bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Novel Core Region, Lacking Heptose and Phosphate, of the Lipopolysaccharide from the Gram‐Negative Bacterium Pseudomonascichorii (Pseudomonadaceae RNA Group 1)
Authors: De Castro Cristina , Molinaro Antonio , Nunziata Rosa , Lanzetta Rosa , Parrilli Michelangelo , Holst Otto 
Published: May 2004

AbstractThe extracted lipopolysaccharides (LPSs) fraction of the plant‐pathogenic bacterium Pseudomonas cichorii contained two different molecules, the first of them an LPS possessing an O‐specific polysaccharide made up of four 2‐acetamido‐2,6‐dideoxy sugars linked linearly in a tetrasaccharide repeating unit. The structure of the second LPS component is reported here: it was of the rough form and contained a novel type of core region. The rough form LPS of Ps. cichorii was de‐O‐acylated by mild hydrazinolysis and then de‐N‐acylated with hot 4 M KOH. The oligosaccharide representing the complete carbohydrate backbone of the LPS was isolated by high‐performance anion‐exchange chromatography. Its structural characterization employed compositional and methylation analyses, matrix‐assisted laser desorption/ionisation mass spectrometry and 1H, 13C and 31P NMR spectroscopy, with application of various 1D and 2D experiments. The carbohydrate backbone of this core region consisted of a hexasaccharide that contained no heptoses, being made up of L‐Rhap, D‐GlcpN and D‐GalpN, besides the characteristic α‐(2→4)‐linked 3‐deoxy‐D‐manno‐oct‐2‐ulosonic acid (Kdo) disaccharide. The first Kdo residue linking the core region to the lipid A was substituted by a GalpN residue. This core region thus represents one of the rather few cases in which this position is not substituted by a manno‐configured sugar. The structure of the LPS carbohydrate backbone is shown in Scheme 1. If not stated otherwise, sugars were D‐configured pyranoses. Kdo is 3‐deoxy‐D‐manno‐oct‐2‐ulosonic acid. The lipid A backbone is N‐ and O‐acylated in the LPSs. − Molecular modelling studies of the LPS carbohydrate backbone and of some of its parts were performed, yielding a preferred conformation that was surprisingly inflexible between the two Kdo residues. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis of Imino Sugar Scaffolds for the Generation of Glycosidase Inhibitor Libraries
Authors: La Ferla Barbara , Bugada Piergiuliano , Cipolla Laura , Peri Francesco , Nicotra Francesco 
Published: May 2004

AbstractWe have synthesized imino sugar scaffolds bearing two points of diversity — the stereocenters located in α positions relative to the nitrogen atom — and three points of orthogonal derivatization — a carboxylic function, the primary hydroxy group, and the ring nitrogen atom. The key steps in the synthetic approach are the chain elongation of aldehyde 5 with the formation of an α,β‐unsaturated ester, the Michael addition of an amine, and the final cyclization. This strategy leads to the preparation of different N‐substituted imino sugar analogues having both α and β structures and of both D and L stereochemistry. Different derivatives have been prepared from the scaffolds we obtained. The carboxymethyl group was coupled to the amino function of different amino acids to afford compounds 30−34, while the selectively accessible primary hydroxy group has been substituted with an azido group to afford compounds 24−26. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Characterisation of the α‐(1→3) Homopolymer of L‐glycero‐D‐manno‐Heptose Units Isolated from the O‐Chain Polysaccharide of Agrobacterium radiobacter
Authors: De Castro Cristina , Sturiale Luisa , Parrilli Michelangelo 
Published: May 2004

AbstractThis paper provides the first report of the molecular primary structure of the O‐chain produced from A. radiobacter group M2−1. The repeating unit was determined, by means of chemical and spectroscopical analyses, to have the following structure: [3)‐α‐L‐glycero‐D‐manno‐heptose‐(1→]n. The relevant feature of this structure is represented by the particular residue involved: L‐glycero‐D‐manno‐heptose. This monosaccharide is almost ubiquitous in Gram‐negative bacteria, but it is exclusively located in the Core region and only in one other case has it is reported as an O‐chain constituent. The knowledge of the chemical structure of the O‐chain of A. radiobacter will be useful for comprehending the bacterium‐host recognition mechanism at the molecular level. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Lewis Acid‐Mediated Diastereoselective Reduction ofN‐Protected β‐Amino Ketones: Influence of the Nature of the Metal Atom and of the Nitrogen Protecting Group
Authors: Bartoli Giuseppe , Bartolacci Massimo , Cortese Manuela , Marcantoni Enrico , Massaccesi Massimo , Pela Roberto , Sambri Letizia 
Published: May 2004

AbstractLewis acid‐mediated chelation and non‐chelation control is one of the most fundamental and practical concepts in modern organic chemistry. Extension of these concepts to the reduction of differentN‐protected α‐substituted β‐amino ketones indicated that diastereoselectivity in the hydride addition step is strongly dependent on the nature of the metal atom and on the type of protecting group. Strongly chelating TiCl4and an electron‐rich nitrogen protecting group promoted thesyndiastereoselectivity in noncoordinating solvents (CH2Cl2) at −78 °C with BH3·py as reducing agent. On the other hand, a Lewis acid as such as CeCl3and a bulkyN‐protecting group gave an excess of theanti‐diastereomer in coordinating solvents (THF) at the same temperature with lithium borohydride (LiBH4) as reducing agent. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Glycosylation of Cyclitols: Synthesis of Neamine‐Type Aminoglycosides
Authors: Verhelst Steven H. L. , Magnée Lisette , Wennekes Tom , Wiedenhof Wouter , van der Marel Gijsbert A. , Overkleeft Herman S. , van Boeckel Constant A. A. , van Boom Jacques H. 
Published: May 2004

AbstractIn this paper, a glycosylation‐based approach towards novel aminoglycoside analogues is presented. Three different cyclitol building blocks were condensed with different thioglycosides to give, after removal of the protective groups, several neamine‐type analogs varying in the positioning and the stereochemistry of the amino functions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
An Efficient Ruthenium‐Catalyzed Formal Synthesis of (−)‐Isoavenaciolide
Authors: Labeeuw Olivier , Blanc Delphine , Phansavath Phannarath , Ratovelomanana‐Vidal Virginie , Genêt Jean‐Pierre 
Published: May 2004

AbstractA formal synthesis of (−)‐isoavenaciolide (1) by two different routes is reported. The first approach, leading to a key precursor 2 of (−)‐isoavenaciolide (1), features the stereoselective construction of the three contiguous stereogenic centers by Evans diastereoselective reduction (d.e. = 80%) of β‐hydroxy ketone 8. In the more efficient second approach, the nine‐step sequence leading to the key precursor 2 involves sequential ruthenium‐catalyzed hydrogenation reactions of β‐keto ester 4 and β‐hydroxy ketone 14 to form the two hydroxyl groups with an excellent control of the anti stereochemistry (d.e. = 99%). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis and Reactivity of a New Nonacarbon Chain Carboxonium Salt − Access to a New Class of Streptocyanine Dyes
Authors: Izquierdo Albert , Guieu Valérie , Gornitzka Heinz , Madaule Yves , Payrastre Corinne 
Published: May 2004

AbstractA new highly reactive nonacarbon chain carboxonium salt 1 was synthesized. It leads, by action of various amines and hydrazone, to a new class of symmetrical nonacarbon chain streptocyanine dyes 3−5. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Cover Picture: Synthesis of a Novel Cyclic Chlorophyll Hetero‐Dyad as a Model Compound for Stacked Chlorophylls Found in Photosynthetic Systems (Eur. J. Org. Chem. 11/2004)
Authors: Kosaka Nobuo , Tamiaki Hitoshi 
Published: May 2004

AbstractThe cover picture shows the molecular structure of a synthetic doubly‐linked cyclic chlorophyll “hetero”‐dyad (left) and its symbolic image using natural leaves (right). Two chlorophyllous κ‐systems are stereospecifically and covalently bonded with two different linkers and close to each other in a nearly parallel fashion. The present synthetic strategy has great potential for the systematic preparation of various cyclic chlorophyll hetero‐dyads. Details of the synthesis and characterization are described in the article by N. Kosaka and H. Tamiaki on p. 2325 ff.
Orthogonal separations of nicotine and nicotine‐related alkaloids by various capillary electrophoretic modes
Authors: Marsh Alex , Clark Brian J. , Altria Kevin D. 
Published: May 2004

AbstractThe migration behaviour of nicotine and related tobacco alkaloids was investigated using three different capillary electrophoretic (CE) modes. Novel separations were achieved both using microemulsion electrokinetic chromatography (MEEKC) and nonaqueous CE (NACE). Improved resolution compared to previous studies was obtained using free‐solution CE (FSCE). Each technique resulted in different, orthogonal separation selectivity. The suitability of each method for application to the analysis of nicotine lozenges is discussed. The FSCE method was applied to the analysis of nicotine lozenges due to its compatibility with an established lozenge extraction solvent. The method used gave good injection precision and linearity. Good agreement of CE and high‐performance liquid chromatography (HPLC) results was obtained. The CE method is therefore considered suitable for the quantitative determination of nicotine in nicotine lozenges.
Genome‐based proteomics
Authors: Agaton Charlotta , Uhlén Mathias , Hober Sophia 
Published: May 2004

AbstractProtein‐protein interactions play crucial roles in various biological pathways and functions. Therefore, the characterization of protein levels and also the network of interactions within an organism would contribute considerably to the understanding of life. The availability of the human genome sequence has created a range of new possibilities for biomedical research. A crucial challenge is to utilize the genetic information for better understanding of protein distribution and function in normal as well as in pathological biological processes. In this review, we have focused on different platforms used for systematic genome‐based proteome analyses. These technologies are in many ways complementary and should be seen as various ways to elucidate different functions of the proteome.
A split–merge‐based region‐growing method for fMRI activation detection
Authors: Lu Yingli , Jiang Tianzi , Zang Yufeng 
Published: May 2004

AbstractWe introduce a hybrid method for functional magnetic resonance imaging (fMRI) activation detection based on the well‐developed split–merge and region‐growing techniques. The proposed method includes conjoining both of the spatio‐temporal priors inherent in split–merge and the prior information afforded by the hypothesis‐led component of region selection. Compared to the fuzzy c‐means clustering analysis, this method avoids making assumptions about the number of clusters and the computation complexity is reduced markedly. We evaluated the effectiveness of the proposed method in comparison with the general linear model and the fuzzy c‐means clustering method conducted on simulated and in vivo datasets. Experimental results show that our method successfully detected expected activated regions and has advantages over the other two methods. Hum. Brain Mapping 22:271–279, 2004. © 2004 Wiley‐Liss, Inc.
Automatic attention to emotional stimuli: Neural correlates
Authors: Carretié Luis , Hinojosa José A. , Martín‐Loeches Manuel , Mercado Francisco , Tapia Manuel 
Published: May 2004

AbstractWe investigated the capability of emotional and nonemotional visual stimulation to capture automatic attention, an aspect of the interaction between cognitive and emotional processes that has received scant attention from researchers. Event‐related potentials were recorded from 37 subjects using a 60‐electrode array, and were submitted to temporal and spatial principal component analyses to detect and quantify the main components, and to source localization software (LORETA) to determine their spatial origin. Stimuli capturing automatic attention were of three types: emotionally positive, emotionally negative, and nonemotional pictures. Results suggest that initially (P1: 105 msec after stimulus), automatic attention is captured by negative pictures, and not by positive or nonemotional ones. Later (P2: 180 msec), automatic attention remains captured by negative pictures, but also by positive ones. Finally (N2: 240 msec), attention is captured only by positive and nonemotional stimuli. Anatomically, this sequence is characterized by decreasing activation of the visual association cortex (VAC) and by the growing involvement, from dorsal to ventral areas, of the anterior cingulate cortex (ACC). Analyses suggest that the ACC and not the VAC is responsible for experimental effects described above. Intensity, latency, and location of neural activity related to automatic attention thus depend clearly on the stimulus emotional content and on its associated biological importance. Hum. Brain Mapp. 22:290–299, 2004. © 2004 Wiley‐Liss, Inc.
Lipomatous hemangiopericytoma of the head and neck: immunohistochemical and dna ploidy analyses
Authors: Alrawi Sadir J. , Deeb George , Cheney Richard , Wallace Paul , Loree Thom , Rigual Nestor , Hicks Wesley , Tan Dongfeng 
Published: May 2004

AbstractBackground.Lipomatous hemangiopericytoma (LHPC) is a newly described rare soft tissue tumor with unpredictable biologic behavior and is difficult to diagnose by conventional histologic parameters. The molecular analyses of this entity to date are sparse. Only a few cases of LHPC have been reported. Although one case of LHPC in the sinonasal region was briefly reported, this is the first case in the head and neck region with detailed clinicopathologic features and molecular analysis of this entity.Methods.We reported a case of LHPC in a 55‐year‐old woman with a slowly growing lesion in the occipital area that was diagnosed by CT and MRI and removed surgically. Immunohistochemical and DNA ploidy analyses were performed.Results.A panel of 16 markers was included for immunohistochemical analysis. Diffuse immunopositivity of CD57 in our case provides supportive evidence that LHPC is linked with HPC because this marker is also present in approximately 50% of conventional HPCs. CD57 should be used in the immunohistochemical panel in any lesion suspected to be LHPC. Furthermore, CD57 along with CD34 and XIIIa is thought to stain for primitive mesenchymal stem cells, suggesting a bimodal/multimodal differentiation of LHPC. By flow cytometry, we found that tumor cells were 100% diploid with the S‐phase fraction (SPF) being 3.21%. A significant positive correlation was detected between nuclear proliferating index and SPF (p < 0.001, by Spearman analysis). These findings provide molecular evidence indicating a benign nature of LHPC.Conclusions.Contrary to the old belief that HPC has an aggressive nature, this variant of tumor looks less aggressive. The patient was followed for 1 year without any evidence of recurrence, supporting our pathologic hypothesis. © 2004 Wiley Periodicals, Inc. Head Neck 26: 544–549, 2004
Prevalence of LMP‐1 gene in tonsils and non‐neoplastic nasopharynxes by nest‐polymerase chain reaction in Taiwan
Authors: Pai Ping‐Ching , Tsang Ngan‐Ming , Tseng Chen‐Kan , Hao Sheng‐Po , Kuo Tseng‐Tong , Wei Kuo‐Chen , Hsueh Chuen , Chuang Chi‐Cheng 
Published: May 2004

AbstractBackground.The purpose of this study was to investigate the frequency of Epstein‐Barr virus (EBV) latent membrane protein‐1 (LMP‐1) in tonsils and non‐neoplastic nasopharynxes in Taiwan.Methods.Nest‐polymerase chain reaction (nest‐PCR) was used to examine the presence of LMP‐1 gene in lymphoid hyperplasia from non‐neoplastic tonsillar and nasopharyngeal tissues and in tonsillar cancers.Results.In 152 cases, 64 biopsy tissues were obtained from lymphoid hyperplasia of nasopharynxes, 57 from tonsillectomy of non‐neoplastic tonsils, and 31 from tonsillar cancers. LMP‐1 was detected in 43.4% of the study group. Nineteen (29.7%) and 29 (50.9%) lymphoid hyperplasias from normal nasopharynxes and tonsils, respectively, and 18 (58.1%) biopsies from tonsillar cancers had positive LMP‐1. The 30–base pair (bp) deleted variant was detected in 89.5% and 82.8% of normal nasopharynxes and tonsils, respectively, and in 66.7% of biopsies from tonsillar cancers (p = .198).Conclusion.This study found that the 30‐bp variant was the predominant type of LMP‐1 from a healthy population in Taiwan. © 2004 Wiley Periodicals, Inc. Head Neck 26: 619–624, 2004
Combined evaluation of expression of telomerase, survivin, and anti‐apoptotic bcl‐2 family members in relation to loss of differentiation and apoptosis in human head and neck cancers
Authors: Sharma Himani , Sen Sudip , Mathur Meera , Bahadur Sudhir , Singh Neeta 
Published: May 2004

AbstractBackground.Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers, and it accounts for 5% of all adult cancers worldwide. Loss of growth control and a marked resistance to apoptosis are considered major mechanisms driving tumor progression. Little is known about the distribution of inhibitors of apoptosis in HNSCC or how they correlate with other biomarkers of malignancy, such as telomerase, an enzyme that plays a critical role in cellular immortalization. The objective of this study was to assess the protein expression of anti‐apoptotic members of Bcl‐2 family and survivin and correlate them with telomerase activity.Methods.We compared anti‐apoptotic protein expression in tumor tissue sections of 50 HNSCC patients and 19 histopathologically normal tissues by immunohistochemistry and Western blotting. Apoptotic index was studied by TUNEL assay. Telomerase activity was determined by polymerase chain reaction (PCR)–enzyme‐linked immunosorbent assay (ELISA).Results.Bcl‐2, Bcl‐XL, and survivin were found to be significantly upregulated in tumor tissues as compared with the normal tissue. Protein expression of Bcl‐2 and survivin was significantly associated with the loss of differentiation in tumors and that of Bcl‐XL with nodal metastasis. Telomerase activity was found to be upregulated in tumors as compared with the normal tissue (p < .001) and was found to be significantly associated with the loss of differentiation in tumors.Conclusions.Mechanisms that promote both cell proliferation (telomerase activity) and cell survival (expression of inhibitors of apoptosis protein [IAPs]) appear to be activated in HNSCC. This is the first study of its kind to look into the correlation of the apoptotic pathway and proliferation promoting enzyme activity simultaneously in relation to loss of apoptosis and differentiation in HNSCCs. Telomerase activity in these tumors was found to be correlated with Bcl‐2, Bcl‐XL, and survivin overexpression and with reduced apoptosis, thereby suggesting that novel strategies can be developed to control cancer cell growth by co‐targeting telomerase and apoptotic pathways. © 2004 Wiley Periodicals, Inc. Head Neck 26: 733–740, 2004
A two‐component hydrograph separation for three high‐elevation catchments in the Sierra Nevada, California
Authors: Huth A. K. , Leydecker A. , Sickman J. O. , Bales R. C. 
Published: May 2004

AbstractTwo‐component hydrograph separations were performed for three, nested, snowmelt‐dominated catchments in Sequoia National Park. The purpose of the hydrograph separations was to: (i) differentiate between the old and new water contributions to discharge during snowmelt using δ18O signatures; (ii) identify the fraction of snowmelt that travelled through the subsurface (reactive) compartment during the snowmelt period using silica or sodium; and (iii) investigate the impact of changing end‐member signatures on the separations. ‘Old’ water refers to water that was stored in the watershed during the previous year, whereas ‘new’ water is current snowmelt. Hydrograph separations were performed for both a high‐accumulation (1998, annual precipitation 2·4 m) and an average year (1999, 1·3 m). The proportion of old water contribution to discharge during the rising limb of the hydrograph was 10–20%, with 80–100% of snowmelt being reactive, i.e. passing through soil and talus. Estimates of old and new soil water and direct snowmelt entering the stream varied among the catchments in 1999. Differences between these components were minimal in 1998, regardless of varying topography and differing proportions of soil, rock and talus. Using time‐dependent rather than constant δ18O meltwater and silica soil‐water signatures made a meaningful impact on both new and old water, and reactive and unreactive, estimates. Copyright © 2004 John Wiley & Sons, Ltd.
Groundwater flow in anisotropic aquifers reduced to the isotropic case
Authors: Faraoni Valerio 
Published: May 2004

AbstractBy applying the technique of conformal transformation of the metric, widely used in general relativity and cosmology, the analysis of groundwater flow in an anisotropic aquifer (in which the hydraulic conductivity is a tensor) is reduced to the case of an isotropic one. This reduction is achieved for a particular conformal factor of the transformation. Examples of application of this technique are given. Copyright © 2004 John Wiley & Sons, Ltd.
Temporal and spatial variability of cation and silica export in an alpine watershed, Emerald Lake, California
Authors: Meixner T. , Shaw J. R. , Bales R. C. 
Published: May 2004

AbstractA reaction set of possible mineral weathering reactions is proposed to explain observed cation and silica export for the Emerald Lake watershed, a small Sierra Nevada, California catchment. The reaction set was calculated through a stoichiometric mole‐balance method, using a multiyear record of stream flow and snowpack chemical analyses and site‐specific mineral compositions. Reaction‐set calculations were intended to explore how the processes controlling stream cation and silica export depend on differing bedrock mineralogy across the catchment as snowmelt and runoff patterns change over the year. Different regions within the watershed can be differentiated by lake inflow subdrainages, each exhibiting different stream‐flow chemistry and calculated weathering stoichiometry, indicating that different silica and cation generation processes are dominant in wet steep portions of the catchment. Short‐term differences in stream concentrations were assumed to reflect ion exchange equilibria and rapid biological processes, whereas long‐term persistent stream concentration differences in different areas of the catchment were assumed to reflect spatial variability in mineral weathering stoichiometry. Mineralogical analyses of rock samples from the watershed provided site‐specific chemical compositions of major mineral species for reaction calculations. Reaction sets were evaluated by linear regression of calculated versus observed differences between snowmelt and stream‐flow chemistry and by a combined measure. Initially, single weathering reactions were balanced and evaluated to determine the reactions that best explained observed stream chemical export. Next, reactions were combined, using mineral compositions from different rock types to estimate the dependence of ion fluxes on lithology. The seasonal variability of major solute calculated fluxes is low, approximately one order of magnitude, relative to the observed three orders of magnitude variability in basin discharge. Reaction sets using basin‐averaged lithology and Aplite lithologies gave superior explanations of stream chemical composition. Copyright © 2004 John Wiley & Sons, Ltd.