein that keeps “walking” along a microtubule using chemical energy released by ATP hydrolysis. We previously studied the effects of temperature between 15° and 35°C on the moving velocity, force, and processivity of single kinesin molecules using a bead assay [Kawaguchi and Ishiwata, 2000b: Biochem Biophys Res Commun 272:895–899]. However, we could not examine the effects of temperature higher than 35°C because of the thermal damage to proteins. Here, using temperature pulse microscopy (TPM) [Kato et al., 1999: Proc Natl Acad Sci USA 96:9602–9606], we could examine the temperature dependence of the gliding velocity of single kinesin molecules interacting with a microtubule above 35°C up to 50°C (instantaneously, ∼60°C), where the velocity reached 3.68 μm/s, the highest ever reported. The Arrhenius plot showed no breaks between 15° and 50°C with a unique activation energy of about 50 kJ/mol, suggesting that the molecular mechanism of kinesin motility is common over a broad temperature range including physiological temperature. Cell Motil. Cytoskeleton 49:41–47, 2001. © 2001 Wiley‐Liss, Inc.