bluuebunny/crossref_metadata_2025 huggingface dataset:
Bitter Taste Receptors for Saccharin and Acesulfame K
Authors: Kuhn Christina , Bufe Bernd , Winnig Marcel , Hofmann Thomas , Frank Oliver , Behrens Maik , Lewtschenko Tatjana , Slack Jay P. , Ward Cynthia D. , Meyerhof Wolfgang
Published: November 2004

Weight-conscious subjects and diabetics use the sulfonyl amide sweeteners saccharin and acesulfame K to reduce their calorie and sugar intake. However, the intrinsic bitter aftertaste, which is caused by unknown mechanisms, limits the use of these sweeteners. Here, we show by functional expression experiments in human embryonic kidney cells that saccharin and acesulfame K activate two members of the human TAS2R family (hTAS2R43 and hTAS2R44) at concentrations known to stimulate bitter taste. These receptors are expressed in tongue taste papillae. Moreover, the sweet inhibitor lactisole did not block the responses of cells transfected with TAS2R43 and TAS2R44, whereas it did block the response of cells expressing the sweet taste receptor heteromer hTAS1R2-hTAS1R3. The two receptors were also activated by nanomolar concentrations of aristolochic acid, a purely bitter-tasting compound. Thus, hTAS2R43 and hTAS2R44 function as cognate bitter taste receptors and do not contribute to the sweet taste of saccharin and acesulfame K. Consistent with thein vitrodata, cross-adaptation studies in human subjects also support the existence of common receptors for both sulfonyl amide sweeteners.
Molecular Determinants of Ligand Selectivity in a Vertebrate Odorant Receptor
Authors: Luu Percy , Acher Francine , Bertrand Hugues-Olivier , Fan Jinhong , Ngai John
Published: November 2004

The identification of the chemical structure of an odorant by the vertebrate olfactory system is thought to occur through the combinatorial activity from multiple receptors, each tuned to recognize different chemical features. What are the molecular determinants underlying the selectivity of individual odorant receptors for their cognate ligands? To address this question, we performed molecular modeling and site-directed mutagenesis on the ligand-binding region of two orthologous amino acid odorant receptors belonging to the “C family” of G-protein-coupled receptors in goldfish and zebrafish. We identified the critical ligand-receptor interactions that afford ligand binding as well as selectivity for different amino acids. Moreover, predictions regarding binding pocket structure allowed us to alter, in a predictable manner, the receptor preferences for different ligands. These results reveal how this class of odorant receptor has evolved to accommodate ligands of varying chemical structure and further illuminate the molecular principles underlying ligand recognition and selectivity in this family of chemosensory receptors.
Glutamate-Evoked Alterations of Glial and Neuronal Cell Morphology in the Guinea Pig Retina
Authors: Uckermann Ortrud , Vargová Lydia , Ulbricht Elke , Klaus Christoph , Weick Michael , Rillich Katja , Wiedemann Peter , Reichenbach Andreas , Syková Eva , Bringmann Andreas
Published: November 2004

Neuronal activity is accompanied by transmembranous ion fluxes that cause cell volume changes. In whole mounts of the guinea pig retina, application of glutamate resulted in fast swelling of neuronal cell bodies in the ganglion cell layer (GCL) and the inner nuclear layer (INL) (by ∼40%) and a concomitant decrease of the thickness of glial cell processes in the inner plexiform layer (IPL) (by ∼40%) that was accompanied by an elongation of the glial cells, by a thickening of the whole retinal tissue, and by a shrinkage of the extracellular space (by ∼18%). The half-maximal effect of glutamate was observed at ∼250 μm, after ∼4 min. The swelling was caused predominantly by AMPA-kainate receptor-mediated influx of Na+into retinal neurons. Similar but transient morphological alterations were induced by high K+and dopamine, which caused release of endogenous glutamate and subsequent activation of AMPA-kainate receptors. Apparently, retinal glutamatergic transmission is accompanied by neuronal cell swelling that causes compensatory morphological alterations of glial cells. The effect of dopamine was elicitable only during light adaptation but not in the dark, and glutamate and high K+induced strong ereffects in the dark than in the light. This suggests that not only the endogenous release of dopamine but also the responsiveness of glutamatergic neurons to dopamine is regulated by light-dark adaptation. Similar morphological alterations (neuronal swelling and decreased glial process thickness) were observed in whole mounts isolated immediately after experimental retinal ischemia, suggesting an involvement of AMPA-kainate receptor activation in putative neurotoxic cell swelling in the postischemic retina.
Peopling the Age of Elegance: Reinterpreting Spokane's Campbell House--A Collaboration
Authors: Rutherford Janice Williams , Shay Steven E.
Published: November 2004

In the spring of 2001, Janice Williams Rutherford's graduate public history seminar, "Interpreting History through Material Culture" at Washington State University joined in a collaborative project with the staff at Campbell House, a historic house museum owned by the Northwest Museum of Arts and Culture in Spokane, Washington, and outside museum consultant Margaret Piatt. The students undertook the research required to draft a new interpretive script for the museum and worked with staff and consultant to identify appropriate objects and suggest interpretive dialogue gleaned from the archival research. Steven E. Shay, one of the students from the seminar, continued working with museum staff after the academic semester ended to refine the script for adults and school children. The project was a successful learning experience in the area of academic/public collaboration. This article explores its successes and its limitations.
Psychometric Properties of the Spanish Version of the Resilience Scale
Authors: Heilemann MarySue V. , Lee Kathryn , Kury Felix Salvador
Published: November 2004

The purpose of this study is to test the reliability and validity of a Spanish translation of the Resilience Scale (RS), which was originally created in English by Wagnild and Young (1993). A team of bilingual, bicultural translators participated in the translation process to enhance the linguistic accuracy and cultural appropriateness of the Spanish translation. As part of the convenience sample of 315 women of Mexican descent who participated in the larger study, data from 147 women who preferred to read and write in Spanish were used in this analysis. The English version of the RS consists of a 17-item “Personal Competence” subscale and an 8-item “Acceptance of Self and Life” subscale for a total of 25 items. However, two items had low item-total loadings and were removed to form a modified 23-item RS. The exploratory principal components factor analysis, varimax rotation, and subsequent goodness of fit indices were ambivalent on whether a one or two-factor solution was appropriate, but the chi-square difference test clearly demonstrated that the two-factor solution of the Spanish version was more useful in explaining variance than a one-factor solution. Internal consistency reliability was estimated with Cronbach’s alpha (α = 0.93) which was acceptable for the 23-item RS as well as its subscales. Construct validity was demonstrated by a significant positive correlation between resilience and life satisfaction (r = 0.36; p < 0.001), and a significant negative correlation between resilience and depressive symptoms (r = -0.29; p < 0.01). This analysis ultimately supports the appropriateness of the modified 23-item Spanish translation of the RS and its subscales in a sample of urban, low-income women of Mexican descent in the U.S.
Mitochondrial DNA genealogy of chimpanzees in the Nimba mountains and Bossou, West Africa
Authors: Shimada Makoto K. , Hayakawa Sachiko , Humle Tatyana , Fujita Shiho , Hirata Satoshi , Sugiyama Yukimaru , Saitou Naruya
Published: November 2004

The chimpanzee populations of the Bossou and Nimba regions in West Africa were genetically surveyed to 1) reveal the genetic relationship between the Bossou and Nimba populations, and 2) elucidate the evolutionary relationship between the Bossou‐Nimba and other West African populations. The chimpanzee group at Bossou is characterized by its small population size, no evidence of contact with neighboring populations, and no female immigration. It is believed that most females and adolescent males emigrate from this population. To reveal the genetic signature of these characteristics, we examined the genetic diversity of Bossou and two neighboring populations (Seringbara and Yealé) in the Nimba Mountains by sequencing approximately 605 bp of the mitochondrial DNA (mtDNA) control region. A total of 20 distinct mtDNA variants were observed from 56 sequences of noninvasively collected, anonymous samples. Nucleotide diversity in the Nimba Mountain populations was 0.03–0.04, and did not differ significantly from that in the Bossou population. Very few mitochondrial variants are shared among the sites sampled, which suggests that there is little gene flow involving mtDNA. Nevertheless, no clear population structures were revealed in either population. A comparison with published sequences from West African chimpanzees (Pan troglodytes verus) indicates that the variants observed in the Bossou and Nimba regions are scattered throughout the subspecies, rather than clustered according to geographic region. This suggests that the Bossou‐Nimba populations derived only recently from the common ancestral population of the West African chimpanzees, and did not pass through a bottleneck. Am. J. Primatol. 64:261–275, 2004. © 2004 Wiley‐Liss, Inc.
Use of total dietary fiber across four lemur species (Propithecus verreauxi coquereli, Hapalemur griseus griseus, Varecia variegata, and Eulemur fulvus): Does fiber type affect digestive efficiency?
Authors: Campbell J.L. , Williams C.V. , Eisemann J.H.
Published: November 2004

In vivo digestibility and transit of two experimental diets were compared across four lemur species for which gastrointestinal morphology and preliminary data on physiology differ:Varecia variegata (VV), Eulemur fulvus (EF), Propithecus verreauxi (PV), and Hapalemur griseus (HG). Since free‐ranging groups consume varied amounts of slowly fermentable insoluble fiber (IF) and rapidly fermentable soluble fiber (SF), differences in digestibility may be related to variation in the fiber types consumed. To investigate this, two diets were designed to provide 28% of dry matter (DM) as total dietary fiber (TDF). The ratio of IF/SF (g/g) differed across the diets (12.15:1 for the IF diet, and 3.76:1 for the IF/SF diet). The DM digestibility (DMD) of both diets differed across species: DMD was lower for EF and VV (approximately 56–58%), and higher for PV (72%) and HG (76%). The fiber digestibility results were as follows: TDF digestibility was similar for VV and EF (23% and 28%), higher for PV (56%), and highest for HG (66%). IF digestibility was lower for VV and EF (20% and 28%), and higher for PV and HG (53% and 62%). The transit times (TTs) of the two markers Cr and Co were similar (approximately 3.5 hr for VV and EF, 25 hr for PV, and 30 hr for HG). The mean retention times (MRTs) showed the same trend. The results from these captive groups suggest there are large differences in digestive efficiency that are likely related to the varied fiber composition of the free‐ranging diet, and the amount of time the digesta are retained in the gut. Am. J. Primatol. 64:323–335, 2004. © 2004 Wiley‐Liss, Inc.
Physical and hydrodynamic properties of flocs produced during biological hydrogen production
Authors: Zhang Jian‐jun , Li Xiao‐yan , Oh Sang‐Eun , Logan Bruce E.
Published: November 2004

Dense flocs readily form in continuous culture bioreactors used for hydrogen production, but the fractal and hydrodynamic properties of these flocs have not been previously analyzed. We therefore examined the size distribution, fractal dimension, and hydrodynamic properties of flocs formed in a continuous flow, well‐mixed reactor treating synthetic wastewater at a fixed condition of a 4.5 h hydraulic detention time (23°C, pH 5.5). The reactor was operated for a total of 3 months at three different organic loading rates (27, 53, and 80 g‐COD/L‐d) with influent glucose concentrations of 5, 10, and 15 g‐COD/L. At all three loading rates the removal of glucose was nearly complete (98.6–99.4%) and biomass was produced in proportion to the organic loading rate (0.86 ± 0.11, 2.40 ± 0.26, and 4.59 ± 1.55 g/L of MLVSS in the reactor). Overall conversion efficiencies of glucose to hydrogen, evaluated on the basis of a maximum of 4 mol‐H2/mol‐glucose, increased with organic loading rates in the order 17.7%, 23.1%, and 25.6%. The gas contained 56.1 ± 4.9% hydrogen, with the balance as carbon dioxide. No methane gas was detected. Under these conditions, flocs were produced with mean sizes that increased with organic loading, in the order 0.12 cm (5 g‐COD/L), 0.35 cm (10 g‐COD/L), and 0.58 cm (15 g‐COD/L). As the average floc size increased, the flocs became on average denser and less fractal, with fractal dimensions increasing from 2.11 ± 0.17 to 2.48 ± 0.13. Floc porosities ranged from 0.75–0.96, and resulted in aggregate densities that allowed little intra‐aggregate flow through the floc. As a result, average settling velocities were not appreciably larger than those predicted by Stokes' law for spherical, impermeable flocs. Our results demonstrate that dense, relatively impermeable flocs are produced in biohydrogen reactors that have settling properties in reasonable agreement with Stokes' law. © 2004 Wiley Periodicals, Inc.
Theoretical Study on the Reactivities of Stannylene and Plumbylene and the Origin of their Activation Barriers
Authors: Su Ming‐Der
Published: November 2004

The potential energy surfaces corresponding to the reactions of heavy carbenes with various molecules were investigated by employing computations at the B3LYP and CCSD(T) levels of theory. To understand the origin of barrier heights and reactivities, the model system (CH3)2X+Y (X=C, Si, Ge, Sn, and Pb; Y=CH4, SiH4, GeH4, CH3OH, C2H6, C2H4, and C2H2) was chosen for the present study. All reactions involve initial formation of a precursor complex, followed by a high‐energy transition state, and then a final product. My theoretical investigations suggest that the heavier the X center, the larger the activation barrier, and the less exothermic (or the more endothermic) the chemical reaction. In particular, the computational results show that (CH3)2Sn does not insert readily into CH, SiH, CH, GeH, or CC bonds. It is also unreactive towards CC bonds, but is reactive towards C≡C and OH bonds. My theoretical findings are in good agreement with experimental observations. Furthermore, a configuration mixing model based on the work of Pross and Shaik is used to rationalize the computational results. It is demonstrated that the singlet–triplet splitting of a heavy carbene (CH3)2X plays a decisive role in determining its chemical reactivity. The results obtained allow a number of predictions to be made.
Studies on Stereoselective [2+2] Cycloadditions between N,N‐Dialkylhydrazones and Ketenes
Authors: Martín‐Zamora Eloísa , Ferrete Ana , Llera José M. , Muñoz Jesús M. , Pappalardo Rafael R. , Fernández Rosario , Lassaletta José M.
Published: November 2004

Staudinger‐like cycloadditions between chiral, non‐racemic N,N‐dialkylhydrazones 1 and functionalized ketenes constitute an efficient methodology for the stereoselective construction of the β‐lactam ring. The potential for fine tuning of the dialkylamino auxiliary structure, the availability of a high‐yielding deprotection method for the release of the free azetidinones, and the high thermal and chemical stability of hydrazones as N‐dialkylamino imines are highlighted as the key elements for the success of the strategy. This last aspect is of particular importance concerning generality: even hydrazones from easily enolizable aldehydes or from formaldehyde reacted to afford the corresponding cycloadducts with high chemical and stereochemical yields. The syntheses of the β‐amino‐α‐hydroxyacids (2R,3S)‐phenylisoserine (42) and (2R,3S)‐norstatin (45) were accomplished as illustrative examples of the synthetic utility of this procedure. A model system for the cycloaddition of g series auxiliaries was studied by ab initio computational methods. The collected results support a two‐step mechanism through zwitterionic intermediates, and explain the observed absolute and relative stereochemistry in terms of the preferred outward cycloaddition to the Re face of the hydrazone.
Palladium‐Catalyzed Intramolecular Hydroalkylation of Alkenyl‐ β‐Keto Esters, α‐Aryl Ketones, and Alkyl Ketones in the Presence of Me3SiCl or HCl
Authors: Han Xiaoqing , Wang Xiang , Pei Tao , Widenhoefer Ross A.
Published: November 2004

Reaction of 3‐butenyl β‐keto esters or 3‐butenyl α‐aryl ketones with a catalytic amount of [PdCl2(CH3CN)2] (2) and a stoichiometric amount of Me3SiCl or Me3SiCl/CuCl2 in dioxane at 25–70 °C formed 2‐substituted cyclohexanones in good yield with high regioselectivity. This protocol tolerated a number of ester and aryl groups and tolerated substitution at the allylic, enolic, and cis and trans terminal olefinic positions. In situ NMR experiments indicated that the chlorosilane was not directly involved in palladium‐catalyzed hydroalkylation, but rather served as a source of HCl, which presumably catalyzes enolization of the ketone. Identification of HCl as the active promoter of palladium‐catalyzed hydroalkylation led to the development of an effective protocol for the hydroalkylation of alkyl 3‐butenyl ketones that employed sub‐stoichiometric amounts of 2, HCl, and CuCl2 in a sealed tube at 70 °C.
The Mechanism of Magnetic Interactions in the Bulk Ferromagnet para‐(Methylthio)Phenyl Nitronyl Nitroxide (YUJNEW): A First Principles, Bottom‐Up, Theoretical Study
Authors: Deumal Mercè , Bearpark Michael J. , Robb Michael A. , Pontillon Yves , Novoa Juan J.
Published: November 2004

The mechanism of magnetic interactions in the bulk ferromagnet para‐(methylthio)phenyl nitronyl nitroxide crystal (YUJNEW) has been theoretically reinvestigated, using only data from ab initio calculations and avoiding any a priori assumptions. We first calculate the microscopic magnetic interactions (JAB exchange couplings) between all unique radical pairs in the crystal, and then generate the macroscopic magnetic properties from the energy levels of the corresponding Heisenberg Hamiltonian. We thus propose a first principles, bottom‐up (i.e. micro‐to‐macro) approach that brings theory and experiment together. We have applied this strategy to study the magnetism of YUJNEW using data from the previously reported 298 and 114 K crystal structures, and also data from a 10 K neutron diffraction structure fully reported in this work. The magnetic topology at 298 K is two‐dimensional: noninteracting planes, with three different in‐plane JAB pair interactions (+0.24, +0.09, and −0.11 cm−1) and one numerically negligible (+0.02 cm−1) inter‐plane JAB interaction. In contrast, the magnetic topology at 114 and 10 K is three‐dimensional, with two non‐negligible in‐plane JAB constants (+0.11 and +0.07 cm−1 at 114 K; +0.22 and +0.07 cm−1 at 10 K) and one inter‐plane pair interaction (+0.07 cm−1 at 114 K; +0.08 cm−1 at 10 K). Although this three‐dimensional magnetic topology is consistent with YUJNEW being a bulk ferromagnet, there is only a qualitative agreement between computed and experimental magnetic susceptibility χT(T) data at 114 K. However, the experimental χT(T) curve is quantitatively reproduced at 10 K. The heat capacity curve presents a peak at around 0.12 K, close to the estimated experimental peak (0.20 K).
Role of the Special Pair in the Charge‐Separating Event in Photosynthesis
Authors: Ozeki Hidekane , Nomoto Akihiro , Ogawa Kazuya , Kobuke Yoshiaki , Murakami Masataka , Hosoda Kou , Ohtani Masana , Nakashima Satoru , Miyasaka Hiroshi , Okada Tadashi
Published: November 2004

We synthesized special‐pair/electron‐acceptor systems consisting of a complementary slipped cofacial dimer of imidazolyl‐substituted zinc porphyrin, bearing pyromellitdiimide as the electron acceptor. In the case of the dimer, the first and second oxidation potentials were split into a total of four peaks in the differential pulse voltammetry measurement. Furthermore, the shift values of the first oxidation potentials obtained by changing the solvent polarity for the dimer were almost half of those observed for the monomer. These results indicate that the radical cation is delocalized over the whole π system of the dimer. Time‐resolved transient absorption measurements revealed that, relative to the corresponding monomer, the dimer accelerated the charge separation rate, but decelerated the charge recombination rate. The smaller reorganization energy of the slipped cofacial dimer relative to that of the monomeric system demonstrates the significance of the special‐pair arrangement for efficient charge separation in photosynthesis.
Spatial‐spectral holographic MR interpretation
Authors: Kiruluta Andrew J.M.
Published: November 2004

The fundamental MR imaging equation can be derived from a spatial‐spectral holographic wavefront reconstruction formulation similar to that in quantum optics. This spatial‐spectral holographic interpretation arises naturally in MR from the inhomogeneous linewidth broadening (1/πT) due to either an imposed set of linear orthogonal gradients fields or from the intrinsic chemical shift/molecular environment of the spin system. In this work, it is shown experimentally that an inhomogeneously broadened NMR absorber can accomplish key holographic characteristics such as storage, recall, time‐reversal, and matched filtering of gradient weighted RF pulses in a three‐pulse stimulated echo experiment. This interpretation has implications on selective RF pulse design, holographic‐based high‐resolution microscopy applications, and the use of conjugate imaging for field inhomogeneity corrections using the time‐reversed component of the readout. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 23A: 76–88, 2004
Variation of mitochondrial size during the cell cycle: A multiparameter flow cytometric and microscopic study
Authors: Kennady P. Kavin , Ormerod M. G. , Singh Shashi , Pande Gopal
Published: November 2004

Background

Changes in mitochondrial structure and size are observed in response to alterations in cell physiology. Flow cytometry provides a useful tool to study these changes in intact cells. We have used flow cytometry and digital fluorescence microscopy to analyze the variations in mitochondrial size in relation to specific phases of the cell cycle.

Methods

Supravital staining of rat fibroblasts was done with Hoechst 33342 and rhodamine 123, and cells were analyzed in a dual‐laser flow cytometer. Synchronized cells at various stages of the cell cycle were analyzed for changes in mitochondrial size. These cells were also examined by electron microscopy, digital fluorescence microscopy and computerized image analysis to compare the lengths of the mitochondria.

Results

By using fluorescence pulse width analysis, we observed two populations of mitochondria in intact cells. The percentage of cells with small and large mitochondria at specific stages of the cell cycle indicated that mitochondrial size increases during the cell cycle; early G1 phase cells had the smallest mitochondria and the mitotic phase cells had the largest mitochondria. These results were confirmed by microscopic analysis of cells.

Conclusions

Flow cytometry can distinguish the relative mitochondrial size in intact cells, and in combination with digital microscopy it can be used to study mitochondrial variation during the cell cycle. © 2004 Wiley‐Liss, Inc.
„Serengetis unter Wasser”︁
Authors: Unterstell Rembert
Published: November 2004

Der Kieler Meeresökologe Boris Worm warnt vor einer Überfischung der Weltmeere
Der Weg in die Vergangenheit
Authors: Hallmann Heinz W. , Forner Jörg‐Ulrich
Published: November 2004

Wege prägen das Gesicht von Gärten und Parks. Das wussten schon die Pioniere der Landschaftsgärtnerei. Wenn heute historische Wege rekonstruiert werden, ist dies nicht nur für die Denkmalpflege aufschlussreich
Das Klima auf der Luftdruckschaukel
Authors: Brümmer Burghard
Published: November 2004

Das Wetter in unseren Breiten lässt sich gut für einige Tage vorhersagen. Wie es aber um die langfristigen Trends im Klimasystem des Nordatlantiks steht, ist weitgehend unbekannt. Meteorologen erforschen die Grundlagen
An efficient molecular docking using conformational space annealing
Authors: Lee Kyoungrim , Czaplewski Cezary , Kim Seung‐Yeon , Lee Jooyoung
Published: November 2004

Molecular docking falls into the general category of global optimization problems because its main purpose is to find the most stable complex consisting of a receptor and its ligand. Conformational space annealing (CSA), a powerful global optimization method, is incorporated with the Tinker molecular modeling package to perform molecular docking simulations of six receptor–ligand complexes (3PTB, 1ULB, 2CPP, 1STP, 3CPA, and 1PPH) from the Protein Data Bank. In parallel, Monte Carlo with the minimization (MCM) method is also incorporated into the Tinker package for comparison. The energy function, consisting of electrostatic interactions, van der Waals interactions, and torsional energy terms, is calculated using the AMBER94 all‐atom empirical force field. Rigid docking simulations for all six complexes and flexible docking simulations for three complexes (1STP, 3CPA, and 1PPH) are carried out using the CSA and the MCM methods. The simulation results show that the docking procedures using the CSA method generally find the most stable complexes as well as the native‐like complexes more efficiently and accurately than those using the MCM, demonstrating that CSA is a promising search method for molecular docking problems. © 2004 Wiley Periodicals, Inc. J Comput Chem 26: 78–87, 2005
Chromatographic separation of nucleosides using a cross‐linked xylose isomerase crystal stationary phase
Authors: Jokela Jouni , Leisola Matti
Published: November 2004

Cross‐linked xylose isomerase (EC 5.3.1.5., from Streptomyces rubiginosus) crystals (CLXIC) packed into a 7.8×300 mm steel column showed specific affinity towards uridine (Urd), cytidine (Cyd), adenosine (Ado), guanosine (Guo), and thymidine. These nucleosides eluted out of the CLXIC column in the same order as the corresponding nucleoside bases, indicating that the retention depends mainly on the base component of the molecule. The interaction of nucleosides with the CLXIC material was not based merely on ion exchange or hydrophobic interactions but also on the unique properties of the CLXIC column. Decrease in temperature increased the retention but not the resolution factors of the adjacent nucleosides. The CLXIC column maintained its separation capacity even when 100 mg of ribonucleosides in equimass amounts were injected into the column in a volume of 1 mL corresponding to 10% of the total column volume. Analysis of sugar beet molasses, a side stream from sucrose production, showed it to contain 1–2.5 mg mL–1 of Urd, Cyd, Ado, and Guo. The CLXIC column was able to separate and enrich these nucleosides also from highly viscous sugar beet molasses. The CLXIC column was especially efficient in the purification of guanosine. Other commercially interesting sugar beet molasses components such as the acidic compounds betaine, γ‐amino butyric acid, and D‐ and L‐pyroglutamic acids or neutral sucrose did not interact with the CLXIC material.
Capillary columns in liquid chromatography: between conventional columns and microchips
Authors: Saito Yoshihiro , Jinno Kiyokatsu , Greibrokk Tyge
Published: November 2004

Liquid chromatography on columns with small internal diameters has been reviewed as the intermediate technique between conventional liquid chromatography and microchip separations. The development of micro column separations in the early years has been described, starting with the papers of Horváth and co‐workers and Ishii and co‐workers, continuing into the first part of the eighties, then making a leap in time to recent innovations with small‐bore columns. Based on internal diameters a classification of the different analytical HPLC columns has been suggested. The advantages of small‐bore columns have been discussed, with particular emphasis on the advantage of coupling to concentration sensitive detectors when the sample amount is limited. Open tubular columns are treated as a part of the historic background. The recent developments include a brief look into the current status of monolithic columns, the use of packed nano columns and micro columns with electrospray mass spectrometry, and the potential of two‐dimensional comprehensive liquid chromatography. Finally, the coupling of sample preparation to analytical columns and the future applications of the novel technological improvements to the microchip separation methods have been discussed.
Phosphoproteomics by mass spectrometry and classical protein chemistry approaches
Authors: Salih Erdjan
Published: November 2004

The general fields of biological sciences have seen phenomenal transformations in the past two decades at the level of data acquisition, understanding biological processes, and technological developments. Those advances have been made partly because of the advent of molecular biology techniques (which led to genomics) coupled to the advances made in mass spectrometry (MS) to provide the current capabilities and developments in proteomics. However, our current knowledge that ∼30,000 human genes may code for up to 1 million or more proteins disengage the interface between the genome sequence database algorithms and MS to generate a major interest in independent de novo MS/MS sequence determination. Significant progress has been made in this area through procedures to covalently modify peptide N‐ and C‐terminal amino‐acids by sulfonation and guanidination to permit rapid de novo sequence determination by MS/MS analysis. A number of strategies that have been developed to perform qualitative and quantitative proteomics range from 2D‐gel electrophoresis, affinity tag reagents, and stable‐isotope labeling. Those procedures, combined with MS/MS peptide sequence analysis at the subpicomole level, permit the rapid and effective identification and quantification of a large number of proteins within a given biological sample. The identification of proteins per se, however, is not always sufficient to interpret biological function because many of the naturally occurring proteins are post‐translationally modified. One such modification is protein phosphorylation, which regulates a large array of cellular biochemical pathways of the biological system. Traditionally, the study of phosphoprotein structure–function relationships involved classical protein chemistry approaches that required protein purification, peptide mapping, and the identification of the phosphorylated peptide regions and sites by N‐terminal sequence analysis. Recent advances made in mass spectrometry have clearly revolutionized the studies of phosphoprotein biochemistry, and include the development of specific strategies to preferentially enrich phosphoproteins by covalent‐modifications that incorporate affinity tags that use the physicochemical properties of phosphoaminoacids. The phosphoserine/phosphothreonine‐containing proteins/peptides are derivatized under base‐catalyzed conditions by thiol agents; mono‐ and di‐thiol reagents both have been used in such studies. The thiol agent may have: (i) an affinity tag for protein enrichment; (ii) stable‐isotopic variants for relative quantitation; or (iii) a combination of the moieties in (i) and (ii). These strategies and techniques, together with others, are reviewed, including their practical application to the study of phosphoprotein biochemistry and structure–function. The consensus of how classical protein chemistry and current MS technology overlap into special case of proteomics, namely “phosphoproteomics,” will be discussed. © 2004 Wiley Periodicals, Inc., Mass Spec Rev 24:828–846, 2005
Myocytes from congenital myotonic dystrophy display abnormal Na+ channel activities
Authors: Bernareggi Annalisa , Furling Denis , Mouly Vincent , Ruzzier Fabio , Sciancalepore Marina
Published: November 2004

Na+ currents were measured in myocytes from a fetus with congenital myotonic dystrophy type 1 (DM1) using the patch‐clamp whole‐cell technique. Steady‐state activation and inactivation properties of Na+ channels were not substantially different between these cells and age‐matched control cells. However, a decrease in Na+ channel density and a faster rate of recovery from inactivation were found in myocytes from congenital DM1 suggesting that changes in functional Na+ channels may affect cell excitability of muscle cells of patients with this disorder. Muscle Nerve, 2005
Towards a Fundamental Understanding of the Mechanics of Crystal Agglomeration: A Microscopic and Molecular Approach
Authors: Simons Stefaan J. R. , Pratola Federica , Jones Alan G. , Brunsteiner Michael , Price Sally L.
Published: November 2004

A novel experimental apparatus has been developed which enables the measurement of adhesion forces between two crystals suspended in a supersaturated solution and allowed to agglomerate over a fixed time period. The geometry of the crystal surfaces at the contact points and the dynamic development of the bond are captured on video and characterised using an image analysis technique. The experimental apparatus has been designed to allow control of supersaturation, orientation of crystal faces, distance between crystals, relative movement of crystals and contact time. The experimental results show that the agglomerate bond strength, expressed as the agglomerate adhesion force per unit contact area, increases with increasing supersaturation and is higher for faster growing faces than for slower growing faces. In addition, a qualitative comparison has been made between the measured force and a theoretical estimation of the interaction force between crystal faces, determined through molecular modelling. It is shown that the speed of approach of two opposing crystal faces is a key parameter in the nature of the subsequent bond, as is their atomic structure.
Predicting the Performance of Granulation Binders Through Micro‐Mechanistic Observations
Authors: Rossetti Damiano , Simons Stefaan J. R. , Pagliai Paolo , Ward Rob , Fitzpatrick Shaun
Published: November 2004

The selection of an appropriate polymeric binder to be used to agglomerate drug with excipients is a critical issue for the development of high shear wet granulation processes for pharmaceutical tablet systems. The aim of the study reported here is to determine the potential for successful granulation through measurement of the interactions of two polymer binder solutions, hydroxypropyl methylcellulose (HPMC) and polyvinyl‐pyrrolidone (PVP), with individual paracetamol drug crystals. A novel micro‐force balance (MFB) has been used to measure different parameters of the crystal‐to‐binder interaction, including the forces exerted by axially strained liquid bridges formed between either two paracetamol crystals or between a reservoir of binder solution and a single paracetamol crystal, the paracetamol‐to‐binder wettability, the post rupture volume distribution and the residue deposited on each crystal. Video images of the separation sequences were obtained simultaneously for analysis of bridge geometry, contact angles, volume distribution and binder residues. It was found that the formation of liquid bridges and their ability to bond particles together depends on the amount of binder left on a crystal after contacting a reservoir of binder (for example, large binder drop). Crystals in contact with HPMC were able to retain more liquid from a binder reservoir than those contacted with PVP solutions. This behaviour is seen to be more important to the final granule strength than the liquid binding force holding particles together in the wet agglomerate.
Improvements in Silo Design for Moist and Cohesive Bulk Solids by Using a Silo Centrifuge
Authors: Großstück Marco , Schwedes Jörg
Published: November 2004

The Jenike‐method is state of the art in silo design for trouble‐free flow, even for cohesive bulk solids. However, for some bulk solids, especially very cohesive and moist bulk solids, even the correct application of the Jenike‐method can lead to an over‐design of the silo outlet. If a reliable estimation of the critical outlet dimension is possible the dimension as well as the machinery costs can be reduced. Model testing can help to reduce the over‐design but reasonable test equipment and flexibility are only possible with silo centrifuge testing. Results, regarding the state of stress and the critical outlet dimensions, from experiments using a silo centrifuge with cohesive and moist bulk solids are presented. The influence of creeping effects on silo design is investigated using the silo centrifuge with moist gypsum.
5α‐dihydrotestosterone inhibits 1α,25‐dihydroxyvitamin D3‐induced expression of CYP24 in human prostate cancer cells
Authors: Lou Yan‐Ru , Nazarova Nadja , Talonpoika Riikka , Tuohimaa Pentti
Published: November 2004

BACKGROUND

A cross‐talk between 1α,25‐dihydroxyvitamin D3 [1α,25‐(OH)2D3] and 5α‐dihydrotestosterone (DHT) in the growth inhibition has been demonstrated, but the mechanism is unknown.

METHODS

The expression of 25‐hydroxyvitamin D3 24‐hydroxylase (24‐hydroxylase) was measured using a real‐time quantitative RT‐PCR assay and the catabolism of 1α,25‐(OH)2D3 was measured using a radioreceptor assay.

RESULTS

Real‐time RT‐PCR showed that DHT at 1–100 nM significantly inhibited 1α,25‐(OH)2D3‐induced expression of 24‐hydroxylase in LNCaP cells. Furthermore, the catabolism of 1α,25‐(OH)2D3 was decreased by 10 nM DHT. An androgen receptor (AR) antagonist, Casodex antagonized the DHT effect, whereas an AR agonist (due to the mutant AR in LNCaP cells) hydroxyflutamide did not.

CONCLUSIONS

We demonstrated, for the first time, that DHT reduces the ability of 1α,25‐(OH)2D3 to induce 24‐hydroxylase expression. Our results not only support the earlier finding of a cross‐talk between androgen and vitamin D in human prostate cancer cells but also provide a possible mechanism how androgen and vitamin D signaling pathways may interact. © 2004 Wiley‐Liss, Inc.
Cubature grids
Authors: Rees D. , Hall G. G.
Published: November 2004

This article applies group theory to the problem of calculating accurate cubature grids for three‐dimensional (3D) integrals that have an exponential weighting factor. The nodes of a cubature are divided into structures, each with the full symmetry of the octahedral group. The sequence of structures is derived from a basis set of polynomials forming a Sturmian basis for the function space. Several cubatures, of up to eighth degree accuracy, are reported and their features discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Convenient expression of the rate constant for nonadiabatic transition
Authors: Okuno Yoshishige , Mashiko Shinro
Published: November 2004

We derived a convenient expression of the rate constant for nonadiabatic transitions, with the intention of making it possible and practical to calculate the rate constant. For this derivation, we first assume that the seam, at which the adiabatic potential energy surfaces of reactant and product electronic states exhibit an avoided crossing, corresponds to the dividing surface of the nonadiabatic transition. Second, we use the probability that a nonadiabatic transition occurs in the seam. Third, the partition function in the seam is described by the local profile of the adiabatic potential energy surfaces of both the reactant and product electronic states. The rate constant expression thus derived not only gives significant insight into understanding nonadiabatic transitions, but also makes it possible to obtain a rough estimate of the rate constant. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Spin–orbit coupling of spin‐frustrated systems
Authors: Takeda R. , Yamanaka S. , Yamaguchi K.
Published: November 2004

We have investigated the effects of spin–orbit (SO) interactions on noncollinear molecular magnetism by combining the classical Dzyaloshinsky–Moriya (DM) model and ab initio generalized spin orbital (GSO) method. We have derived an estimation scheme of the magnetic anisotropy energy (MAE) and the Dzyaloshinsky vector based on the SO first‐order perturbation theory (SOPT1) for GSO Hartree–Fock (GHF) solutions. We found that the fundamental results of GHF‐SOPT1 method can be reproduced by diagonalizing the core Hamiltonian plus SO terms, and that the spin topologies of odd‐ring systems can be determined by the topological indices of the singly occupied molecular orbitals. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Electrospray tandem mass spectrometry of 2H‐chromenes
Authors: Domingues M. Rosário M. , Domingues Pedro , Oliveira M. Manuel , Carvalho Luis H. M. , Oliveira‐Campos Ana F. , Ferrer Correia António J.
Published: November 2004

Several 2H‐chromenes derived from carbazoles were analyzed by electrospray tandem mass spectrometry. The 2H‐chromenes constitute an important class of compounds that exhibit photochromic activity. The fragmentation pathways of the protonated molecular species [M+H]+ were studied, and main fragmentation pathways of these compounds were identified. Fragmentation pathways of [M+D]+ ions were also studied in order to obtain information about the location of the ionizing proton or deuteron. It was found that the proton is not preferentially located on the nitrogen atom. The charge is preferentially located as a tertiary carbocation, resulting from the uptake of the proton (or deuteron) by the zwitterionic open structure of the chromenes. The major fragmentation occurred by cleavage of the γ‐bond relative to the carbocation center, leading to a fragment at m/z 191 (C5H or C14H9N+), which are the most abundant fragment ions for almost all compounds. The presence of substituents in the chromene ring does not change this behavior. Other observed common fragmentation pathways included loss of CH (15 Da), loss of CO (28 Da), combined loss of CO and CH3 (43 Da), and loss of the phenyl ring via combined loss of C6H4 and CH (−91 Da) and combined loss of C6H6 and CO (−106 Da). Copyright © 2004 John Wiley & Sons, Ltd.
Coupling of nanoflow liquid chromatography to matrix‐assisted laser desorption/ionization mass spectrometry: real‐time liquid chromatography run mapping on a MALDI plate
Authors: Nägele Edgar , Vollmer Martin
Published: November 2004

The major obstacle in the use of matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) instruments in the analysis of complex proteome samples is the lack of a direct coupling of a highly resolving separation technique with the mass spectrometer itself. To overcome this drawback, a spotting device for capillary and nanoflow liquid chromatography (LC) with a special liquid deposition principle for lowest volumes was developed. The instrument is able to perform MALDI spotting in real time in order to deposit the LC run on the MALDI plate, and therefore couples the high resolution power of nano‐RP‐HPLC separation directly with MALDI‐MS. This work describes the development and optimization of a method for spotting with online matrix addition, and illustrates its use in the analysis of a complex proteome sample. Copyright © 2004 John Wiley & Sons, Ltd.
Density and distribution of potential prey for larval fish in the main channel of a floodplain river: pelagic versus epibenthic meiofauna
Authors: King A. J.
Published: November 2004

Fish larvae require high densities of appropriately sized prey items for their survival and recruitment. It has been widely assumed that inundated floodplains are the major source of high densities of prey in floodplain rivers. This study examined the density and distribution of both pelagic and epibenthic meiofauna in a range of potential larval fish nursery habitats within the main channel of an Australian floodplain river. Although sufficient densities of meiofauna were found in the main channel environment to sustain fish larvae, the prey source was predominantly in the epibenthic zone, where the density of meiofauna was on average 100 times greater than in the pelagic zone. There was no apparent relationship between the density of meiofauna, both epibenthic and/or pelagic, and the preferred nursery habitats of fish larvae. This study suggests that an abundant prey resource for developing fish larvae may exist in main channel environments without inputs from the inundated floodplain. However, further studies are required to determine the relative contributions and importance of prey resources on inundated floodplains compared to the main channel environment for larval survival and cohort strength between successive years. Additionally, this study highlights the importance of sampling the epibenthos, and suggests that the significance of epibenthic meiofauna has been severely underestimated in many previous studies. Copyright © 2004 John Wiley & Sons, Ltd.
Physiological and biochemical analyses of microcystin‐RR toxicity to the cyanobacterium Synechococcus elongatus
Authors: Hu Zhi‐quan , Liu Yong‐ding , Li Dun‐hai
Published: November 2004

Freshwater Microcystis may form dense blooms in eutrophic lakes. It is known to produce a family of related cyclic hepatopeptides (microcystins, MC) that constitute a threat to aquatic ecosystems. Most toxicological studies of microcystins have focused on aquatic animals and plants, with few examining the possible effects of microcystins on phytoplankton. In this study we chose the unicellular Synechococcus elongatus (one of the most studied and geographically most widely distributed cyanobacteria in the picoplankton) as the test material and investigated the biological parameters: growth, pigment (chlorophyll‐a, phycocyanin), photosynthetic activity, nitrate reductase activity, and protein and carbohydrate content. The results revealed that microcystin‐RR concentrations above 100 μg · L−1 significantly inhibited the growth of Synechococcus elongatus. In addition, a change in color of the toxin‐treated algae (chlorosis) was observed in the experiments. Furthermore, MC‐RR markedly inhibited the synthesis of the pigments chlorophyll‐a and phycocyanin. A drastic reduction in photochemical efficiency of PSII (Fv/Fm) was found after a 96‐h incubation. Changes in protein and carbohydrate concentrations and in nitrate reductase activity also were observed during the exposure period. This study aimed to evaluate the mechanisms of microcystin toxicity on a cyanobacterium, according to the physiological and biochemical responses of Synechococcus elongatus to different doses of microcystin‐RR. The ecological role of microcystins as an allelopathic substance also is discussed in the article. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 571–577, 2004.
Thermodynamics of Quantum Information Systems — Hamiltonian Description
Authors: Alicki Robert , Horodecki Michał , Horodecki Paweł , Horodecki Ryszard
Published: November 2004

It is often claimed, that from a quantum system of d levels, and entropy S and heat bath of temperature T one can draw kT lnd–TS amount of work. However, the usual arguments basing on Szilard engine, are not fully rigorous. Here we prove the formula within Hamiltonian description of drawing work from a quantum system and a heat bath, at the cost of entropy of the system. We base on the derivation of thermodynamical laws and quantities in [10] within weak coupling limit. Our result provides fully physical scenario for extracting thermodynamical work form quantum correlations [4]. We also derive Landauer's principle as a consequence of the second law within the considered model.