bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of regenerated silk fibroin: Effects of freezing temperature, alcohol addition, and molecular weight
Authors: Nam Jin , Park Young Hwan 
Published: August 2002

AbstractRegenerated silk fibroin (RSF) was prepared by dissolving in a CaCl2/ethanol/H2O solvent system, freezing, and lyophilization. The effect of freezing temperature, alcohol addition, and molecular weight on the morphological and conformational changes were investigated through scanning electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, circular dichroism spectroscopy, and differential scanning calorimetry analysis. However, the addition of a small amount of methanol induced the morphological change of RSF to a fine‐particle aggregate, which resulted from the formation of a β‐sheet crystalline structure. The lower the freezing temperature was, the more the formation of aggregates was favored, and the finer powder aggregates were formed. As the amount of added hydrophilic alcohol such as methanol and ethanol increased in the silk fibroin solution, a spherical powder form was changed to fine aggregates with the enhancement of thermal stability and crystallinity. On the other hand, RSFs prepared with a hydrophobic alcohol such as 1‐butanol or 1‐octanol showed a lump‐like or sheet‐like shape of morphology without any changes in conformational transition. It is concluded that the molecular weight of the silk fibroin and the type and amount of alcohol were determining factors in the morphological features of RSF, especially the size and shape of fibroin particles. A uniform ultrafine powder of RSF with a spherical form (∼ 1 μm) can be obtained when the molecular weight and the alcohol addition to the silk fibroin solution are controlled. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3008–3021, 2001
Study of a compatibilized ultra‐high‐molecular‐weight polyethylene and polyurethane blend
Authors: Yuan Hao , Hu Ping 
Published: August 2002

AbstractUltra‐high‐molecular‐weight polyethylene (UHMWPE) and thermoplastic polyester‐type polyurethane (PU) were blended with polyethylene‐grafted maleic anhydride (PE‐g‐MAH) added as a compatibilizer. A dual roller was used as a mixer, and all specimens were produced by the compression molding method. It was found that without compatibilizer, UHMWPE and PU were immiscible polymers and mixing PE‐g‐MAH reduced the size of the dispersed PU domains by a factor of 10 to reach 0.5–5 μm and caused a more uniform distribution of the PU phase in the UHMWPE matrix. Also, PE‐g‐MAH influenced the crystallinity of UHMWPE, increased the amorphous region in the UHMWPE phase, and improved interfacial adhesion. The threshold concentration of compatibilizer was 10 wt %, and the compatibilized UHMWPE/PU composites had improved mechanical properties and lower wear rate than the uncompatibilized composite. At some ratio points, compatibilizer composites even had better wear‐resistance properties than pure UHMWPE. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3290–3295, 2001
Phase structure and viscoelastic properties of compatibilized blends of PET and HDPE recyclates
Authors: Pluta Mirosław , Bartczak Zbigniew , Pawlak Andrzej , Galeski Andrzej , Pracella Mariano 
Published: August 2002

AbstractImmiscible blends of recycled poly(ethylene terephthalate) (R‐PET), containing some amount of polymeric impurities, and high‐density polyethylene (R‐PE), containing admixture of other polyolefins, in weight compositions of 75 : 25 and 25 : 75 were compatibilized with selected compatibilizers: maleated styrene–ethylene/butylene–styrene block copolymer (SEBS‐g‐MA) and ethylene–glycidyl methacrylate copolymer (EGMA). The efficiency of compatibilization was investigated as a function of the compatibilizer content. The rheological properties, phase structure, thermal, and viscoelastic behavior for compatibilized and binary blends were studied. The results are discussed in terms of phase morphology and interfacial adhesion among components. It was shown that the addition of the compatibilizer to R‐PET‐rich blends and R‐PE‐rich blends increases the melt viscosity of these systems above the level characteristic for the respective binary blends. The dispersion of the minor phase improved with increasing compatibilizer content, and the largest effects were observed for blends compatibilized with EGMA. Calorimetric studies indicated that the presence of a compatibilizer had a slight affect on the crystallization behavior of the blends. The dynamic mechanical analysis provided evidence that the occurrence of interactions of the compatibilizer with blend components occurs through temperature shift and intensity change of a β‐relaxation process of the PET component. An analysis of the loss spectra behavior suggests that the optimal concentration of the compatibilizers in the considered blends is close to 5 wt %. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1423–1436, 2001
Diffusion coefficients of additives in polymers. I. Correlation with geometric parameters
Authors: Reynier Alain , Dole Patrice , Humbel Stephane , Feigenbaum Alexandre 
Published: August 2002

AbstractDiffusion coefficients of a broad range of molecules with molecular weight ranging from 100 to 800 g/mol have been measured in polypropylene, by solid/solid contact methods (without liquid contact), at 40°C. The behaviors of the different molecules are compared to those of linear alkanes. The diffusion coefficients are correlated to parameters describing size, shape, and flexibility of the molecules. The concept of weighted fractionated volume is introduced using molecular modeling. It enables the classification of the molecules according to modes of molecule displacement (crawling, jumps, or dual mode). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2422–2433, 2001
Water transparency and health of coastal salt marshes: simple enclosure experiments on nutrient dynamics
Authors: Basset Alberto , Carlucci Domenica , Fiocca Annita , Vignes Fabio 
Published: August 2002

Abstract1. In many coastal salt marshes, water transparency is decreased by the resuspension of sediments. We analyse the influence of suspended not‐photosynthetic matter on the regulation of phosphorus (P) dynamics in the water column, compared with the role of phytoplankton and sediments.2. Field surveys and manipulative experiments of P enrichment in light and dark enclosures, open and closed at their bottom, were performed in the brackish Lake Alimini Grande (Otranto, LE, Italy).3. Water transparency in Alimini Grande was inversely related to seston organic mass, 98.8% of which was composed of dead organic matter and heterotrophic organisms.4. P enrichment experiments showed an increase of the phytoplankton biomass with time from the beginning of the manipulation (4.9 times) in the light enclosures, but also an exponential decrease of P concentration in all the enclosures, even in the dark one closed at the bottom.5. The rate of P removal from the water column was not significantly affected by phytoplankton activity, even though P concentration was always lower in light than in dark enclosures, or by the activity of sediments.6. Dead suspended organic matter with associated micro‐organisms seemed to remove nutrients very efficiently from the water column in Lake Alimini Grande, contributing significantly to control the potential risk of lake eutrophication. Copyright © 2001 John Wiley & Sons, Ltd.
Pharmacokinetics and metabolism of the novel synthetic C‐nucleoside, 1‐(2‐deoxy‐β‐D‐ribofuranosyl)‐2,4‐difluoro‐ 5‐iodobenzene: a potential mimic of 5‐iodo‐2′‐deoxyuridine
Authors: Khalili Panteha , Naimi Ebrahim , Knaus Edward E. , Wiebe Leonard I. 
Published: August 2002

Abstract1‐(2‐Deoxy‐β‐D‐ribofuranosyl)‐2,4‐difluoro‐5‐iodobenzene (5‐IDFPdR) is one of the several unnatural 1‐(2‐deoxy‐β‐D‐ribofuranosyl)‐2,4‐difluoro‐5‐substituted‐benzenes recently synthesized for evaluation as anticancer, antiviral and diagnostic imaging agents. This class of C‐nucleosides was designed to exploit several potential advantages relative to classical 5‐substituted‐2′‐deoxyuridines, including stability towards phosphorolysis by pyrimidine phosphorylase, increased lipophilicity that may alter their ability to cross the blood–brain‐barrier, and a greater resistance towards catabolism and deiodination.The physiochemical evaluation of 5‐IDFPdR showed high lipophilicity (log P=2.8), moderately high protein binding (70–75%), stability towards phosphorolysis (e.g. no evidence of metabolic deglycosylation) by thymidine phosphorylase, and minimal microsomal metabolism in vitro. Pharmacokinetic studies of 5‐IDFPdR in rat were characterized by a short elimination half‐life (9–12 min), modest urinary elimination in pooled 0–24 h urine specimens (10–14%, including 2% as unconjugated drug) and high oral bioavailability (F=0.96). Both glucuronide and sulfate metabolites were present in urine. Glucuronidation was the predominant conjugation pathway. Copyright © 2002 John Wiley & Sons, Ltd.
One week of exposure to 50 Hz, vertical magnetic field does not reduce urinary 6‐sulphatoxymelatonin excretion of male wistar rats
Authors: Bakos József , Nagy Noémi , Thuróczy György , Szabó László D. 
Published: August 2002

AbstractThe effect of exposure to 100 or 50 μT, 50 Hz, vertical magnetic field on the excretion of 6‐sulphatoxymelatonin (6SM) in the nocturnal urine of rats was studied. Twelve male Wistar rats were kept under 12:12 hr light:dark conditions. The nocturnal urine of animals was collected in metabolic cages over 4 consecutive weeks. The concentration of 6SM in the rat urine was measured by 125I radioimmunoassay and normalized to creatinine concentration. After the first week of urine collection, 6 rats were exposed to 100 µT or 50 µT flux density magnetic fields (MF) for 8 hr daily for 1 week. It was found that the excretion of the primary metabolite of melatonin in the urine, 6SM, did not show statistically significant changes during and after magnetic field exposure. Bioelectromagnetics 23:245–248, 2002. © 2002 Wiley‐Liss, Inc.
Hydra and Niccolo Paganini (1782–1840)—two peas in a pod? The molecular basis of extracellular matrix structure in the invertebrate, Hydra
Authors: Sarras Michael P. , Deutzmann Rainer 
Published: August 2002

AbstractThe body wall of Hydra is organized as an epithelial bilayer with an intervening extracellular matrix (ECM). Molecular and biochemical analyses of Hydra ECM have established that it contains components similar to those seen in more complicated vertebrates such as human. In terms of biophysical parameters, Hydra ECM is highly flexible; a property that facilitates continuous movements along the organism's longitudinal and radial axis. A more rigid ECM, as in vertebrates, would not be compatible with this degree of movement. The flexible nature of Hydra ECM can now be explained in part by the unique structure of the organism's collagens. Interestingly, some aspects of the structural features of Hydra collagens mimic what is seen in Ehlers‐Danlos syndrome, an inherited condition in humans that results in an abnormally flexible ECM that can be debilitating in extreme cases. This review will focus on structure–function relationships of the ECM of Hydra. BioEssays 23:716–724, 2001. © 2001 John Wiley & Sons, Inc.
Bridging the gap between developmental systems theory and evolutionary developmental biology†
Authors: Robert Jason Scott , Hall Brian K. , Olson Wendy M. 
Published: August 2002

AbstractMany scientists and philosophers of science are troubled by the relative isolation of developmental from evolutionary biology. Reconciling the science of development with the science of heredity preoccupied a minority of biologists for much of the twentieth century, but these efforts were not corporately successful. Mainly in the past fifteen years, however, these previously dispersed integrating programmes have been themselves synthesized and so reinvigorated. Two of these more recent synthesizing endeavours are evolutionary developmental biology (EDB, or “evo‐devo”) and developmental systems theory (DST). While the former is a bourgeoning and scientifically well‐respected biological discipline, the same cannot be said of DST, which is virtually unknown among biologists. In this review, we provide overviews of DST and EDB, summarize their key tenets, examine how they relate to one another and to the study of epigenetics, and survey the impact that DST and EDB have had (and in future should have) on biological theory and practice. BioEssays 23:954–962, 2001. © 2001 John Wiley & Sons, Inc.
Luminescence Literature 2000
Authors: Kricka L. J. 
Published: August 2002

AbstractThe journal provides comprehensive literature searches on all aspects of luminescence which will be published in most issues. These lists have been produced regularly since 1986—some by year and some by specialized topic. This survey of papers on Firefly and marine bacterial bioluminescence is drawn from the 2000 literature and covers the biology of these organisms and the applications of genes and proteins from these organisms in analysis.
Dimethylsulfoxide‐stabilized conformer of guanine‐adenine repeat strand of DNA
Authors: Kypr Jaroslav , Vorlíčková Michaela 
Published: August 2002

AbstractCircular dichroism spectroscopy and other methods are used to show that the addition of dimethylsulfoxide causes reversible folding of the (GA)10 strand of DNA into an ordered single‐stranded conformer. The ordered conformer melts in a cooperative way and it does not contain protonated adenine. The (TA)10, (A)20, and (G)20 are all unstable in this conformer. To the best of our knowledge, this is the first known ordered conformer of DNA that is stabilized by dimethylsulfoxide. This conformer might be a DNA analog of the protein α helix, which is an interesting idea for thinking about the evolution of DNA. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 81–84, 2001
Structural insight into the role of the second intracellular loop of the bradykinin 2 receptor in signaling and internalization
Authors: Piserchio Andrea , Prado Gregory N. , Zhang Ran , Yu Jun , Taylor Linda , Polgar Peter , Mierke Dale F. 
Published: August 2002

AbstractThe second cytoplasmic loop (IC2) of the bradykinin B2 receptor plays a vital role in its dynamic life cycle including the activation, internalization, desensitization, and resensitization of this receptor. Here, we probe the structure and function of the IC2, with particular emphasis on threonine‐137, which is crucial for signal transduction and internalization. Mutation of this threonine to proline (T137P) produces wild type (WT) signaling and complete inhibition of internalization. Incorporation of aspartate (T137D) leads to a marked reduction in receptor signaling but with WT receptor uptake. The T137D mutation coupled with serine to alanine substitution of S335 and S341 within the distal C‐terminus recovers signaling, leading to an actually enhanced arachidonic acid release and phosphoinositide turnover compared to WT bradykinin B2 receptor (BKB2R). To provide a structural basis for the actions of this mutant, the conformational features of IC2 (both WT and mutant) were investigated by high‐resolution NMR. The NMR analysis illustrated two prominent α‐helices at the N‐ (L123–M138) and C‐termini (A149–I156) of the IC2 receptor domain. Incorporating these structural characteristics into a model of BKB2R, we determined that the entire N‐terminal helix of IC2 is incorporated as TM3, placing Y131 1.5 helical turns into TM3 and T137 at the membrane surface. The NMR data indicated no structural changes upon substitution of T137D. These results suggest that the altered signaling of the T137D mutant can be attributed to the introduction of a negative charge, indicating that phosphorylation of this residue takes place and participates in the life cycle of this receptor. Additionally, the return to WT signal capacity of the mutation T137D/S335A/S341A, to overcome the deleterious T137D substitution points to a functional interaction between the IC2 and the C‐terminus. © 2002 John Wiley & Sons, Inc. Biopolymers 63: 239–246, 2002; DOI 10.1002/bip.10072
Assignment of the 1511 cm−1 UV resonance Raman marker band of hemoglobin to tryptophan
Authors: Zhao Xiaojie , Chen Ruopian , Raj Vishwa , Spiro Thomas G. 
Published: August 2002

AbstractNew UV resonance Raman (UVRR) data provide convincing evidence that a characteristic 1511 cm−1 band in the T − R difference spectra of hemoglobin is due to the overtone of the Trp W18 fundamental at 756 cm−1. Measured isotope shifts for 2‐H and 15‐N substitution at the indole NH group are twice as large for the 1511 cm−1 band as for W18, and the 1511 cm−1 intensity scales with that of W18 in the difference spectrum. Moreover, the UVRR excitation profile of the 1511 cm−1 band tracks that of another tryptophan band, W16. Both are redshifted in hemoglobin, relative to aqueous tryptophan, reflecting H bonding within a hydrophobic environment in the protein. The 2×W18 assignment had been thrown into question by the observation of remnant 1511 cm−1 intensity in the T − R spectra of hemoglobin labeled with tryptophan‐d5, a substitution that shifts W18 over 50 cm−1. However, reexamination of the data suggests that this remnant intensity may result from a subtraction artifact arising from the downshift of another difference band, W3, from 1549 cm−1 in unlabeled protein to 1522 cm−1 in labeled protein. Restoration of the 2×W18 assignment establishes that the 1511 cm−1 difference band, which is a useful indicator of the extent of T‐state formation in hemoglobin, arises from the same residue, Trpβ37, that gives rise to essentially all of the T − R signal from tryptophan. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 158–162, 2001
Femtosecond and picosecond fluorescence of native bacteriorhodopsin and a nonisomerizing analog
Authors: Haacke S. , Schenkl S. , Vinzani S. , Chergui M. 
Published: August 2002

AbstractThe spectrally and temporally resolved fluorescence properties of native bacteriorhodopsin (bR) and bR reconstituted with a nonisomerizing analog of the retinal Schiff base (bR5.12) are examined. The first attempt to experimentally monitor the excited state relaxation processes in both type of pigments using ultrafast fluorescence spectroscopy is reported. The fluorescence is emitted from retinal molecules in an all‐trans configuration. Substantial energy relaxation involves very fast intramolecular and intermolecular vibrational modes and these are shown to occur on a time scale faster than isomerization. The possible contribution of dielectric interaction between the retinal Schiff base and the protein environment for the excited state energy relaxation is discussed. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 306–309, 2002
GFP‐visualized immobilized enzymes: Degradation of paraoxon via organophosphorus hydrolase in a packed column
Authors: Wu Chi‐Fang , Cha Hyung Joon , Valdes James J. , Bentley William E. 
Published: August 2002

AbstractA versatile gene‐fusion technique for immobilizing and visualizing biologically active enzymes which includes from the N to C‐termini, an affinity histidine tag, the green fluorescent protein (GFP), a proteolytic enzyme (enterokinase, EK) cleavage site and the enzyme of interest, were developed. Specifically, the organophosphorus hydrolase was bound to the affinity (His6)‐reporter(GFP)‐EK fusion elements. Organophosphorus hydrolase (OPH) is capable of degrading a variety of pesticides and nerve agents. In the case of immobilized OPH, paraoxon was rapidly degraded when pumped through a packed column. In reaction mixtures containing CHES buffer at pH 6.9, a continual decay in OPH activity was observed and importantly, this was monitored by GFP fluorescence. This decay in activity was fully restored, along with fluorescence, upon washing with PBS buffer. Many subsequent experiments were performed at varied pH and in different background buffer solutions. In all cases when there was OPH activity there was also marked fluorescence from the GFP fusion partner. Likewise, when OPH activity was lost, so was GFP fluorescence and, importantly, both were regenerated when washed in the presence of the kosmotropic salt, phosphate. Recently, Waldo et al. (1999) showed that GFP fluorescence from whole cells indicated the extent of proper folding of normally aggregated proteins designed via directed evolution. The present work demonstrates an application wherein GFP fluorescence indicates stability and activity of its fusion partner. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 212–218, 2002.
The water‐dependence of the catalytic activity of bilirubin oxidase suspensions in low‐water systems
Authors: Alston Mark J. , Freedman Robert B. 
Published: August 2002

AbstractWe investigated the enzymic activity of bilirubin oxidase when it is suspended as a lyophilized powder in a low‐water system. The enzyme required buffer salts and a source of water to show activity. This study investigated the complete range of water thermodynamic activity (aw) by combining the use of salt hydrates and two‐phase systems with concentrated solutes in the aqueous phase. When free water was added, activity reached a maximum at a defined water content, but this maximum increased with buffer content, suggesting that there was competition for water with the buffer salts from which the enzyme was lyophilized. Alternatively, a range of salt hydrates was used, each able to fix the water activity (aw) at a different value. By providing water to the organic solvent phase in this way, the dependency of enzyme activity upon aw was investigated and shown to be independent of buffer concentration. However, the optimum aw was uncertain because the available aw range for salt hydrates is ≤0.90. Investigation of the remaining water activity range was made possible by using an aw depressor (sorbitol) to lower the aw of a two‐phase system. The optimum aw for the bilirubin oxidase activity in this two‐phase system was aw = 0.936, independent of buffer concentration. The study therefore confirmed the need to control the water `available' to low‐water systems and the dependence of enzyme activity on water thermodynamic activity (aw) not water content. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 651–657, 2002; DOI 10.1002/bit.10103
Asymmetric sulfoxidations mediated by α‐chymotrypsin
Authors: Das Prasanta Kumar , Caaveiro Jose M. M. , Luque Susana , Klibanov Alexander M. 
Published: August 2002

AbstractThe oxidation of aryl alkyl sulfides with H2O2 in aqueous solution is a reasonably facile reaction producing racemic sulfoxides. We show that in the presence of the hydrolytic enzyme α‐chymotrypsin such a sulfoxidation is accelerated and, more importantly, becomes stereoselective. With phenyl isobutyl sulfide as a model, the chymotrypsin‐mediated, highly asymmetric oxidation is shown to occur in the hydrophobic binding pocket of the enzyme active site. The stereoselectivity of the chymotrypsin‐mediated sulfoxidations is correctly explained by means of structure‐based molecular modeling of the enzyme‐sulfide complexes. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 104–109, 2002; DOI 10.1002/bit.10187