bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphological Control of Tapered and Multi‐Junctioned Carbon Tubular Structures
Authors: Bhimarasetti G. , Sunkara M.K. , Graham U.M. , Davis B.H. , Suh C. , Rajan K.
Published: October 2003

Thin walled, carbon tubular structures (see Figure and also cover) with varying inner diameters in the form of nozzles, straight tubes, tube‐on‐cones, and funnels have been synthesized by in‐situ control of gallium‐carbon wetting behavior using gas phase chemistry. In addition, carbon tubular structures with large internal diameters have been coalesced during growth to create Y‐junctions suitable for micro/nano‐fluidic applications.
Nanoparticle Inks for Directed Assembly of Three‐Dimensional Periodic Structures
Authors: Li Q. , Lewis J.A.
Published: October 2003

Colloidal inks, comprised of concentrated barium titanate nanoparticle gels, were directly assembled via a robotically controlled deposition technique. 3D periodic lattices were created through layer‐by‐layer patterning of parallel rods, whose periodicity far exceeded the dimension of the nanoparticle building blocks. The Figure shows a scanning electron microscopy image of a 3D periodic lattice (top view).
Coating BaTiO3 Nanolayers on Spherical Ni Powders for Multilayer Ceramic Capacitors
Authors: Lee J.‐Y. , Lee J.‐H. , Hong S.‐H. , Lee Y.K. , Choi J.‐Y.
Published: October 2003

A nanometer‐thick BaTiO3 coating layer has been prepared on spherical Ni. The BaTiO3 coating effectively retards the low‐temperature sintering between Ni particles and improves the resistance against Ni oxidation. This technology provides a useful tool to fabricate highly integrated multilayer ceramic capacitors (MLCCs). The Figure shows the nanometer‐thick BaTiO3 hollow spheres after core (Ni) removal.
Synthesis of Hierarchical Superstructures Consisting of BaCrO4 Nanobelts in Catanionic Reverse Micelles
Authors: Shi H. , Qi L. , Ma J. , Cheng H. , Zhu B.
Published: October 2003

A variety of novel BaCrO4 nanostructures, such as nanobelts and their tree‐like superstructures (see Figure), have been synthesized in a unique catanionic reverse micelle system by simply changing the mixing ratio between the anionic and cationic surfactants. This synthetic method provides a simple, novel method for direct assembly of inorganic nanobelts into hierarchical superstructures.
Does chromosome 22 have anything to do with sex determination: Further studies on a 46,XX,22q11.2 del male
Authors: Erickson Robert P. , Skinner Steve , Jacquet Hélène , Campion Dominique , Buckley Patrick G. , Mantripragada Kiran K. , Dumanski Jan P.
Published: October 2003

Several years ago, we presented a patient with true hermaphroditism and partial duplication of chromosome 22 and no evidence of SRY (Aleck et al. [1999: Am J Med Genet 85:2–4]). Recently a 46,XX male with velocardiofacial syndrome and a deletion of 22q11.2 and no evidence of Y chromosomal loci in blood DNA was reported (Phelan et al. [2003: Am J Med Genet 116A:77–79]). We have restudied this patient as he enters puberty. Because chromosomal deletions sometimes involve micro rearrangements of nearby material, we have extensively studied this individual's chromosome 22 looking for evidence of any gene duplication. We studied a number of variable number tandem repeat (VNTR) loci along chromosome 22 in the patient and both parents. Normal Mendelian inheritance of the VNTRs was found. We then used quantitative multiplex PCR of short fluorescent fragments (QMPSF) to delineate the 22q11.2 deletion in this patient (Jacquet et al. [2002: Hum Molec Genet 11:2243–2249]) and found a pattern of deletion typical of the velocardiofacial DiGeorge syndrome. Finally, the patient's DNA has been analyzed using a full coverage human chromosome 22 genomic microarray (array comparative genomic hybridization [CGH]) for evidence of rearrangements outside the classical velocardiofacial DiGeorge associated deletion (Buckley et al. [2002: Hum Molec Genet 11:3221–3229]). The array‐CGH profile of this patient confirms the deletion encompassing the typically deleted region associated with the velocardiofacial DiGeorge syndrome and provides no support for additional gene copy number aberrations on 22q. Thus, there is no evidence of any chromosome 22 trisomic material. In this case, the rare events of sex reversal and 22q11.2 deletion may have occurred together by chance. © 2003 Wiley‐Liss, Inc.
Is Jaffe–Campanacci syndrome just a manifestation of neurofibromatosis type 1?
Authors: Colby Randall S. , Saul Robert A.
Published: October 2003

This article describes four patients with non‐ossifying fibromas (NOFs) and multiple café‐au‐lait spots. Two of the patients were diagnosed with NOFs when they presented with a femur fracture. The other two patients were diagnosed with NOFs because of complaints of leg problems. In addition, axillary freckles and Lisch nodules were present in all four patients and multiple cutaneous neurofibromas in two patients. These four patients fulfilled the diagnostic criteria for neurofibromatosis type 1 (NF1) and also have been diagnosed with Jaffe–Campanacci syndrome. We propose that Jaffe–Campanacci syndrome is a manifestation of NF1 and suggest that patients with NF1 should have more rigorous radiographic screening of the long bones during early adolescence or adulthood to determine the presence or absence of NOFs. Appropriate intervention (exercise restriction, bracing, and/or surgery) might decrease the long‐term disability associated with Jaffe–Campanacci syndrome. © 2003 Wiley‐Liss, Inc.
Normal cognition and behavior in a Smith‐Lemli‐Opitz syndrome patient who presented with Hirschsprung disease
Authors: Mueller C. , Patel S. , Irons M. , Antshel K. , Salen G. , Tint G.S. , Bay C.
Published: October 2003

Smith‐Lemli‐Opitz syndrome (SLOS) is an autosomal recessive disorder of cholesterol biosynthesis. It is caused by mutations in the gene encoding the enzyme 7‐dehydrocholesterol Δ7‐reductase (DHCR7), which catalyzes the final step in cholesterol biosynthesis, usually resulting in cholesterol deficiency. We report a 3.5‐year‐old girl who has cognition in the low average range and normal behavior, but in whom molecular studies identified two missense mutations in DHCR7: V326L and F284L. She was born at term following an uncomplicated pregnancy and delivery, and presented at 12 days of age with poor feeding, abdominal distention, and jaundice. Colonic biopsy was consistent with Hirschsprung disease. On physical examination she had mild ptosis, a long philtrum, mild micrognathia, a short, upturned nose, and subtle 2,3 syndactyly. Her 7‐dehydrocholesterol (7‐DHC) level was markedly elevated at 8.7 mg/dl (normal 0.10 ± 0.05), and her cholesterol level was normal at 61 mg/dl (normal for newborn period 50–80 mg/dl). Karyotype analysis was normal, 46,XX. Breast milk feeding was initiated and continued for 18 months. Cholesterol supplementation was implemented at 100 mg/kg/day at 3 months, which resulted in increased cholesterol levels and reduced dehydrocholesterol levels. Neuropsychological testing has shown functioning in the low average range, between the 14th and 18th centiles when compared to peers. This is markedly higher than most children with SLOS. She has no behavioral problems. MRI and MRS testing of the brain revealed no structural abnormalities. This is in contrast to a recently reported case by Prasad et al. [2002: Am J Med Genet 108:64–68] with a mild phenotype, behavioral problems, and abnormal MRI, who is compound heterozygote for both a null and missense mutation. Our case suggests that patients with severe feeding disorders with or without Hirschprung disease and postnatal onset microcephaly may warrant screening for SLOS. © 2003 Wiley‐Liss, Inc.
Genetic syndromes among individuals with mental retardation
Authors: Stevenson Roger E. , Procopio‐Allen Ashley M. , Schroer Richard J. , Collins Julianne S.
Published: October 2003

Individuals with mental retardation more commonly have malformations and other structural anomalies than individuals without mental retardation. In many cases, the associated anomalies comprise recognizable syndromes caused by genetic or environmental insults. To co‐occurrence of structural anomalies with mental retardation thus assists in the diagnostic evaluation, particularly in infants and young children. The coexistence of structural and mental abnormalities also suggests that both originated in the embryonic period of development. © 2003 Wiley‐Liss, Inc.
Toriello–Carey syndrome: Delineation and review
Authors: Toriello Helga V. , Carey John C. , Addor Marie‐Claude , Allen William , Burke Leah , Chun Nicole , Dobyns William , Elias Ellen , Gallagher Renata , Hordijk Roel , Hoyme Gene , Irons Mira , Jewett Tamison , LeMerrer Martine , Lubinsky Mark , Martin Rick , McDonald‐McGinn Donna , Neumann Luitgard , Newman William , Pauli Richard , Seaver Laurie , Tsai Anna , Wargowsky David , Williams Marc , Zackai Elaine
Published: October 2003

Toriello and Carey [1988: Am J Med Genet 31:17–23] first described a syndrome with component manifestations of corpus callosum agenesis, unusual facial appearance, Robin sequence, and other anomalies. This was termed the Toriello–Carey syndrome by Lacombe et al. [1992: Am J Med Genet 42:374–376]. Since then, 11 reports describing 16 additional children have been published; in addition, we have had the opportunity to review over 30 unpublished cases. However, for various reasons, only 25 of the unpublished patients were included in this review. Based on this total, we can begin to better delineate this syndrome, as well as provide some information on natural history. © 2003 Wiley‐Liss, Inc.
X‐linked cubitus valgus with mental retardation and typical face
Authors: Jones Kenneth Lyons , Kosaki Kenjiro , Hall Bryan D.
Published: October 2003

In 1973, Jones and Smith described two maternal male first cousins with a similar pattern of malformation, including mental retardation, cubitus valgus, and unusual facies. The purpose of this report is to describe three additional cases, a 10‐year‐old male and his 30‐year‐old maternal uncle and an unrelated 15‐year‐old boy, bringing to five the total number of individuals with this disorder. The principal features include moderate mental retardation, mild microcephaly, a short philtrum, deep‐set, downslanting palpebral fissures, multiple nevi, and striking cubitus valgus. Documentation of this disorder in two maternal male first cousins as well as in a male and his maternal uncle support an X‐linked recessive mode of inheritance for this condition. © 2003 Wiley‐Liss, Inc.
The hedgehog signaling network
Authors: Cohen, M. Michael
Published: October 2003

In the hedgehog signaling network, mutations result in various phenotypes, including, among others, holoprosencephaly, nevoid basal cell carcinoma syndrome, Pallister‐Hall syndrome, Greig cephalopolysyndactyly, Rubinstein‐Taybi syndrome, isolated basal cell carcinoma, and medulloblastoma. Active Hedgehog ligand is double lipid modified with a C‐terminal cholesterol moiety and an N‐terminal palmitate. Transport active Hedgehog from the signaling cell to the responding cell occurs through three mechanisms: 1). formation of multimeric Hedgehog which makes it soluble; 2). function of Dispatched in releasing the lipid‐anchored protein from the signaling cell; and 3). movement across the plasma membrane of the responding cell by Tout‐velu‐dependent synthesis of heparan sulfate proteoglycan. In the responding cell, active Hedgehog binds to its receptor Patched, a 12‐pass transmembrane protein, which frees Smoothened, an adjacent 7‐pass transmembrane protein, for downstream signaling. Patched and Smoothened may shuttle oppositely between the plasma membrane and endocytic vesicles in response to active Hedgehog ligand. In downstream signaling, Cubitus interruptus (Gli proteins in vertebrates), Costal 2, Fused, and Suppressor of Fused form a tetrameric complex. Cubitus interruptus is a bifunctional transcription regulator. In the absence of active Hedgehog ligand, a truncated transcriptional repressor is generated that binds target genes and blocks their transcription. In the presence of active Hedgehog ligand, a full length transcriptional activator binds target genes and upregulates their transcription. Target genes include Wingless (Wnt gene family in vertebrates), Decapentaplegic (Bone Morphogenetic Proteins in vertebrates), and Patched. The upregulation of Patched expression, resulting in Patched protein at the cell membrane, sequesters Hedgehog and limits its spread beyond the cells in which it is produced. Thus, a balance is created by the antagonism of Hedgehog and Patched, whose relative concentrations alternate with respect to each other. Many more factors that are essential for the hedgehog signaling network are also discussed: Megalin, Rab23, Hip, GAS1, PKA, GSK3, CK1, Slimb, SAP18, and CBP. © 2003 Wiley‐Liss, Inc.
GTF2I hemizygosity implicated in mental retardation in Williams syndrome: Genotype–phenotype analysis of five families with deletions in the Williams syndrome region
Authors: Morris Colleen A. , Mervis Carolyn B. , Hobart Holly H. , Gregg Ronald G. , Bertrand Jacquelyn , Ensing Gregory J. , Sommer Annemarie , Moore Cynthia A. , Hopkin Robert J. , Spallone Patricia A. , Keating Mark T. , Osborne Lucy , Kimberley Kendra W. , Stock A. Dean
Published: October 2003

Most individuals with Williams syndrome (WS) have a 1.6 Mb deletion in chromosome 7q11.23 that encompasses the elastin (ELN) gene, while most families with autosomal dominant supravalvar aortic stenosis (SVAS) have point mutations in ELN. The overlap of the clinical phenotypes of the two conditions (cardiovascular disease and connective tissue abnormalities such as hernias) is due to the effect of haploinsufficiency of ELN. SVAS families often have affected individuals with some WS facial features, most commonly in infancy, suggesting that ELN plays a role in WS facial gestalt as well. To find other genes contributing to the WS phenotype, we studied five families with SVAS who have small deletions in the WS region. None of the families had mental retardation, but affected family members had the Williams Syndrome Cognitive Profile (WSCP). All families shared a deletion of LIMK1, which encodes a protein strongly expressed in the brain, supporting the hypothesis that LIMK1 hemizygosity contributes to impairment in visuospatial constructive cognition. While the deletions from the families nearly spanned the WS region, none had a deletion of FKBP6 or GTF2I, suggesting that the mental retardation seen in WS is associated with deletion of either the centromeric and/or telomeric portions of the region. Comparison of these five families with reports of other individuals with partial deletions of the WS region most strongly implicates GTF2I in the mental retardation of WS. © 2003 Wiley‐Liss, Inc.
A new recessive syndrome with VATER‐like defects, pulmonary hypertension, abnormal ears, blue sclera, laryngeal webs, and persistent growth deficiency
Authors: Braddock Stephen R.
Published: October 2003

VATER association is a term frequently used to describe children with multiple malformations. However, occasionally these children have malformations that are not typical of VATER defects and may represent unique multiple malformation syndromes with specific prognoses and recurrence risks. Two siblings with a heretofore previously undescribed multiple malformation syndrome are presented whose features include vertebral defects, cardiac abnormalities, pulmonary hypertension, laryngeal webs, blue sclerae, and persistent growth deficiency. Autosomal recessive inheritance is suggested. These cases suggest that other individuals labeled VATER association with multiple other defects should be reviewed more closely to give accurate prognosis and recurrence risk information to families. © 2003 Wiley‐Liss, Inc.
Reciprocal translocation associated with multiple exostoses in seven members of a three generation family and discovered through an infertile male
Authors: Pramparo Tiziano , Gregato Giuliana , De Gregori Manuela , Friso Alessandra , Clementi Maurizio , Ardenghi Patrizia , Rocchi Mariano , Zuffardi Orsetta , Tenconi Romano
Published: October 2003

We report a four generations family with multiple exostoses segregating with a reciprocal translocation t(8;19)(q24.11;q13.13) in 8 members of three generations. FISH investigations detected a breakage of the dosage‐sensitive EXT1 gene. Although three members of the family died perinatally from unknown causes and one carrier had four spontaneous abortions, the translocation was discovered only when the cytogenetic analysis was requested in an affected male because of oligozoospermia. In fact, it is well known that infertile males may be carriers of reciprocal or Robertsonian translocations with a higher frequency than the general population. This family stresses the importance of requesting the cytogenetic analysis in all cases in which a dominant disease segregates with repeated miscarriages and/or newborn deaths of unknown cause. © 2003 Wiley‐Liss, Inc.
Moebius sequence and hypogonadotrophic hypogonadism
Authors: Jennings Juliet E. , Costigan Colm , Reardon William
Published: October 2003

A distinct form of Moebius sequence is associated with hypogonadotrophic hypogonadism. There have been five such cases to date. We now add a further case with detailed neurologic, endocrine, and autopsy findings and offer a hypothesis drawing parallels with the already established basis of hypogonadotrophic hypogonadism in the X‐linked form of Kallman syndrome. © 2003 Wiley‐Liss, Inc.
A summarization system for Chinese news from multiple sources
Authors: Chen Hsin‐Hsi , Kuo June‐Jei , Huang Sheng‐Jie , Lin Chuan‐Jie , Wung Hung‐Chia
Published: October 2003

This article proposes a summarization system for multiple documents. It employs not only named entities and other signatures to cluster news from different sources, but also employs punctuation marks, linking elements, and topic chains to identify the meaningful units (MUs). Using nouns and verbs to identify the similar MUs, focusing and browsing models are applied to represent the summarization results. To reduce information loss during summarization, informative words in a document are introduced. For the evaluation, a question answering system (QA system) is proposed to substitute the human assessors. In large‐scale experiments containing 140 questions to 17,877 documents, the results show that those models using informative words outperform pure heuristic voting‐only strategy by news reporters. This model can be easily further applied to summarize multilingual news from multiple sources.
Selective Recognition of Configurational Substates of Zinc Cyclam by Carboxylates: Implications for the Design and Mechanism of Action of Anti‐HIV Agents
Authors: Liang Xiangyang , Weishäupl Michael , Parkinson John A. , Parsons Simon , McGregor Pamela A. , Sadler Peter J.
Published: October 2003

The interaction of metal cyclams with carboxylate groups is thought to play an important role in their binding to the CXCR4 chemokine receptor and in their anti‐HIV activity. Here we report the synthesis of acetate, phthalate, perchlorate and chloride complexes of ZnII cyclam (1,4,8,11‐tetraazacyclotetradecane). The X‐ray crystal structures of [Zn(cyclam)(phthalate)]n(CH3OH)2n and [Zn(cyclam)(H2O)2](OAc)2 contain octahedral ZnII centres. Phthalate acts as a bridging ligand in the former complex, binding through monodentate carboxylate groups, and giving rise to infinite chains in the lattice together with extensive hydrogen bonding between carboxylate donor oxygen atoms and amine and methanol acceptor atoms. The uncoordinated acetate groups and the aqua ligand in the acetate complex are also involved in a rich network of hydrogen bonds and this may account for the unusually long ZnO distance (2.27 Å). In both crystalline complexes, the macrocycle adopts the trans‐III (S,S,R,R) configuration. 1D 1H NMR spectra of all four complexes have been fully assigned by a combination of 2D [1H, 1H] COSY and TOCSY, and [1H, 13C] and [1 H, 15N] HSQC NMR data. In aqueous solution, the stable trans‐III configuration found in the solid‐state equilibrates slowly (hours at 298 K) with trans‐I (R,S,R,S) and cis‐V (R,R,R,R) configurations. The trans‐III configuration is predominant in aqueous solution for both the chloride and perchlorate complexes, but for the acetate and phthalate complexes, the cis‐V configuration dominates. Carboxylate groups appear to stabilize the cis‐V configuration in solution through ZnII coordination and hydrogen bonding. Titration of the chloride ZnII–cyclam complex with acetate confirmed that carboxylates strongly induce formation of the cis‐V configuration. This implies that carboxylates can exert a strong influence over configurational selectivity. Cyclam NH hydrogen bonding is prevalent both in the solid state and in solution, and is relevant to the anti‐HIV activity of ZnII and other metal cyclam complexes and to their ability to recognize the CXCR4 transmembrane co‐receptor.
Photoresponsive Supramolecular Systems: Self‐Assembly of Azodibenzoic Acid Linear Tapes and Cyclic Tetramers
Authors: Rakotondradany Felaniaina , Whitehead M. A. , Lebuis Anne‐Marie , Sleiman Hanadi F.
Published: October 2003

A new strategy to effect photoinduced control over molecular self‐assembly is reported. This strategy uses the reversible trans–cis photoisomerization of a novel azobenzene system, where the trans‐ and cis‐forms self‐assemble into dramatically different higher‐order structures. The trans‐azobenzene form of this molecule associates into infinite hydrogen‐bonded linear tapes, while the cis‐azobenzene form undergoes hydrogen‐bonded self‐assembly into cyclic tetramers. This results in a second level of association, where the cis‐hydrogen‐bonded supramolecular cycles ultimately form long, rod‐like aggregates through stacking interactions.
Folding versus Self‐Assembling
Authors: Li Alexander D. Q. , Wang Wei , Wang Li‐Qiong
Published: October 2003

Model foldable polymers with sequences of rigid hydrophobic chromophores and flexible hydrophilic tetra(ethylene glycol) were synthesized and used as a paradigm for studying molecular‐folding and self‐assembly phenomena. Our results demonstrate that intramolecular association or folding prevails over intermolecular interaction or self‐assembling in the concentration region from 1 μM to 0.1 M. Importantly, folded polymeric nanostructures have absorption and fluorescence properties that are distinct from those of unfolded polymers or free monomers. We hypothesize that the origins of folding and self‐assembly come from interactions between molecular units, and that the key parameter that regulates the on‐and‐off of such interactions is the distance R separating the two molecular units. Each molecular unit produces a characteristic force field, and when another molecular unit enters this field, the probability that the two units will interact increases significantly. A preliminary estimate of the radius of such a force field for the perylene tetracarboxylic diimide chromophore is about 90–120 Å. As a result, phenomena associated with folding or self‐assembly of molecular species are observed when these conditions are met in solution.
pH‐Sensitive Modulation of the Second Hydration Sphere in Lanthanide(III) Tetraamide–DOTA Complexes: A Novel Approach to Smart MR Contrast Media
Authors: Woods Mark , Zhang Shanrong , Ebron Von Howard , Sherry A. Dean
Published: October 2003

The lanthanide(III) complexes of three tetraamide DOTA bearing pyridyl, phenolic and hydroxypyridyl substituents have been studied by NMR, luminescence and cyclic voltammetry. The relaxivity profiles of the gadolinium complexes of the pyridyl and phenolic ligands were flat and essentially the same between pH 2 and 8. The hydroxypyridyl ligand, however, exhibited two regions of enhanced relaxivity. The small relaxivity enhancement (25 %) at lower pH (pH 2–4) has been attributed to an increase in the prototropic exchange of the coordinated water molecule while the slightly larger enhancement (84 %) at higher pH (pH 6–9) reflects deprotonation of the ligand amide protons. Deprotonation of the amides results in the formation of an intramolecular acid–base pair interaction with the phenolic protons and this, in turn, causes a highly organized second hydration sphere to come into effect, thereby increasing the relaxivity. The water relaxivity of the Gd3+‐hydroxypyridyl complex is further enhanced upon binding to serum albumin.
Link between biological signaling and increased enantioseparations of acids using glycopeptide antibiotics
Authors: Reilly J. , Sanchez‐Felix M. , Smith N.W.
Published: October 2003

The vancomycin analog A82846B has been shown to provide excellent selectivity as a chiral recognition agent for some acidic test analytes in capillary electrophoresis (CE) and high‐performance liquid chromatography (HPLC). In both modes A82846B outperforms vancomycin as a chiral selector. A82846B has enhanced antibacterial activity data in comparison to vancomycin, which is probably due to the increased dimerization constant of over 100 in magnitude in comparison to vancomycin. The link between the electrophoretic and chromatographic separations observed and the biological activity of A82846B is discussed. Dimerization of A82846B in solution was proposed as a theory as to why A82846B gave such enhanced separations for acidic racemates. Further literature and experimental studies support the theory. Chirality 15:731–742, 2003. © 2003 Wiley‐Liss, Inc.
Absolute configuration determination of chiral molecules in the solution state using vibrational circular dichroism
Authors: Freedman Teresa B. , Cao Xiaolin , Dukor Rina K. , Nafie Laurence A.
Published: October 2003

Advances in the measurement, calculation, and application of vibrational circular dichroism (VCD) for the determination of absolute configuration are described. The purpose of the review is to provide an up‐to‐date perspective on the capability of VCD to solve problems of absolute stereochemistry for chiral molecules primarily in the solution state. The scope of the article covers the experimental methods needed for the accurate measurement of VCD spectra and the theoretical steps required to systematically deduce absolute configuration. Determination of absolute configuration of a molecule by VCD requires knowledge of its conformation or conformational distribution, and hence VCD analysis necessarily provides solution‐state conformation information, in many cases available by no other method, as an additional benefit. Comparisons of the advantages and limitations of VCD relative to other available chiroptical methods of analysis are also presented. Chirality 15:743–758, 2003. © 2003 Wiley‐Liss, Inc.
Photoreaction of a racemate proceeding through radical or ion pairs. The effect of circularly polarized light on the enantiomeric excess of recovered reactant
Authors: Pagni Richard M. , Bartmess John
Published: October 2003

A simple theory has been developed to explain how circularly polarized light will affect the outcome of a photoreaction of a racemic substrate proceeding through ion pairs or radical pairs. One can calculate the enantiomeric excess and amount of recovered substrate at any stage of the reaction. Chirality 15:772‐776, 2003. © 2003 Wiley‐Liss, Inc.
G‐quartet self‐assembly under osmotic pressure: remote control by vesicle shrinking rather than stress
Authors: Sakai Naomi , Matile Stefan
Published: October 2003

Does osmotic pressure stimulate assembly or disassembly of supramolecules in vesicles? Self‐assembly was conceivable as intravesicular response to osmotic shrinking upon application of extravesicular overpressure, whereas disassembly was conceivable as a response to bilayer stress in hyperosmotic vesicles. Self‐assembly of guanosine 5′‐monophosphates (GMPs) into G‐quartets was selected to investigate the nature of remote control of supramolecular chemistry within vesicles by osmotic pressure. Using circular dichroism spectroscopy to selectively detect G‐quartets, we found that extravesicular overpressure stimulates intravesicular self‐assembly, whereas underpressure stimulates disassembly. G‐quartet self‐assembly by osmotic pressure exhibited ion‐selective metal‐cation templation, as expected. The key conclusions are that supramolecular chemistry within vesicles is governed by vesicle shape rather than vesicle stress and that detection of osmotic pressure by CD spectroscopy is an interesting alternative to the commonly used methods based on fluorescence self‐quenching. Chirality 15:766–771, 2003. © 2003 Wiley‐Liss, Inc.
Using stereocartography for predicting efficacy of stereoinduction by chiral catalysts
Authors: Lipkowitz Kenny B. , Sakamoto Taka , Stack Jonathan
Published: October 2003

A computational method called stereocartography is used to examine regions around chiral catalysts that are most stereoinducing during Diels‐Alder reactions. Geometries and atomic charges of catalysts are first generated quantum mechanically. The transition state of the reaction being catalyzed is then computed quantum mechanically and those enantiomeric transition states are used as probes to determine where around the catalyst stereoinduction is optimal. A description of how to treat catalysts with multiple conformations is given. In this article seven catalysts containing a variety of ligand motifs and metals were evaluated. The hypothesis that the region of maximum stereoinduction must be spatially coincident with the site of chemistry for a catalyst to be efficient is upheld. Chirality 15:759–765, 2003. © 2003 Wiley‐Liss, Inc.
A novel L‐neopentylglycine derivative as auxiliary for copper‐catalyzed asymmetric Michael reactions
Authors: Christoffers Jens , Schuster Katja
Published: October 2003

L‐Neopentylglycine diethylamide (4a). was prepared from the new unnatural amino acid L‐neopentylglycine (1). The utilization of amide 4a as a chiral auxiliary in the copper(II)‐catalyzed asymmetric Michael reaction was investigated in comparison with L‐valine diethylamide (4b). Cyclic β‐oxocarboxylates 7 react with 4a and 4b to give the respective enaminoesters 8, which were converted with methyl vinyl ketone (9) in the presence of 10 mol% Cu(OAc)2 · H2O at room temperature in acetone to yield the optically active Michael addition products (R)‐10a, b with high selectivity independent of the starting enamine. In the case of the seven‐membered β‐oxocarboxylate 7c, however, the valine‐derived enamine 8f led to higher enantioselectivity for product 10c. Despite the bulkiness of the neopentyl group, the isopropyl group with an α‐branch has a better stereoinducing effect. Chirality 15:777–782, 2003. © 2003 Wiley‐Liss, Inc.
Enantioseparation of chiral alcohols by complex formation and subsequent supercritical fluid extraction
Authors: Székely Edit , Simándi Béla , Fogassy Elemér , Kemény Sándor , Kmecz Ildikó
Published: October 2003

The very first application of supercritical fluid extraction (SFE) on enantioseparation of alcohols is discussed. Resolution of three chiral alcohols (trans‐2‐chloro‐cyclohexanol, trans‐2‐bromo‐cyclohexanol, and trans‐2‐iodo‐cyclohexanol) were performed by partial complexation with (−)‐O,O′‐dibenzoyl‐(2R,3R)‐tartaric acid monohydrate (DBTA). DBTA formed diastereomeric complexes with all S,S‐enantiomers stable enough to extract the unreacted alcohols with supercritical carbon dioxide. Resolution efficiency increased with the size of halogen substituents, and by the proper selection of molar ratio, pure (−)‐R,R‐trans‐2‐iodo‐cyclohexanol (ee > 99%, yield: 39%) or (+)‐S,S‐trans‐2‐iodo‐cyclohexanol (ee = 98%, yield: 8%) were prepared in one process step. Achieved resolution efficiency values were much higher in all resolution procedures than in any other known enantioseparation of these racemic compounds. The developed method offers an environmentally friendly, efficient alternative of currently applied resolution processes, also on a preparative scale. Chirality 15:783–786, 2003. © 2003 Wiley‐Liss, Inc.
Absolute configuration of (−)‐2,6‐dimethyl‐10‐(p‐tolyl)‐2,6(E)‐undecadiene from Cistus monspeliensis
Authors: Pietsch Martin , König Wilfried A. , Joulain Daniel
Published: October 2003

(−)‐2,6‐Dimethyl‐10‐(p‐tolyl)‐2,6(E)‐undecadiene (1) is a major constituent in the essential oil of Cistus monspeliensis, an aromatic shrub common in Mediterranian countries. 1 was isolated by column chromatography, subjected to ozonolyses, and the absolute configuration was determined by enantioselective gas chromatographic correlation with the ozonolysis product of the sesquiterpene hydrocarbon ar‐curcumene with known absolute configuration. Chirality 15:794–798, 2003. © 2003 Wiley‐Liss, Inc.
Effects from hydrogen bonding and rigidity on selectivity in tartaric acid‐based chiral selectors for enantioselective liquid chromatography
Authors: Oxelbark Joakim , Sellén Inga‐Britt
Published: October 2003

Tartaric acid‐based selectors 1 ((R,R)‐O,O′‐Bis(dimethylbenzoyl)‐N,N′‐diallyl‐N,N′‐dimethyl tartaramide) and 2 ((R,R)‐N‐allyl‐O,O′‐bis(dimethylbenzoyl) tartarimide) were synthesized, immobilized on silica, and evaluated as chiral stationary phases in enantioselective chromatography. Comparison with the commercially available column Kromasil‐CHI‐1, based on selector 3 ((R,R)‐O,O′‐Bis(dimethylbenzoyl)‐N,N′‐diallyl tartaramide) resulted in the conclusion that amide NH functions are essential to chiral recognition on this sorbent. Furthermore, NH functions contribute significantly to retention of analytes except for alcohols. It was also found that flexibility of the benzoyl moieties is essential to selectivity. Chirality 15:787–793, 2003. © 2003 Wiley‐Liss, Inc.
Trennmethoden für Graphit‐Nanoröhren
Authors: Groß Michael
Published: October 2003

Stellen Sie sich eine einzelne Schicht von graphitartig angeordneten Kohlenstoffatomen vor — ein perfektes Wabenmuster aus lauter gleichseitigen Sechsecken. Wenn man diese Ebene zu einem Zylinder aufrollt, erhält man Graphit‐Nanoröhren. Je nachdem, in welcher Richtung man gerollt hat, werden diese Röhren metallische oder Halbleiter‐Eigenschaften haben.
Kleinste Chips für Handys
Authors: Borchard‐Tuch Claudia
Published: October 2003

Seit ihrer Einführung vor über 20 Jahren sind Mobiltelefone auf eine handliche Größe geschrumpft. Hierzu hat die Miniaturisierung ihrer wichtigsten Bauelemente — der Chips — entscheidend beigetragen. Damit verbunden sind deutlich gestiegene Ansprüche an deren strukturelle Homogenität und Oberflächenstruktur sowie die Reinheit der Elektronik‐Chemikalien.
Cytoarchitecture, topography, and descending supraspinal projections in the anterior central nervous system of Branchiostoma lanceolatum
Authors: Ekhart Daniel , Korf Horst‐Werner , Wicht Helmut
Published: October 2003

The central nervous system (CNS) of the chordate amphioxus (Branchiostoma lanceolatum) is divisible into a spinal cord and an anterior portion in some ways equivalent to the brain of craniates. The present study reports on this anterior portion, with respect to general topography, cytoarchitecture, and cells that give rise to descending supraspinal projections. The anterior portion of the CNS is located adjacent to the first four myomeres and rostral to the first giant cell of Rohde—it can be divided into several regions that differ with respect to their cytoarchitecture. The tip of the neural tube is formed by a small anterior vesicle; caudally, there is a much larger region that is intercalated between the anterior vesicle and the first cell of Rohde. This intercalated region, in turn, consists of three subdivisions: an anterior subdivision adjacent to myomere 1, an intermediate subdivision adjacent to myomere 2, and a posterior one adjacent to myomeres 3 and 4. After injections of tracers into the spinal cord a large number of cells were labeled in the intercalated region. The spinally projecting cells were not evenly distributed: their number was decreased in the center of the intermediate subdivision. These subdivisions, which have previously not been noted, may be aligned with the expression domains of regulatory genes (e.g., AmphiOtx, AmphiHox) in larval lancelets. In particular, the center of the intermediate subdivision may correspond to a “nonHox/nonOtx” domain in the CNS of the larva. A similar embryonic domain occurs in the brain of craniates in which it develops into the isthmus cerebri that separates mid‐ and hindbrain. A close structural and topographical inspection of the corresponding region of adult lancelets reveals, however, that this region is not the homolog of an isthmus, but a uniquely derived, autapomorphic feature of lancelets. J. Comp. Neurol. 466:319–330, 2003. © 2003 Wiley‐Liss, Inc.
Aging of the human cerebellum: A stereological study
Authors: Andersen Birgitte Bo , Gundersen Hans Jørgen G. , Pakkenberg Bente
Published: October 2003

Cerebella from 19 normal Caucasian males, ages 19–84 years, were studied using stereological methods. Cerebellum was divided into four different regions: the anterior and posterior lobe, the vermis, and the flocculonodular lobe. Total volume of the cerebellar cortex and white matter, cerebellar surface area, total Purkinje and granule cell number, and the distribution of the volumes of the Purkinje cells and their nuclei were estimated in all four regions. The global white matter was reduced by 26% with age; the mean volume of the Purkinje cell body was decreased by 33% with no decrease in the volume of the Purkinje cell nuclei. A tendency towards a 16% total cerebellar volume loss was seen without a concomitant neuron loss. No global Purkinje or granule cell loss was detected with age, total Purkinje cell number being 28 × 106 (coefficient of variation, CV = 0.16) and total granule cell number 109 × 109 (CV = 0.17). However, a significant change was observed with age in the anterior lobe, where a selective 40% loss of both Purkinje and granule cells was found. Furthermore, a 30% loss of volume, mostly due to a cortical volume loss, was recorded in the anterior lobe, which is predominantly involved in motor control. J. Comp. Neurol. 466:356–365, 2003. © 2003 Wiley‐Liss, Inc.
Local commissural interneurons integrate information from intersegmental coordinating interneurons
Authors: Mulloney Brian , Hall Wendy M.
Published: October 2003

The information that coordinates movements of swimmerets on different segments of the crayfish abdomen is conducted by interneurons that originate in each abdominal ganglion. These interneurons project axons to neighboring ganglia and beyond. To discover the anatomy of these axons in their target ganglia, we used Neurobiotin and dextran‐Texas Red microelectrodes to fill them near their targets. Coordinating axons coursed through these target ganglia close to the midline and extended only a few short branches that did not approach the lateral neuropils. Two of the three types of coordinating axons made direct synaptic connections with a class of local commissural interneurons that relayed the information to targets in the swimmeret pattern‐generating circuits. These commissural interneurons, named here ComInt 1 neurons, followed a particular route to cross the midline and reach their targets. ComInt 1 neurons were nonspiking; they received EPSPs from the coordinating axons near the midline and transmitted this information to their targets in the lateral neuropils using graded transmission. The output of each ComInt 1 was restricted to a single local circuit and had opposite effects on the power‐stroke and return‐stroke motor neurons driven by that circuit. ComInt 1 neurons were direct postsynaptic targets of both descending and ascending coordinating axons that originated in other anterior and posterior ganglia. Because of phase differences in the impulses in these different coordinating axons, their signals arrived simultaneously at each ComInt 1. We discuss these findings in the context of alternative models of the intersegmental coordinating circuit. J. Comp. Neurol. 466:366–376, 2003. © 2003 Wiley‐Liss, Inc.
Consequences of interspecies antennal imaginal disc transplantation on organization of olfactory glomeruli and pheromone blend discrimination
Authors: Vickers Neil J. , Poole Kathy , Linn Charles E.
Published: October 2003

The antennal imaginal disc was transplanted between male larvae of two different heliothine moth species, Heliothis virescens (HV) and Helicoverpa zea (HZ). Males of these species respond to distinct pheromone blends, have different peripheral and central olfactory neuron specificities, as well as distinct arrangements of antennal lobe olfactory glomeruli, in the specialized male macroglomerular complex (MGC). After pupal development and adult eclosion, unilateral (with one antennal disc left intact) and bilateral antennal transplant males were assayed in a wind tunnel to both species' pheromone blends to determine their ability to discriminate between the two signals. The postmetamorphic developmental effects of interspecific transplantation upon the primary olfactory centers in the moth brain were then examined in these same individuals. Behavioral tests showed that both types of unilateral transplant continued to exhibit upwind anemotactic flight to the normal recipient blend with occasional flights to the donor blend. In contrast, bilateral transplants preferred the HV pheromone blend regardless of the direction of transplant, with some males of each type also responding to the HZ blend. Neuroanatomic evaluation of the MGC revealed that the donor arrangement of MGC glomeruli was induced in 73% HZ donor to HV recipient transplants and 56% of the reciprocal transplant. Surprisingly, several V‐Z bilateral transplant males responded to both HV and HZ pheromone blends and had two HV MGC structures. This behavioral outcome was unexpected, because responses to the HV blend are mediated by inputs that are normally antagonistic to HZ males and the normal HV antenna lacks olfactory receptor neurons capable of responding to the essential minor pheromone component of the HZ blend. These data indicate a plasticity in developmental pathways regulating the expression of peripheral olfactory receptor neurons and in the glomerular processing of species‐specific olfactory information. J. Comp. Neurol. 466:377–388, 2003. © 2003 Wiley‐Liss, Inc.
Stereologic analysis of estrogen receptor alpha (ERα) expression in rat hypothalamus and its regulation by aging and estrogen
Authors: Chakraborty Tandra R. , Hof Patrick R. , Ng Laurie , Gore Andrea C.
Published: October 2003

The estrogen receptor alpha (ERα) in the hypothalamus plays important roles in the regulation of reproductive development, physiology, and behavior. However, the expression of the ERα may change during aging or in response to varying estrogen levels. The present study measured changes in the numbers of ERα‐expressing cells in specific hypothalamic and preoptic nuclei of ovariectomized female Sprague‐Dawley rats at three ages (young [3–4 months], middle‐aged [10–12 months], or old [24–26 months]) and with or without estrogen replacement. Numbers of ERα‐immunoreactive neurons were quantified in four regions relevant to reproductive function: the anteroventral periventricular nucleus (AVPV), medial preoptic nucleus (MPN), arcuate nucleus (ARH), and ventromedial nucleus (VMN), using an unbiased stereologic approach. In the AVPV and VMN, significant age‐related increases in the numbers of ERα‐expressing cells from the middle‐aged to the old group were detected, and no differences were observed in the MPN and ARH, indicating that ERα neuron number is maintained or even elevated during aging. No significant effects of estrogen on ERα cell number were detected in any of the four regions studied. Therefore, ERα cell number in the rat hypothalamus and preoptic area changes with aging in a region‐specific manner. J. Comp. Neurol. 466:409–421, 2003. © 2003 Wiley‐Liss, Inc.
Nanoscopic Structure of a Metallo‐supramolecular Polyelectrolyte–Amphiphile Complex, Elucidated by X‐ray Scattering and Molecular Modeling
Authors: Meister Annette , Förster Günter , Thünemann Andreas F. , Kurth Dirk G.
Published: October 2003

A combination of molecular modeling and X‐ray scattering was used to elucidate the structure of the metallosupramolecular polyelectrolyte–amphiphile complex (PAC) self‐assembled from FeII, 1,4‐bis(2,2′:6′,2″‐terpyridin‐4′‐yl)benzene, and dihexadecyl phosphate (DHP). An approximate structure of the semi‐ordered material was derived from the analysis of the X‐ray scattering data. The experimental data provided sufficient input for obtaining a useful starting configuration for molecular modeling. Various models of the supramolecular architecture are presented and discussed in terms of their total energies and scattering patterns. In an iterative approach each level of the structural hierarchy was refined until satisfactory agreement of calculated and experimental scattering patterns was reached. The remarkable sensitivity of the simulated scattering curves to even the smallest structural changes at all length scales restricts the arbitrariness of modeling. The final model of PAC consists of flat lamellae of alternating strata of interdigitated DHP monolayers and nematically ordered polyelectrolyte chains.
Locating Dynamic Species with X‐ray Crystallography and NMR Spectroscopy: Acetone in p‐tert‐Butylcalix[4]arene
Authors: Udachin Konstantin A. , Enright Gary D. , Ratcliffe Christopher I. , Ripmeester John A.
Published: October 2003

The exact location and orientation of dynamic species in structural studies continues to be a serious challenge, yet it is of paramount importance in modeling guest–host interactions so as to improve our understanding of the multiple weak interactions that govern many chemical and biological processes. The acetone guest in the tBC (p‐tert‐butylcalixarene) host presents such a challenge, as initial guest positions obtained from single crystal X‐ray diffraction (XRD) are incompatible with the 2H NMR spectrum. A detailed consideration of the diffraction data showed that more complicated structural models could be constructed that were consistent with the NMR data and still yielded satisfactory diffraction residuals. These models agree that one acetone methyl group is inserted into the deep cavity, and that it exchanges with the second methyl group outside. The outside methyl group in turn can switch positions with the carbonyl group, but the distribution of the methyl and carbonyl groups over the two sites is not equal. One factor that poses additional difficulty in deciding between models is whether the actual space group is tetragonal (P4/n), or twinned monoclinic (P2/n). All of the structural models considered here disagree substantially with the one proposed in an earlier publication.
Electric‐Field‐Induced Capillary Attraction between Like‐Charged Particles at Liquid Interfaces
Authors: Langevin Dominique
Published: October 2003

Birds of a feather, flock together. In a recent paper in Nature, Nikolaides and co‐workers discuss the much debated issue of capillary attraction between like‐charged particles at liquid interfaces. They show quite convincingly that dipolar electric fields induce surface charges that distort the interface; the dipolar interaction causes repulsion, while the interfacial distortion causes capillary attraction. The behaviour observed has broad implications for interfacial and colloid chemistry, when charged particles are present at fluid interfaces.