bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solution structure of the main α‐amylase inhibitor from amaranth seeds
Authors: Martins José C. , Enassar Mohammed , Willem Rudolph , Wieruzeski Jean‐Michel , Lippens Guy , Wodak Shoshana J. 
Published: March 2003

The most abundant α‐amylase inhibitor (AAI) present in the seeds of Amaranthus hypochondriacus, a variety of the Mexican crop plant amaranth, is the smallest polypeptide (32 residues) known to inhibit α‐amylase activity of insect larvae while leaving that of mammals unaffected. In solution, 1H NMR reveals that AAI isolated from amaranth seeds adopts a major trans (70%) and minor cis (30%) conformation, resulting from slow cis–trans isomerization of the Val15–Pro16 peptide bond. Both solution structures have been determined using 2D 1H‐NMR spectroscopy and xplor followed by restrained energy refinement in the consistent‐valence force field. For the major isomer, a total of 563 distance restraints, including 55 medium‐range and 173 long‐range ones, were available from the NOESY spectra. This rather large number of constraints from a protein of such a small size results from a compact fold, imposed through three disulfide bridges arranged in a cysteine‐knot motif. The structure of the minor cis isomer has also been determined using a smaller constraint set. It reveals a different backbone conformation in the Pro10–Pro20 segment, while preserving the overall global fold. The energy‐refined ensemble of the major isomer, consisting of 20 low‐energy conformers with an average backbone rmsd of 0.29 ± 0.19 Å and no violations larger than 0.4 Å, represents a considerable improvement in precision over a previously reported and independently performed calculation on AAI obtained through solid‐phase synthesis, which was determined with only half the number of medium‐range and long‐range restraints reported here, and featured the trans isomer only. The resulting differences in ensemble precision have been quantified locally and globally, indicating that, for regions of the backbone and a good fraction of the side chains, the conformation is better defined in the new solution structure. Structural comparison of the solution structure with the X‐ray structure of the inhibitor when bound to its α‐amylase target in Tenebrio molitor shows that the backbone conformation is only slightly adjusted on complexation, while that of the side chains involved in protein–protein contacts is similar to those present in solution. Therefore, the overall conformation of AAI appears to be predisposed to binding to its target α‐amylase, confirming the view that it acts as a lid on top of the α‐amylase active site.
Phosphorylation of proteins in the light‐dependent signalling pathway of a filamentous cyanobacterium
Authors: Hübschmann Thomas , Jorissen Helena J. M. M. , Börner Thomas , Gärtner Wolfgang , de Marsac Nicole Tandeau 
Published: March 2003

The genome of the filamentous cyanobacterium Calothrix sp. PCC7601 contains two genes, cphA and cphB, encoding proteins with similarity to plant phytochromes and bacterial histidine kinases. In vitro, CphA and CphB readily attach a tetrapyrrole chromophore to develop spectrally active holoproteins that are photointerconvertible between a red light‐absorbing and a far‐red light‐absorbing form. Together with the putative response regulators, RcpA and RcpB, the putative histidine kinases, CphA and CphB, are suggested to constitute two two‐component systems of light‐dependent signal transduction. In this report, we demonstrate the kinase activity of both CphA and CphB. In vitro experiments carried out on the purified proteins show that CphA and CphB are autophosphorylated in the presence of ATP and that phospho‐CphA is capable of efficient phosphotransfer to RcpA as is phospho‐CphB towards RcpB. The autophosphorylation and the phosphorelay are dependent on light. Both activities are reduced under red light vs. far‐red light irradiation. No phosphoryl transfer occurred between phospho‐CphA and RcpB or between phospho‐CphB and RcpA. The response regulators RcpA and RcpB can receive a phosphoryl moiety also from the small phospho‐donor acetyl phosphate. The stability of the phosphorylated regulators is not affected by CphA and CphB or light.
Characterization of human muscle type cofilin (CFL2) in normal and regenerating muscle
Authors: Thirion Christian , Stucka Rolf , Mendel Bettina , Gruhler Albrecht , Jaksch Michaela , Nowak Kristen J. , Binz Nicolette , Laing Nigel G. , Lochmüller Hanns 
Published: March 2003

Cofilins are actin binding proteins and regulate actin assembly in vivo. Numerous cofilin homologues have been characterized in various organisms including mammals. In mice, a ubiquitously expressed cofilin (CFL1) and a skeletal muscle specific cofilin (CFL2) have been described. In the present study, we identified and characterized a human CFL2 gene localized on chromosome 14, with high homology to murine CFL2. Furthermore, we provide evidence for differentially spliced CFL2 transcripts (CFL2a and CFL2b). CFL2b is expressed predominantly in human skeletal muscle and heart, while CFL2a is expressed in various tissues. Genetic defects of CFL2 were excluded for one human muscle disorder, the chromosome 14 linked distal myopathy MPD1, and shown to be only possible to be a rare cause of another, nemaline myopathy. In a mouse model of mechanically induced muscle damage the changes of cofilin expression were monitored during the first 10 days of regeneration, with dephosphorylated CFL2 being the major isoform at later stages of muscle regeneration. A similar predominance of dephosphorylated CFL2 was observed in chronically regenerating dystrophin‐deficient muscles of Duchenne muscular dystrophy patients. Therefore, the CFL2 isoform may play an important role in normal muscle function and muscle regeneration.
Rapid and cooperative binding of factor XII to human umbilical vein endothelial cells
Authors: Schousboe Inger 
Published: March 2003

When activated, factor XII (FXII) has been shown to play a role in a series of proteolytic cascades including systems as the fibrinolytic, the coagulation, the kallikrein–kinin and the complement. How FXII is activated in vivo remains poorly understood as the concentration and density of surface bound negative charges known to trigger the activation in vitro is far from sufficient in vivo. Specific binding of FXII to cellular receptors in the blood stream may, however, solve this problem which may be a question of inter molecular vicinity enhanced by binding to any surface. Here we report that the Zn2+‐dependent binding of FXII to endothelial cells is rapid, saturable, specific and cooperative. Each endothelial cell from the human umbilical veins was found to bind (417 ± 202) × 103 molecules of FXII with a Kd of (65 ± 23) nM and a Hill coefficient of 2.1. The binding was inhibited by α‐FXIIa but not by β‐FXIIa. The Kd for binding α‐FXIIa was (50 ± 27) nM. The rate of association was found to be 1.9 × 105m−1· min−1. A confirmed inhibition by HK increased the Kd without affecting the maximal number of binding sites and the Hill coefficient. The concentration of HK in serum did not prevent binding of FXII/FXIIa to cells incubated with serum supplemented with Zn2+. The optimal concentration of Zn2+ was 15 µm for binding factor XII/FXIIa whether purified or in serum.
A novel chitinase having a unique mode of action from Aspergillus fumigatus YJ‐407
Authors: Xia Guoqing , Jin Chunsheng , Zhou Ju , Yang Shoujun , Zhang Shuzheng , Jin Cheng 
Published: March 2003

Chitinases are produced throughout the growth process of fungi and are thought to play important roles in morphogenesis. Aspergillus fumigatus, is an important pathogen of immunocompromised individuals in which it causes pneumonia and invasive disseminated disease with high mortality; it is also known to produce chitinase. We have induced an exceptionally stable extracellular chitinase in A. fumigatus YJ‐407, which could be isolated readily in a homogeneous form by using ammonium sulfate precipitation followed by DEAE‐cellulose chromatography and preparative PAGE. The molecular mass of this chitinase was estimated to be 46 000 by SDS/PAGE, and its isoelectric point was pH 5.6. The enzyme was most active at pH 5.0 and 60 °C, and was inhibited strongly by Hg2+, Pb2+, Ag+, Fe2+, Mn2+ and Zn2+. The enzyme was stable over a broad pH range 4–8 and below 45 °C. Tryptophan and carboxyl groups were found to be essential for the enzyme activity. The Michaelis constants for swollen chitin and chitosan were 1.12 mg·mL−1 and 1.84 mg·mL−1, respectively. The enzyme showed maximum activity towards glycol chitin and partially deacetylated chitosan, and lower activity towards colloidal chitin. Analysis of the hydrolysis product showed that the enzyme has both endo‐ and exo‐hydrolytic activities. In addition, a transglycosyl activity was also observed.
Recombinant human factor VIII‐specific affinity ligands selected from phage‐displayed combinatorial libraries of protein A
Authors: Nord Karin , Nord Olof , Uhlén Mathias , Kelley Brian , Ljungqvist Charlotta , Nygren Per‐Åke 
Published: March 2003

Factor VIII‐specific affibodies were selected from phage displayed libraries constructed by combinatorial mutagenesis of an α helical bacterial receptor domain derived from staphylococcal protein A. Bead‐immobilized recombinant human factor VIII (rVIII) (80 and 90 kDa chains) protein was used during competitive biopannings in the presence of free 80‐kDa chain protein, resulting in the selection of several binders that showed dissociation constants (Kd) in the range 100–200 nmas determined by biosensor analyses. One variant (ZrVIII:3, 90‐kDa chain specific) was further characterized in small‐scale affinity chromatography experiments, and showed efficient and selective recovery of biologically active rVIII from Chinese hamster ovary cell supernatant‐derived feed stocks. The purity of the enriched rVIII was comparable with rVIII material purified by immunoaffinity chromatography using a 90‐kDa chain‐specific monoclonal antibody. Interestingly, epitope mapping showed that the monoclonal antibody and the affibody ligand competed for the same or at least overlapping epitopes on rVIII. In addition, the ZrVIII:3variant was produced by peptide synthesis with a C‐terminal cysteine to enable directed coupling to solid supports. This 59‐residue protein was analyzed by circular dichroism and showed a secondary structure content similar to that of the parental Z domain used as scaffold. In biosensor studies, the synthetic affibody was immobilized recruiting the C‐terminal cysteine residue, and demonstrated to bind both recombinantly produced and plasma‐derived factor VIII. From a secondary library, constructed by re‐randomization of relevant positions identified after alignment of the first‐generation variants, a panel of affinity‐improved second‐generation affibodies were selected of which one clone showed a dissociation constant (Kd) for rVIII of 5 nm. Several of these variants also showed higher apparent binding efficiencies towards rVIII when analyzed as immobilized ligands in biosensor experiments. Taken together, the results suggest that affibody ligands produced by bacterial or synthetic routes could be of interest as an alternative to monoclonal antibodies in purification processes or as diagnostic or monitoring tools.
Female Choice, Female Reluctance to Mate and Sexual Selection on Body Size in the Dung Fly Sepsis cynipsea
Authors: Blanckenhorn Wolf U. , Mühlhäuser Claudia , Morf Cornelia , Reusch Thomas , Reuter Max 
Published: March 2003

AbstractWe investigated the mechanisms of sexual selection in the common dung fly Sepsis cynipsea and how these affect selection on body size at the population level. Because of the presumed costs associated with mating, we predicted that there would be a decrease in the general reluctance of females to mate with any particular male at higher male densities at the mating site, a fresh cow pat, resulting in indirect female choice and a decrease in the strength of sexual selection. In contrast, classical direct female choice and male‐male competition should result in increased selection intensities because more opportunities for choice and competition exist at higher densities. Female reluctance to mate and female assessment of males are expressed in prominent female behaviour to repel mates in several insect species, including S. cynipsea. Laboratory pair‐wise choice experiments showed that large males were more likely to obtain copulations, which also ensued more promptly, suggesting female assessment of male quality (direct female choice). There was a basic influence of male activity but little further effect of male scramble competition on the outcome of mating. Another laboratory experiment showed a decrease in female shaking duration per male, associated with an asymptote in the shaking duration per female, as male density and harassment increased, but did not show the increase in mating frequency predicted by the female reluctance hypothesis. A study estimating sexual selection differentials in the field showed that directional selection for larger males was present overall and was negatively related to seasonally mediated variation in male density. Our study suggests that direct female choice in combination with indirect female choice (due to an interaction of female reluctance to mate and male persistence) is most consistent with the behavioural and selection patterns observed in S. cynipsea, but male effects cannot be definitively excluded.
Testing for Effects of UV‐B Radiation on Anti‐Predator Behavior in Amphibians: A Critique and Some Suggestions
Authors: Cummins Clive P. 
Published: March 2003

AbstractIn a recent paper, Kats et al. (2000) reported three experiments intended to test for effects of UV‐B radiation (hereafter, UV‐B) on predator‐avoidance behaviors in three amphibian species. They introduced their study in the context of concern about increasing penetration of solar UV‐B to ground level, owing to loss of stratospheric ozone, and its possible effects on amphibian populations. Kats et al. concluded from their results: `ultraviolet exposure may have important sub‐lethal effects in amphibians that could adversely effect (sic) their fitness'. As Kats et al. cited field studies that apparently demonstrated lethal effects of ambient levels of UV‐B on amphibians, their conclusion that sub‐lethal effects may occur is not obviously contentious. Furthermore, their experiments appear to be based on accepted methods. Nevertheless, I contend that the conclusions drawn by Kats et al. are not justified by the results they reported. Here, I discuss some problems with their study and suggest some possible improvements for future studies.
Identification of the Sex Responsible for Recognition and the Method of Ejection of Parasitic Eggs in Some Potential Common Cuckoo Hosts
Authors: Soler Manuel , Martín‐Vivaldi Manuel , Pérez‐Contreras Tomás 
Published: March 2003

AbstractEgg rejection is the most common defence used by hosts against avian brood parasites and experimental studies have provided some of the best documented demonstrations of the coevolutionary process. However, the sex responsible for egg ejection and whether eggs are grasped or punctured are two essential questions that remain unanswered for most host species. In this paper, by filming the behaviour of individuals of three different species confronted with a foreign egg experimentally introduced into their nests, we first determine the relationship between recognition (when the birds aggressively pecked the experimental egg) and ejection. Secondly, we demonstrate that in the species where only the female incubates, only the female recognizes and ejects the model egg, whereas in the two species where both sexes incubate, both sexes eject the foreign egg. Finally, the large host species ejected the model egg by grasping it with the bill, whereas the two small species ejected it by puncturing it first. Furthermore, our data suggest that puncture ejection is more costly than grasping ejection considered both in terms of energetic and ejection costs.
The Neuroendocrine Function of Allosuckling
Authors: Roulin Alexandre 
Published: March 2003

AbstractIn mammals, females occasionally nurse offspring that are not their own. The function of allosuckling for foster females remains puzzling given that lactation is energetically costly and augments the risk of pathogen transmission. Current hypotheses suggest that allosuckling is not adaptive resulting from misguided parental behaviour, females reciprocate by nursing each other's offspring, females nurse preferentially related offspring for inclusive fitness benefits, females involved in allosuckling events evacuate extra milk or improve their maternal skills. These hypotheses received only little empirical evidence, and a recent review suggested that they are not mutually exclusive and do not exclude alternatives. Based on the established fact that teat stimulation by neonates leads to an elevated production of prolactin, I develop the hypothesis called ‘neuroendocrine function of allosuckling’ (NFA). The hypothesis postulates that the nursing of alien offspring allows females to increase and/or maintain prolactin concentration in the case own offspring do not stimulate their teats enough. This neurohormone enhances immunocompetence, the immunological quality and the quantity of milk whilst reducing female's fertility. The NFA suggests that via teat stimulation by the genetic offspring, and if necessary by foster ones, females can optimally adjust prolactin concentration, as both hypo‐ and hyper‐prolactinaemia entail physiological and immunological costs. The hypothesis does not only provide an explanation as to why females may nurse alien offspring but is also useful to understand the consequences of allosuckling. Indeed, even if mothers do not nurse alien offspring to control their prolactin production, allosuckling will alter the concentration of this crucial neurohormone.
Effect of three species of bacteria on damping‐off, root rot development, and ectomycorrhizal colonization of lodgepole pine and white spruce seedlings
Authors: Pedersen E. A. , Reddy M. S. , Chakravarty P. 
Published: March 2003

SummaryInteractions between three species of bacteria (Burkholderia cepacia, Pseudomonas chlororaphis and Pseudomonas fluorescens), an ectomycorrhizal fungus (Paxillus involutus), and three root pathogenic fungi (Fusarium moniliforme, Fusarium oxysporum and Rhizoctonia solani) were studied. Burkholderia cepacia significantly reduced the in vitro mycelial growth of P. involutus, whereas, B. cepacia, Ps. chlororaphis, Ps. fluorescens and P. involutus reduced the mycelial growth of F. moniliforme, F. oxysporum and R. solani. Culture filtrates of B. cepacia, Ps. chlororaphis, Ps. fluorescens and P. involutus reduced conidial germination and increased the formation of chlamydospores of F. moniliforme and F. oxysporum. Burkholderia cepacia also reduced the formation of ectomycorrhizal short roots by P. involutus on lodgepole pine (Pinus contorta) and white spruce (Picea glauca) seedlings 2 months after inoculation. However, no significance difference in mycorrhizal short roots was observed after 4 months. The fungicide Anchor (a mixture of carboxine and thiram) significantly reduced root rot severity and increased the survival of lodgepole pine seedlings grown in a growth mix infested with F. moniliforme, F. oxysporum and R. solani. Control of the diseases of white spruce caused by these pathogens was not as successful. Treatment of seeds with either B. cepacia or P. involutus alone significantly increased the survival of seedlings grown in a mix that was inoculated with F. moniliforme and reduced the root rot severity caused by F. moniliforme and F. oxysporum, but not R. solani. Higher seedling survival and lower root rot severity were observed when conifer seeds were concomitantly inoculated with one of the bacterial species, P. involutus and Anchor.
Heterobasidion annosum group S identified in north‐eastern China
Authors: Dai Y‐C. , Korhonen K. 
Published: March 2003

SummarySamples of Heterobasidion annosum were collected in two stands of mixed forest in Changbaishan Nature Reserve in north‐eastern China. Pure cultures were isolated from 15 specimens growing on Abies, Picea, Pinus and Populus. Mating tests showed that all these collections belong to the S inter‐sterility group. The compatibility of Chinese homokaryons with S homokaryons from Europe was 100%. Clamp connections appeared almost equally in both strains of each pairing, and no distinct demarcation line formed in the pairings. The mating frequency of Chinese isolates with the European F group was also high, approximately 94%. These matings, however, were usually unilateral and a more or less distinct demarcation line was present in most of the pairings. The Chinese isolates were completely intersterile with the European P group. The S group of H. annosum in north‐eastern China appears to have similar morphology and ecology as in Europe. It is common on Abies and Picea, but is not a serious pathogen in the pristine forests of north‐eastern China.
Effects of benomyl and captan on growth and mycorrhizal colonization of Sitka‐spruce (Picea sitchensis) and ash (Fraxinus excelsior) in Irish nursery soil
Authors: O'neill J. J. M. , Mitchell D. T. 
Published: March 2003

SummaryThe effects of two fungicides (benomyl and captan ‐ at recommended doses and up to three soil drenches) on root development and mycorrhizal colonization of Sitka‐spruce (Picea sitchensis) and ash (Fraxinus excelsior) were examined after 20 weeks growth, under environmentally controlled conditions, in soil from an Irish tree nursery. Although four mycorrhizal types have been found on Sitka‐spruce at the nursery, only one ectomycorrhizal type (Piceirhiza horti‐inflata) was identified on the short roots in this study. An inoculant (Vaminoc: MicroBio Ltd, Hemel Hempstead, UK) was used to inoculate ash and 20‐week‐old seedlings had a higher arbuscular mycorrhizal (AM) colonization in comparison with uninoculated controls. Multiple applications (2–3) of benomyl reduced the length of root and shoot and shoot dry mass of Sitka‐spruce, whereas in ash, it only depressed root length. Benomyl decreased the numbers of ectomycorrhizas of Sitka‐spruce and arbuscular mycorrhizal colonization of Vaminoc‐inoculated ash. A single application of captan stimulated root length and ectomycorrhizal colonization of Sitka‐spruce and root dry mass in ash compared with uninoculated controls. Applications of captan reduced arbuscular mycorrhizal colonization of Vaminoc‐inoculated ash to levels near to those of uninoculated controls. Of the two fungicides used, benomyl had the most deleterious effect on root length and mycorrhizal colonization of Sitka‐spruce and ash.
First report of bacterial wilt caused by Ralstonia solanacearum on eucalypts in South Africa
Authors: Coutinho T. A. , Roux J. , Riedel K‐H. , Terblanche J. , Wingfield M. J. 
Published: March 2003

Summary Ralstonia solanacearum, the causal agent of bacterial wilt, has one of the widest host ranges of all phytopathogenic bacteria. This pathogen was first reported on Eucalyptus spp. in the late 1980s in Brazil. Since then, there have been reports of its occurrence on this host in Australia, China and Venezuela. Early in 1997, an 18‐month‐old clonally propagated Eucalyptus grandis × Eucalyptus camaldulensis (GC) hybrid in Zululand, KwaZulu/Natal, showed signs of wilting. The vascular tissue of infected trees was dicoloured and bacterial exudation was produced from cut surfaces. The bacterium was consistently isolated from diseased tissue, purified and identified as R. solanacearum biovar 3 race 1, using the BioLog bacterial identification system. Inoculation trials were conducted on three E. grandis × E. camaldulensis clones (GC515, GC550 and GC505). Clone GC550 displayed wilting after 3 days and all cuttings subsequently died. Clones GC515 and GC505 appeared to be less susceptible with cuttings not showing signs of disease until 7 days after inoculation. After 14 days, 90 and 80%, respectively, of cuttings of these two clones had died. This is the first report of bacterial wilt on Eucalyptus in South Africa.