bluuebunny/crossref_metadata_2025 huggingface dataset:
Platinum−Nitrogen Bond Rearrangements in Isomeric cis‐PtII(NH3)2‐bis(9‐methyladenine) Complexes under Alkaline Conditions
Authors: Arpalahti Jorma , Klika Karel D.
Published: December 2003

The migration of coordinated PtII in the adenine ring was studied in basic aqueous solutions for the isomeric bis(9‐methyladenine) complexes: cis‐[Pt(NH3)2(9‐made‐N7)2]2+ (1) and cis‐[Pt(NH3)2(9‐made‐N1)(9‐made‐N7)]2+ (2). In both compounds, coordinated PtII migrates from the endocyclic nitrogen N(7) or N(1), respectively, to the exocyclic amino group, upon displacement of an NH2 proton, to give the same first‐generation product, viz. cis‐[Pt(NH3)2(9‐made‐N6)(9‐made‐N7)]2+ (3). Although both reactions undergo an intramolecular reaction, the N(1)⇄N(6) step is faster and far more efficient than the N(7)⇄N(6) step. This may be attributed to the more favorable electronic effects and to the spatial positioning of the N(1)‐bound PtII in comparison to the platinum coordinated to the N(7) site. However, the contribution of a Dimroth‐type rearrangement to the overall N(1)⇄N(6) conversion cannot be completely ruled out. Attempts to obtain second migration in the N(6),N(7)‐bound species to give the N(6),N(6) species were unsuccessful. Rather, prolonged treatment of the N(6),N(7)‐bound complex in strongly basic solution resulted in the deamination of the N(7)‐bound 9‐methyladenine yielding a mixed ligand complex consisting of N(6)‐bound 9‐methyladenine and N(7)‐bound 9‐methylhypoxanthine, i.e. cis‐[Pt(NH3)2(9‐made‐N6)(9‐mhyp‐N7)]2+ (4). To the best of our knowledge, this is the first example of such a deamination reaction in PtII complexes. Both reaction products, 3 and 4, were characterized by 1H and 195Pt NMR spectroscopy and by X‐ray crystallography of the diperchlorate. In dicationic 3 and 4, the N(6)‐bound 9‐made exists in the rare imino tautomer with the N(1) site bearing a proton. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Heterobimetallic Calix[4]arene Complexes: Interconversion of Dimeric (Ca, Sr or Ba)/TiIV Complexes with a Monomeric K/TiIV Complex
Authors: Petrella Antonella J. , Roberts Nicholas K. , Raston Colin L. , Craig Donald C. , Thornton‐Pett Mark , Lamb Robert N.
Published: December 2003

Reaction of calix[4]arene with alkaline earth metals (Ca/Sr/Ba) in methanol followed by the addition of various titanium(IV) sources afforded novel dimeric 1:1 alkaline earth/titanium(IV) calix[4]arene complexes. In each complex the central core of the crystallographically imposed centrosymmetric dimer consists of a rhombus of alternating alkaline earth metals and μ3‐oxo‐centres. Five terminal methanol ligands form seven‐coordinate calcium and strontium centres, while the barium centres are bridged by two additional methanol ligands, making them nine‐coordinate. Each oxo centre is the apical ligand of a square‐pyramidal titanium(IV) centre, whose basal plane ligands are the four phenolate oxygens from a calix[4]arene in the symmetrical cone‐conformation. Deprotonation of calix[4]arene with potassium metal, followed by the addition of a titanium(IV) source containing at least one acetylacetonate ligand, formed a mixed potassium/titanium complex based on one calix[4]arene. The potassium cation in this complex binds within the π‐basic calix[4]arene cavity, whilst titanium is octahedrally complexed in the exo‐position, by four phenolates and one acetylacetonate. The alkaline earth titanium dimers and potassium/titanium monomers could be interconverted merely by changing the solvent, with the appropriate cations and ligands present in solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Stereodiscrimination in Phosphanylthiolato Nickel(II) Complexes
Authors: Duran Josep , Polo Alfonso , Real Julio , Benet‐Buchholz Jordi , Poater Albert , Solà Miquel
Published: December 2003

The presence of a stereogenic carbon centre (R or S) in the racemic ligand 1‐(diphenylphosphanyl)propane‐2‐thiol induces a conformational preference (λ or δ) in the five‐membered chelate ring of its 2:1 and 2:2 coordination compounds with NiII: the mononuclear trans‐[Ni{SCH(CH3)CH2PPh2‐P,S}2] (1) and the binuclear trans‐[Ni{μ‐SCH(CH3)CH2PPh2‐P,S}(Cl)]2 (2). Both complexes exist as mixtures of two diastereomers: racemic‐trans (Rλ, Rλ and Sδ, Sδ) and meso‐trans (Rλ, Sδ), in an equilibrium displaced towards the more stable isomer, the meso‐trans for 1 (calculated ΔE = < −0.1 kcal·mol−1) and the racemic‐trans for 2 (calculated ΔE = −5.1 kcal·mol−1). This phenomenon is especially evident for complex 2, in which an efficient chiral recognition between the two enantiomeric forms of the racemic ligand was observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Heterobimetallic Calix[4]arene Complexes: Interconversion of Dimeric (Ca, Sr or Ba)/TiIV Complexes with a Monomeric K/TiIV Complex (Eur. J. Inorg. Chem. 23/2003)
Authors: Petrella Antonella J. , Roberts Nicholas K. , Raston Colin L. , Craig Donald C. , Thornton‐Pett Mark , Lamb Robert N.
Published: December 2003

The cover picture shows the structures of two new types of calix[4]arene complexes obtained by deprotonating the calixarene with an alkaline earth metal, or potassium metal, followed by reaction with selected titanium(IV) compounds. The alkaline earth metals form dimeric alkaline earth‐titanium(IV) complexes, containing at the core a rhombus of alternating alkaline earth metal and μ3‐oxo centres. Each oxo centre of the rhombic core is the apical ligand of a square‐pyramidal titanium(IV) centre, whose basal plane donors are the four phenolate oxygen atoms from a calix[4]arene arrayed in the symmetrical cone conformation. Terminal methanol ligands surround the alkaline earth centres, and simultaneously hydrogen‐bond to the adjacent phenolate oxygen atoms. Potassium reacts with calix[4]arene and the titanium(IV) source to give a monomeric mixed potassium‐titanium complex. The potassium cation binds within the κ‐basic calix[4]arene cavity, whilst the titanium centre is octahedrally complexed in the exo position by four phenolate and one acetylacetonate ligands. A solution pathway exists for the interconversion between the potassium‐titanium calix[4]arene monomer and the alkaline earth‐titanium dimers, where the product is dictated by the choice of solvent. Details are discussed in the article by R. N. Lamb et al. on p. 4153 ff.
Analytical separations in open‐tubular capillary electrochromatography
Authors: Kapnissi‐Christodoulou Constantina P. , Zhu Xiaofeng , Warner Isiah M.
Published: December 2003

This review represents a summary of recent progress in open‐tubular capillary electrochromatography (OT‐CEC) for chiral and achiral separations. The OT‐CEC approach is an alternative to packed‐CEC that could eliminate the problems associated with retaining frits and silica particles. In OT‐CEC, the stationary phase is immobilized on the inner walls of the capillary. Preparation of the stationary phase is critical for OT‐CEC. The preparation methods for capillary columns include (i) adsorption, (ii) covalent bonding and/or cross‐linking, (iii) porous layers, (iv) chemical bonding after etching, (v) sol‐gel, and (vi) molecular imprinting. Major developments, potential applications, technical difficulties and advantages associated with these wall coatings in OT‐CEC are presented. In addition, the coupling of OT‐CEC with mass spectrometry (MS) is briefly reviewed. Several applications of this hyphenated technique for analytical separations are also summarized.
Recent advances in capillary electrophoresis and capillary electrochromatography of pollutants
Authors: Dabek‐Zlotorzynska Ewa , Chen Heidi , Ding Luyi
Published: December 2003

Recent advances in capillary electrophoresis (CE) and capillary electrochromatography (CEC) separation, detection and sample preparation methodologies applied for the determination of a variety of pollutants is overviewed. The reviewed literature illustrates the wide range of CE applications, indicating the continuing interest in CE and CEC in the environmental field.
Applications of affinity interactions in capillary electrophoresis
Authors: Heegaard Niels H. H.
Published: December 2003

Capillary electrophoresis (CE) has proven useful for the study of reversible molecular interactions. This is because highly efficient and reproducible separations take place in an environment where molecular interactions may contribute to selectivity without being inhibited by adverse buffer conditions. Affinity CE may be used to estimate quantitative binding data (binding constants and in some cases binding stoichiometries and rate constants) for various molecular interactions. Specific binding interactions (e.g., based on antibodies or aptamers) may also be utilized to quantitatively measure specific analytes using CE. Applications within these areas are here reviewed with focus on the last three years and with emphasis on novel concepts as well as innovative methodology and technology. It is concluded that the affinity CE approach is of growing versatility and will continue to play an integral role in discovering, characterizing, and exploiting biomolecular interactions.
Engineering Microtools in Polymers to Study Cell Biology
Authors: Jiang X. , Whitesides G.M.
Published: December 2003

Recent advances in surface engineering and soft lithography provide tools to fabricate patterned surfaces and microfluidic devices with dimensions comparable to the sizes of single mammalian cells. These technologies enable the studies of individual cells on spatially well‐defined, patterned surfaces, and in contact with patterned liquid media. They provide information about cells impossible to obtain from traditional biochemical techniques.
The extinct sloth lemurs of Madagascar
Authors: Godfrey Laurie R. , Jungers William L.
Published: December 2003

Paleontological expeditions to Madagascar over the past two decades have yielded large quantities of bones of extinct lemurs. These include abundant postcranial and cranial remains of new species belonging to a group of giant extinct lemurs that we have called sloth lemurs due to their remarkable postcranial convergence with arboreal sloths. New fossils have come from a variety of locations in Madagascar, including caves in the Northwest (Anjohibe) and the Ankarana Massif, located in the extreme north, as well as pits in the karstic plains near Toliara in southwestern Madagascar. The most spectacular of these is the extremely deep pit (>100 m) called Ankilitelo, the “place of the three kily trees.” These new materials provide insights into the adaptive diversity and evolution of sloth lemurs. New carpal and pedal bones, as well as vertebrae and other portions of the axial skeletons, allow better reconstruction of the positional behavior of these animals. New analytical tools have begun to unlock the secrets of life‐history adaptations of the Palaeopropithecidae, making explicit exactly what they had in common with their relatives, the Indriidae. Paleoecological research has elucidated the contexts in which they lived and the likely causes of their disappearance.
Dinner at Baby's: Werewolves, dinosaur jaws, hen's teeth, and horse toes
Authors: Weiss Kenneth , Sholtis Samuel
Published: December 2003

Occasionally traits arise that appear to be atavistic throwbacks to the remote past. How can this make evolutionary sense?
Isocyanates, aminoisocyanates and amines from fires—a screening of common materials found in buildings
Authors: Blomqvist Per , Hertzberg Tommy , Dalene Marianne , Skarping Gunnar
Published: December 2003

Isocyanates, aminoisocyanates and amines were quantified from the combustion of 24 different materials or products typically found in buildings. Small‐scale combustion experiments were conducted in the cone calorimeter, where generally well‐ventilated combustion conditions are attained. Measurements were further made in two different full‐scale experiments.

Isocyanates and amino‐compounds were sampled using an impinger‐filter sampling system with a reagent solution of di‐n‐butylamine in toluene. Filter and impinger solution were analysed separately using LC‐MS technique. Further the particulate distribution in the smoke gases was determined by impactor technique, and selected gaseous compounds quantified by FTIR.

It was found in the small‐scale that isocyanates were produced from the majority of the materials tested. The highest concentration was found for glass wool insulation, and further high concentrations were found for PUR products, particleboard, nitrile rubber and melamine. Lower concentrations were found for wood and cable‐products. Amino‐isocyanates and amines were generally found from PUR products only.

The distribution of isocyanates between the particulate‐ and fluid phases varied for the different materials and a tendency to enrichment of particles was seen for some of the materials. Further, when comparing the potential health hazard between isocyanates and other major fire gases (based on NIOSH IDLH‐values) it was found that isocyanates in several cases represented the greatest hazard. Copyright © 2003 John Wiley & Sons, Ltd.
Low dissipative high‐order numerical simulations of supersonic reactive flows
Authors: Sjögreen Björn , Yee H. C.
Published: December 2003

We report the performance of a newly developed low dissipative sixth‐order spatial and fourth‐order temporal scheme (J. Comput. Phys. 1999; 150: 199; RIACS Report 01.01, NASA Ames Research Centre, October 2000) for multiscale supersonic reactive flows that contain shock waves. The accuracy and efficiency of the scheme are compared with a low‐dissipative fifth‐order weighted ENO (WENO) scheme (ICASE Report No. 95‐73, 1995). This paper confirms and complements the grid convergence study of Sjögreen and Yee where a complex shock/shear/boundary‐layer interactions model was also included. A 2D viscous flow consisting of a planar Mach 2 in air interacting with a circular zone of hydrogen bubbles in two different initial configurations is considered. The two initial configurations are a single bubble and two non‐aligned bubbles. The gradient in pressure across the shock in conjunction with the gradient in fluid density between the air and hydrogen produce a large increase in vorticity as the shock passes through the hydrogen fuel. As can be seen in the study of Don and Quillen (J. Comput. Phys. 1995; 122: 244), Don and Gottlieb (SIAM J. Numer. Anal. 1998; 35: 2370) and the present grid convergence tudy, the size, spacing and velocity of the fine‐scale vortical structures are very difficult to accurately simulate numerically. The difficulty in obtaining well‐resolved multiscale combustion flows by all methods considered will be illustrated. Published in 2003 by John Wiley & Sons, Ltd.
Distributed parallel computation for complex rotational flows of non‐Newtonian fluids
Authors: Baloch A. , Webster M. F.
Published: December 2003

Complex rotational flows of non‐Newtonian fluids are simulated through finite element methods. The predictions have direct relevance to dough kneading, associated with the food industry. The context is taken as two‐dimensional and one of stirring material within a cylindrical vessel. Three stirrer shapes are considered, placed in eccentric location with respect to the cylinder centre. The motion is driven by the rotation of the outer vessel wall. Variation with change in rheology and change in stirrer shapes are analysed, with respect to flow kinematics, stress fields, rate‐of‐work and power consumed. Computations are performed for Newtonian, shear‐thinning and viscoelastic fluids, at various viscosity levels to gradually approximate more realistic dough‐like response. For viscoelastic fluids, Phan‐Thien/Tanner constitutive models are adopted. The numerical method employed is based on a finite element semi‐implicit time‐stepping Taylor–Galerkin/pressure‐correction scheme, posed in a cylindrical polar co‐ordinate system. Simulations are conducted via distributed parallel processing, performed on a networked cluster of workstations, employing message passing. Parallel performance timings are compared against those obtained working in sequential mode. Ideal linear speed‐up with the number of processors is observed for viscoelastic flows under this coarse‐grained implementation. Copyright © 2003 John Wiley & Sons, Ltd.
Inexact information aided, low‐cost, distributed genetic algorithms for aerodynamic shape optimization
Authors: Karakasis Marios K. , Giotis Alexios P. , Giannakoglou Kyriakos C.
Published: December 2003

Despite its robustness, the design and optimization of aerodynamic shapes using genetic algorithms suffers from high computing cost requirements, due to excessive calls to Computational Fluid Dynamics tools for the evaluation of candidate solutions. To alleviate this problem, either the use of distributed genetic algorithms or the implementation of surrogate evaluation models have separately been proposed in the past. A distributed genetic algorithm relies on the handling of population subsets that evolve in a semi‐isolated manner by regularly exchanging their best individuals. It is known that distributed schemes generally outperform single‐population ones. On the other hand, the implementation of less costly surrogate evaluation tools, such as the autocatalytic radial basis function networks developed by the authors for the purpose of getting rid of most of the ‘useless’ exact evaluations, reduces considerably the computational cost. The aim of the present paper is to employ a surrogate evaluation model in the context of a distributed genetic algorithm and to demonstrate that the combination of both results in maximum economy in CPU cost. In addition, whenever a multiprocessor system is available, the gain is much more pronounced, since the new optimization method maximizes parallel efficiency. The proposed method is used to solve inverse design and optimization problems in aeronautics and turbomachinery. Copyright © 2003 John Wiley & Sons, Ltd.
Changes in chemical composition during development of grass pea (Lathyrus sativus L.) seeds
Authors: Lisiewska Zofia , Korus Anna , Kmiecik Waldemar
Published: December 2003

The level of chemical components was determined in seeds of grass pea (Lathyrus sativus L.), cv. Krab, harvested at a dry matter content between 25.9 and 49.6 g/100 g of the raw material, and divided into five degrees of maturity. The results presented suggest that, in general, with an increasing maturity of seeds, the level of the following components increased if related to fresh matter: starch, dietary fibre, acids, total and protein nitrogen, total amino acids and sulphur amino acids, ash and its alkalinity, magnesium, calcium, total phosphorus and phytic phosphorus, and thiamine. The following components were reduced: vitamin C, riboflavin, carotenoids, β‐carotene, and chlorophylls. No such regularity could be found with respect to the accumulation of sugars, essential amino acids, and iron. By expressing the results in dry matter, increases were noted in starch, protein nitrogen, and thiamine. The content of sugars, total nitrogen, total amino acids, essential and sulphur amino acids, ash and its alkalinity, magnesium, phosphorus, vitamin C, riboflavin, carotenoids, β‐carotene, and chlorophylls were reduced while that of dietary fibre, iron, calcium, and phytic phosphorus varied.
Effect of the volatile constituents isolated from Thymus albicans, Th. mastichina, Th. carnosus and Thymbra capitata in sunflower oil
Authors: Miguel Maria G. , Figueiredo A. Cristina , Costa Monya M. , Martins Denise , Duarte João , Barroso José G. , Pedro Luis G.
Published: December 2003

The composition of essential oils isolated from Thymus albicans and Thymbra capitata collected in Algarve (Portugal), Th. mastichina collected in Algarve and Estremadura (Portugal) and Th. carnosus also collected in Algarve, during the flowering phase, was analysed by gas chromatography (GC) and GC coupled to mass spectrometry (GC‐MS). The antioxidant capacity of the oils as well as some of their main components was determined by periodic evaluation of the peroxide values in sunflower oils stored at 60°C. These peroxide values were compared to that of butylated hydroxytoluene (BHT) and control (without adding antioxidants) under the same experimental conditions. The oils of Th. albicans and Th. mastichina, collected in Algarve, were dominated by 1,8‐cineole (68% and 45%, respectively), whereas linalool (52%) was the main component from the oils isolated from Th. mastichina collected in Estremadura. Carvacrol (68%) was the major component present in the oils of Thymbra capitata while borneol (18%), terpinen‐4‐ol (11%) and camphene (9%) were the major ones in the essential oil of Th. carnosus. The essential oils as well as some of their main components showed higher antioxidant capacity than that of the synthetic antioxidant BHT. At the end of the experiment (57 days), BHT showed a percentage of inhibition of 20%, while that of the essential oils ranged from 46% for Th. carnosus, to 59% for Th. mastichina collected in Estremadura.
An update on the processing of high‐protein rice products
Authors: Shih Fred F.
Published: December 2003

The component of protein in rice, at 7–9% by weight, is relatively low, but the total amount of rice protein potentially available is significant because the production of rice worldwide, at 380 million tons annually, is huge. Rice proteins are recognized as nutritional, hypoallergenic, and healthy for human consumption, and rice protein products have been in demand in recent years. However, because of difficulties in the processing, rice protein products, particularly high‐protein content ones, have not been readily available. Two of the main sources of rice protein, rice bran and, to a lesser extent, broken rice kernels, have been under‐used and under‐priced. This report provides an update on the processing of these sources for rice proteins. Methods of protein processing are highlighted including the traditional alkaline extraction, enzyme‐assisted extraction, and the novel uses of physical treatment prior to water extraction. Also discussed are effects of processing on the functional and nutritional properties of rice protein.
Bioaccessibility of calcium, iron and zinc from three legume samples
Authors: Sahuquillo Amparo , Barberá Reyes , Farré Rosaura
Published: December 2003

Legumes can be a source of mineral elements but also of antinutritional factors which can affect their absorption. An in vitro method including gastrointestinal digestion was used to estimate mineral bioavailability. Soluble (bioaccessible) and insoluble calcium, iron and zinc from white beans, chickpeas and lentils were determined after gastrointestinal digestion. The influence of the original sample weight on the soluble mineral fraction was also estimated. The results obtained show that white beans are the legumes with the highest bioaccessible calcium and iron contents. Lentils have a high iron content but its bioaccessibility is much lower than that of iron from white beans and chickpeas. An increase in sample weight increases the amount of bioaccessible element available for intake, but the increase is not always proportional.
Reasoning about non‐linear AR models using expectation maximization
Authors: Arnold M.
Published: December 2003

A simplified version of the expectation maximization (EM) algorithm is applied to search for optimal state sequences in state‐dependent AR models whereby no prior knowledge about the state equation is necessary. These sequences can be used to draw conclusions about functional dependencies between the observed process and estimated AR coefficients. Consequently this approach is especially helpful in the identification of functional–coefficient AR models where the coefficients are controlled by the process itself. The approximation of regression functions in first‐order non‐linear AR models and the localization of multiple thresholds in self‐exciting threshold autoregressive models are demonstrated as examples. Copyright © 2003 John Wiley & Sons, Ltd.
Systematic patterns before and after large price changes: evidence from high frequency data from the Paris Bourse
Authors: Hamelink Foort
Published: December 2003

This paper examines the intra‐day behaviour of asset prices shortly before and after large price changes. Whereas similar studies so far have been based on daily closing prices, I use three years of high frequency data of 120 stocks listed on the French stock exchange. Various systematic patterns, in addition to those often reported in the literature, emerge from this data. Evidence is found that prices do overreact and that a correction takes place after large price movements, especially those on the downside. The correction does not take place immediately after the large price change. Prior to this, some very significant and sometimes economically important patterns can be observed. When the bid–ask spread is taken into account, I still find some ex post profitable trading strategies that are, however, too small in magnitude to suggest market inefficiency. Copyright © 2003 John Wiley & Sons, Ltd.
Transplantation of glial‐restricted precursor cells into the adult spinal cord: Survival, glial‐specific differentiation, and preferential migration in white matter
Authors: Han Steve S.W. , Liu Ying , Tyler‐Polsz Carla , Rao Mahendra S. , Fischer Itzhak
Published: December 2003

Glial‐restricted precursor (GRP) cells are among a number of candidate cells for transplantation repair of CNS injury. The isolation and characterization of these cells in vitro have been described previously, but their in vivo properties are not well understood. We examined the fate and migration of grafted fetal GRP cells harvested from alkaline phosphatase‐expressing transgenic rats into intact and injured spinal cord. Transplanted GRP cells survived for at least 6 weeks and differentiated along astrocytic and oligodendrocytic but not neuronal lineages. Cells grafted into the intact spinal cord exhibited robust migration along longitudinal white matter tracts and by 6 weeks migrated more than 15 mm. In contrast, migration of GRP cells in the gray matter was very limited. We then examined the phenotypic properties of proliferating endogenous precursors in response to injury by BrdU labeling. The predominant proliferating population seen after injury consisted of GRP‐like cells with Nkx2.2/olig2 phenotype. Incorporation of BrdU by endogenous cells suggests that the environment provides proliferation signals and is permissive to glial precursor survival. To test if exogenous GRP cells would respond similarly, we transplanted GRP cells into a lateral funiculus injury. GRP cells survived and differentiated along glial lineages and migrated along white matter tracts in the injured spinal cord. Directed homing toward the lesion was not seen and there was no significant bias in differentiation between cells transplanted into injured and uninjured spinal cord. GRP cell transplants may therefore provide a cellular transplant that can respond to appropriate endogenous cues to produce therapeutic molecules and new glial cells after injury. © 2003 Wiley‐Liss, Inc.
Satellite cell proliferation in murine sensory ganglia in response to scarification of the skin
Authors: Elson Karen , Simmons Anthony , Speck Peter
Published: December 2003

Satellite cells (SCs) ensheathe neuronal cell bodies of sensory ganglia and provide mechanical and metabolic support for neurons. In mice, grossly detrimental stimuli such as nerve crush or cut, or explant culture of ganglia induce proliferation of SCs. It is unknown whether SC proliferation occurs in response to the less severe trauma that might commonly occur in a physiological situation. Our aim was to determine the response of SCs to mild trauma, such as scratching the skin. SC proliferation, measured by bromodeoxyuridine (BrdU) uptake, and immune cells, measured by CD45 labelling, were quantified at various times during the 7 days after scarification or abrasion of flank skin. We show that minimal skin trauma, such as scarification or light abrasion, triggers proliferation of SCs. Sections of control mice nervous tissue show <10 BrdU+ cells/ganglionic profile. In contrast, sections of traumatised mice show >50 BrdU+ cells/ganglionic profile, even after simply scratching the skin. The lack of CD45+ cells shows that the proliferating cells are not immune cells. We suggest that SCs in mice are a labile cell population able to proliferate rapidly in response to minimal nerve trauma. This finding has implications for the role of SCs in nervous system repair. © 2003 Wiley‐Liss, Inc.
Olig genes are expressed in a heterogeneous population of precursor cells in the developing spinal cord
Authors: Liu Ying , Rao Mahendra S.
Published: December 2003

Recent results from multiple laboratories have identified Olig genes as important in regulating glial differentiation. Here we show that Olig2 expression at early stages of development (prior to E16.5) identifies a domain in the developing spinal cord, which contains a heterogeneous population of progenitors that includes stem cells and glial progenitors. We show that Nkx2.2 and Olig2, which are present initially in nonoverlapping domains, are coexpressed at later stages, likely due to a second wave of Olig expression. We find that Olig1, like Olig2, is present in cells that coexpress astrocytic and radial glial markers and that Olig1/2 double knockouts lead to a loss of oligodendrocytes with preservation of NG2 expression. These results coupled with previously published data indicate that Olig1/2 and Nkx2.2, while clearly important in regulating early progenitor cell differentiation, do not unambiguously demonstrate the existence of an oligodendrocyte‐neuron precursor or negate the existing retroviral lineage and clonal analysis data that suggest the existence of other types of precursors such as oligodendrocyte‐astrocyte precursors or neuronal precursors. Published 2003 Wiley‐Liss, Inc.
The 4C5 antigen is associated with Schwann cell migration during development and regeneration of the rat peripheral nervous system
Authors: Yfanti Eleni , Sidera Katerina , Margaritis Lukas H. , Patsavoudi Evangelia
Published: December 2003

The monoclonal antibody 4C5 recognizes a cell surface antigen of the developing central nervous system (CNS) and peripheral nervous system (PNS). In vitro antibody perturbation experiments have shown that the 4C5 antigen is involved in horizontal and vertical migration processes of granule cells during development of the rodent cerebellum. Moreover, results concerning the cellular localization and temporal expression of the 4C5 antigen during development and after injury of the rat sciatic nerve suggested that it may participate in Schwann cell migrations that occur during the above processes. To test this possibility, we examined the effects of our function‐blocking antibody on Schwann cell migration in three in vitro bioassays: in tissue cultures from developing sciatic nerve, in dorsal root ganglion cultures on cryostat sections of normal or denervated adult sciatic nerve, and in pure Schwann cell cultures. The results showed that the presence of monoclonal antibody 4C5 in all the above culture systems strongly inhibited Schwann cell migration, indicating that the 4C5 antigen participates in migration processes that take place during development and regeneration of the peripheral nervous system. Moreover, staining of migrating Schwann cells in the presence of monoclonal antibody 4C5 with rhodamine‐phalloidin showed that 4C5 antigen activity is associated with actin cytoskeletal organization of these cells, and more specifically with lamellipodia formation. © 2003 Wiley‐Liss, Inc.
Transamination by Polymeric Enzyme Mimics
Authors: Zhou Wenjun , Liu Lei , Breslow Ronald
Published: December 2003

Pyridoxamine was linked to a series of polyethylenimines (PEIs) with Mn=600, 1800, 10,000, and 60,000, both simply permethylated and with additional attached dodecyl chains. They were examined in the transamination of pyruvic acid and of phenylpyruvic acid, and showed MichaelisMenten behavior. The values of k2 and of KM determined showed only small variations with polymer size. Thus, the previously reported strong advantage of pyridoxamines attached to the Mn=60,000 PEI, relative to simple pyridoxamine alone, is seen to almost the same extent with the smaller PEIs.
A Facile Enzymatic Synthesis of Isotopically Labeled 2‐Methyl‐D‐erythritol 2,4‐Cyclodiphosphate by Spinach Chloroplast Stroma
Authors: Gao Wenyun , Raschke Maja , Alpermann Henriette , Zenk Meinhart H.
Published: December 2003

For the investigation of the ultimate and penultimate steps of the deoxyxylulose phosphate pathway in plants and microorganisms, and to solve intracellular transport problems, we have developed a facile enzymatic preparation of 2‐methyl‐D‐erythritol 2,4‐cyclodiphosphate in highly radioactive form. Use has been made of spinach chloroplast stroma, as well as the stroma of Capsicum annuum and Narcissus pseudonarcissus chromoplasts, which were shown to transform differently labeled 1‐deoxy‐D‐xylulose 5‐phosphate quantitatively into that cyclic diphosphate in the presence of cofactors. This method can also be exploited to synthesize milligram quantities of 13C‐labeled cyclic diphosphate. It is shown that recombinant Escherichia coli deoxyxylulose phosphate synthase is catalytically active and can be used to synthesize the labeled starting material for further enzymatic work, as well as for feeding of intact plants. The pH and temperature stability of the deoxyxylulose 5‐phosphate and the cyclic diphosphate have been determined. Uniformly 13C‐ or 14C‐labeled pyruvate, and uniformly 13C‐ or 14C‐labeled D‐glyceraldehyde 3‐phosphate were synthesized in almost quantitative yields from uniformly 13C‐ or 14C‐labeled D‐glucose en route to deoxyxylulose 5‐phosphate.
Mechanistic Investigation of Phenylalanine Ammonia Lyase by Using N‐Methylated Phenylalanines
Authors: Viergutz Sandra , Poppe László , Tomin Anna , Rétey János
Published: December 2003

N‐Methyl‐L‐phenylalanine (5), N‐methyl‐4‐nitro‐L‐phenylalanine (6), and N,N‐dimethyl‐4‐nitro‐L‐phenylalanine (7⋅H+) were investigated as substrates or inhibitors of phenylalanine ammonia lyase from Petroselinum crispum. Whereas the former was a reluctant substrate (Km =6.6 mM, kcat =0.22 s−1), no reverse reaction could be detected by using methylamine and (E)‐cinnamate (2). The Km value for ammonia in the reverse reaction by using (E)‐cinnamate (2) was determined to be 4.4 and 2.6M at pH 8.8 and 10, respectively. The N‐methylated 4‐nitro‐L‐phenylalanines 6 and 7 showed only strong inhibitory effects (Ki =130 nM and 8 nM, resp.). These and former results are discussed in terms of the mechanism of action of phenyalalanine and histidine ammonia lyases.
Facile Orthoester Formation in a Model Compound of the Taxol Oxetane: Are Biologically Active Epoxy Esters, Orthoesters, and Oxetanyl Esters Latent Electrophiles?
Authors: Giner José‐Luis , Faraldos Juan A.
Published: December 2003

A steroidal oxetanyl ester was synthesized in eight steps as a biomimetic model of taxol oxetane. The model compound was surprisingly reactive under acidic conditions, rearranging in the absence of H2O to a [2.2.1]‐bicyclic orthoester. Both the oxetanyl ester and the orthoester readily hydrolyze to produce the same triol monoacetate. On the basis of the oxetanyl ester/orthoester rearrangement, a novel biochemical function is suggested for the epoxy esters and oxetanyl esters found in taxoids whereby dioxonium ions, generated from these functional groups, react with cellular proteins to form mixed orthoesters or ethers. A similar process could be involved in the mechanism of action of natural orthoesters such as resiniferatoxin.
Natural Products Chemistry: New Opportunities, Uncertain Future
Authors: Meinwald Jerrold , Eisner Thomas
Published: December 2003

Natural products chemistry, a field greatly invigorated nowadays by its partnership with chemical ecology, is currently being de‐emphasized. We argue that such curtailment will restrain an exploratory process of immense scientific promise.
Enantioselective Synthesis of a Polyfunctionalized Tetracycle Related to Pentacyclic Triterpenes by Using an Anionic Cycloaddition Reaction
Authors: Rouillard Alain , Bonin Marc‐André , Deslongchamps Pierre
Published: December 2003

Herein we report a convergent enantioselective synthesis of a polyfunctionalized ABCD tetracycle by using an anionic cycloaddition reaction between a chiral bicyclic CD Nazarov intermediate (see 6), derived from the (−)‐Weiland–Mischer ketone, and an achiral cyclohexenone (see 5) adequately functionalized to furnish the ring A of pentacyclic triterpenes (Scheme 5). The chiral bicyclic CD Nazarov intermediate forms ring B upon cycloaddition with the achiral cyclohexenone to yield an ABCD tetracycle with a cis‐anti‐trans‐anti‐trans configuration (see 4). Further transformations on this adduct allowed reduction of the angular aldehyde function at C(10) to a Me group (→17) and introduction of an unsaturation at C(5)C(6) by using the ketone function at C(7) (→ 3; Scheme 6).
Designing New α,β‐Unsaturated Thioesters for the Catalytic, Enantioselective FriedelCrafts Alkylation of Indoles
Authors: Bandini Marco , Melloni Alfonso , Tommasi Simona , Umani‐Ronchi Achille
Published: December 2003

A new class of α,β‐unsaturated S‐(1,3‐benzoxazol‐2‐yl) thioesters of type 2 have been synthesized and effectively employed as electrophiles in the stereoselective alkylation of indoles. The combination of electronic as well as steric properties of such Michael acceptors allowed us to carry out FriedelCrafts alkylations of various substituted indoles in the presence of a catalytic amount (20 mol‐%) of chiral cationic [PdII(Tol‐binap)] complexes. With the optimized catalytic system (PdCl2(MeCN)2/Tol‐binap/AgSbF6), the desired β‐indolyl‐substituted thioderivatives 4 were obtained in good yield, with an enantiomeric excess (ee) of up to 86%. The remarkable versatility of the enantiomerically enriched thioesters 4 was demonstrated by quantitatively transforming them into optically active β‐indolyl esters and amides under mild conditions. With this stereoselective, catalytic FriedelCrafts reaction, we open up the way towards new α,β‐unsaturated compounds that could be suitable candidates for the preparation of a number of optically active β‐substituted carboxylic compounds.
Microphysiometric Measurement of PAF Receptor Responses to Ginkgolides
Authors: Krane Sonja , Kim So Ra , Abrell Leif M. , Nakanishi Koji
Published: December 2003

Microphysiometry was used to evaluate the effects of terpene trilactone and flavonoid constituents of Ginkgo biloba on human platelet‐activating‐factor receptor (PAFR). Inhibition of the platelet‐activating factor response by terpene trilactones was confirmed using this functional assay. Ginkgolide B (GB) and 10‐O‐benzyl‐GB showed the strongest inhibition (81 and 93%, resp.) of the PAFR response, while the flavonoids rutin, quercetin, and kaempferol showed negligible response inhibition. G. biloba extract mixtures were also tested, and results indicate possible synergistic effects among various components.
Inhibition of Diamino Pelargonic Acid Aminotransferase, an Enzyme of the Biotin Biosynthetic Pathway, by Amiclenomycin: A Mechanistic Study
Authors: Mann Stéphane , Florentin Dominique , Lesage Denis , Drujon Thierry , Ploux Olivier , Marquet Andrée
Published: December 2003

The mechanism of action of amiclenomycin (1a), a naturally occuring inhibitor of diaminopelargonic acid aminotransferase, has been established. The enzyme catalyzes the formation of an aromatic adduct between the inhibitor and pyridoxal‐5′‐phosphate. The structure of the adduct, determined by mass spectrometry, is in agreement with the reported X‐ray crystal structure. Kinetic parameters, characteristic of kcat inhibitors, have been observed, with a KI value of 2 μM and a kinact value of 0.4 min−1. The irreversibility of the inactivation observed, in spite of the absence of covalent bond between the inhibitor and the protein, reveals the high affinity of the adduct for the active site. Two other cis‐1‐amino‐4‐substituted‐cyclohexa‐2,5‐dienes, 3a and 4a, were also found to efficiently inhibit the enzyme. The trans‐isomers were either much less potent (1b) or inactive (3b and 4b). The aminocyclohexadiene moiety, which is, apparently, responsible for the inhibition, could constitute an original pharmacophore for the design of new herbicides.
Amphiphilic Homochiral Oligopeptides Generated via Phase Separation of Nonracemic α‐Amino Acid Derivatives and Lattice‐Controlled Polycondensation in a Phospholipid Environment
Authors: Rubinstein Irina , Bolbach Gérard , Weygand Markus J. , Kjaer Kristian , Weissbuch Isabelle , Lahav Meir
Published: December 2003

Racemic S‐ethyl thioesters of Nε‐stearoyllysine (= S‐ethyl (R,S)‐2‐amino‐6‐(stearoylamino)hexanethioate) and S‐ethyl thioesters of γ‐stearyl glutamic acid (=stearyl (R,S)‐4‐amino‐5‐(ethylsulfanyl)‐5‐oxopentanoate) self‐assemble as separated two‐dimensional crystalline monolayers within an achiral phospholipid environment of racemic 1,2‐dipalmitoylglycerol (DPG) and 1,2‐dipalmitoylglycero‐3‐phosphoethanolamine (DPPE), as demonstrated by grazing‐incidence X‐ray‐diffraction (GIXD) measurements performed on the surface of H2O. Lattice‐controlled polycondensation within these crystallites with deuterium‐enantiolabeled monomers was initiated by injecting aqueous solutions of Ag+ or I2/KI beneath the monolayers, which yielded mixtures of diastereoisomeric oligopeptides containing up to six to eight repeating units, as analyzed by MALDI‐TOF mass spectrometry. Analysis of the diastereoisomeric distribution showed an enhanced relative abundance of the oligopeptides with homochiral sequences containing three or more repeating units. Within the DPPE monolayers, the nucleophilic amino group of the phospholipid operates as an initiator of polymerization at the periphery of the monomer two‐dimensional crystallites. Enhanced relative abundance of enantiomerically enriched homochiral oligopeptides was obtained by the polycondensation of nonracemic monomers. This enhancement indicated a phase separation into racemic and enantiomorphous monomer crystallites within the phospholipid environment, although this separation could not be observed directly by GIXD. A possible role that might have been played by crystalline assemblies for the abiotic generation and amplification of oligopeptides with homochiral sequences is discussed.
The Regulation of the Calcium Signal by Membrane Pumps
Authors: Krebs Joachim , Helms Volkhard , Griesinger Christian , Carafoli Ernesto
Published: December 2003

Calcium may have a static, structure‐stabilizing role in biological organs like the bones and the teeth, or may fulfill a dynamic function in cells as a regulator of signal‐transduction pathways. This is made possible by the properties of the Ca2+ ion (e.g., high dehydration rate, great flexibility in coordinating ligands, largely irregular geometry of the coordination sphere). Since Ca2+ is a universal carrier of signals, the control of its homeostasis is of central importance for the organism. It involves exchanges between the skeleton (which is the major calcium reservoir) and the extracellular and intracellular fluids. It also involves the intestine and the kidney, the organs of Ca absorption and release, respectively. The highly integrated homeostasis process consists of a number of hormonally controlled feedback loops, and an elaborate system of membrane channels, exchangers, and pumps that control the Ca2+ flux into and out of cells.
Informal learning and the transfer of learning: How managers develop proficiency
Authors: Enos Michael D. , Kehrhahn Marijke Thamm , Bell Alexandra
Published: December 2003

This study examined how the extent to which managers engaged in informal learning, perceptions of support in
the transfer environment, and level of managerial proficiency related to transfer of learning in twenty core
managerial skills. The results suggested that informal learning is predominantly a social process and that
managers with high levels of proficiency who experience low levels of coworker, supervisor, and organizational
support learn managerial skills mostly from informal learning and transfer learning more frequently. New
perspectives are offered on the interrelationship between informal learning and transfer of learning, the role of
metacognition and self‐regulation in informal learning, and the influence of informal learning in the
development of managerial proficiency.
An examination of learning transfer system characteristics across organizational settings
Authors: Holton Elwood F. , Chen Hsin‐Chih , Naquin Sharon S.
Published: December 2003

No previous research in the United States has compared and contrasted learning transfer systems across
organizations and training types, primarily because no standard instruments were used in previous research.
This study, based on a subset of responses in the Learning Transfer System Inventory response database, is the
first to conduct such a comparison. Using a subset of 1,099 respondents, transfer systems are compared across
three organization types, eight organizations, and nine types of training. MANOVA and univariate ANOVA were
used to compare transfer systems. The results suggest that transfer systems differ across organizational types,
organizations, and training types. Implications for HRD practice and future research directions are
discussed.
Genesis of the European initiative in insolvency law
Authors: Omar Paul J.
Published: December 2003

This article deals with the history behind the initiative that led to the adoption of the European Insolvency Regulation 2000. It covers the background to the proposals, the content of the various drafts that have merged over the past four decades and criticism of the proposals by commentators. Copyright © 2003 John Wiley & Sons, Ltd.
Migrant remittances and family ties: a case study in China
Authors: Cai Qian
Published: December 2003

The migration of China's population, especially rural‐to‐urban migration, has attracted considerable attention from both researchers and policy‐makers. However, few studies have considered the issue of remittances sent home by migrants. This subject is of importance for three reasons: first, remittances have become a striking feature of Chinese internal migration; second, remittances are a unique form of transfers which tell something about intra‐familial relationships; and, third, the study of remittances is relatively absent in the the China migration literature to date. Guided by the theories of family adaptive strategy, altruism, and self‐interest, this study explores how temporary vs. permanent migration status influences migrants' propensity to remitting and the amount remitted. It also considers how family ties, both emotional and economical, affect migrants' remitting behaviour. The data are drawn from the Hubei Survey of Fertility, Migration and Social Change and we show that family ties are the most important and distinct factors in affecting migrants' remittances. Temporary migration status, being male and wage also have positive and statistically significant effects. Education, surprisingly, has little influence on either the decision to remit or the amount to remit. In conclusion, we consider the policy implications of these findings. Copyright © 2003 John Wiley & Sons, Ltd.