bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi‐stage tandem mass spectrometry of metal cationized leucine enkephalin and leucine enkephalin amide
Authors: Barr J. M. , Van Stipdonk M. J. 
Published: January 2005

AbstractWe have examined the multi‐stage collision induced dissociation (CID) of metal cationized leucine enkephalin, leucine enkephalin amide, and the N‐acetylated versions of the peptides using ion trap mass spectrometry. In accord with earlier studies, the most prominent species observed during the multi‐stage CID of alkali metal cationized leucine enkephalin are the [bn + 17 + Cat]+ ions. At higher CID stages (i.e. >MS4), however, dissociation of the [b2 + 17 + Cat]+ ion, a cationized dipeptide, results in the production of [an − 1 + Cat]+ species. The multi‐stage CID of Ag+ cationized leucine enkephalin can be initiated with either the [bn − 1 + Ag]+ or [bn + 17 + Ag]+ ions produced at the MS/MS stage. For the former, sequential CID stages cause, in general, the loss of CO, and then the loss of the imine of the C‐terminal amino acid, to reveal the amino acid sequence. Similar to the alkali cationized species, CID of [b2 − 1 + Ag]+ produces prominent [an − 1 + Ag]+ ions. The multi‐stage CID of argentinated peptides is reminiscent of fragmentation observed for protonated peptides, in that a series of (bn) and (an) type ions are generated in sequential CID stages. The Ag+ cation is similar to the alkali metals, however, in that the [bn + 17 + Ag]+ product is produced at the MS/MS and MS3 stages, and that sequential CID stages cause the elimination of amino acid residues primarily from the C‐terminus. We found that N‐acetylation of the peptide significantly influenced the fragmentation pathways observed, in particular by promoting the formation of more easily interpreted (in the context of unambiguous sequence determination) dissociation spectra from the [b2 + 17 + Li]+, [b2 + 17 + Na]+ and [b2 − 1 + Ag]+ precursor ions. Our results suggest, therefore, that N‐acetylation may improve the efficacy of multi‐stage CID experiments for C‐terminal peptide sequencing in the gas phase. For leucine enkephalin amide, only the multi‐stage CID of the argentinated peptide allowed the complete amino acid sequence to be determined from the C‐terminal side. Copyright © 2002 John Wiley & Sons, Ltd.
Electrospray liquid chromatography/mass spectrometry fingerprinting of Acanthophis (death adder) venoms: taxonomic and toxinological implications
Authors: Fry Bryan G. , Wickramaratna Janith C. , Hodgson Wayne C. , Alewood Paul F. , Kini R. M. , Ho Hao , Wüster Wolfgang 
Published: January 2005

AbstractDeath adders (genus Acanthophis) are unique among elapid snakes in both morphology and venom composition. Despite this genus being among the most divergent of all elapids, the venom has been historically regarded as relatively quite simple. In this study, liquid chromatography/mass spectrometry (LC/MS) analysis has revealed a much greater diversity in venom composition, including the presence of molecules of novel molecular weights that may represent a new class of venom component. Furthermore, significant variation exists between species and populations, which allow for the LC/MS fingerprinting of each species. Mass profiling of Acanthophis venoms clearly demonstrates the effectiveness of this technique which underpins fundamental studies ranging from chemotaxonomy to drug design. Copyright © 2002 John Wiley & Sons, Ltd.
Detection and identification of quinonemethide triterpenes in Peritassa campestris by mass spectrometry
Authors: Rodrigues‐Filho Edson , Barros Fábio A. P. , Fernandes João B. , Braz‐Filho Raimundo 
Published: January 2005

AbstractAnalysis of tingenone and tingenol quinonemethide triterpenes was made by gas chromatography/mass spectrometry (GC/MS) of their trimethylsilyl (TMS) ethers. An extra TMS group, in addition to those predicted from the known structures, is added to these compounds during the derivatization process. The electron impact mass spectra showed base peaks at m/z 549 and 623, respectively, for the TMS derivatives of tingenone and tingenol, and electrospray (ES) and collision‐activated dissociation (CAD) studies indicate that these ions correspond to losses of a methyl group from the derivatives studied. A mechanism, based on ES‐MS/MS studies, is suggested for the derivatization and fragmentation pattern. Copyright © 2002 John Wiley & Sons, Ltd.
Hydrogen/deuterium exchange for higher specificity of protein identification by peptide mass fingerprinting
Authors: Bienvenut Willy V. , Hoogland Christine , Greco Anna , Heller Manfred , Gasteiger Elisabeth , Appel Ron D. , Diaz Jean‐Jacques , Sanchez Jean‐Charles , Hochstrasser Denis F. 
Published: January 2005

AbstractGenome sequencing projects produce large amounts of information that could be translated into potential protein sequences. Such amounts of material continuously increase protein database sizes. At present, 22 times more protein sequences are available in the SWISS‐PROT and TrEMBL databases than 8 years ago in SWISS‐PROT. One of the methods of choice for protein identification makes use of specific endoproteolytic cleavage followed by matrix‐assisted laser desorption/ionisation mass spectrometric (MALDI‐MS) analysis of the digested product. Since 1993, when this technique was first demonstrated, the conditions required for a correct identification have changed dramatically. Whilst 4–5 peptides with an uncertainty of 2–3 Da were sufficient for a correct identification in 1993, 10–13 peptides with less than 60 ppm mass error are now required for human and E. coli proteins. This evolution is directly related to the continuous increase in protein database sizes, which causes an increase in the number of false positive matches in identification results. Use of an information complement deduced from the primary protein sequence, in the process of identification by peptide mass fingerprints, can help to increase confidence in the identification results. In this article, we propose the exchange of labile hydrogen atoms with deuterium atoms to provide an alternative information complement. The exchange reaction with optimised techniques has shown an average 95% of hydrogen/deuterium (H/D) exchange on tryptic peptides. This level of exchange was sufficient to single out one or more peptides from a list of potential candidate proteins due to the dependence of H/D exchange on the peptide primary structure. This technique also has clear advantages in the identification of small proteins where direct protein identification is impaired by the limited number of endoproteolytic peptides. Then, information related to primary sequence obtained with this technique could help to identify proteins with high confidence without any expensive tandem mass spectrometry instruments. Copyright © 2002 John Wiley & Sons, Ltd.
Side‐chain radical losses from radical cations allows distinction of leucine and isoleucine residues in the isomeric peptides Gly‐XXX‐Arg
Authors: Wee Sheena , O'Hair Richard A. J. , McFadyen W. David 
Published: January 2005

AbstractSequencing of peptides via low‐energy collision‐induced dissociation of protonated peptides typically yields bn and yn sequence ions. The isomeric residues leucine and isoleucine rarely can be distinguished in these experiments since they give bn and yn sequence ions of the same m/z. Siu's pioneering work on electrospray ionization of copper complexes of peptides (Chu IK, Rodriquez CF, Lau TC, Hopkinson AC, Siu KWM. J. Phys. Chem. B 2000; 104: 3393) provides a way of forming radical cations of peptides in the gas phase. This method was used to generate M+· ions of the two isomeric peptides Gly‐Leu‐Arg and Gly‐Ile‐Arg in order to compare their fragmentation reactions. Both radical cations fragment to give even electron y2 and y1 sequence ions as well as side‐chain radical losses of CH3 and CH3CH2 for isoleucine and (CH3)2CH for leucine. In contrast the [M + H]+ and [M + 2H]2+ ions do not allow distinction between the isomeric leucine and isoleucine peptides. Copyright © 2002 John Wiley & Sons, Ltd.
Lyapunov–Krasovskii functionals and frequency domain: delay‐independent absolute stability criteria for delay systems
Authors: Bliman Pierre‐Alexandre 
Published: January 2005

AbstractThe present paper is devoted to the study of absolute stability of delay systems with nonlinearities subject to sector conditions. We construct quadratic candidate Lyapunov–Krasovskii functional, whose decreasingness along trajectories is expressed in terms of linear matrix inequalities. We then show that the feasibility of the latter implies some frequency‐domain conditions, which may be seen as delay‐independent versions of the circle criterion and the Popov criterion. Copyright © 2001 John Wiley & Sons, Ltd.
Global stabilization of chemical reactors with classical PI control
Authors: Alvarez‐Ramirez Jose 
Published: January 2005

AbstractThis paper is devoted to the stabilization of chemical reactors with classical PI control. Roughly speaking, it is proven that if the isothermal dynamics are globally asymptotically stable, global stabilization of the chemical reactor dynamics is achieved via temperature control with classical PI compensation. Copyright © 2001 John Wiley & Sons, Ltd.
An invariant‐based approach to the design of hybrid control systems
Authors: Stiver James A. , Koutsoukos Xenofon D. , Antsaklis Panos J. 
Published: January 2005

AbstractIn this paper, a methodology for hybrid control design is presented. The hybrid systems of interest are characterized by a feedback architecture of a continuous nonlinear plant with a discrete‐event controller. The natural invariants of the continuous dynamics are used to partition the state space into regions and to synthesize simple and efficient control laws. The paper contains a complete description of the approach including a description of the hybrid control system modelling, of the invariant‐based approach for the design of the partition, and of the controller synthesis methodology illustrated by examples. The implementation and optimization of the approach are also discussed. The approach presented in this paper not only describes a viable methodology to hybrid design, but also addresses fundamental issues in hybrid system theory that arise in reachability analysis and verification approaches that are based on partitions of the continuous state space. Copyright © 2001 John Wiley & Sons, Ltd.
Optimal setpoint chasing in dynamic positioning of deep‐water drilling and intervention vessels
Authors: Sørensen Asgeir J. , Leira Bernt , Peter Strand Jann , Larsen Carl M. 
Published: January 2005

AbstractConventional controller designs for dynamic positioning of ships and floating marine structures have so far been based on the principle on automatic positioning in the horizontal‐plane about desired position and heading co‐ordinates defined by the operator. A three degrees‐of‐freedom multivariable controller either of linear or nonlinear type, normally with feedback signals from surge, sway and yaw position and velocities, has been regarded as adequate for the control objective. For floating structures with small waterplane area such as semi‐submersibles, feedback from roll and pitch angular rotation velocity may also be included to avoid thrust‐induced roll and pitch motions that are caused by the hydrodynamic and the geometrical couplings between the horizontal and vertical planes. However, for certain marine operations this control philosophy may not be the most appropriate approach ensuring safety and cost effectiveness. For drilling and work‐over operations the main positioning objective is to minimize the bending stresses along the riser and the riser angle magnitudes at the well head on the subsea structure, and at the top joint as well. A positioning control strategy solely based on manual setting of the desired position co‐ordinates may not be the most optimal solution for these applications. In this paper a new hybrid dynamic positioning controller, that also accounts for riser angle offsets and bending stresses is proposed. It is shown that a significant reduction in riser angle magnitude can be achieved. Simulations with a drilling semi‐submersible demonstrate the effect of the proposed control strategy. Copyright © 2001 John Wiley & Sons, Ltd.
An intelligent control concept for formation flying satellites
Authors: Vadali S. R. , Vaddi S. S. , Alfriend K. T. 
Published: January 2005

AbstractThis paper deals with the determination of initial conditions and the design of fuel‐balancing orbit control laws for a formation of satellites. Hill's equations describe the linearized dynamics of relative motion between two satellites. They admit bounded relative orbit solutions as special cases. Predictably, these bounded solutions break down in the presence of nonlinearities and perturbations. A method for determining the initial conditions that result in quasi‐periodic relative orbits over the short term, in the presence of J2 perturbation, is presented. The control acceleration or equivalently, the fuel required to cancel the perturbation on a satellite depends upon its orbital inclination with respect to that of the reference satellite. An intelligent control concept that exploits the physics of the relative motion dynamics is presented. Analysis shows that this concept minimizes the total fuel consumption of the formation and maintains equal, average fuel consumption for each satellite. The concept is implemented using a novel, disturbance accommodating control design process. Numerical simulations and analytical results are in excellent agreement with each other. Copyright © 2002 John Wiley & Sons, Ltd.
Impact of an urban centre on the nitrogen cycle processes of epilithic biofilms during a summer low‐water period *
Authors: Teissier S. , Garabetian F. , Torre M. , Dalger D. , Labroue L. 
Published: January 2005

AbstractNitrogen transformations in epilithic biofilms of a large gravel bed river, the Garonne, France, has been studied upstream (one site) and downstream (four sites) of a large urban centre (Toulouse, 740 000 inhabitants).High biomass, up to 49 g AFDM m−2 (ashes free dry matter) and 300 mg chlorophyll a m−2 (Chl. a), were recorded at 6 and 12 km downstream from the main wastewater treatment plant outlet. The lowest records upstream and larger downstream (less than 16 g AFDM m−2 or 120 mg Chl. a m−2) could be explained by recent water fall (early summer low‐water period).Measurements of nitrogen exchange at the biofilm–overlying water interface were performed in incubation chambers under light and dark conditions. The addition of acetylene at the mid‐incubation time allowed evaluation of both nitrification (variation in NH4+ flux after the ammonium monooxygenase inhibition) and denitrification (N2O accumulation related to the inhibition of N2O reduction). Denitrification (Dw) and nitrification rates were maximum at sites close to the city discharges in dark conditions (up to 9.1 and 5.6 mg N m−2 h−1, respectively). Unexpected denitrification activities in light conditions (up to 1.4 mg N m−2 h−1) at these sites provided evidence for enhanced nitrogen self‐purification downstream.As confirmed by most probable number (MPN) counts, high nitrification rates in biofilm close downstream were related to enhanced (more than almost 3 log) nitrifying bacteria densities (up to 7.6×109 MPN m−2). Downstream of an urban centre, nitrogen transformations in the biofilm appeared to be influenced by the occurrence of an adapted microflora which is inoculated or stimulated by anthropic pollution. Copyright © 2002 John Wiley & Sons, Ltd.
Seasonal changes of fish diversity in the main channel of the large lowland River Oder
Authors: Wolter Christian , Bischoff Antje 
Published: January 2005

AbstractBetween June 1998 and May 2000 an adult fish sampling was carried out in the lowland River Oder using bottom otter trawls in the mid channel and electric fishing at the shorelines. This study focused on the lateral connectivity between mid channel and river margins with the aim to characterize the importance of mid‐channel sections as fish habitat.Altogether 15 660 fish of 30 species were sampled, 8169 fish of 20 species in the mid‐channel section and 7491 fish of 27 species at the shoreline. At the shoreline we observed significantly higher fish densities (345.4±51.8 fish per 1000 m3 compared to 5.2±1.0, mean±standard error) and numbers of species (11.1±0.5, respectively, 5.2±0.3). However, three species were exclusively in the mid channel and a further six more frequent there. The mid channel was dominated by silver bream (Abramis bjoerkna) representing 75.6% of the total catch. It was generally colonized by bigger fish (22.1±0.12 cm total length compared to 13.0±0.08 cm).According to the observed significant habitat preferences, we classified a guild of potamal species, which shift during their first year of life to mid‐channel habitats and exhibited the highest relative abundance there. To this guild belong the following species: silver bream, common bream (Abramis brama), blue bream (Abramis ballerus), whitefin gudgeon (Gobio albipinnatus), zander (Sander lucioperca) and wels (Silurus glanis). Copyright © 2001 John Wiley & Sons, Ltd.
Regional‐scale effects of flow regulation on lowland riverine fish communities in New South Wales, Australia
Authors: Gehrke P.C. , Harris J.H. 
Published: January 2005

AbstractLowland reaches of 40 rivers in New South Wales, Australia, were designated as ‘regulated’ or ‘unregulated’, depending upon the degree to which flows were modified by the operation of a dam upstream. Five replicate rivers of each type were selected from the North Coast, South Coast, Darling and Murray regions in the State. Fish communities in each river were sampled in summer and winter in two consecutive years. Regulated and unregulated rivers contained significantly different fish communities, although communities in each region retained characteristic features. The proportion of native species in the total catch was greater in unregulated rivers in all regions, ranging from 27% in the Murray region to 100% in South Coast rivers. In regulated rivers, native species made up 20% of the catch in the Murray region compared with a maximum of 99% in the North Coast. Carp, Cyprinus carpio, were the main alien species contributing to changes in the proportional abundance of native fish. Native species most affected by river regulation were western carp gudgeons, Hypseleotris spp., bony herring, Nematalosa erebi, and striped gudgeons, Gobiomorphus australis. Fifteen native species showed some effect of river regulation on their population structures. Individual species showed positive, negative or mixed positive and negative, effects of regulation, at population, species or community levels. Three abundant alien species and seven native species showed only positive or mixed responses, whereas 13 native species exhibited only negative effects. Flow regulation has reduced the resilience of New South Wales rivers and native fish communities to invasion by alien species. New research has commenced to investigate whether recently introduced environmental flow rules are effective in reducing the effects of river flow alteration on fish communities in New South Wales rivers. Copyright © 2001 John Wiley & Sons, Ltd.
Effects of flood interruption on species richness, diversity and floristic composition of woody regeneration in the Upper Rhine alluvial hardwood forest
Authors: Deiller Anne‐Frédérique , Walter Jean‐Michel N. , Trémolières Michèle 
Published: January 2005

AbstractRegulation works in the Upper Rhine carried out since the 19th century have drastically modified the floodplain forest ecosystem in the Alsace Plain. These works have disconnected the largest part of the riparian forest from the river and interrupted the flooding. This study aims at assessing the effects of the flood interruption on woody regeneration in three hardwood stands: one still liable to flooding, the second one unflooded for 30 years and the third one unflooded for 130 years. Fieldwork was carried out to determine the species richness of seed rain, seed bank and extant vegetation of the regeneration understorey. The potential species richness was calculated using the first‐order jackknife estimator. In addition, floristic composition and diversity indices of extant vegetation were calculated. Results show that species richness of the seed bank is lower than seed rain and extant vegetation. The species richness of the extant vegetation increases with the duration of interruption of the floods in the Rhine forest as a result of introduction of flood‐intolerant species in the unflooded forest. Although species richness of the extant vegetation was the lowest in the flooded site, Shannon–Weaver diversity and equitability were found to be the highest, because the disturbance caused by floods allows a more equal coexistence of several species. Conversely, in the unflooded sites, a small number of species represent most of the woody individuals of the regeneration phase. Implications of flood restoration on species richness and diversity of the regeneration compartment are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Field experiments on stranding in juvenile atlantic salmon (Salmo salar) and brown trout (Salmo trutta) during rapid flow decreases caused by hydropeaking
Authors: Saltveit S.J. , Halleraker J.H. , Arnekleiv J.V. , Harby A. 
Published: January 2005

AbstractField experiments showed that sudden reductions in river flow may cause high mortality of juvenile salmonids through stranding. A 75‐m2 enclosure in the drawdown zone of a regulated river was stocked with a known number of wild 0+ and/or 1+ wild Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). The number stranded was estimated by counting the surviving fish collected in a bag as they left the enclosure.In general, a far higher incidence of fish stranding was found during winter conditions (<4.5°C) compared with the higher temperatures during late summer and early autumn. This is probably mainly because of lower fish activity during the cold season and a substrate seeking behaviour especially during daytime. Stranding was lower at night, probably because of a predominant night active behaviour. Hatchery salmon behaved oppositely to wild fish, and studies based on cultivated fish may give wrong conclusions as to the consequences of hydropeaking. Searching for fish in the substrate underestimated the consequences of sudden flow reductions, as fish were difficult to find. Stranding is not equal to mortality, as fish were found to survive for several hours in the substrate after dewatering. Long shut down procedures of the turbines during daytime, decreased stranding of Atlantic salmon (7–9 cm) drastically under spring conditions. Temperature, season and light conditions have the most pronounced effect on stranding of juvenile salmonids. It is possible to reduce stranding by taking into account these ecological considerations during hydropeaking operations. Copyright © 2001 John Wiley & Sons, Ltd.