bluuebunny/crossref_metadata_2025 huggingface dataset:
Safety of hydroxychloroquine in pregnant patients with connective tissue diseases: A study of one hundred thirty‐three cases compared with a control group
Authors: Costedoat‐Chalumeau Nathalie , Amoura Zahir , Duhaut Pierre , Huong Du Le Thi , Sebbough Djamel , Wechsler Bertrand , Vauthier Danièle , Denjoy Isabelle , Lupoglazoff Jean‐Marc , Piette Jean‐Charles
Published: November 2003

Objective

The use of hydroxychloroquine (HCQ) in pregnancy remains controversial. The recent demonstration that HCQ passes across the placenta, with cord blood concentrations nearly identical to those found in maternal blood, emphasizes the need for careful evaluation of pregnancies in women receiving HCQ. However, only small series of HCQ‐treated pregnant women have been reported, and most of these studies had no control group. We now report our experience with 133 pregnancies in women being treated with HCQ, resulting in 117 live births. Results in the HCQ group are compared with those in a control group.

Methods

One hundred thirty‐three consecutive pregnancies in 90 women treated with 200 mg of HCQ either twice daily (122 pregnancies) or once daily (11 pregnancies) were studied. These pregnancies were compared with 70 consecutive pregnancies in 53 women with similar disorders who did not receive HCQ. Electrocardiography was performed in 47 children of mothers treated with HCQ and in 45 children in the control group.

Results

Eighty‐eight percent of pregnancies in the HCQ group and 84% of those in the control group ended successfully with a live birth. The outcomes of pregnancy were not statistically different between groups. One child in each group died of causes related to prematurity. Three malformations were observed in the HCQ group (1 hypospadias, 1 craniostenosis, and 1 cardiac malformation) versus 4 in the control group. On the electrocardiograms, the PR interval and the corrected QT interval were not statistically different between groups. No visual, hearing, growth, or developmental abnormalities were reported in any of the children at the last follow‐up (ages 12–108 months; mean age 26 months).

Conclusion

Our findings support preliminary evidence for the safety of HCQ therapy during pregnancy. This treatment probably should be maintained throughout pregnancy in patients with systemic lupus erythematosus.
Triplets with systemic lupus erythematosus
Authors: Kamat Sona S. , Pepmueller Peri H. , Moore Terry L.
Published: November 2003

We present herein the first case report of identical triplets who developed systemic lupus erythematosus (SLE). The children were diagnosed as having SLE in reverse birth order at ages 8, 9, and 11 years. Although genetically identical, each sibling manifested different clinical signs and symptoms; however, all 3 children did manifest skin rash, fatigue, and biopsy‐proven glomerulonephritis at different ages. Findings of laboratory studies were similar, including positivity for antinuclear antibodies, anti–native DNA, and anti–double‐stranded DNA, as well as low levels of complement. These findings confirmed SLE in each sibling.
Risk factors for progression of lumbar spine disc degeneration: The Chingford Study
Authors: Hassett G. , Hart D. J. , Manek N. J. , Doyle D. V. , Spector T. D.
Published: November 2003

Objective

Few data exist concerning the natural history of lumbar spine disc degeneration and associated risk factors. We therefore undertook this study to examine the radiographic progression of lumbar spine disc degeneration over the course of 9 years in a population‐based inception cohort of women from the Chingford Study.

Methods

Seven hundred ninety‐six paired lumbar spine radiographs were read by a single reader for anterior osteophytes (AO) and disc space narrowing (DSN) using the Lane atlas at each lumbar disc space (L1–5). Disc degeneration was defined using thresholds of AO and DSN grade 1+ in one or more vertebrae (L1–5) within a subject. Progression was defined as an increase in grade in an affected year‐1 vertebra. Potential risk factors were assessed using odds ratios and 95% confidence intervals adjusted for age, body mass index (BMI), and other potential confounders in logistic regression models using the STATA statistical package.

Results

The mean ± SD age at baseline was 53.8 ± 6.0 years, and mean ± SD BMI was 25.4 ± 4.1 kg/m2. Progression rates for AO and DSN were 4% per annum and 3% per annum, respectively. Progression of DSN was predicted by age, back pain, and radiographic hip and knee osteoarthritis (OA). Progression of AO was predicted by age and radiographic hip OA, with borderline significance for BMI >30 kg/m2. No significant effects were seen for smoking, physical activity, hormone replacement therapy use, multiparity, or hand OA.

Conclusion

This is the first population‐based longitudinal study to assess progression of the individual radiographic features of AO and DSN in lumbar spine disc degeneration. We demonstrated progression rates of 3–4% per annum, with important risk factors for progression, including age, back pain, and radiographic OA at the hip and knee.
The influence of fetal loss on the presence of fetal cell microchimerism: A systematic review
Authors: Khosrotehrani Kiarash , Johnson Kirby L. , Lau Joseph , Dupuy Alain , Cha Dong Hyun , Bianchi Diana W.
Published: November 2003

Objective

Fetal cells enter the maternal circulation during most pregnancies. Their persistence for years occurs in only some women and has been associated with several autoimmune diseases such as systemic sclerosis. The objective of this study was to determine whether pregnancy history influences the persistence of fetal microchimeric cells.

Methods

We reviewed all reports of studies on fetal cell microchimerism, defined as male DNA in maternal tissue, that describe individual pregnancy histories, disease diagnoses, and microchimerism status. The total numbers of pregnancies, births, and sons, the history of fetal loss (spontaneous abortion and elective termination), and the presence of a maternal autoimmune disease were tested as factors potentially associated with persistent microchimerism.

Results

One hundred twenty‐four subjects from 11 studies met the inclusion criteria. Only fetal loss was significantly associated with the presence of microchimerism (odds ratio 2.4, 95% confidence interval 1.2–6.0).

Conclusion

These results suggest that fetomaternal cell trafficking following fetal loss may be important for the engraftment of microchimeric cells in maternal tissue. This may be due to an increased amount of fetomaternal transfusion or to transfer of a cell type that is more likely to engraft. We recommend that investigators in future studies on microchimerism report detailed pregnancy information, since these data are critical for the understanding of factors that influence the development of fetal cell microchimerism.
Recombinant human tumor necrosis factor receptor (etanercept) for treating ankylosing spondylitis: A randomized, controlled trial
Authors: Davis John C. , Van Der Heijde Désirée , Braun Jurgen , Dougados Maxime , Cush John , Clegg Daniel O. , Kivitz Alan , Fleischmann Roy , Inman Robert , Tsuji Wayne ,   for the Enbrel Ankylosing Spondylitis Study Group
Published: November 2003

Objective

To determine the safety and efficacy of etanercept in a multicenter, randomized, placebo‐controlled, double‐blind trial of adults with moderate to severe active ankylosing spondylitis (AS).

Methods

Patients (n = 277) were treated with either etanercept 25 mg (n = 138) or placebo (n = 139) subcutaneously twice weekly for 24 weeks. The primary outcome measures were the percentages of patients achieving the Assessments in Ankylosing Spondylitis 20% response (ASAS20) at weeks 12 and 24. Other outcome measures included the percentage of patients achieving higher ASAS responses, and the safety of etanercept in patients with AS. All outcome measures were assessed at 2, 4, 8, 12, and 24 weeks.

Results

Treatment with etanercept resulted in dramatic improvement. The ASAS20 was achieved by 59% of patients in the etanercept group and by 28% of patients in the placebo group (P < 0.0001) at week 12, and by 57% and 22% of patients, respectively, at week 24 (P < 0.0001). All individual ASAS components, acute‐phase reactant levels, and spinal mobility measures were also significantly improved. The safety profile of etanercept was similar to that reported in studies of patients with rheumatoid arthritis or psoriatic arthritis. The only adverse events that occurred significantly more often in the etanercept group were injection‐site reactions, accidental injuries, and upper respiratory tract infections.

Conclusion

Etanercept is a highly effective and well tolerated treatment in patients with active AS.
The release of crosslinked peptides from type II collagen into human synovial fluid is increased soon after joint injury and in osteoarthritis
Authors: Lohmander L. Stefan , Atley Lynne M. , Pietka Terri A. , Eyre David R.
Published: November 2003

Objective

To determine concentrations of crosslinked C‐telopeptide fragments of type II collagen (CTX‐II) in synovial fluid (SF) from patients with joint injury, osteoarthritis (OA), or other knee arthritides.

Methods

Two study groups were used: a cross‐sectional group, which included healthy‐knee volunteers (reference group [REF]) and patients with pseudogout (PPA), an anterior cruciate ligament tear with or without a meniscus tear (INJ), or primary knee OA (POA); and a longitudinal group, which included patients with arthroscopic cartilage changes or septic arthritis. CTX‐II was quantified by competition enzyme‐linked immunosorbent assay (ELISA) based on a monoclonal antibody that recognized the C‐terminus of the peptide EKGPDP as a proteolytic neoepitope. Aggrecan fragments, matrix metalloproteinases 1 and 3, and tissue inhibitor of metalloproteinases 1 were determined by ELISAs.

Results

Concentrations of CTX‐II in SF were higher in patients with PPA, INJ, and POA than in the REF group (P < 0.001). After joint injury, mean levels of CTX‐II in SF were increased above REF levels at all time intervals (P < 0.001), and were highest within hours after trauma. In those in the longitudinal study group with joint cartilage damage, variation coefficients for CTX‐II were 81% (between patients) and 64% (within patient), monitored over 1 year. In a patient with septic arthritis, SF CTX‐II increased at the onset of symptoms, and peaked 30‐fold higher than the baseline. Concentrations of all biomarkers decreased with successful treatment.

Conclusion

This is the first report to describe the release into SF of soluble molecular fragments specific for the degradation of mature, crosslinked, type II collagen (CII) in human OA and joint injury. The results provide strong evidence that the integrity of the CII network of cartilage is compromised soon after joint injury and in arthritis. This early degradation of CII may represent an important treatment target.
Comparing the efficacy of cyclooxygenase 2–specific inhibitors in treating osteoarthritis: Appropriate trial design considerations and results of a randomized, placebo‐controlled trial
Authors: Gibofsky Allan , Williams Gary W. , McKenna Frank , Fort John G.
Published: November 2003

Objective

To compare the efficacy of the cyclooxygenase 2 (COX‐2)–specific inhibitors celecoxib and rofecoxib in treating the signs and symptoms of osteoarthritis (OA).

Methods

In this randomized, placebo‐controlled, double‐blind, multicenter study, 475 patients with OA of the knee received either celecoxib 200 mg/day (n = 189), rofecoxib 25 mg/day (n = 190), or placebo (n = 96) for 6 weeks. Arthritis assessments were performed at baseline, week 3, and week 6 (or at the time of early termination).

Results

In primary measures of efficacy (OA pain score on a 100‐mm visual analog scale [VAS] and total domain score on the Western Ontario and McMaster Universities Osteoarthritis Index), celecoxib 200 mg/day and rofecoxib 25 mg/day demonstrated similar efficacy. At week 6, celecoxib was associated with a 34‐mm mean improvement on the VAS for OA pain, compared with 31.6 mm for rofecoxib and 21.2 mm for placebo. The difference between celecoxib and rofecoxib was −2.5 mm, with an upper limit of the 95% confidence interval of 2.7 mm and within the prespecified definition of noninferiority. Secondary measures of efficacy showed similar results. All differences in primary and secondary measures of efficacy between the 2 active treatments and placebo were statistically significant (P < 0.02), whereas all of the comparisons of efficacy between celecoxib and rofecoxib met the predefined criteria for noninferiority. All treatments were well tolerated throughout the study, with similar proportions of patients withdrawing due to adverse events.

Conclusion

Celecoxib 200 mg/day and rofecoxib 25 mg/day are equally efficacious in treating the signs and symptoms of OA.
The emancipatory character of action research, its history and the present state of the art
Authors: Boog Ben W. M.
Published: November 2003

Right from the start, action research was intended to be emancipatory research, and it still is. This article will underpin this by outlining its history and the present state of the art. Though a variety of action research approaches have developed along divergent theoretical pathways, it will be stressed that these approaches share the most important characteristics of action research and are basically different applications of different action theories. They are all supported by a participatory worldview and are meant to be a double‐sided process of research, self research and education directed at individual empowerment and collective empowerment and/or emancipation. Since the relationship between the researcher and the subjects being researched is crucial for the success of action research as an emancipatory or empowering activity, this article will maintain that the most important task of action researchers is to develop refined heuristics concerning this communication. The article will end by making some recommendations for the improvement of action research as an emancipatory practice. Copyright © 2003 John Wiley & Sons, Ltd.
’︁No limits‚: doing participatory action research with young people in Northumberland
Authors: Bostock Jan , Freeman Jane
Published: November 2003

People's health needs tend to be responded to by professionally led, individualistic and reactive services, rather than preventive interventions, or by drawing on lay expertise. In this project, we used a participatory approach to involve young people in researching their needs and views of how sources of support can be improved and developed. We present the background to the work undertaken; the participatory methods used; results and recommendations. The young people emphasized their preferences for informal support rather than counselling services; and changes in the attitudes of professionals towards young people, rather than major new service developments. We discuss the implications of a participatory approach to the research and to the individuals involved. Copyright © 2003 John Wiley & Sons, Ltd.
From participative research to participative practice—a study in youth care
Authors: Roose Rudi , De Bie Maria
Published: November 2003

In this contribution the development in action research of a participative care practice in youth care is discussed. The study was prompted by the intention of the Flemish government to reform youth care. The initial research‐question was how youth care can be organized in such a way that it (also) represents an added value for the client(s). The aim was to find out to what extent the reorganization of youth care could contribute to a social service that enhances a dignified existence for their clients and contributes to a participative care. Hence, the aim of the research was not just to reorganize youth care, but also to develop a participative care practice. The research findings highlight the tension between a reorganization that takes as its starting point an expert way of thinking, and the realization of participative care in which the clients' perspective is taken as central point of departure. Against the background of this tension, the question to what extent care workers actually have room to realize a participative care practice turned out to be one of the most important issues within the research. Copyright © 2003 John Wiley & Sons, Ltd.
4‐Fluorophenylglycine as a Label for 19F NMR Structure Analysis of Membrane‐Associated Peptides
Authors: Afonin Sergii , Glaser Ralf W. , Berditchevskaia Marina , Wadhwani Parvesh , Gührs Karl‐Heinz , Möllmann Ute , Perner Andrea , Ulrich Anne S.
Published: November 2003

The non‐natural amino acid 4‐fluorophenylglycine (4F‐Phg) was incorporated into several representative membrane‐associated peptides for dual purpose. The 19F‐substituted ring is directly attached to the peptide backbone, so it not only provides a well‐defined label for highly sensitive 19F NMR studies but, in addition, the D and L enantiomers of the stiff side chain may serve as reporter groups on the transient peptide conformation during the biological function. Besides peptide synthesis, which is accompanied by racemisation of 4F‐Phg, we also describe separation of the epimers by HPLC and removal of trifluoroacetic acid. As a first example, 18 different analogues of the fusogenic peptide “B18” were prepared and tested for induction of vesicle fusion; the results confirmed that hydrophobic sites tolerated 4F‐Phg labelling. Similar fusion activities within each pair of epimers suggest that the peptide is less structured in the fusogenic transition state than in the helical ground state. In a second example, five doubly labelled analogues of the antimicrobial peptide gramicidin S were compared by using bacterial growth inhibition assays. This cyclic β‐sheet peptide could accommodate both L and D substituents on its hydrophobic face. As a third example, we tested six analogues of the antimicrobial peptide PGLa. The presence of d‐4F‐Phg reduced the biological activity of the peptide by interfering with its amphiphilic α‐helical fold. Finally, to illustrate the numerous uses of l‐4F‐Phg in 19F NMR spectroscopy, we characterised the interaction of labelled PGLa with uncharged and negatively charged membranes. Observing the signal of the free peptide in an aqueous suspension of unilamellar vesicles, we found a linear saturation behaviour that was dominated by electrostatic attraction of the cationic PGLa. Once the peptide is bound to the membrane, however, solid‐state 19F NMR spectroscopy of macroscopically oriented samples revealed that the charge density has virtually no further influence on the structure, alignment or mobility of the peptide.
Mutagenic Stabilization of the Photocycle Intermediate of Green Fluorescent Protein (GFP)
Authors: Wiehler Jens , Jung Gregor , Seebacher Christian , Zumbusch Andreas , Steipe Boris
Published: November 2003

The optical spectra of the Aequorea victoria green fluorescent protein (GFP) are governed by an equilibrium between three different chromophore states. Mutants that predominantly show either the protonated (A) or the deprotonated (B) form of the chromophore have previously been described. In contrast, the I form, which is formed by rapid excited‐state deprotonation of the A form of the chromophore, has only been described as an obligatory photochemical intermediate. We report the design of a new GFP mutant with a stabilized I form. For this purpose, we introduced two isosteric point mutations, Thr203Val and Glu222Gln, that selectively raise the potential energy of both the A and the B form. Knowledge of the absorption spectrum of the I form at room temperature allows the detailed analysis of concentration dependent changes in bulk wild‐type(wt)‐GFP spectra, as well as the determination of the dimerization constant of GFP. This information expands the use of GFP to that of a spectral probe for protein concentration. We determined energy differences between the chromophore ground states in the monomer and the dimer and reconstructed part of the potential energy surface.
Gene Expression within Cell‐Sized Lipid Vesicles
Authors: Nomura Shin‐ichiro M. , Tsumoto Kanta , Hamada Tsutomu , Akiyoshi Kazunari , Nakatani Yoichi , Yoshikawa Kenichi
Published: November 2003

Functional protein synthesis was observed in cell‐sized lipid vesicles following encapsulation of a gene‐expression system. Expression of rsGFP (red‐shifted green fluorescent protein) within individual vesicles was observed by fluorescence microscopy. Interestingly, at the early stage of the reaction, the expression efficiency inside the vesicle was remarkably higher than that in the solution outside. The synthesized rsGFP in individual vesicles is safe from attack by proteinase K added to the external aqueous solution. Studies on cell‐sized vesicles expressing protein should contribute to a fundamental understanding of certain aspects of living systems and will be useful for practical applications, such as the construction of microreactors.
Chemical and Enzymatic Synthesis of Fluorinated‐Dehydroalanine‐Containing Peptides
Authors: Zhou Hao , Schmidt Dawn M. Z. , Gerlt John A. , van der Donk Wilfred A.
Published: November 2003

Michael acceptors have long been recognized as reactive functionalities that may link a biologically active molecule to its cellular target. 1,2‐Dehydro amino acids are potential Michael acceptors present in a large number of natural products, but their reactivity is modulated by the deactivating nature of the α‐amino group engaged in an amide bond. We describe here the preparation of 3‐fluoro‐1,2‐dehydroalanine moieties within peptides that significantly enhance the reactivity of the Michael acceptor. Two different routes were designed to access these compounds, one relying on chemical means to introduce the desired functionality and the second taking advantage of a peptide epimerase. In the chemical approach, the fluoro‐Pummerer reaction of cysteine derivatives afforded 3‐fluorocysteine residues that were oxidized to the corresponding sulfoxides, followed by thermolytic elimination to provide the desired 3‐fluorodehydroalanines. The mechanism of the fluoro‐Pummerer reaction was investigated and several possible pathways were ruled out. The enzymatic approach utilized the dipeptide epimerase YcjG from Escherichia coli. Difluorinated alanine was incorporated at the C terminus of a dipeptide by chemical means. The resulting peptide proved to be a substrate for YcjG, which catalyzed fluoride elimination to provide the 3‐fluorodehydroalanine‐containing peptide. Mechanistic investigations showed that fluoride elimination occurred faster than epimerization and at a rate close to that of epimerization of Ala‐Ala.
Real‐Time Polymerase Chain Reaction
Authors: Wilhelm Jochen , Pingoud Alfred
Published: November 2003

Real‐time PCR is the state‐of‐the‐art technique to quantify nucleic acids for mutation detection, genotyping and chimerism analysis. Since its development in the 1990s, many different assay formats have been developed and the number of real‐time PCR machines of different design is continuously increasing. This review provides a survey of the instruments and assay formats available and discusses the pros and cons of each. The principles of quantitative real‐time PCR and melting curve analysis are explained. The quantification algorithms with internal and external standardization are derived mathematically, and potential pitfalls for the data analysis are discussed. Finally, examples of applications of this extremely versatile technique are given that demonstrate the enormous impact of real‐time PCR on life sciences and molecular medicine.
On the Mechanism of the Laccase–Mediator System in the Oxidation of Lignin
Authors: Crestini Claudia , Jurasek Lubo , Argyropoulos Dimitris S.
Published: November 2003

In an effort to elucidate the role of phenolic and non‐phenolic lignin subunits in a laccase mediator (LM) system, vanillyl alcohol was oxidized with laccase in the presence and absence of the mediator 1‐hydroxybenzotriazol (HBT). Furthermore, the role of phenolic, aliphatic hydroxyl, and carboxylic acid moieties in lignin degradation was elucidated by selectively blocking them. The modified samples were then subjected to laccase and laccase–HBT treatments. On the basis of this data it was possible to establish the role of this mediator. HBT mediates the oxidation of lignin by inducing side‐chain oxidation and oxygen‐addition products rather than oxidative coupling reactions.
Gas‐Phase Activation and Reaction Dynamics of Chiral Ion–Dipole Complexes
Authors: Filippi Antonello , Speranza Maurizio
Published: November 2003

A family of enantiomerically pure oxonium ions, that is O‐protonated 1‐aryl‐1‐methoxyethanes, has been generated in the gas phase by the (CH3)2Cl+ methylation of the corresponding 1‐arylethanols. Some information on their reaction dynamics was obtained from a detailed kinetic study of their inversion of configuration and dissociation. The activation parameters of the inversion reaction are found to obey two different isokinetic relationships depending upon the nature and the position of the substituents in the oxonium ions. In contrast, the activation parameters of the dissociation reaction obey a single isokinetic relationship. The inversion and dissociation rate constants do not follow simple linear free‐energy relationships. This complicated kinetic picture has been rationalized in terms of different activation dynamics in gaseous CH3Cl, which, in turn, determine the reaction dynamics of the oxonium ion. When the predominant activation of the oxonium ion involves resonant energy exchange from the 1015 cm−1 CH3 rocking mode of unperturbed CH3Cl, the inversion reaction proceeds through the dynamically most favored TS, characterized by the unassisted CαO bond elongation. When, instead, the activation of the oxonium ions requires the formation of an intimate encounter complex with CH3Cl, the inversion reaction takes place via the energetically most favored TS, characterized by multiple coordination of the CH3OH moiety with the Hα and Hortho atoms of the benzylic residue. The activation dynamics operating in the intimate encounter complex with CH3Cl is also responsible for the dissociation of most selected oxonium ions.
Facial Selectivity of the (R)‐1,3‐Dimethyl‐1‐Cyclohexyl Cation in the Gas Phase
Authors: Filippi Antonello
Published: November 2003

The model reaction between the (R)‐1,3‐dimethyl‐1‐cyclohexyl cation (I) and methanol has been investigated under gas‐phase radiolytic conditions (750 Torr; 25–120 °C) with the aim of evaluating the intrinsic factors that govern the facial selectivity of biased carbocations. The peculiarity of the experimental approach allows the formation of different CH318OH⋅I ionic adducts. Subsequent conversion of these adducts to give the corresponding E/Z covalent products follows different reaction coordinates, which are characterized by their own activation parameters. On the grounds of density functional theory (DFT) results, several [CH3OH⋅I] structures have been located on the relevant potential‐energy surface (PES). The experimental results point to a gas‐phase facial selectivity, which is mainly governed by entropic factors that arise as a result of the occurrence of different noncovalent ion–molecule “facial adducts” (FA). The formation of FAs may also play an important role in both the reaction dynamics and the positional selectivity. The present results cannot be interpreted by any of the models based on solution‐phase experiments.
Structural Study of the Thermal and Photochemical Spin States in the Spin Crossover Complex [Fe(phen)2(NCSe)2]
Authors: MacLean Elizabeth J. , McGrath Catherine M. , O'Connor Charles J. , Sangregorio Claudio , Seddon Jon M. W. , Sinn Ekk , Sowrey Frank E. , Teat Simon J. , Terry Ann E. , Vaughan Gavin B. M. , Young Nigel A.
Published: November 2003

The first structural data for [Fe(phen)2(NCSe)2] (obtained using the extraction method of sample preparation) in its high‐spin, low‐spin and LIESST induced metastable high‐spin states have been recorded using synchrotron radiation single crystal diffraction. The space group for all of the spin states was found to be Pbcn. On cooling from the high‐spin state (HS‐1) at 292 K through the spin crossover at about 235 K to the low‐spin state at 100 K (LS‐1) the iron coordination environment changed to a more regular octahedral geometry and the FeN bond lengths decreased by 0.216 and 0.196 Å (FeN(phen)) and 0.147 Å (FeN(CSe)). When the low‐spin state was illuminated with visible light at about 26 K, the structure of this LIESST induced metastable high‐spin state (HS‐2) was very similar to that of HS‐1 with regards to the Fephen bond lengths, but there were some differences in the bond lengths in the Fe–NCSe unit between HS‐1 and HS‐2. When HS‐2 was warmed in the dark to 50 K, the resultant low‐spin state (LS‐2) had an essentially identical structure to LS‐1. In all spin states, all of the shortest intermolecular contacts (in terms of van der Waals radii) involved the NCSe ligand, which may be important in describing the cooperativity in the solid state. The quality of the samples was confirmed by magnetic susceptibility and IR measurements.
Aromaticity of Benzene in the Facial Coordination Mode: A Structural and Theoretical Study
Authors: Wadepohl Hubert , Entrialgo Castaño Maria
Published: November 2003

The effects of facial coordination of benzene to a trinuclear transition‐metal cluster have been studied by structure correlation and DFT calculational methods. Data taken from the X‐ray crystal structures of twelve complexes [{(η‐C5H4R″)Co}3(μ3‐η2:η2:η2‐C6H4RR′)]1 b–1 mwere analyzed by using standard statistical methods. The prototypal facial arene ligand is considerably expanded with respect to free benzene and shows a small but highly significant Kekulè distortion (dCC=1.42, 1.45 Å). DFT MO calculations were carried out on the model complexes [{(η‐C5H5)M}3(μ‐η2:η2:η2‐C6H6)]1 a(M=Co),2(M=Rh), and3(M=Ir). Ring currents in the facial benzene and apical cyclopentadienyl ligands have been assessed by nucleus independent chemical shift (NICS) calculations. Compared to the free ligand (with the optimizedD6hstructure as well as withD3hand aC3vgeometries similar to that in the prototypal facial arene), facial benzene exhibits somewhat reduced but still substantial cyclic electron delocalization (CED). The calculated order of CED is benzene ∼[(CO)3Cr(η‐C6H6)]4 > 1 > 2 > 3.
Nanomorphology of Polymer Frameworks and their Role as Templates for Generating Size‐Controlled Metal Nanoclusters
Authors: Artuso Frederica , D'Archivio Angelo A. , Lora Silvano , Jerabek Karel , Králik Milan , Corain Benedetto
Published: November 2003

The microporous (gel‐type) functional resin co‐poly‐N,N‐dimethylacrylamide (DMAA) (88 % mol)/methacrylic acid (MAA) (8 % mol)/N,N′‐methylenebisacrylamide (MBAA) (4 % mol) (MPIF(H)) is employed as the hosting framework for the production of resin‐supported Pd0 nanoclusters. The obtained composite MPIF−Na+/Pd0 is prepared upon reducing, in ethanol, MPIF−Pd2+0.5, obtained upon previous homogeneous dispersion of “Pd2+” inside the resin particles (XRMA control) through ion‐exchange. Metal nanoclusters appear to be size‐controlled (2.0±0.2 nm) and are seen to reasonably fit the predominant resin “nanopores” diameter, determined in ethanol (3.2 nm) by means of inverse steric exclusion chromatography (ISEC).
Controlling Multivalent Interactions in Triply‐Threaded Two‐Component Superbundles
Authors: Balzani Vincenzo , Clemente‐León Miguel , Credi Alberto , Lowe James N. , Badjić Jovica D. , Stoddart J. Fraser , Williams David J.
Published: November 2003

We have investigated the 1H NMR spectra, the absorption spectra, the fluorescence spectra and decays, and the electrochemical properties of i) a tritopic receptor in which three benzo[24]crown‐8 macrorings are fused onto a triphenylene core, ii) a trifurcated trication wherein three dibenzylammonium ions are linked 1,3,5 to a central benzenoid core, and iii) their 1:1 adduct which constitutes a triply‐threaded, two‐component supramolecular bundle. X‐Ray crystallography has established the precise geometry of this paucivalent recognition motif in the solid state. In addition to [N+‐H⋅⋅⋅O] hydrogen bonding and [C‐H⋅⋅⋅O] interactions between the NH2+ centers on the three dibenzylammonium ion containing arms of the trication and the three crown ether rings in the tritopic receptor, there is a stabilizing [π⋅⋅⋅π] stacking interaction between the two aromatic cores. Mass spectrometry and 1H NMR spectroscopy have confirmed the integrity of the 1:1 adduct beyond the solid state, provided the solvents are relatively apolar (e.g., chloroform and acetonitrile). The intense fluorescence emissions of the two recognition components are quenched upon association with the concomitant appearance of a lower energy, broad fluorescence band originating from the π–π stacking in the 1:1 adduct of the aromatic cores in the two matching components. Titration experiments, including Job plots, establish the 1:1 stoichiometry of the adduct, an observation which is also confirmed by electrochemical experiments. The electrochemical results show that, both in the tritopic receptor and in the superbundle itself, the first oxidation process is associated with the hexaalkoxytriphenylene core. The successive oxidation processes of the peripheral dioxybenzene units are affected by charge‐transfer interactions in the tritopic receptor, whereas, in the superbundle, such units are not interacting. In acetonitrile solution, dethreading/rethreading of the 1:1 adduct can be controlled quantitatively by addition of base and acid. Dethreading and rethreading is also observed by 1H NMR spectroscopy when dimethylsulfoxide is added to a solution of the 1:1 adduct in equal volumes of acetonitrile and chloroform. A trifurcated trication where methyl groups are located on the para positions of the three dibenzylammonium ions, which are linked 1,3,5 to the neutral benzenoid core, has been employed to demonstrate that dethreading of the 1:1 adduct involves doubly‐threaded and singly‐threaded species, that is, the paucivalent site is dismembered in a sequence of logical steps involving stable intermediates. This molecular recognition system is a rare example of a supramolecular entity based on a cooperative binding motif that can be switched on and off by chemical means.
Photomechanical Control of the Electronic Properties of Linear π‐Conjugated Systems
Authors: Jousselme Bruno , Blanchard Philippe , Gallego‐Planas Nuria , Levillain Eric , Delaunay Jacques , Allain Magali , Richomme Pascal , Roncali Jean
Published: November 2003

Photodynamic molecular architectures have been synthesized by covalent fixation of a photoisomerizable dimethylazobenzene group at two fixed points of conformationally flexible π‐conjugated quater‐ and sexithiophene chains. Theoretical geometry optimization shows, in excellent agreement with crystallographic structures, that the mode of fixation of the azo group plays a determining role in the geometry of the final molecular architecture and on its ability to perform the expected photoinduced molecular motion. Thus, covalent fixation ofmeta‐dimethylazobenzene on a quaterthiophene chain results in a conformationally locked system in which photoisomerization of the azo group is hindered. However, the experimental results of optical,1H NMR spectroscopic, and electrochemical investigations show that when an azobenzene group is connected at theparapositions of the phenyl rings,trans‐to‐cisphotoisomerization of the azo group induces a conformational transition and dimensional changes in the underlying π‐conjugated oligothiophene chain. These experimental results unequivocally show that the photochemically induced geometrical changes produce in turn an increase in the HOMO level and a narrowing of the HOMO–LUMO gap. This therefore provides the first evidence of photomechanical control of the electronic properties of linear π‐conjugated systems.
Resorcinarenes as Templates
Authors: Gibb Bruce C.
Published: November 2003

Metal ions are superb at templating the synthesis of small macrocycles that are decorated with Lewis basic sites. However, for the synthesis of larger macrocycles, or the synthesis of macrocycles devoid of an array of Lewis basic sites, metal ions are less useful. Here we demonstrate that resorcinarenes can be used as templates to engender the efficient formation of large crown ethers. A three step process of 1) tethering moieties to the template, 2) linking those moieties, and 3) then cleaving off the template leads to the efficient formation of a family of aromatic crown ethers. If adaptable, this approach will prove useful for the construction of macrocycles that are hard to obtain from a step‐wise synthesis.
Activation and Functionalization of White Phosphorus at Rhodium: Experimental and Computational Analysis of the [(triphos)Rh (η1:η2‐P4RR′)]Y Complexes (triphos=MeC(CH2PPh2)3; R=H, Alkyl, Aryl; R′=2 Electrons, H, Me)
Authors: Barbaro Pierluigi , Ienco Andrea , Mealli Carlo , Peruzzini Maurizio , Scherer Otto J. , Schmitt Guido , Vizza Francesco , Wolmershäuser Gotthelf
Published: November 2003

Thermal reaction of white phosphorus with [(triphos)RhH3] (1) in THF affords [(triphos)Rh(η1:η2‐P4H)] (2), triphos=MeC(CH2PPh2)3. Similar complexes [(triphos)Rh(η1:η2‐P4R)] (R=Me (7), Et (8), Ph (9)) also form at lower temperature by the reaction of P4 and [(triphos)Rh(R)(η2‐C2H4)] with elimination of ethene. In contrast, a double‐insertion process follows the reaction of [(triphos)Rh(H)(η2‐C2H4)] and P4 to generate tetraphosphido ethyl complex 8. Compounds 2, 7, 8 and 9 are thermally unstable and eventually decompose into the cyclotriphosphorus complex [(triphos)Rh(η3‐P3)] (3) plus other unidentified phosphorus‐containing species. Otherwise, PH3 or PH2R is generated in the presence of H2. The formation of PH3 and 3 is quantitative starting from the precursor 2. The electrophilic attack of MeOTf or HBF4 on the P4R ligand in the complexes 2, 7–9 is regioselective, and yields a cationic product of formula [(triphos)Rh(η1:η2‐P4RR′)]+. The direct attack on the substituted p‐R phosphorus atom is demonstrated by crossing experiments. Complexes of the latter type have been isolated in the solid state for the combinations R=H and R′=Me (11) or R=Ph and R′=Me (12). The latter species, [(triphos)Rh(η1:η2‐P4PhMe′)]OTf⋅2 CH2Cl2 (OTf=triflate), has been characterised by X‐ray methods. The geometry at the metal is better described as a trigonal bipyramidal than pseudo‐octahedral. In fact, the P4RR′ unit acts as a bidentate ligand with its exocyclic PR2 donor group and the endocyclic, dihapto‐coordinated PP linkage. The latter group lies in the equatorial plane, in a similar way to a classic olefin ligand that is coordinated to a butterfly‐shaped L4M fragment (M=d8). DFT calculations on a model of 2 and all possible protonated isomers confirm that double substitution at the exocyclic P‐donor positions of the open P4 unit is energetically favoured. A multinuclear and multidimensional NMR analysis confirms that this structure is maintained in solution for both the parent and the protonated compounds.
Coordination Solids via Assembly of Adaptable Components: Systematic Structural Variation in Alkaline Earth Organosulfonate Networks
Authors: Côté Adrien P. , Shimizu George K. H.
Published: November 2003

A family of alkaline earth organosulfonate coordination solids is reported. In contrast to more typical crystal engineering approaches, these solids are sustained by the assembly of building blocks that are coordinatively adaptable rather than rigid in their bonding preferences. The ligand, 4,5‐dihydroxybenzene‐1,3‐disulfonate, L, progressively evolves from a 0D, 1D, 2D, to a 3D microporous network with the Group II cations Mg2+, Ca2+, Sr2+, and Ba2+, (compounds 1–4), respectively. This trend in dimensionality can be explained by considering factors such as hard–soft acid–base principles and cation radii, a rationalization which follows salient crystal engineering principles. The selective gas sorption properties of the microporous 3D network [Ba(L)(H2O)]⋅H2O, 4, with different gaseous guests are also presented.
Trimeric Perfluoro‐ortho‐phenylenemercury: A Versatile Lewis Acidic Host
Authors: Haneline Mason R. , Taylor Robert E. , Gabbaï François P.
Published: November 2003

Trimeric perfluoro‐ortho‐phenylenemercury (1) constitutes one of the simplest trifunctional Lewis acidic hosts. In addition to cooperative effects arising from the proximity of the mercury(II) centers, the electron‐withdrawing properties of the backbone and the accessibility of the electrophilic sites lead to the facile complexation of neutral and electron rich substrates. The planarity of the structure as well as its overall polarizability compounded with relativistic effects at mercury also permits the occurrence of non‐covalent interactions and accounts for the tendency of this compound to form cofacial dimers. Collectively, the Lewis acidic properties of 1 as well as its ability to engage in non‐covalent interactions can be held responsible for its ability to form extended binary supramolecular stacks with arenes. The photoluminescence observed in some of these supramolecular complexes corresponds to the phosphorescence of the aromatic substrate and indicate the occurrence of a mercury heavy atom effect.
Sensitized Near‐Infrared Emission from Complexes of YbIII, NdIII and ErIII by Energy‐Transfer from Covalently Attached PtII‐Based Antenna Units
Authors: Shavaleev Nail M. , Moorcraft Lucy P. , Pope Simon J. A. , Bell Zöe R. , Faulkner Stephen , Ward Michael D.
Published: November 2003

A series of dinuclear platinum(II)–lanthanide(iii) complexes has been prepared in which a square‐planar PtII unit, either [(PPh3)2Pt(pdo)] (H2pdo=5,6‐dihydroxyphenanthroline) or [Cl2Pt(dppz)] [dppz=2,3‐bis(2‐pyridyl)pyrazine], is connected to a {Ln(dik)3} unit (“dik”=a 1,3‐diketonate ligand). The mononuclear complexes [(PPh3)2Pt(pdo)] and [Cl2Pt(dppz)] both have external, vacant N,N‐donor diimine‐type binding sites that react with various [Ln(dik)3(H2O)2] units to give complexes [(PPh3)2Pt(μ‐pdo)Ln(tta)3] (series A; Htta=thenoyltrifluoroacetone), [Cl2Pt(μ‐dppz)Ln(tta)3] (series B); and [Cl2Pt(μ‐dppz)Ln(btfa)3] (series C; Hbtfa=benzoyltrifluoroacetone); in all of these the lanthanide centres are eight‐coordinate. The lanthanides used exhibit near‐infrared luminescence (Nd, Yb, Er). Crystal structures of members of each series are described. In all complexes, excitation into the Pt‐centred absorption band (at 520 nm for series A complexes; 440 nm for series B and C complexes) results in characteristic near‐IR luminescence from the Nd, Yb or Er centres in both the solid state and in CH2Cl2, following energy‐transfer from the Pt antenna chromophore. This work demonstrates how d‐block‐derived chromophores, with their intense and tunable electronic transitions, can be used as sensitisers to achieve near‐infrared luminescence from lanthanides in suitably designed heterodinuclear complexes based on simple bridging ligands.
Phosphodiester Cleavage of Ribonucleoside Monophosphates and Polyribonucleotides by Homo‐ and Heterodinuclear Metal Complexes of a Cyclohexane‐Based Polyamino–Polyol Ligand
Authors: Jancsó Attila , Mikkola Satu , Lönnberg Harri , Hegetschweiler Kaspar , Gajda Tamás
Published: November 2003

The ability of the dinuclear complexes of tdci [1,3,5‐trideoxy‐1,3,5‐tris(dimethylamino)‐cis‐inositol] to promote the cleavage of the phosphodiester bonds of nucleoside 2′,3′‐cyclic monophosphates, dinucleoside monophosphates and polyribonucleotides has been studied. The homodinuclear copper(II) and zinc(II) complexes efficiently promote the hydrolysis of cyclic nucleotides. The second‐order rate constant (k2≈0.44 M−1 s−1) estimated for the cleavage of 2′,3′‐cAMP induced by dinuclear copper(II) complexes is about 107 times greater than that for the hydroxide‐ion‐catalysed reaction. The complex selectively cleaves the 2′OP bond of 2′,3′‐cUMP and forms the 3′‐product in 91 % yield. An equimolar mixture of copper(II), zinc(II) and tdci proved to be more efficient than either of the binary systems: a 7–20‐fold rate enhancement was observed for the cleavage of 2′,3′‐cNMP substrates. The half‐life for the hydrolysis of 2′,3′‐cAMP decreased from 300 days to five minutes at 25 °C when the concentration of each of the three components was 2.5 mM. In contrast to the copper(II) or zinc(II) complexes of tdci, the heterodinuclear species promoted the hydrolysis of several dinucleoside monophosphates. For two ApA isomers, cleavage of the 3′,5′‐bond was about 6.5 times faster than cleavage of the 2′,5′‐bond. On the basis of the kinetic data, a trifunctional mechanism is suggested for the heterodinuclear‐complex‐promoted cleavage of the phosphodiester bond. Double Lewis acid activation occurs when the metal ions bind to the phosphate oxygen atoms. In particular, a metal‐bound hydroxide ion serves as a general base or a nucleophilic catalyst, and, presumably, a zinc(II)‐bound aqua ligand behaves as a general acid and facilitates the departure of the leaving alkoxide group. The effect of the complexes on the hydrolysis of poly(U), poly(A) and type III native RNA was also investigated, and, for the first time, kinetic data on the cleavage of the phosphodiester bonds of polyribonucleotides by a dinuclear complex was obtained.
Cover Picture: Trimeric Perfluoro‐ortho‐phenylenemercury: A Versatile Lewis Acidic Host (Chem. Eur. J. 21/2003)
Authors: Haneline Mason R. , Taylor Robert E. , Gabbaï François P.
Published: November 2003

The cover picture shows how trimeric perfluoro‐ortho‐phenylene mercury (center), one of the simplest trifunctional Lewis acidic hosts, interacts with organic molecules to afford various adducts. The planarity of this trinuclear complex as well as its overall polarizability compounded with relativistic effects at mercury permits the occurrence of noncovalent interactions and accounts for the tendency of this compound to form cofacial dimers as observed in the structure of the acetone adduct (top left). With a triply coordinated acetone molecule, the structure of this adduct also substantiates the cooperative effects that arise from the proximity and accessibility of the mercury centers. The complexation of arenes, such as benzene (bottom left) and naphthalene (bottom right), also occurs and leads to the formation of binary stacks in which the arene establishes multiple linkages with the mercury centers of the trifunctional Lewis acids. In addition to displaying unusual coordination environment, the arene units present in those stacks exhibit remarkable phosphorescent properties. For more details, see the paper by F. P. Gabbaï, R. E. Taylor, and M. R. Haneline on p. 5188 ff.
Children's attitudes to parents', teachers' and employers' perceptions of term‐time employment
Authors: Leonard Madeleine
Published: November 2003

This article is concerned with examining working children's perceptions of how adults in a range of different settings view their employment. In particular, the article explores how participation in the labour market influences adult‐child relationships within the home, at school and at work. Children interact with adults across a variety of different spheres. Dependence and independence permeate children's relationships with adults in different social settings. Entry to the labour market and access to earnings promotes responsibility among children and encourages self‐reliance. The purpose of the article is to assess the extent to which these traits affect children's interaction with adults within and across the social spaces of the home, school and place of employment. Copyright © 2003 John Wiley & Sons, Ltd.