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  • 1
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    Editorial: Flank dynamics, sector collapses, lahars, and rockfalls: analysis, monitoring, and modelling of small to large scale volcanic slope instability (2020)
    Springer
    Details
    Publication Date: 2020-11-12
    Description: Slope dynamics in volcanic environments comprise a wide spectrum of phenomena, from large lateral collapse to shallow debris remobilization, which may represent a major threat for human communities and infrastructures. Many volcanos built up from the ocean floor and large portions of the volcano edifice are submerged. In these settings, only the edifice’s summit can be investigated by terrestrial remote sensing and in-situ approaches. Growth and destruction, including tectonics and gravitational phenomena, affect entire volcano flanks and are not limited to the physical boundary of the sea level but could comprise their subaqueous parts.
    Description: Published
    Description: 2615–2618
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: JCR Journal
    Keywords: volcanoes ; flanks ; volcano-tectonics ; structure ; collapse ; stability ; 04.08. Volcanology ; 05.08. Risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Electronic Resource
    Electronic Resource
    A screen of yeast respiratory mutants for sensitivity against the mycotoxin citrinin identifies the vacuolar ATPase as an essential factor for the toxicity mechanism (2000)
    Springer
    Current genetics 37 (2000), S. 227-284 
    Details
    ISSN: 1432-0983
    Keywords: Key words Citrinin ; Pet mutants ; Mitochondrial biogenesis ; Vacuolar ATPase ; YKL118W disruption ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In countries with a hot climate the mycotoxin citrinin represents a serious problem in fungal food-poisoning. In humans the renal system is affected the most and the mitochondrial respiratory chain was identified as a possible sensitive target for this toxin. In addition, citrinin has an antifungal activity that also inhibits the growth of the yeast Saccharomyces cerevisiae. So far the precise mode of action and the subcellular targets for citrinin have not been identified. Therefore, we decided to use the model organism yeast for a genetic approach to identify genes that play a role in the sensitivity against this mycotoxin. A large collection of conditional respiratory deficient yeast mutants was screened for sensitivity against citrinin. One special pet-ts mutant was identified that exhibited a higher sensitivity against citrinin. The genetic system of yeast allowed the isolation of the respective wild-type gene. This yeast gene encodes the Vph2p subunit that is essential for the correct assembly of the vacuolar ATPase. Isolation of the mutated gene and gene-disruption experiments of VPH2 and the partially overlapping small YKL118W gene verified this finding. The wild-type VPH2 gene restores all defects of the mutants. In contrast to this, YKL118W gave no complementation and the null mutant showed no phenotype. Thereby the yeast vacuolar ATPase was found to be important for the toxic effect of citrinin in yeast cells. The consequences of this finding for the molecular mechanism of citrinin action and its relation to the mitochondrial respiratory chain are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940070001
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  • 3
    Electronic Resource
    Electronic Resource
    Recessive mutations in SUP35 and SUP45 genes coding for translation release factors affect chromosome stability in Saccharomyces cerevisiae (2000)
    Springer
    Current genetics 37 (2000), S. 285-291 
    Details
    ISSN: 1432-0983
    Keywords: Key words Translation release factors ; Chromosome stability ; Microtubules ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chromosome stability in suppressor mutants for SUP35 and SUP45 genes coding for translation release factors was studied. We obtained spontaneous and UV-induced sup35 or sup45 mutants in a haploid strain disomic for chromosome III and tested the stability of an extra copy of this chromosome. The majority of the mutants showed increased chromosome instability. This phenotype was correlated with an increased sensitivity to the microtubule-poisoning drug benomyl which affects chromosome segregation at anaphase. Our data suggest that termination-translation factors eRF3 and eRF1 control chromosome transmission at mitotic anaphase in Saccharomyces cerevisiae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050529
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  • 4
    Electronic Resource
    Electronic Resource
    Surface Instability of Laminated Coatings upon Inelastic Deformation (2000)
    Springer
    Mechanics of composite materials 36 (2000), S. 475-480 
    Details
    ISSN: 1573-8922
    Keywords: stability ; three-dimensional theory ; tribotechnics ; elastoplastic deformations ; viscoelasticity ; surface ; tracking and dead loads ; laminated coating ; piecewise-homogeneous model ; active loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The problem of surface instability of laminated coatings with inelastic properties is considered within the framework of a model of piecewise-homogeneous media on the basis of the three-dimensional linearized theory of stability. A general statement of the problem is formulated and the basic characteristic equations are derived. The solutions of particular problems are obtained for elastoplastic and viscoelastic models of solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006758600457
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  • 5
    Electronic Resource
    Electronic Resource
    On the Stability of Nonconservative Systems with Estimation of the Attraction Domain (2000)
    Springer
    Journal of dynamical and control systems 6 (2000), S. 503-510 
    Details
    ISSN: 1573-8698
    Keywords: nonconservative mechanical systems ; stability ; Lyapunov functions ; attraction domain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mechanical systems subjected to dissipative, gyroscopic, conservative, and also nonconservative positional forces are considered. The question of the effect of dissipative, gyroscopic, and conservative forces on the motion stability of a mechanical systems is determined by classical Kelvin–Chetaev theorems [1]. The presence of nonconservative positional forces considerably complicates the situation and excludes direct application of these theorems. Applying Lyapunov's functions method the condition of asymptotic stability of a mechanical system under the action of all listed above forces is obtained. Moreover, the estimation of the attraction domain in phase space is found. The precession system which is used in the solution of some problems in the applied theory of the gyroscopic systems is also examined. The connection between the stability of origin and precession systems is detected. Theoretical results are applied to the stabilization problem of stationary motion of the balanced gimbal suspension gyro by means of external moments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009500527061
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  • 6
    Electronic Resource
    Electronic Resource
    Stability of Solutions of Stochastic Functional Differential Equations with an Infinite Previous History and Poisson Switchings. II (2000)
    Springer
    Cybernetics and systems analysis 36 (2000), S. 699-721 
    Details
    ISSN: 1573-8337
    Keywords: stability ; stochastic functional differential equations ; previous history ; Poisson switchings ; "dangling spider" model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract To study the stability of the stochastic "dangling spider" model, the second Lyapunov method is substantiated for stochastic differential functional equations with the whole previous history.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009428806622
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  • 7
    Electronic Resource
    Electronic Resource
    POL32, a subunit of the Saccharomyces cerevisiae DNA polymerase δ, defines a link between DNA replication and the mutagenic bypass repair pathway (2000)
    Springer
    Current genetics 38 (2000), S. 178-187 
    Details
    ISSN: 1432-0983
    Keywords: Key wordsPOL32 ; SRS2 ; DNA repair ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pol32 is a subunit of Saccharomyces cerevisiae DNA polymerase δ required in DNA replication and repair. To gain insight into the function of Pol32 and to determine in which repair pathway POL32 may be involved, we extended the analysis of the pol32Δ mutant with respect to UV and methylation sensitivity, UV-induced mutagenesis; and we performed an epistasis analysis of UV sensitivity by combining the pol32Δ with mutations in several genes for postreplication repair (RAD6 group), nucleotide excision repair (RAD3 group) and recombinational repair (RAD52 group). These studies showed that pol32Δ is deficient in UV-induced mutagenesis and place POL32 in the error-prone RAD6/REV3 pathway. We also found that the increase in the CAN1 spontaneous forward mutation of different rad mutators relies entirely or partially on a functional POL32 gene. Moreover, in a two-hybrid screen, we observed that Pol32 interacts with Srs2, a DNA helicase required for DNA replication and mutagenesis. Simultaneous deletion of POL32 and SRS2 dramatically decreases cellular viability at 15 °C and greatly increases cellular sensitivity to hydroxyurea at the permissive temperature. Based on these findings, we propose that POL32 defines a link between the DNA polymerase and helicase activities, and plays a role in the mutagenic bypass repair pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940000149
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  • 8
    Electronic Resource
    Electronic Resource
    Protein Spray-Freeze Drying. Effect of Atomization Conditions on Particle Size and Stability (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 1374-1382 
    Details
    ISSN: 1573-904X
    Keywords: particle size ; PLG microspheres ; protein delivery ; spray-freeze drying ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the effect of atomization conditions on particle size and stability of spray-freeze dried protein. Methods. Atomization variables were explored for excipient-free (no zinc added) and zinc-complexed bovine serum albumin (BSA). Particle size was measured by laser diffraction light scattering following sonication in organic solvent containing poly(lactide-co-glycolide) (PLG). Powder surface area was determined from the N2 vapor sorption isotherm. Size-exclusion chromatography (SEC) was used to assess decrease in percent protein monomer. Fourier-transform infrared (FTIR) spectroscopy was employed to estimate protein secondary structure. PLG microspheres were made using a non-aqueous, cryogenic process and release of spray-freeze dried BSA was assessed in vitro. Results. The most significant atomization parameter affecting particle size was the mass flow ratio (mass of atomization N2 relative to that for liquid feed). Particle size was inversely related to specific surface area and the amount of protein aggregates formed. Zinc-complexation reduced the specific surface area and stabilized the protein against aggregation. FTIR data indicated perturbations in secondary structure upon spray-freeze drying for both excipient-free and zinc-complexed protein. Conclusions. Upon sonication, spray-freeze dried protein powders exhibited friability, or susceptibility towards disintegration. For excipient-free protein, conditions where the mass flow ratio was 〉 ∼0.3 yielded sub-micron powders with relatively large specific surface areas. Reduced particle size was also linked to a decrease in the percentage of protein monomer upon drying. This effect was ameliorated by zinc-complexation, via a mechanism involving reduction in specific surface area of the powder rather than stabilization of secondary structure. Reduction of protein particle size was beneficial in reducing the initial release (burst) of the protein encapsulated in PLG microspheres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007570030368
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  • 9
    Electronic Resource
    Electronic Resource
    Formulation Development and Antitumor Activity of a Filter-Sterilizable Emulsion of Paclitaxel (2000)
    Springer
    Pharmaceutical research 17 (2000), S. 175-182 
    Details
    ISSN: 1573-904X
    Keywords: paclitaxel ; emulsions ; filter-sterization ; particle size ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Paclitaxel is currently administered i.v. as a slow infusion of asolution of the drug in an ethanol:surfactant:saline admixture. However,poor solubilization and toxicity are associated with this drug therapy.Alternative drug delivery systems, including parenteral emulsions, areunder development in recent years to reduce drug toxicity, improveefficacy and eliminate premedication. Methods. Paclitaxel emulsions were prepared by high-shearhomogenization. The particle size of the emulsions was measured by dynamiclight scattering. Drug concentration was quantified by HPLC and invitro drug release was monitored by membrane dialysis. The physicalstability of emulsions was monitored by particle size changes in boththe mean droplet diameter and 99% cumulative distribution. Paclitaxelpotency and changes in the concentration of known degradants wereused as chemical stability indicators. Single dose acute toxicity studieswere conducted in healthy mice and efficacy studies in B16 melanomatumor-bearing mice. Results. QW8184, a physically and chemically stable sub-micronoil-in-water (o/w) emulsion of paclitaxel, can be prepared at high drugloading (8-10 mg/mL) having a mean droplet diameter of 〈100 nmand 99% cumulative particle size distribution of 〈200 nm. In vitro release studies demonstrated low and sustained drug release both inthe presence and absence of human serum albumin. Based on singledose acute toxicity studies, QW8184 is well tolerated both in miceand rats with about a 3-fold increase in the maximum-tolerated-dose(MTD) over the current marketed drug formulation. Using the B16mouse melanoma model, a significant improvement in drug efficacywas observed with QW8184 over Taxol®. Conclusions. QW8184, a stable sub-micron o/w emulsion of paclitaxelhas been developed that can be filter-sterilized and administered i.v.as a bolus dose. When compared to Taxol®, this emulsion exhibitedreduced toxicity and improved efficacy most likely due to thecomposition and dependent physicochemical characteristics of the emulsion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007565230130
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  • 10
    Electronic Resource
    Electronic Resource
    MUS81 encodes a novel Helix-hairpin-Helix protein involved in the response to UV- and methylation-induced DNA damage in Saccharomyces cerevisiae (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 812-827 
    Details
    ISSN: 1617-4623
    Keywords: Key words DNA repair ; Helix-hairpin-Helix motif ; Methylmethane sulfonate (MMS) ; Saccharomyces cerevisiae ; UV radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gene MUS81 (Methyl methansulfonate, UV sensitive) was identified as clone 81 in a two-hybrid screen using the Saccharomyces cerevisiae Rad54 protein as a bait. It encodes a novel protein with a predicted molecular mass of 72,316 (632 amino acids) and contains two helix-hairpin-helix motifs, which are found in many proteins involved in DNA metabolism in bacteria, yeast, and mammals. Mus81p also shares homology with motifs found in the XPF endonuclease superfamily. Deletion of MUS81 caused a recessive methyl methansulfonate- and UV-sensitive phenotype. However, mus81Δ cells were not significantly more sensitive than wild-type to γ-radiation or double-strand breaks induced by HO endonuclease. Double mutant analysis suggests that Rad54p and Mus81p act in one pathway for the repair of, or tolerance to, UV-induced DNA damage. A complex containing Mus81p and Rad54p was identified in immunoprecipitation experiments. Deletion of MUS81 virtually eliminated sporulation in one strain background and reduced sporulation and spore viability in another. Potential homologs of Mus81p have been identified in Schizosaccharomyces pombe, Caenorhabditis elegans and Arabidopsis thaliana. We hypothesize that Mus81p plays a role in the recognition and/or processing of certain types of DNA damage (caused by UV and MMS) during repair or tolerance processes involving the recombinational repair pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380000241
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  • 11
    Electronic Resource
    Electronic Resource
    Structure-function relationships in replication origins of the yeast Saccharomyces cerevisiae: higher-order structural organization of DNA in regions flanking the ARS consensus sequence (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 854-866 
    Details
    ISSN: 1617-4623
    Keywords: Key words Autonomously replicating sequence (ARS) ; Anti-bent DNA ; DNA structure ; Replication origin ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to better understand the involvement of the DNA molecule in the replication initiation process we have characterized the structure of the DNA at Autonomously Replicating Sequences (ARSs) in Saccharomyces cerevisiae. Using a new method for anti-bent DNA analysis, which allowed us to take into account the bending contribution of each successive base plate, we have investigated the higher-order structural organization of the DNA in the region which immediately surrounds the ARS consensus sequence (ACS). We have identified left- and right-handed anti-bent DNAs which flank this consensus sequence. The data show that this organization correlates with an active ACS. Analysis of the minimum nucleotide sequence providing ARS function to plasmids reveals an example where the critical nucleotides are restricted to the ACS and the right-handed anti-bent DNA domain, although most of the origins considered contained both left- and right-handed anti-bent DNAs. Moreover, mutational analysis shows that the right-handed form is necessary in order to sustain a specific DNA conformation which is correlated with the level of plasmid maintenance. A model for the role of these individual structural components of the yeast replication origin is presented. We discuss the possible role of the right-handed anti-bent DNA domain, in conjunction with the ACS, in the process of replication initiation, and potentialities offered by the combination of left- and right-handed structural components in origin function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380000253
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  • 12
    Electronic Resource
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    Characterization of staurosporine-sensitive mutants of Saccharomyces cerevisiae: vacuolar functions affect staurosporine sensitivity (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 877-888 
    Details
    ISSN: 1617-4623
    Keywords: Key words Staurosporine ; Vacuolar-type proton pumping ATPase ; Vacuolar protein sorting ; ATP-binding cassette transporter ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutations at several loci affect the sensitivity of the yeast Saccharomyces cerevisiae to staurosporine. We report here the characterization of novel staurosporine- and temperature-sensitive mutants (stt). Cloning and integration mapping showed that the genes STT2/STT6, STT5, STT7, STT8 and STT9 are allelic to VPS18, ERG10, GPI1, VPS34 and VPS11, respectively. The products of ERG10 and GPI1, respectively, catalyze mevalonate and glycosyl phosphatidylinositol anchor synthesis, while VPS18 and VPS11 genes belong to the class C VPS (Vacuolar Protein Sorting) genes, and the VPS34 gene is classified as a class D VPS. Therefore, staurosporine sensitivity is affected by ergosterol and glycolipid biosynthesis and by vacuolar functions. We found that other vps mutants belonging to classes C and D exhibit staurosporine sensitivity, and that they show calcium sensitivity and fail to grow on glycerol as the sole carbon source; both of the last two characteristics are shared by vacuolar H+-ATPase mutants (vma). As vma mutants were also found to show staurosporine-sensitive growth, staurosporine sensitivity is likely to be affected by acidification of the vacuole. Moreover, wild type yeast cells are more sensitive to staurosporine in alkaline media than in acidic media, suggesting that staurosporine is exported from the cytosol by H+/drug antiporters. Pleiotropic drug resistance (PDR) genes also provide some resistance to staurosporine, because Δpdr5, Δsnq2 and Δyor1 strains are more sensitive to staurosporine than the wild-type strain. This suggests that staurosporine is also exported by the ATP-binding cassette (ABC) transporters on the plasma membrane. vma mutants and vps mutants of classes C and D vps are sensitive to hygromycin B and vanadate, while ABC transporter-depleted mutants do not show such sensitivity, indicating that two systems differ in their ability to protect the cell against different types of drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380000255
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  • 13
    Electronic Resource
    Electronic Resource
    Multiple copies of MRG19 suppress transcription of the GAL1 promoter in a GAL80 -dependent manner in Saccharomyces cerevisiae (2000)
    Springer
    Molecular genetics and genomics 262 (2000), S. 1113-1122 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsGAL regulon ; Transcription ; Saccharomyces cerevisiae ; Galactose suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A plasmid clone that suppresses galactose toxicity in a gal7 yeast strain has been isolated from a multicopy genomic DNA library. Molecular analysis revealed that the region responsible for the suppression of galactose toxicity corresponds to the ORF YPR030w, which was named MRG19. A CEN-based plasmid carrying the above ORF was unable to suppress the toxicity. Galactokinase activity was substantially reduced in cell extracts obtained from transformants bearing multiple copies of MRG19. Multiple copies of MRG19 were also able to suppress galactokinase expression driven by the CYC1 promoter but not the TEF1 promoter. Multiple copies of MRG19 could not suppress GAL1-driven galactokinase expression in a gal80 strain. However, MRG19-mediated suppression of CYC1-driven galactokinase expression was independent of GAL80 function. These results imply that multiple copies of MRG19 suppress galactokinase expression probably at the level of transcription. In agreement with this idea, multiple copies of MRG19 also suppress β-galactosidase expression driven by the GAL1 promoter in a GAL80-dependent manner. Disruption of MRG19 leads to an increase in the cell density at stationary phase in synthetic complete medium. MRG19 encodes a previously uncharacterised 124-kDa protein that shows no sequence homology to any known proteins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008654
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  • 14
    Electronic Resource
    Electronic Resource
    Involvement of the Inverted Repeat of the yeast 2-micron plasmid in Flp site-specific and RAD52-dependent homologous recombination (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 81-89 
    Details
    ISSN: 1617-4623
    Keywords: Key words Flp recombinase ; Site-specific recombination ; Homologous recombination ; RAD52 ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Site-specific recombination within the Saccharomyces cerevisiae 2-micron DNA plasmid is catalyzed by the Flp recombinase at specific Flp Recognition Target (FRT) sites, which lie near the center of two precise 599-bp Inverted Repeats (IRs). However, the role of IR DNA sequences other than the FRT itself for the function of the Flp reaction in vivo is not known. In the present work we report that recombination efficiency differs depending on whether the FRT or the entire IR serves as the substrate for Flp. We also provide evidence for the involvement of the IR in RAD52-dependent homologous recombination. In contrast, the catalysis of site-specific recombination between two FRTs does not require the function of RAD52. The efficiency of Flp site-specific recombination between two IRs cloned in the same orientation is about one hundred times higher than that obtained when only the two FRTs are present. Moreover, we demonstrate that a single IR can activate RAD52-dependent homologous recombination between two flanking DNA regions, providing new insights into the role of the IR as a substrate for recombination and a new experimental tool with which to study the molecular mechanism of homologous recombination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008678
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  • 15
    Electronic Resource
    Electronic Resource
    Ambient pH signalling in ascomycetous yeasts involves homologues of theAspergillus nidulans genes palF and palH (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 505-513 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsYarrowia lipolytica ; Saccharomyces cerevisiae ; Ambient pH signalling ; Signal transduction ; Transmembrane protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Yarrowia lipolytica, the transcription factor Rim101p mediates both pH regulation and control of mating and sporulation. Like its homologues PacC of Aspergillus nidulans and Rim101p of Saccharomyces cerevisiae, YlRim101p is activated by proteolytic C-terminal processing, which occurs in response to a signal transduced by a pathway involving several PAL gene products. We report here the cloning and sequencing of two of these genes, PAL2 and PAL3. PAL2 encodes a putative 632-residue protein with six possible transmembrane segments, which differs from the transmembrane proteins Rim9p of S. cerevisiae and PalI of A. nidulans, but is homologous to A. nidulans PalH and to the product of the ORF YNL294c, a predicted polypeptide of unknown function in S. cerevisiae. PAL3 encodes an 881-residue polypeptide that is homologous to PalF of A. nidulans and to a newly identified putative polypeptide of S. cerevisiae. Both PAL2 and PAL3 are expressed constitutively, regardless of ambient pH. Mutations in these genes affect growth at alkaline pH and sporulation in both Y. lipolytica and in S. cerevisiae. They affect invasiveness of haploid strains in S. cerevisiae only, and conjugation in Y. lipolytica only. These results highlight the conservation of the Pal pathway initially described in A. nidulans.
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    URL: http://dx.doi.org/10.1007/s004380051195
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  • 16
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    Electronic Resource
    Endopolygalacturonase genes and enzymes from Saccharomyces cerevisiae and Kluyveromyces marxianus (2000)
    Springer
    Current genetics 38 (2000), S. 264-270 
    Details
    ISSN: 1432-0983
    Keywords: Key words Endopolygalacturonase ; Saccharomyces cerevisiae ; Kluyveromyces marxianus ; Pectinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gene encoding endopolygalacturonase (EC 3.2.1.15) has been cloned, sequenced and expressed from three strains of Saccharomyces cerevisiae (including non-secretors) and three strains of Kluyveromyces marxianus. Both control and coding regions showed small differences within each species, one including loss of a potential glycosylation site. Two non-secreting S. cerevisiae strains (FY1679 and var. uvarum) had non-transcribed copies of functional genes. Maximum enzyme activity was achieved with the S. cerevisiae FY1679 gene in an expressing vector, with an enzyme activity of 51 μmol of reducing sugar released from polygalacturonic acid μg protein−1 min−1, the highest so far reported for a yeast.
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    URL: http://dx.doi.org/10.1007/s002940000160
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  • 17
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    Hydraulic analysis of free-surface flows with solidification (2000)
    Springer
    Archive of applied mechanics 70 (2000), S. 17-29 
    Details
    ISSN: 1432-0681
    Keywords: Key words free-surface flow ; solidification ; strip casting ; steady state ; nonuniqueness ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The paper is concerned with a one-dimensional analysis of plane open-channel flow with continuous solidification. The process is of relevance for recent developments in the casting of steel and other metals. The bottom of the channel consists of a rotating casting roll and a horizontal cooling table, where the solidified material is withdrawn with given velocity. The study is restricted to the region downstream of the top of the casting roll. Surface tension is neglected. In the main part of the analysis inviscid fluid flow is considered since the Reynolds number is very large in the applications. It is found that the steady-state solutions are nonunique in a certain parameter range. In addition to a continuous solution, there are two solutions including hydraulic jumps, with one hydraulic jump being located on the casting roll, the other one on the cooling table. Regarding the stability of the non unique solutions, the evolution of disturbances is investigated numerically as an initial-value problem. It is concluded that the hydraulic jump on the cooling table is unstable, while the other discontinuous solution as well as the continuous solution are stable for sufficiently small disturbances. Which stable solution is attained in the steady state, depends on the history of the process. Friction at the liquid/solid interface is taken into account in the last part of the analysis. A constant friction coefficient is assumed. It is found that the history of the process determines the steady-state solution if, and only if, the friction coefficient is sufficiently small. For larger values of the friction coefficient, the steady-state solution is unique and independent of the history of the transient process. Furthermore, for sufficiently large friction coefficients, stable hydraulic jumps are found, in contrast to the inviscid case, also on the cooling table.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004199900031
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  • 18
    Electronic Resource
    Electronic Resource
    A gene of the major facilitator superfamily encodes a transporter for enterobactin (Enb1p) in Saccharomyces cerevisiae (2000)
    Springer
    BioMetals 13 (2000), S. 65-72 
    Details
    ISSN: 1572-8773
    Keywords: major facilitator superfamily ; iron transport ; siderophores ; enterobactin ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract While in fungi iron transport via hydroxamate siderophores has been amply proven, iron transport via enterobactin is largely unknown. Enterobactin is a catecholate-type siderophore produced by several enterobacterial genera grown in severe iron deprivation. By using the KanMX disruption module in vector pUG6 in a fet3Δ background of Saccharomyces cerevisiae we were able to disrupt the gene YOL158c Sce of the major facilitator super family (MFS) which has been previously described as a gene encoding a membrane transporter of unknown function. Contrary to the parental strain, the disruptant was unable to utilize ferric enterobactin in growth promotion tests and in transport assays using 55Fe-enterobactin. All other siderophore transport properties remained unaffected. The results are evidence that in S. cerevisiae the YOL158c Sce gene of the major facilitator super family, now designated ENB1, encodes a transporter protein (Enb1p), which specifically recognizes and transports enterobactin.
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    URL: http://dx.doi.org/10.1023/A:1009250017785
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    Stability of Attractive Bose–Einstein Condensates (2000)
    Springer
    Journal of statistical physics 101 (2000), S. 731-746 
    Details
    ISSN: 1572-9613
    Keywords: attractive Bose–Einstein condensates ; nonlinear Schrödinger equation ; stability ; ground state ; variational arguments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We propose the critical nonlinear Schrödinger equation with a harmonic potential as a model of attractive Bose–Einstein condensates. By an elaborate mathematical analysis we show that a sharp stability threshold exists with respect to the number of condensate particles. The value of the threshold agrees with the existing experimental data. Moreover with this threshold we prove that a ground state of the condensate exists and is orbital stable. We also evaluate the minimum of the condensate energy.
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    URL: http://dx.doi.org/10.1023/A:1026437923987
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    The Equation of State of Lakes (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 1-17 
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    ISSN: 1573-1421
    Keywords: lakes ; density ; compressibility ; expansibility ; conductivity ; stability ; pvt properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In recent years, a number of workers have studied the stability of deep lakes such as Lake Tanganyika, Lake Baikal and Lake Malawi. In this paper, the methods that can be used to determine the effect that the components of lakes have on the equation of state are examined. The PVT properties of Lakes have been determined by using apparent molal volume data for the major ionic components of the lake. The estimated PVT properties (densities, expansibility and compressibilities) of the lakes are found to be in good agreement with the PVT properties (P) of seawater diluted to the same salinity. This is similar to earlier work that showed that the PVT properties of rivers and estuarine waters could also be estimated from the properties of seawater. The measured densities of Lake Tanganyika were found to be in good agreement (± 2 × 10-6 g cm-3) with the values estimated from partial molal properties and the values of seawater at the same total salinity (ST = 0.568‰). The increase in the densities of Lake Tanganyika waters increased due to changes in the composition of the waters. The measured increase in the measured density (45 × 10-6 g cm-3) is in good agreement (46 × 10-6 g cm-3) with the values calculated for the increase in Na+, HCO3 -, Mg2+, Ca2+ and Si(OH)4. Methods are described that can be used to determine the conductivity salinity of lakes using the equations developed for seawater. By combining these relationships with apparent molal volume data, one can relate the PVT properties of the lake to those of seawater.
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    URL: http://dx.doi.org/10.1023/A:1009626325650
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    Concerning a Technique for Increasing Stability of Climbing Robots (2000)
    Springer
    Journal of intelligent and robotic systems 27 (2000), S. 195-209 
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    ISSN: 1573-0409
    Keywords: wall-climbing robot ; electromagnetic grippers ; stability ; additional support element ; sliding and turning over conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Legged-climbing robot is considered. Each foot of the robot has an electromagnet system for robot"s holding on a metal surface. This surface can be both vertical and inclined, including negative slope. Analytical calculation of robot stability under turn over or sliding conditions has been made. Critical slopes have been determined. One of these slopes corresponds to minimal reserve of robot stability towards sliding and another to minimal reserve of robot stability towards turning-over. As total reserve of stability of a robot is always equal to the minimal one of these reserves. Additional support elements of elastic material with high coefficient of friction, along with electromagnet, allows to increase minimal reserve of robot stability towards sliding. The use of such support elements leads to redistributing force of normal support reaction between electromagnet (which surface has low coefficient of friction) and additional support element (which surface has high coefficient of friction). It is just what leads to increasing the total friction force and as a consequence to increasing of minimal reserve of robot stability towards sliding.
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    URL: http://dx.doi.org/10.1023/A:1008158332368
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    Activity and stability of Cu/ZnO/Al2O3 catalyst promoted with B2O3 for methanol synthesis (2000)
    Springer
    Catalysis letters 68 (2000), S. 55-58 
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    ISSN: 1572-879X
    Keywords: promoting effect ; B2O3 ; Cu/ZnO/Al2O3 catalyst ; methanol synthesis ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The addition of B2O3 to a Cu/ZnO/Al2O3 catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B2O3-containing Cu/ZnO/Al2O3 catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst.
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    URL: http://dx.doi.org/10.1023/A:1019010831562
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    Stability and excitation of potassium promoter in iron catalysts – the role of KFeO2 and KAlO2 phases (2000)
    Springer
    Catalysis letters 67 (2000), S. 129-134 
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    ISSN: 1572-879X
    Keywords: potassium desorption ; stability ; excitation ; iron catalyst ; Rydberg atoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Well‐characterized catalyst model compounds of KAlO2 and KFeO2 are investigated by thermal desorption of potassium from the material. The desorbing fluxes of ions, atoms and highly excited states (field ionizable Rydberg states) were studied with surface and field ionization detectors in a vacuum apparatus. From the Arrhenius plots the activation energies for desorption of K and K+ were determined. The chemical state of potassium at the surfaces is concluded to be: ionic on KAlO2 (with the K desorption barrier of 1.76 eV) and covalent on KFeO2 (barrier of 2.73 eV). These results agree with the data obtained earlier for industrial catalysts for ammonia and styrene production. They are interpreted in terms of the Schottky cycle, which is completed for KAlO2 and fails for KFeO2. This failure indicates a non‐equilibrium desorption process. K Rydberg states are only found to desorb from KFeO2, in agreement with the suggestion that such states in some way are responsible for the catalytic activity.
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    The Dynamics of a Fish Stock Exploited in Two Fishing Zones (2000)
    Springer
    Acta biotheoretica 48 (2000), S. 207-218 
    Details
    ISSN: 1572-8358
    Keywords: Dynamical population ; fishing efforts ; metapopulation ; time scales ; aggregation method ; equilibrium ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities.
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    URL: http://dx.doi.org/10.1023/A:1010208910738
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    A New ADI Scheme for Solving Three-Dimensional Parabolic Equations with First-Order Derivatives and Variable Coefficients (2000)
    Springer
    Journal of computational analysis and applications 2 (2000), S. 293-308 
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    ISSN: 1572-9206
    Keywords: parabolic equations ; ADI scheme ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An ADI scheme for solving three-dimensional parabolic equations withfirst-order derivatives and variable coefficients has been developed basedon our previous papers and the idea of the modified upwind differencescheme. This ADI scheme is second-order accurate and unconditionallystable. Further, a small parameter can be chosen which makes it suitablefor simulating fast-transient phenomena or for computations on fine spatialmeshes. The method is illustrated with numerical examples.
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    Bifurcation Phenomena from Standing Pulse Solutions in Some Reaction-Diffusion Systems (2000)
    Springer
    Journal of dynamics and differential equations 12 (2000), S. 117-167 
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    ISSN: 1572-9222
    Keywords: singular perturbation ; standing pulses ; stability ; Hopf bifurcation ; reaction-diffusion system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Bifurcation phenomena from standing pulse solutions of the problem $$\varepsilon \tau u_t = \varepsilon ^2 u_{xx} + f(u,v),{\text{ }}v_t = v_{xx} + g(u,v)$$ is considered. ε(〉0) is a sufficiently small parameter and τ is a positive one. It is shown that there exist two types of destabilization of standing pulse solutions when τ decreases. One is the appearance of travelling pulse solutions via the static bifurcation and the other is that of in-phase breathers via the Hopf bifurcation. Furthermore which type of destabilization occurs first with decreasing τ is discussed for the piecewise linear nonlinearities f and g.
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    Normal Form Invariants Around Spin-orbit Periodic Orbits (2000)
    Springer
    Celestial mechanics and dynamical astronomy 78 (2000), S. 227-241 
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    ISSN: 1572-9478
    Keywords: stability ; normal form ; spin-orbit resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider a model of spin-orbit interaction, describing the motion of an oblate satellite rotating about an internal spin-axis and orbiting about a central planet. The resulting second order differential equation depends upon the parameters provided by the equatorial oblateness of the satellite and its orbital eccentricity. Normal form transformations around the main spin-orbit resonances are carried out explicitly. As an outcome, one can compute some invariants; the fact that these quantities are not identically zero is a necessary condition to prove the existence of nearby periodic orbits (Birkhoff fixed point theorem). Moreover, the nonvanishing of the invariants provides also the stability of the spin-orbit resonances, since it guarantees the existence of invariant curves surrounding the periodic orbit.
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    URL: http://dx.doi.org/10.1023/A:1011161605935
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    Determination of primary structure of amberjack myosin heavy chain and its relationship with structural stability of various fish myosin rods (2000)
    Springer
    Fish physiology and biochemistry 23 (2000), S. 283-294 
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    ISSN: 1573-5168
    Keywords: amberjack ; myosin heavy chain ; cDNA ; α-helix ; coiled coils ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural stability of fish myosin depends upon species and temperatures of water in which fish live. Primary, secondary, and quaternary structures of myosin heavy chain (MyHC) from three species of fish living at different temperature ranges have been compared with those of rabbit MyHC in order to investigate the differences in stability. Primary structure of MyHC, although being accessible for warm-water and cold-water fish (carp and walleye pollack), was not available in previous for tropical-water fish literature; so in this study primary structure of MyHC of the tropical-water fish amberjack has been determined by cloning and sequencing its cDNA. The MyHC has 1938 amino acid residues (AA), which are almost as much as as those of carp and walleye pollack. The amberjack MyHC is 91–95% homologous with other fish and rabbit MyHCs. There is a discernible difference between animal species with stable myosin rod (amberjack, carp, and rabbit) and walleye pollack with unstable rod. Stable rod species have a high probability of forming coiled-coil around the COOH-terminal end of the rod, while the pollack has a low coiled-coil formation probability. In addition, the average scores of the coiled-coil for myosin rod were rabbit (1.738) 〉 amberjack (1.691) 〉 carp (1.680) 〉 walleye pollack (1.674) which correlated exactly with the observed stability. The results suggest that coiled-coil forming ability, particularly around the COOH-terminal end, directs structural stability of fish myosin rod.
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    Partial Assembly of the Yeast Mitochondrial ATP Synthase 1 (2000)
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    Journal of bioenergetics and biomembranes 32 (2000), S. 391-400 
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    ISSN: 1573-6881
    Keywords: ATP synthase ; F1-ATPase ; Saccharomyces cerevisiae ; petite mutants ; epistasis ; mitochondrion ; pet mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The mitochondrial ATP synthase is a molecular motor that drives the phosphorylation ofADP to ATP. The yeast mitochondrial ATP synthase is composed of at least 19 differentpeptides, which comprise the F1 catalytic domain, the F0 proton pore, and two stalks, oneof which is thought to act as a stator to link and hold F1 to F0, and the other as a rotor.Genetic studies using yeast Saccharomyces cerevisiae have suggested the hypothesis thatthe yeast mitochondrial ATP synthase can be assembled in the absence of 1, and even 2, ofthe polypeptides that are thought to comprise the rotor. However, the enzyme complexassembled in the absence of the rotor is thought to be uncoupled, allowing protons to freelyflow through F0 into the mitochondrial matrix. Left uncontrolled, this is a lethal process andthe cell must eliminate this leak if it is to survive. In yeast, the cell is thought to lose ordelete its mitochondrial DNA (the petite mutation) thereby eliminating the genes encodingessential components of F0. Recent biochemical studies in yeast, and prior studies in E. coli,have provided support for the assembly of a partial ATP synthase in which the ATP synthaseis no longer coupled to proton translocation.
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    Electron microscopy of the K2 killer effect of Saccharomyces cerevisiae T206 on a mesophilic wine yeast (2000)
    Springer
    Antonie van Leeuwenhoek 78 (2000), S. 117-122 
    Details
    ISSN: 1572-9699
    Keywords: electron microscopy ; killer effect ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A mesophilic wine yeast, Saccharomyces cerevisiae CSIR Y217 K − R − was subjected to the K2 killer effect of Saccharomyces cerevisiae T206 K + R + in a liquid grape medium. The lethal effect of the K2 mycoviral toxin was confirmed by methylene blue staining. Scanning electron microscopy of cells from challenge experiments revealed rippled cell surfaces, accompanied by cracks and pores, while those unaffected by the toxin, as in the control experiments, showed a smooth surface. Transmission electron microscopy revealed that the toxin damaged the cell wall structure and perturbed cytoplasmic membranes to a limited extent.
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    Destabilization for quasivariational inequalities of reaction-diffusion type (2000)
    Springer
    Applications of mathematics 45 (2000), S. 161-176 
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    ISSN: 1572-9109
    Keywords: reaction-diffusion system ; unilateral conditions ; quasivariational inequality ; Leray-Schauder degree ; eigenvalue ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We consider a reaction-diffusion system of the activator-inhibitor type with unilateral boundary conditions leading to a quasivariational inequality. We show that there exists a positive eigenvalue of the problem and we obtain an instability of the trivial solution also in some area of parameters where the trivial solution of the same system with Dirichlet and Neumann boundary conditions is stable. Theorems are proved using the method of a jump in the Leray-Schauder degree.
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    Pseudohyphal growth is induced in Saccharomyces cerevisiae by a combination of stress and cAMP signalling (2000)
    Springer
    Antonie van Leeuwenhoek 78 (2000), S. 187-194 
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    ISSN: 1572-9699
    Keywords: cAMP ; pseudohyphae ; Saccharomyces cerevisiae ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Saccharomyces cerevisiae pseudohyphae formation may be triggered by nitrogen deprivation and is stimulated by cAMP. It was observed that even in a medium with an adequate nitrogen supply, cAMP can induce pseudohyphal growth when S. cerevisiae uses ethanol as carbon source. This led us to investigate the effects of the carbon source and of a variety of stresses on yeast morphology. Pseudohyphae formation and invasive growth were observed in a rich medium (YP) with poor carbon sources such as lactate or ethanol. External cAMP was required for the morphogenetic transition in one genetic background, but was dispensable in strain Σ1278b which has been shown to have an overactive Ras2/cAMP pathway. Pseudohyphal growth and invasiveness also took place in YPD plates when the yeast was subjected to different stresses: a mild heat-stress (37 °C), an osmotic stress (1 m NACl), or addition of compounds which affect the lipid bilayer organization of the cell membrane (aliphatic alcohols at 2%) or alter the glucan structure of the cell wall (Congo red). We conclude that pseudohyphal growth is a physiological response not only to starvation but also to a stressful environment; it appears to require the coordinate action of a MAP kinase cascade and a cAMP-dependent pathway.
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    Stabilization of smoothness priors time-varying autoregressive models (2000)
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    Circuits, systems and signal processing 19 (2000), S. 423-435 
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    ISSN: 1531-5878
    Keywords: Time-varying autoregressive models ; stability ; smoothness priors ; Tihkonov regularization ; constrained optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The stability of time-varying autoregressive (AR) models is an important issue in such applications as time-varying spectrum estimation and electroencephalography simulation and estimation. In some cases, such as time-varying spectrum estimation, the models that exhibit roots near unit moduli are difficult to use. Thus a tighter stability condition such as stability with a positive margin is needed. A time-varying AR model is stable with a positive margin if the moduli of the roots of the time-varying characteristic polynomial are somewhat less than unity for every time instant. Recently, a new method for the estimation of the time-varying AR models was introduced. This method is based on the interpretation of the underdetermined time-varying prediction equations as an ill-posed inverse problem that is solved by Tikhonov regularization. The method is referred to as the deterministic regression smoothness priors (DRSP) scheme. In this paper, a stabilization method in which the DRSP scheme is augmented with nonlinear stability constrainst is proposed. The problem is formulated so that stability with a positive margin can also be achieved. The problem is solved iteratively with an exterior point algorithm. The performance of the algorithm is studied with a simulation. It is shown that the proposed approach is well suited to stable modeling of signals containing narrowband transitions.
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    Evaluation of genotype, environment, and genotype-by-environment interaction for capsaicinoids in Capsicum annuum L. (2000)
    Springer
    Euphytica 111 (2000), S. 185-190 
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    ISSN: 1573-5060
    Keywords: chile ; double haploid ; pepper ; pungency ; stability ; within-genotype variance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The response, in terms of capsaicinoid content, of chile (Capsicum annuum L.) genotypes to different environments was studied. Double haploidlines, an F1 hybrid, and an open-pollinated cultivar estimated the genotype, environment, and genotype-by-environment interaction effect on the total capsaicinoids and on individual capsaicinoids. Significant differences were observed among the genotypes and among genotype-by-environment interactions over the environments. Among the genotypes in an environment, the within-genotype variances were also significantly different. The double haploid line, HDA 207, had low within-genotype variance for individual and total capsaicinoids, with the exception of the isomer of dihydrocapsaicin. Also for HDA 270, the genotype-by-environment interaction was negligible for individual and total capsaicinoids, Indicating stability across environments.
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    Recurrent selection in oat for adaptation to diverse environments (2000)
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    Euphytica 113 (2000), S. 195-205 
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    ISSN: 1573-5060
    Keywords: Avena ; genetic correlation ; genotype-environmentinteraction ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In order to test if selection can improve a population's adaptation to diverse environments simultaneously, three cycles of recurrent selection based on grain yield in Iowa, Idaho, and Norway were practiced in an oat (Avena sativaL.) population developed from North American, Scandinavian, and wild species (A. sterilis L.) germplasm sources. Specific objectives were to determine if selection: increased mean yields across environments and within all environments; changed the genetic correlation of yields in different environments; and changed genetic variation for yield within the population. We evaluated 100 to 210 randomly-chosen families from each cycle of selection at three Iowa locations, in Idaho, and in Norway for two years. Grain yield within each location and mean yields across locations increased significantly over cycles of selection. Mean yields across locations expressed as a percent of the original population mean increased at a rate of 2.6% per year. Several families from the third cycle population exhibited both high mean yields across locations and consistently high yields within all locations. Average genetic correlations of yield in different environments were higher in the second cycle than in the original population. A trend of reduced genetic variation and heritability was observed in Iowa only. These results suggest that we successfully improved mean population yield both within and across locations, and yield stability across environments, and in developing families with outstanding adaptation to diverse environments.
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    Molecular Modeling of the Complexes between Saccharomyces cerevisiae Phosphoenolpyruvate Carboxykinase and the ATP Analogs Pyridoxal 5′-Diphosphoadenosine and Pyridoxal 5′-Triphosphoadenosine. Specific Labeling of Lysine 290 (2000)
    Springer
    The protein journal 19 (2000), S. 67-73 
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    ISSN: 1573-4943
    Keywords: Homology modeling ; rotational energy barrier ; simulated annealing ; pyridoxal 5′-diphosphoadenosine ; pyridoxal 5′-triphosphoadenosine ; Saccharomyces cerevisiae ; phosphoenolpyruvate carboxykinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics calculations have been employed to obtain models of the complexes between Saccharomyces cerevisiae phosphoenolpyruvate (PEP) kinase and the ATP analogs pyridoxal 5′-diphosphoadenosine (PLP-AMP) and pyridoxal 5′-triphosphoadenosine (PLP-ADP), using the crystalline coordinates of the ATP-pyruvate-Mn2+-Mg2+ complex of Escherichia coli PEP carboxykinase [Tari et al. (1997), Nature Struct. Biol. 4, 990–994]. In these models, the preferred conformation of the pyridoxyl moiety of PLP-ADP and PLP-AMP was established through rotational barrier and simulated annealing procedures. Distances from the carbonyl-C of each analog to ε-N of active-site lysyl residues were calculated for the most stable enzyme-analog complex conformation, and it was found that the closest ε-N is that from Lys290, thus predicting Schiff base formation between the corresponding carbonyl and amino groups. This prediction was experimentally verified through chemical modification of S. cerevisiae PEP carboxykinase with PLP-ADP and PLP-AMP. The results here described demonstrate the use of molecular modeling procedures when planning chemical modification of enzyme-active sites.
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    Hexose transporters of tomato: molecular cloning, expression analysis and functional characterization (2000)
    Springer
    Plant molecular biology 44 (2000), S. 687-697 
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    ISSN: 1573-5028
    Keywords: gene expression ; heterologous expression ; H+/hexose symporter ; Lycopersicon esculentum ; quantitative PCR ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A full-length (LeHT2) and two partial (LeHT1 and LeHT3) cDNA clones, encoding hexose transporters, were isolated from tomato (Lycopersicon esculentum) fruit and flower cDNA libraries. Southern blot analysis confirmed the presence of a gene family of hexose transporters in tomato consisting of at least three members. The full-length cDNA (LeHT2) encodes a protein of 523 amino acids, with a calculated molecular mass of 57.6 kDa. The predicted protein has 12 putative membrane-spanning domains and belongs to the Major Facilitator Superfamily of membrane carriers. The three clones encode polypeptides that are homologous to other plant monosaccharide transporters and contain conserved amino acid motifs characteristic of this superfamily. Expression of the three genes in different organs of tomato was investigated by quantitative PCR. LeHT1 and LeHT3 are expressed predominantly in sink tissues, with both genes showing highest expression in young fruit and root tips. LeHT2 is expressed at relatively high levels in source leaves and certain sink tissues such as flowers. LeHT2 was functionally expressed in a hexose transport-deficient mutant (RE700A) of Saccharomyces cerevisiae. LeHT2-dependent transport of glucose in RE700A exhibited properties consistent with the operation of an energy-coupled transporter and probably a H+/hexose symporter. The K m of the symporter for glucose is 45 μM.
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    Effects of Ca2+ on the Activity and Stability of Methanol Dehydrogenase (2000)
    Springer
    The protein journal 19 (2000), S. 469-473 
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    ISSN: 1573-4943
    Keywords: Methanol dehydrogenase ; Ca2+ ; binding ; activity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of exogenously added Ca2+ on the enzymatic activity and structural stability of methanol dehydrogenase were studied for various Ca2+ concentrations. Methanol dehydrogenase activity increased significantly with increasing concentration of Ca2+, approaching saturation at 200 mM Ca2+. The effect of Ca2+ on the activation of MDH was time dependent and Ca2+ specific and was due to binding of the metal ions to the enzyme. Addition of increasing concentration of Ca2+ caused a decrease of the intrinsic tryptophan fluorescence intensity in a concentration-dependent manner to a minimum at 200 mM, but with no change in the fluorescence emission maximum wavelength or the CD spectra. The results revealed that the activation of methanol dehydrogenase by Ca2+ occurred concurrently with the conformational change. In addition, exogenously bound Ca2+ destabilized MDH. The potential biological significance of these results is discussed.
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    Debonding of the interface as 'crack arrestor' (2000)
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    International journal of fracture 105 (2000), S. 57-79 
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    ISSN: 1573-2673
    Keywords: Interface toughness ; interface debonding ; stability ; adhesive interface ; bimaterial.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, we studied the interface debonding when a crack perpendicularly approaches an interface between two dissimilar elastic materials. An interface toughness law was first defined according to an adhesive model governing the interface fracture. By analysing the interaction between the normally approaching crack and the interface crack and by tacking account of the adhesive forces at ends of the interfacial crack, a model for studying the interface debonding and the debonding stability was established. It is observed that the interface debonding toughness depends strongly on the mixed mode locally produced over the plastic adhesive zone of the interface. Moreover, the interface debonding may be unstable, i.e. the interface debonding length may jump from an initial value to a certain final value under critical remote loading. This jump may be surprisedly important in certain cases. These results agree with the experimental works gathered so far and can be used to explain the mechanism of 'crack arrestor' formed by an interface.
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    Numerical Investigation of a Stability Theorem Arising from the 2-Dimensional Analysis of an Iterative Optimal Control Algorithm (2000)
    Springer
    Multidimensional systems and signal processing 11 (2000), S. 109-124 
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    ISSN: 1573-0824
    Keywords: 2-D linear systems ; optimal control ; stability ; unit memory linear repetitive processes ; numerical methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Because many optimal control problems require solution using iterative procedures they fall naturally in the realm of 2-D systems where the two dimensions are response time horizon and iteration index, respectively. The paper uses this observation to employ 2-D systems theory, in the form of unit memory repetitive process techniques, to analyse local stability and convergence behaviour of a continuous optimal control algorithm based on dynamic system optimisation and parameter estimation. Existing work is extended to incorporate unmatched terminal constraints. Necessary and sufficient conditions for stability are obtained whose evaluation require the solution of a difficult eigenvalue problem. The paper shows how solutions can be achieved using numerical and graphical facilities of MATLAB.
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    The Jump Behavior and Stability Analysis for 2-D Singular Systems (2000)
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    Multidimensional systems and signal processing 11 (2000), S. 339-358 
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    ISSN: 1573-0824
    Keywords: 2-D systems ; descriptor systems ; singular systems ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, we discussthe jump behavior and stability problems for 2-D linear shift-invariantsingular systems under the standard boundary conditions. It isshown that once a boundary condition or the input is inadmissiblein the classical sense, a group of non-causal or backward jumpsof the system states will be incited. This interpretation releasesthe conventional admissibility constraints on the boundary conditionsand inputs. Based on this observation, a systematic stabilitytheory is developed for 2-D singular systems. The well-knownbasic stability theorem for the 1-D singular systems or 2-D regularsystems is thus extended to the 2-D singular case.
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    Structure, Mechanical Properties, and Mechanics of Intracranial Saccular Aneurysms (2000)
    Springer
    Journal of elasticity 61 (2000), S. 49-81 
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    ISSN: 1573-2681
    Keywords: collagen structure ; stability ; rupture criterion ; growth mechanics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Intracranial saccular aneurysms remain an enigma; it is not known why they form, why they enlarge, or why only some of them rupture. Nonetheless, there is general agreement that mechanics plays an essential role in each aspect of the natural history of these potentially deadly lesions. In this paper, we review recent findings that discount limit point instabilities under quasi-static increases in pressure and resonance under dynamic loading as possible mechanisms of enlargement of saccular aneurysms. Indeed, recent histopathological data suggest that aneurysms enlarge due to a stress-mediated process of growth and remodeling of collagen, the primary load-bearing constituent within the wall. We submit that advanced theoretical, experimental, and numerical studies of this process are essential to further progress in treating this class of pathologies. The purpose of this review is to provide background and direction that encourages elasticians to contribute to this important area of research.
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    Perron–Frobenius Theory and Symmetry of Solutions to Nonlinear PDE's (2000)
    Springer
    Letters in mathematical physics 53 (2000), S. 313-320 
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    ISSN: 1573-0530
    Keywords: partial differential equations ; nonlinearities ; symmetries ; stability ; minimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We suggest a simple but general method of establishing symmetry properties of stable solutions of nonlinear elliptic equations. The method relies on characterization of symmetry breaking with a help of zero modes and on a generalization of the Perron–Frobenius theory.
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    On the Robust Stability of 2D Schur Polynomials (2000)
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    Journal of optimization theory and applications 106 (2000), S. 431-439 
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    ISSN: 1573-2878
    Keywords: multidimensional polynomial theory ; robustness ; Kharitonov theorem ; stability ; Schur polynomials ; inverse Kharitonov problem ; Rouché theorem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this note, the problem of the robust stability for a two-dimensional (two-variable) Schur polynomial which is the characteristic polynomial of a discrete-time linear time-invariant system is investigated. A new approach based on the Rouché theorem is adopted. The extension to the robust stability for multidimensional (multivariable) polynomials is also provided. Interesting sufficient conditions for such robust stability are derived. A two-dimensional example is included to support the theoretical result.
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    Upper and Lower Semicontinuity for Set-Valued Mappings Involving Constraints (2000)
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    Journal of optimization theory and applications 106 (2000), S. 527-550 
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    ISSN: 1573-2878
    Keywords: vector optimization ; set-valued mappings ; constraint sets ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In vector optimization, several authors have studied the upper and lower semicontinuity for mappings involving constraints in topological vector spaces partially ordered through a cone with nonempty interior. In this paper, we give conditions about the upper and lower semicontinuity in the case that the ordering cone in the parameter space has possibly empty interior, as it happens in many function spaces and seqence spaces.
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    Mixed Solutions for Weak Stackelberg Problems: Existence and Stability Results (2000)
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    Journal of optimization theory and applications 105 (2000), S. 417-440 
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    ISSN: 1573-2878
    Keywords: mixed solutions ; weak Stackelberg problems ; existence ; stability ; weak convergence of probability measures
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    Topics: Mathematics
    Notes: Abstract We are concerned with ∈-mixed solutions for weak Stackelberg problems corresponding to two-player nonzero-sum noncooperative games. Two cases are considered: (i) mixed strategies for only the second player; (ii) mixed strategies for both players. After giving basic results relating convergence of functions and weak convergence of probability measures, we establish existence and stability results for ∈-mixed solutions under general assumptions of minimal character without any convexity assumption. Our results improve previous work of Mallozzi and Morgan (Refs. 1–2).
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    Optimum Radius of Robust Stability for Schur Polynomials (2000)
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    Journal of optimization theory and applications 104 (2000), S. 165-174 
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    ISSN: 1573-2878
    Keywords: Systems theory ; stability ; robust stability ; linear systems ; discrete-time systems ; robustness ; polynomial theory ; Kharitonov theorem ; inverse Kharitonov problem ; Rouche theorem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The paper investigates the problem of the robust stability of Schur polynomials. Recently, a new approach based on the Rouche theorem of classical complex analysis has been adopted for the solution of this problem. In this paper, an improvement of the previous solution is presented. This is the optimum solution of the robust stability problem for Schur polynomials, which is obtained by solving a minimization problem and is better than other methods in robust stability literature. Three numerical examples are given to illustrate the proposed method.
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    Extended Well-Posedness Properties of Vector Optimization Problems (2000)
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    Journal of optimization theory and applications 106 (2000), S. 165-182 
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    ISSN: 1573-2878
    Keywords: Vector optimization ; asymptotically minimizing sequences ; extended well-posedness ; stability ; vector variational principle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, the concept of extended well-posedness of scalar optimization problems introduced by Zolezzi is generalized to vector optimization problems in three ways: weakly extended well-posedness, extended well-posedness, and strongly extended well-posedness. Criteria and characterizations of the three types of extended well-posedness are established, generalizing most of the results obtained by Zolezzi for scalar optimization problems. Finally, a stronger vector variational principle and Palais-Smale type conditions are used to derive sufficient conditions for the three types of extended well-posedness.
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    Stability Properties of a Bond Portfolio Management Problem (2000)
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    Annals of operations research 99 (2000), S. 251-265 
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    ISSN: 1572-9338
    Keywords: stochastic programming ; bond portfolio management ; interest ratescenarios ; stability ; sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The bond portfolio management problem is formulated as a multiperiod two-stage or multistage stochastic program based on interest rate scenarios. These scenarios depend on the available market data, on the applied estimation and sampling techniques, etc., and are used to evaluate coefficients of the resulting large scale mathematical program. The aim of the contribution is to analyze stability and sensitivity of this program on small changes of the coefficients – the (scenario dependent) values of future interest rates and prices. We shall prove that under sensible assumptions, the scenario subproblems are stable linear programs and that also the optimal first-stage decisions and the optimal value of the considered stochastic program possess acceptable continuity properties.
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    A Multiclass Feedback Queueing Network with a Regular Skorokhod Problem (2000)
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    Queueing systems 36 (2000), S. 327-349 
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    ISSN: 1572-9443
    Keywords: multiclass networks ; networks with feedback ; Skorokhod Problem ; Skorokhod Mapping ; Lipschitz continuity ; stability ; load conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider a four-class two-station network with feedback, with fluid inputs and a head-of-the-line generalized processor sharing discipline at each station. We derive the Skorokhod Problem associated with the network and obtain algebraic sufficient conditions for Lipschitz continuity of the associated Skorokhod Map. This provides the first example of a multiclass network with feedback for which the associated Skorokhod Problem has been proved to be regular. As an elementary application, we show that under the conditions which guarantee Lipschitz continuity the network is stable if and only if the usual load conditions apply.
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    Performance analysis of a slotted-ALOHA protocol on a capture channel with fading (2000)
    Springer
    Queueing systems 34 (2000), S. 1-35 
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    ISSN: 1572-9443
    Keywords: multiple access ; CDMA ; rates of convergence ; stability ; functional limit theorems ; transient analysis ; Markov-modulated capture channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the slotted ALOHA protocol on a channel with a capture effect. There are M 〈 ∞ users each with an infinite buffer. If in a slot, i packets are transmitted, then the probability of a successful reception of a packet is q i. This model contains the CDMA protocols as special cases. We obtain sufficient rate conditions, which are close to necessary for stability of the system, when the arrival streams are stationary ergodic. Under the same rate conditions, for general regenerative arrival streams, we obtain the rates of convergence to stationarity, finiteness of stationary moments and various functional limit theorems. Our arrival streams contain all the traffic models suggested in the recent literature, including the ones which display long range dependence. We also obtain bounds on the stationary moments of waiting times which can be tight under realistic conditions. Finally, we obtain several results on the transient performance of the system, e.g., first time to overflow and the limits of the overflow process. We also extend the above results to the case of a capture channel exhibiting Markov modulated fading. Most of our results and proofs will be shown to hold also for the slotted ALOHA protocol without capture.
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    On the Robustness of Gaussian Elimination with Partial Pivoting (2000)
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    BIT 40 (2000), S. 62-73 
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    ISSN: 1572-9125
    Keywords: Gaussian elimination ; stability ; pivoting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It has been recently shown that large growth factors might occur in Gaussian Elimination with Partial Pivoting (GEPP) also when solving some plausibly natural systems. In this note we argue that this potential problem could be easily solved, with much smaller risk of failure, by very small (and low cost) modifications of the basic algorithm, thus confirming its inherent robustness. To this end, we first propose an informal model with the goal of providing further support to the comprehension of the stability properties of GEPP. We then report the results of numerical experiments that confirm the viewpoint embedded in the model. Basing on the previous observations, we finally propose a simple scheme that could be turned into (even more) accurate software for the solution of linear systems.
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    Stochastic Methods for Ill-Posed Problems (2000)
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    BIT 40 (2000), S. 226-240 
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    ISSN: 1572-9125
    Keywords: Stochastic differential equations ; regularisation ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper is devoted to the numerical analysis of ill-posed problems of evolution equations in Banach spaces using certain classes of stochastic one-step methods. The linear stability properties of these methods are studied. Regularisation is given by the choice of the regularisation parameter as α = $$\sqrt {\tau _n }$$ , where τ n is the stepsize and provides the convergence on smooth initial data. The case of the approximation of well-posed problems is also considered.
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    Runge-Kutta Methods for the Numerical Solution of Stiff Semilinear Systems (2000)
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    BIT 40 (2000), S. 611-639 
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    ISSN: 1572-9125
    Keywords: Runge-Kutta methods ; stability ; convergence ; stiff problems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper studies the stability and convergence properties of general Runge-Kutta methods when they are applied to stiff semilinear systems y′(t) = J(t)y(t) + g(t, y(t)) with the stiffness contained in the variable coefficient linear part. We consider two assumptions on the relative variation of the matrix J(t) and show that for each of them there is a family of implicit Runge-Kutta methods that is suitable for the numerical integration of the corresponding stiff semilinear systems, i.e. the methods of the family are stable, convergent and the stage equations possess a unique solution. The conditions on the coefficients of a method to belong to these families turn out to be essentially weaker than the usual algebraic stability condition which appears in connection with the B-stability and convergence for stiff nonlinear systems. Thus there are important RK methods which are not algebraically stable but, according to our theory, they are suitable for the numerical integration of semilinear problems. This paper also extends previous results of Burrage, Hundsdorfer and Verwer on the optimal convergence of implicit Runge-Kutta methods for stiff semilinear systems with a constant coefficients linear part.
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    Stability of Linear Inequality Systems Measured by the Hausdorff Metric (2000)
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    Set-valued analysis 8 (2000), S. 253-266 
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    ISSN: 1572-932X
    Keywords: Hausdorff metric ; linear inequality systems ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we propose a Hausdorff metric to measure the “distance” between two linear inequality systems on a real normed space X. For this topology, which comes through a pseudo-metric in the set Σ of linear inequality systems, the closedness of the feasible set mapping is studied, and at the same time a characterization of the stability of the subset Σ c of consistent sytems is given.
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    Yeast Intracellular Water Determination by Thermogravimetry (2000)
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    Journal of thermal analysis and calorimetry 59 (2000), S. 643-648 
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    ISSN: 1572-8943
    Keywords: drying ; intracellular water ; Saccharomyces cerevisiae ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The intracellular water content of a microorganism is an important parameter which is a determinant factor of its physiological properties. It is usually measured by complex and time consuming procedures. Thermogravimetry using infrared balance has been used for this purpose, through the identification of different drying steps occurring during the analysis. This work employs the same method with much smaller samples, using conventional thermogravimetric equipment in a simpler and faster way than other conventional procedures. Commercial yeast (Saccharomyces cerevisiae ) washed samples are analyzed in isothermal procedures which are run in about 30 min. The drying rate curve, when plotted as a function of the residual mass of the cells, allows the identification of the step where the intracellular water is lost and the determination of its content. The obtained values, on extracellular water free basis, are in the range of 65 to 69% and agree with those measured by other techniques.
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    Diagonally implicit Runge–Kutta methods for 3D shallow water applications (2000)
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    Advances in computational mathematics 12 (2000), S. 229-250 
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    ISSN: 1572-9044
    Keywords: numerical analysis ; shallow water problems ; DIRK methods ; stability ; 65L06 ; 65L20 ; 65M12 ; 65M20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We construct A‐stable and L‐stable diagonally implicit Runge–Kutta methods of which the diagonal vector in the Butcher matrix has a minimal maximum norm. If the implicit Runge–Kutta relations are iteratively solved by means of the approximately factorized Newton process, then such iterated Runge–Kutta methods are suitable methods for integrating shallow water problems in the sense that the stability boundary is relatively large and that the usually quite fine vertical resolution of the discretized spatial domain is not involved in the stability condition.
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    On the Stability of Functional Equations and a Problem of Ulam (2000)
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    Acta applicandae mathematicae 62 (2000), S. 23-130 
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    ISSN: 1572-9036
    Keywords: stability ; functional equations ; Cauchy difference ; semigroup ; inequalities ; approximate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we study the stability of functional equations that has its origins with S. M. Ulam, who posed the fundamental problem 60 years ago and with D. H. Hyers, who gave the first significant partial solution in 1941. In particular, during the last two decades, the notion of stability of functional equations has evolved into an area of continuing research from both pure and applied viewpoints. Both classical results and current research are presented in a unified and self-contained fashion. In addition, related problems are investigated. Some of the applications deal with nonlinear equations in Banach spaces and complementarity theory.
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    Stability of constant coefficient linear singular systems with delay (2000)
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    Circuits, systems and signal processing 19 (2000), S. 13-25 
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    ISSN: 1531-5878
    Keywords: Singular systems ; delay ; consistency condition ; stability ; instability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, the general class of singular systems with delay and linear constant coefficient singular systems with delay are discussed. First, several definitions of stability are presented for singular systems with delay, and general sufficient stability conditions and instability conditions are obtained. Second, stability and instability are analyzed for linear constant coefficient singular systems with delay.
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    Stability and Hopf Bifurcation of Four-Wheel-Steering Vehicles Involving Driver's Delay (2000)
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    Nonlinear dynamics 22 (2000), S. 361-374 
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    ISSN: 1573-269X
    Keywords: 4WS vehicle ; time delay ; stability ; Hopf bifurcation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A mathematical model is presented for four-wheel-steeringvehicles, with the time delay in driver's response and the nonlinearityin lateral tyre forces taken into account. It is proved that thevehicle-driver system has a trivial steady state motion, as well aseight non-trivial steady state motions due to the nonlinearity of tyreforces. The asymptotic stability and Hopf bifurcation of the trivialsteady state are analyzed for two control strategies ofrear-wheel-steering. It is shown through the numerical simulations thatthe four-wheel-steering technique based on the bilinear control strategyworks better when the driver's response involves time delay.
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    Study of Stability of a Stochastic Model of the "Dangling Spider" Problem. III (2000)
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    Cybernetics and systems analysis 36 (2000), S. 916-924 
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    ISSN: 1573-8337
    Keywords: stochastic model ; "dangling spider problem" ; stability ; Lyapunov-Krasovskii functional
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract To study the stability of the stochastic "dangling spider" model, the second Lyapunov method is substantiated for stochastic differential functional equations with the entire previous history.
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    1,3-Dihydrobenzo[c]thienylium (thiophthalylium) salts. (Review) (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 115-133 
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    ISSN: 1573-8353
    Keywords: thiophthalylium salts ; methods of preparation ; structure ; stability ; reactivity ; electrophilic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methods of preparation, chemical reactions, the structures and reactivity of thiophthalylium ions are reviewed.
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    Solving A $$\underline x $$ = $$\underline b $$ Using a Modified Conjugate Gradient Method Based on Roots of A (2000)
    Springer
    Journal of scientific computing 15 (2000), S. 441-456 
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    ISSN: 1573-7691
    Keywords: modified conjugate gradient method ; conjugate gradient method ; Krylov space ; convergence rate ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the modified conjugate gradient procedure for solving A $$\underline x $$ = $$\underline b $$ in which the approximation space is based upon the Krylov space associated with A 1/p and $$\underline b $$ , for any integer p. For the square-root MCG (p=2) we establish a sharpened bound for the error at each iteration via Chebyshev polynomials in $$\sqrt A$$ . We discuss the implications of the quickly accumulating effect of an error in $$\sqrt A$$ $$\underline b $$ in the initial stage, and find an error bound even in the presence of such accumulating errors. Although this accumulation of errors may limit the usefulness of this method when $$\sqrt A$$ $$\underline b $$ is unknown, it may still be successfully applied to a variety of small, “almost-SPD” problems, and can be used to jump-start the conjugate gradient method. Finally, we verify these theoretical results with numerical tests.
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    URL: http://dx.doi.org/10.1023/A:1011132730828
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    Associative Memories in Infinite Dimensional Spaces (2000)
    Springer
    Neural processing letters 12 (2000), S. 129-144 
    Details
    ISSN: 1573-773X
    Keywords: associative memory ; dynamical systems ; Glauber dynamics ; Hopfield model ; infinite dimensional state space ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A generalization of the Little–Hopfield neural network model for associative memories is presented that considers the case of a continuum of processing units. The state space corresponds to an infinite dimensional euclidean space. A dynamics is proposed that minimizes an energy functional that is a natural extension of the discrete case. The case in which the synaptic weight operator is defined through the autocorrelation rule (Hebb rule) with orthogonal memories is analyzed. We also consider the case of memories that are not orthogonal. Finally, we discuss the generalization of the non deterministic, finite temperature dynamics.
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    URL: http://dx.doi.org/10.1023/A:1009689025427
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    Research on stability of moving jet containing dense suspended solid particles (2000)
    Springer
    Applied mathematics and mechanics 21 (2000), S. 1390-1400 
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    ISSN: 1573-2754
    Keywords: suspended solid particles ; continuum phase-coupled model ; stability ; moving jet ; numerical computation ; O359
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The spatial stability equation of moving jet containing dense suspended solid particles was derived out by means of the continuum phase-coupled model. The stability curves of moving jet for different downstream distances, Reynolds number of flow-field, particle properties and velocities of jetting device are got by the finite difference method based on the asymptotic method and the Eulerian conservative difference scheme. Founded on the analysis of the obtained stability curves it is found that the positive velocity of jetting device widens the unstable frequency range of flow-field but the effect of the negative one is contrary. In addition, particles existing in the flow-field curb the instability of flow-field and the effect enhances with the decrease of Reynolds number of flow-field. These conclusions benefit learning the development of moving two-phase jet.
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    URL: http://dx.doi.org/10.1007/BF02459217
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    Analysis and calculation of the nonlinear stability of the rotational composite shell (2000)
    Springer
    Applied mathematics and mechanics 21 (2000), S. 209-216 
    Details
    ISSN: 1573-2754
    Keywords: composite material ; rotational shell ; stability ; nonlinear ; O347.3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract By adopting the energy method, a new method to calculate the stability of the composite shell of revolution is presented. This method takes the influence of nonlinear prebuckling deformations and stresses on the buckling of the shell into account. The relationships between the prebuckling deformations and strains are calculated by nonlinear Kármán equations. The numerical method is used to calculate the energy of the total system. The nonlinear equations are solved by combining gradient method and amendatory Newton iterative method. The computer program is also developed. An example is given to demonstrate the accuracy of the method presented.
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    URL: http://dx.doi.org/10.1007/BF02458522
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    Convergence and stability of recursive damped least square algorithm (2000)
    Springer
    Applied mathematics and mechanics 21 (2000), S. 237-242 
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    ISSN: 1573-2754
    Keywords: system identification ; damped least square ; recursive algorithm ; convergence ; stability ; O231 ; O241
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The recursive least square is widely used in parameter identification. But it is easy to bring about the phenomena of parameters burst-off. A convergence analysis of a more stable identification algorithm-recursive damped least square is proposed. This is done by normalizing the measurement vector entering into the identification algorithm. It is shown that the parametric distance converges to a zero mean random variable. It is also shown that under persistent excitation condition, the condition number of the adaptation gain matrix is bounded, and the variance of the parametric distance is bounded.
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    URL: http://dx.doi.org/10.1007/BF02458525
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    Highly Active and Stable Pt-USY in the Low-Temperature de-NOx HC-SCR (2000)
    Springer
    Reaction kinetics and catalysis letters 71 (2000), S. 33-40 
    Details
    ISSN: 1588-2837
    Keywords: Pt-USY ; de-NOx ; HC-SCR ; propene ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Selective catalytic reduction of NOx by propene has been investigated on Pt-USY and compared to other Pt-catalysts. The catalyst was characterized by XRD, Ar adsorption at 87 K, TEM, and CO chemisorption, and tested in a gas mixture system in excess oxygen. Pt-USY shows an excellent activity in the reaction, with a molar NOx conversion of 90% at 475 K. Stability during time-on-stream and resistance to SO2 and H2O in the feed stream has also been investigated. Pt-USY performs better under lean-burn conditions than other Pt-catalysts on ZSM-5, Al2O3, or SiO2. The selectivity to N2 was similar for all the catalysts (∼30%), the other major product being N2O.
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    URL: http://dx.doi.org/10.1023/A:1010365628369
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    Numerical solutions for a coupled non-linear oscillator (2000)
    Springer
    Journal of mathematical chemistry 28 (2000), S. 325-340 
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    ISSN: 1572-8897
    Keywords: numerical method ; stability ; Hopf bifurcation ; coupled oscillator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A second-order accurate numerical method has been proposed for the solution of a coupled non-linear oscillator featuring in chemical kinetics. Although implicit by construction, the method enables the solution of the model initial-value problem (IVP) to be computed explicitly. The second-order method is constructed by taking a linear combination of first-order methods. The stability analysis of the system suggests the existence of a Hopf bifurcation, which is confirmed by the numerical method. Both the critical point of the continuous system and the fixed point of the numerical method will be seen to have the same stability properties. The second-order method is more competitive in terms of numerical stability than some well-known standard methods (such as the Runge–Kutta methods of order two and four).
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    URL: http://dx.doi.org/10.1023/A:1011025104111
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    Analysis of coupled-mode flutter of pipes conveying fluid on the elastic foundation (2000)
    Springer
    Applied mathematics and mechanics 21 (2000), S. 1177-1186 
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    ISSN: 1573-2754
    Keywords: elastic foundation ; pipe conveying fluid ; coupled-mode flutter ; stability ; power series method ; 0353
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The governing equation of solid-liquid couple vibration of pipe conveying fluid on the elastic foundation was derived. The critical velocity and complex frequency of pipe conveying fluid on Winkler elastic foundation and two-parameter foundation were calculated by power series method. Compared with pipe without considering elastic foundation, the numerical results show that elastic foundation can increase the critical flow velocity of static instability and dynamic instability of pipe. And the increase of foundation parameters may increase the critical flow velocity of static instability and dynamic instability of pipe, thereby delays the occurrence of divergence and flutter instability of pipe. For higher mass ratio β, in the combination of certain foundation parameters, pipe behaves the phenomenon of restabilization and redivergence after the occurrence of static instability, and then coupled-mode flutter takes place.
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    The gel microdrop secretion assay: Identification of a low productivity subpopulation arising during the production of human antibody in CHO cells (2000)
    Springer
    Cytotechnology 34 (2000), S. 27-37 
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    ISSN: 1573-0778
    Keywords: CHO cells ; gel microdrops ; human antibody ; population parameters ; productivity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The long-term stability of high-level expression is the mostimportant factor to consider when choosing cell lines for the expression of recombinant proteins. Declining volumetricyields in large-scale fermentation can be caused by changes affecting the cell population as a whole such as loss in viability, depletion of nutrients or accumulation of metabolites affecting cell growth. Alternatively, geneticinstability may lead to the outgrowth of a less productive,metabolically favored sub-population. Currently a variety ofparameters are measured to monitor the condition of cells infermenters including glucose uptake, lactate accumulation andoxygen consumption; in addition, periodic viable cell countsallow the determination of the growth rate and viability of the population. All of these methods measure the condition ofthe cell population as a whole and changes must involve a significantly large proportion of the total culture in orderto be detectable. Here we report on a method that allows theevaluation of the productivity of individual cells. Using the gel microdrop secretion assay, we detected the appearance ofa sub-population of cells with lower productivity. Subsequentanalysis of the culture confirmed the existence of lower productivity cells with a lower vector copy number. Therefore,the single cell secretion assay proved to be a rapid method todetect and isolate a low productivity variant of the producer cell line.
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    URL: http://dx.doi.org/10.1023/A:1008186113245
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    Optimal Model Reduction with a Frequency Weighted Extension (2000)
    Springer
    Dynamics and control 10 (2000), S. 255-276 
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    ISSN: 1573-8450
    Keywords: continuous-time systems ; frequency weighted model reduction ; gradient flow ; optimization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Inthis paper, a model reduction technique based on optimizationis presented. The objective function minimized is the impulseenergy of the overall system. An extension of the technique tothe frequency weighted case is also presented, where single-sidedor double-sided weightings can be incorporated in the reductionprocedure. The paper proposes an alternative to find an optimizationsolution by solving ordinary differential equations which aregradient flow associated with the objective function to be minimized.Two examples are presented to illustrate the effectiveness ofthe method.
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    Partial Compensation for Mismatched Uncertain Discrete Systems (2000)
    Springer
    Dynamics and control 10 (2000), S. 47-61 
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    ISSN: 1573-8450
    Keywords: stability ; robust control ; Lyapunov approach ; discrete system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Control design of nonlinear discrete-time uncertain systems with (possibly fast) uncertain parameters is considered. We study the effect of only partially compensating the uncertainty. The optimal choice of a design parameter, which indicates the amount of compensation, is recommended.
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    URL: http://dx.doi.org/10.1023/A:1008395928788
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    Substrate specificity of yeast invertase in transglycosylation reactions (2000)
    Springer
    Chemistry of natural compounds 36 (2000), S. 88-89 
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    ISSN: 1573-8388
    Keywords: Saccharomyces cerevisiae ; yeast invertase ; active enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The substrate specificity of purified yeast invertase isolated fromSaccharomyces cerevisiae in transglycosylation reactions was determined. The enzyme is specific for primary alcohols. The yeast activity is a function of the alkyl length and substrate hydrophobicity (n-butyl, isobutyl, isoamyl alcohols).
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    Bifurcations of a cantilevered pipe conveying steady fluid with a terminal nozzle (2000)
    Springer
    Acta mechanica Sinica 16 (2000), S. 264-272 
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    ISSN: 1614-3116
    Keywords: nonlinear dynamics ; bifurcation ; stability ; fluid-solid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper studies interactions of pipe and fluid and deals with bifurcations of a cantilevered pipe conveying a steady fluid, clamped at one end and having a nozzle subjected to nonlinear constraints at the free end. Either the nozzle parameter or the flow velocity is taken as a variable parameter. The discrete equations of the system are obtained by the Ritz-Galerkin method. The static stability is studied by the Routh criteria. The method of averaging is employed to examine the analytical results and the chaotic motions. Three critical values are given. The first one makes the system lose the static stability by pitchfork bifurcation. The second one makes the system lose the dynamical stability by Hopf bifurcation. The third one makes the periodic motions of the system lose the stability by doubling-period bifurcation.
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    URL: http://dx.doi.org/10.1007/BF02487667
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    Stability and chaotic motion in columns of nonlinear viscoelastic material (2000)
    Springer
    Applied mathematics and mechanics 21 (2000), S. 987-994 
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    ISSN: 1573-2754
    Keywords: stability ; chaos ; averaging method ; Galerkin method ; viscoelastic column ; O322
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The dynamical stability of a homogeneous, simple supported column, subjected to a periodic axial force, is investigated. The viscoelastic material is assumed to obey the Leaderman nonlinear constitutive relation. The equation of motion was derived as a nonlinear integro-partial-differential equation, and was simplified into a nonlinear integro-differential equation by the Galerkin method. The averaging method was employed to carry out the stability analysis. Numerical results are presented to compare with the analytical ones. Numerical results also indicate that chaotic motion appears.
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    Long-term monitoring of benthic macroinvertebrate community structure: a perspective from a Colorado river* (2000)
    Springer
    Aquatic ecology 34 (2000), S. 261-278 
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    ISSN: 1573-5125
    Keywords: discharge effects on lotic invertebrates ; disturbance ; persistence ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites indicated that several chemical parameters, including conductivity, un-ionized NH3-N and NO2-N have increased since the beginning of the study within most sites. Levels of some parameters (e.g., dissolved oxygen, un-ionized NH3-N) violated aquatic life standards a few times during the study. Over 175 taxa of macroinvertebrates (primarily insects) were collected in the study reach from 1981–1996. Results from detrended correspondence analyses (DCA) on macroinvertebrate data indicated that this stretch of the river exhibited little longitudinal change beyond the two farthest upstream sites. There was a decline in macroinvertebrate density and total number of taxa within most individual sites during 1983–1984, corresponding with the highest recorded discharge in 75 years (1983) and a prolonged, heavy spring runoff in 1984. Taxa richness and density recovered to pre-1983 levels within a few months to a year following the high flows at most sites. These findings suggested that the macroinvertebrate assemblages had low resistance to disturbance, but high resilience. However, the results from DCAs and Kendall's Coefficient of Concordance (W) on individual sites for the entire study period suggested a similar macroinvertebrate community structure through time. It would appear that the composition and abundance of the lotic macroinvertebrate assemblages in the Poudre River has remained relatively constant over the long-term. This has occurred even with some potentially negative changes in water chemistry and increased urban development.
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    Comparative effects of Saccharomyces cerevisiae cultivation under copper stress on the activity and kinetic parameters of plasma-membrane-bound H+-ATPases PMA1 and PMA2 (1999)
    Springer
    Archives of microbiology 171 (1999), S. 273-278 
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    ISSN: 1432-072X
    Keywords: Key words Plasma membrane H+-ATPase ; PMA1 ; ATPase ; PMA2 ATPase ; Saccharomyces cerevisiae ; Copper stress ; Copper tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The major yeast plasma membrane H+-ATPase is encoded by the essential PMA 1 gene. The PMA 2 gene encodes an H+-ATPase that is functionally interchangeable with the one encoded by PMA 1 , but it is expressed at a much lower level than the PMA 1 gene and it is not essential. Using genetically manipulated strains of Saccharomyces cerevisiae that exclusively synthesize PMA1 ATPase or PMA2 ATPase under control of the PMA1 promoter, we found that yeast cultivation under mild copper stress leads to a similar activation of PMA2 and PMA1 isoforms. At high inhibitory copper concentrations (close to the maximum that allowed growth), ATPase activity was reduced from maximal levels; this decrease in activity was less important for PMA2 ATPase than for PMA1 ATPase. The higher tolerance to high copper stress of the artificial strain synthesizing PMA2 ATPase exclusively, as compared to that synthesizing solely PMA1 ATPase, correlated both with the lower sensitivity of PMA2 ATPase to the deleterious effects of copper in vivo and with its higher apparent affinity for MgATP, and suggests that plasma membrane H+-ATPase activity plays a role in yeast tolerance to copper.
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    Starvation in yeast increases non-adaptive mutation (1999)
    Springer
    Current genetics 35 (1999), S. 77-81 
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    ISSN: 1432-0983
    Keywords: Key words Adaptive mutations ; 6-N-hydroxylaminopurine ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The frequency of reversion in a histidine-requiring mutant of Saccharomyces cerevisiae increases about ten-fold in stationary cells during histidine starvation. Histidine starvation enhances a similar frequency of reversion in a tryptophan-requiring mutant. Starvation, therefore, enhances mutation frequencies in a non-adaptive manner. The base analogue 6-N-hydroxylaminopurine (HAP) added prior to plating on medium with limited histidine strongly increases reversion of the histidine mutant. HAP-induced reversion increases further in stationary starving cells with the same kinetics as that which increases spontaneous reversion. Adding HAP to the stationary starving cells does not produce any effect.
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    Strand interruptions confer strand preference during intracellular correction of a plasmid-borne mismatch in Saccharomyces cerevisiae (1999)
    Springer
    Current genetics 35 (1999), S. 499-505 
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    ISSN: 1432-0983
    Keywords: Key words Heteroduplex repair ; Strand discrimina-tion ; Strand interruptions ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Site-directed mutagenesis was used to construct yeast centromere plasmids in which a strand nick or gap could be placed 5′ or 3′, on either strand, to a reporter gene (SUP4-o) carrying defined base mismatches. The plasmids were then transformed into yeast cells and the direction and efficiency of mismatch repair were assayed by scoring colouring of the transformant colonies. Strands that were nicked were consistently corrected more often than intact strands, but the effect was very small. However, placement of a small gap at the same positions as the nicks resulted in a marked increase in selection for the gapped strand and an enhanced efficiency of mismatch repair. Both the preference for the gapped strand and correction of the mismatch were offset by deletion of the mismatch repair gene PMS1. Together, the results suggest that strand interruptions can direct intracellular mismatch correction of plasmid-borne base mispairs in yeast.
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    Cysteine uptake by Saccharomyces cerevisiae is accomplished by multiple permeases (1999)
    Springer
    Current genetics 35 (1999), S. 609-617 
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    ISSN: 1432-0983
    Keywords: Key words Cysteine uptake ; Amino-acid permeases ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Uptake by Saccharomyces cerevisiae of the sulphur-containing amino acid L-cysteine was found to be non-saturable under various conditions, and uptake kinetics suggested the existence of two or more transport systems in addition to the general amino-acid permease, Gap1p. Overexpression studies identified BAP2, BAP3, AGP1 and GNP1 as genes encoding transporters of cysteine. Uptake studies with disruption mutants confirmed this, and identified two additional genes for transporters of cysteine, TAT1 and TAT2, both very homologous to BAP2, BAP3, AGP1 and GNP1. While Gap1p and Agp1p appear to be the main cysteine transporters on the non-repressing nitrogen source proline, Bap2p, Bap3p, Tat1p, Tat2p, Agp1p and Gnp1p are all important for cysteine uptake on ammonium-based medium. Furthermore, whereas Bap2p, Bap3p, Tat1p and Tat2p seem most important under amino acid-rich conditions, Agp1p contributes significantly when only ammonium is present, and Gnp1p only contributes under the latter condition.
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    Mutant allele pso7-1, that sensitizes Saccharomyces cerevisiae to photoactivated psoralen, is allelic with COX11, encoding a protein indispensable for a functional cytochrome c oxidase (1999)
    Springer
    Current genetics 36 (1999), S. 124-129 
    Details
    ISSN: 1432-0983
    Keywords: Key words Psoralen sensitivity ; Cytochrome oxidase ; Saccharomyces cerevisiae ; Oxidative stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yeast gene PSO7 was cloned from a genomic library by complementation of the pso7-1 mutant's sensitivity phenotype to 4-nitroquinoline-1-oxide (4NQO). Sequence analysis revealed that PSO7 is allelic to the 1.1-kb ORF of the yeast gene COX11 which is located on chromosome XVI and encodes a protein of 28-kDa localized in the inner mitochondrial membrane. Allelism of PSO7/COX11 was verified by non-complementation of 4NQO-sensitivity in diploids homo- and hetero-allelic for the pso7-1 and cox11::TRP1 mutant alleles. Sensitivity to 4NQO was the same in exponentially growing cells of the pso7-1 mutant and the cox11::TRP1 disruptant. Allelism of COX11 and PSO7 indicates that the pso7 mutant's sensitivity to photoactivated 3-carbethoxypsoralen and to 4NQO is not caused by defective DNA repair, but rather is due to an altered metabolism of the pro-mutagen 4NQO in the absence of cytochrome oxidase (Cox) in pso7-1/cox11::TRP1 mutants/disruptants. Lack of Cox might also lead to a higher reactivity of the active oxygen species produced by photoactivated 3-carbethoxypsoralen. The metabolic state of the cells is important for their sensitivity phenotype since the largest enhancement of sensitivity to 4NQO between wild-type (WT) and the pso7 mutant occurs in exponentially growing cells, while cells in stationary phase or growing cells in phosphate buffer have the same 4NQO resistance, irrespective of their WT/mutant status. Strains containing the pso7-1 or cox11::TRP1 mutant allele were also sensitive to the oxidative stress-generating agents H2O2 and paraquat. Mutant pso7-1, as well as disruptant cox11::TRP1, harboured mitochondria that in comparison to WT contained less than 5% and no detectable Cox activity, respectively.
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    Analysis of the genes activated by the FLO8 gene in Saccharomyces cerevisiae (1999)
    Springer
    Current genetics 36 (1999), S. 256-261 
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    ISSN: 1432-0983
    Keywords: Key wordsFLO8 ; Transcriptional regulation ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is thought that the FLO8 gene encodes a transcriptional activator of the dominant flocculation gene FLO1 in Saccharomycescerevisiae. To determine other genes which are regulated by FLO8, a detailed comparison of the transcripts from the FLO8 and Δflo8 strains was carried out. In addition to the FLO1 gene, it was found that transcription of the FLO11 and STA1 genes is positively regulated by FLO8. In flo8 strains, not only transcripts of the FLO11, STA1, and FLO1 genes but also invasive growth, extracellular glucoamylase production, and flocculation were undetected. From these results, it is suggested that FLO8 regulates these characteristics via the transcriptional regulation of the FLO11, STA1, and FLO1 genes.
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    Purification and some properties of an α-amylase glucoamylase fusion protein from Saccharomyces cerevisiae (1999)
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 561-564 
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    ISSN: 1573-0972
    Keywords: α-Amylase ; fusion protein ; glucoamylase ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A fusion gene containing the Bacillus subtilis α-amylase gene and Aspergillus awamori glucoamylase cDNA was expressed in Saccharomyces cerevisiae. The resulting bifunctional fusion protein having both α-amylase and glucoamylase activities secreted into the culture medium was purified to apparent homogeneity by affinity chromatography and gel filtration on Sephadex G-100. The enzyme had an apparent molecular mass of 150 kDa and showed an optimum pH and temperature of 6.0 and 60 °C, respectively. The main hydrolysis products from soluble starch were glucose and maltose.
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    Saké brewing characteristics and multidrug resistance of trichothecin-resistant yeast mutants (1999)
    Springer
    World journal of microbiology and biotechnology 15 (1999), S. 629-630 
    Details
    ISSN: 1573-0972
    Keywords: Ethanol ; multi-drug resistance ; Saccharomyces cerevisiae ; trichothecin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Trichothecin-resistant mutants were isolated from saké yeast. These mutants were subjected to saké brewing, and showed a higher ethanol productivity than did the parents. They showed multidrug resistance, and resistance to organic compounds. We considered that the higher ethanol productivity of the mutants was related to their resistance to organic compounds and to their ethanol tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008946001006
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    Direct observation of oxidative stress on the cell wall of Saccharomyces cerevisiae strains with atomic force microscopy (1999)
    Springer
    Molecular and cellular biochemistry 201 (1999), S. 17-24 
    Details
    ISSN: 1573-4919
    Keywords: Saccharomyces cerevisiae ; atomic force microscope ; bioscope ; organic synthesis ; molecular biology ; oxidative stress ; pore enlargement ; cell wall ; baker's yeast ; biotechnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We imaged pores on the surface of the cell wall of three different industrial strains of Saccharomyces cerevisiae using atomic force microscopy. The pores could be enlarged using 10 mM diamide, an SH residue oxidant that attacks surface proteins. We found that two strains showed signs of oxidative damage via changes in density and diameter of the surface pores. We found that the German strain was resistant to diamide induced oxidative damage, even when the concentration of the oxidant was increased to 50 mM. The normal pore size found on the cell walls of American strains had diameters of about 200nm. Under conditions of oxidative stress the diameters changed to 400nm. This method may prove to be a useful rapid screening process (45-60 min) to determine which strains are oxidative resistant, as well as being able to screen for groups of yeast that are sensitive to oxidative stress. This rapid screening tool may have direct applications in molecular biology (transference of the genes to inside of living cells) and biotechnology (biotransformations reactions to produce chiral synthons in organic chemistry.
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    URL: http://dx.doi.org/10.1023/A:1007007704657
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    Characterization of Saccharomyces cerevisiae strains expressing ira1 mutant alleles modeled after disease-causing mutations in NF1 (1999)
    Springer
    Molecular and cellular biochemistry 202 (1999), S. 109-118 
    Details
    ISSN: 1573-4919
    Keywords: NF1 mutations ; IRA1 ; Saccharomyces cerevisiae ; RAS2 ; GAP activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The 2818 amino acids of neurofibromin, the product of the human NF1 gene, include a 230 amino acid Ras-GAP related domain (GRD). Functions which may be associated with the rest of the protein remain unknown. However, many NF1 mutations in neurofibromatosis 1 patients are found downstream of the GRD, suggesting that the C-terminal region of the protein is also functionally important. Since the C-terminal region of neurofibromin encompassing these mutations is homologous with the corresponding regions in the two Saccharomyces cerevisiae Ras-GAPs, Ira1p and Ira2p, we chose yeast as a model system for functional exploration of this region (Ira-C region). Three missense mutations that affect the Ira-C region of NF1 were used as a model for the mutagenesis of IRA1. The yeast phenotypes of heat shock sensitivity, iodine staining, sporulation efficiency, pseudohyphae formation, and GAP activity were scored. Even though none of the mutations directly affected the Ira1p-GRD, mutations at two of the three sites resulted in a decrease in the GAP activity present in ira1 cells. The third mutation appeared to disassociate the phenotypes of sporulation ability and GAP activity. This and other evidence suggest an effector function for Ira1p.
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    URL: http://dx.doi.org/10.1023/A:1007058427880
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    Convergence of Delayed Dynamical Systems (1999)
    Springer
    Neural processing letters 10 (1999), S. 267-271 
    Details
    ISSN: 1573-773X
    Keywords: recurrent neural networks ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper, we point out that the conditions given in [1] are sufficient but unnecessary for the global asymptotically stable equilibrium of a class of delay differential equations. Instead, we prove that under weaker conditions, it is still global asymptotically stable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018753013035
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    Emergence of symmetric, modular, and reciprocal connections in recurrent networks with Hebbian learning (1999)
    Springer
    Biological cybernetics 81 (1999), S. 211-225 
    Details
    ISSN: 1432-0770
    Keywords: Key words: Hebbian learning rule ; attractor dynamics ; symmetric connections ; multiplicative normalization ; self-organization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. While learning and development are well characterized in feedforward networks, these features are more difficult to analyze in recurrent networks due to the increased complexity of dual dynamics – the rapid dynamics arising from activation states and the slow dynamics arising from learning or developmental plasticity. We present analytical and numerical results that consider dual dynamics in a recurrent network undergoing Hebbian learning with either constant weight decay or weight normalization. Starting from initially random connections, the recurrent network develops symmetric or near-symmetric connections through Hebbian learning. Reciprocity and modularity arise naturally through correlations in the activation states. Additionally, weight normalization may be better than constant weight decay for the development of multiple attractor states that allow a diverse representation of the inputs. These results suggest a natural mechanism by which synaptic plasticity in recurrent networks such as cortical and brainstem premotor circuits could enhance neural computation and the generation of motor programs.
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    URL: http://dx.doi.org/10.1007/s004220050557
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  • 90
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    Isolation, Characterization, and Stability of Positional Isomers of Mono-PEGylated Salmon Calcitonins (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 813-818 
    Details
    ISSN: 1573-904X
    Keywords: calcitonin ; polyethylene glycol ; PEGylation ; peptide ; tryptic digestion ; stability ; HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To separate and characterize the different positional isomers of mono-PEGylated salmon calcitonins (mono-PEG-sCTs) and to evaluate the effects of the PEGylation site on the stability of different mono-PEG-sCTs in rat kidney homogenate. Methods. Mono-PEG-sCTs were prepared using succinimidyl carbonate monomethoxy polyethylene glycol (5,000 Da) and separated by gel-filtration HPLC followed by reversed-phase HPLC. To characterize PEGylated sCTs, matrix-assisted laser desorption ionization time of flight mass spectrometry (M ALDI-TOF MS) and reversed-phase HPLC of the trypsin digested samples were performed. Mono-PEG-sCTs and sCT in rat kidney homogenates were measured by column-switching reversed-phase HPLC with on-line detection of the radioiodinated samples using a flow-through radioisotope detector. Results. Three different mono-PEGylated sCTs were separated by reversed-phase gradient HPLC. From the MALDI-TOF MS analysis, the average molecular weight of mono-PEG-sCTs was confirmed as around 8650 Da. The presence of PEG moiety in the mono-PEG-sCTs was also manifested by the fact that the distance between two adjacent mass spectum lines was 44 Da which corresponds to PEG monomer unit. Tryptic digestion analysis demonstrated that these mono-PEG-sCTs are 3 positional isomers of N-terminus, Lys18- and Lys11-residue modified mono-PEGylated sCTs. The degradation half-life of these 3 positional isomers in rat kidney homogenates significantly increased in order of the N-terminus (125.5 min), Lys11- (157.3 min), and Lysl8-residue modified mono-PEGylated sCT (281.5 min) over the native sCT (4.8 min). Conclusions. Three positional isomers of mono-PEGylated sCTs were purified and characterized. Of these, the resistance to proteolytic degradation was highest for the Lysl8-residue modified mono-PEG-sCT. These studies demonstrate that the in vivo stability of PEGylated sCTs is highly dependent on the site of PEG molecule attachment.
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    URL: http://dx.doi.org/10.1023/A:1018861616465
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    Preparation and Characterization of Carmustine Loaded Polyanhydride Wafers for Treating Brain Tumors (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 762-765 
    Details
    ISSN: 1573-904X
    Keywords: polymer implant ; brain cancer ; carmustine ; polyanhydride ; stability ; controlled release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011995728760
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    Formulation and Lyoprotection of Poly(Lactic Acid-Co-Ethylene Oxide) Nanoparticles: Influence on Physical Stability and In Vitro Cell Uptake (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 859-866 
    Details
    ISSN: 1573-904X
    Keywords: nanoparticles ; poly(lactic acid) ; poly(lactic acid-co-ethylene oxide) ; freeze-drying ; stability ; flow cytometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the feasibility of producing freeze-dried poly-(ethylene oxide) (PEO)-surface modified nanoparticles and to study their ability to avoid the mononuclear phagocytic system (MPS), as a function of the PEO chain length and surface density. Methods. The nanoparticles were produced by the salting-out method using blends of poly(D,L-lactic acid) (PLA) and poly(D,L-lactic acid-co-ethylene oxide) (PLA-PEO) copolymers. The nanoparticles were purified by cross-flow filtration and freeze-dried as such or with variable amounts of trehalose as a lyoprotectant. The redispersibility of the particles was determined immediately after freeze-drying and after 12 months of storage at −25° C. The uptake of the nanoparticles by human monocytes was studied in vitro by flow cytometry. Results. PLA-PEO nanoparticles could be produced from all the polymeric blends used. Particle aggregation after freeze-drying was shown to be directly related to the presence of PEO. Whereas this problem could be circumvented by use of trehalose, subsequent aggregation was shown to occur during storage. These phenomena were possibly related to the specific thermal behaviours of PEO and trehalose. In cell studies, a clear relationship between the PEO content and the decrease of uptake was demonstrated. Conclusions. The rational design of freeze-dried PEO-surface modified nanoparticles with potential MPS avoidance ability is feasible by using the polymer blends approach combined with appropriate lyoprotection and optimal storage conditions.
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    URL: http://dx.doi.org/10.1023/A:1018826103261
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    A human gene, hSGT1, can substitute for GCR2, which encodes a general regulatory factor of glycolytic gene expression in Saccharomyces cerevisiae (1999)
    Springer
    Molecular genetics and genomics 260 (1999), S. 535-540 
    Details
    ISSN: 1617-4623
    Keywords: Key words Gene expression ; Glycolysis ; GCR ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To determine whether similar regulatory mechanisms control the expression of glycolytic genes in yeast and human cells, we screened a human brain cDNA library for clones which complement the growth defect of the gcr2 mutant of Saccharomyces cerevisiae, and isolated hSGT1 (human suppressor of GCR two). Further work confirmed that the rescue of growth was associated with recovery of glycolytic enzyme activities, and that hSGT1 did not complement the growth defect of a gcr1 mutant. A hybrid protein comprising hSgt1p and the DNA-binding domain of Gal4p (GBD) activated a GAL1-lacZ reporter gene fusion, suggesting that the cloned gene may be a transcriptional activator. Two-hybrid experiments in yeast also indicate that hSgt1p interacts with Gcr1p. Northern analysis showed that hSGT1 is highly expressed in muscle and heart. Although the predicted amino acid sequence of hSgt1p does not display significant similarity to Gcr2p, we speculate that their functions may be analogous.
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    URL: http://dx.doi.org/10.1007/s004380050926
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    The Saccharomyces cerevisiae RAD54 gene is important but not essential for natural homothallic mating-type switching (1999)
    Springer
    Molecular genetics and genomics 260 (1999), S. 551-558 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsRAD54 ; Saccharomyces cerevisiae ; Recombination ; Mating-type ; DNA repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Homothallic Saccharomyces cerevisiae strains switch their mating-type in a specific gene conversion event induced by a DNA double strand break made by the HO endonuclease. The RAD52 group genes control recombinational repair of DNA double strand breaks, and we examined their role in native homothallic mating-type switching. Surprisingly, we found that the Rad54 protein was important but not essential for mating-type switching under natural conditions. As an upper limit, we estimate that 29% of the rad54 spore clones can successfully switch their mating-type. The RAD55 and RAD57 gene products were even less important, but their presence increased the efficiency of the process. In contrast, the RAD51 and RAD52 genes are essential for homothallic mating-type switching. We propose that mating-type switching in RAD54 mutants occurs stochastically with a low probability, possibly reflecting different states of chromosomal structure.
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    URL: http://dx.doi.org/10.1007/s004380050928
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    Genetic evidence for interactions between yeast importin α (Srp1p) and its nuclear export receptor, Cse1p (1999)
    Springer
    Molecular genetics and genomics 261 (1999), S. 788-795 
    Details
    ISSN: 1617-4623
    Keywords: Key words Cse1p ; Srp1p ; Importin ; Nuclear transport ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yeast Srp1p protein functions as an import receptor for proteins bearing basic nuclear localization signals. Cse1p, the yeast homolog of mammalian CAS, recycles Srp1p back to the cytoplasm after import substrates have been released into the nucleoplasm. In this report we describe genetic interactions between SRP1 and CSE1. Results from genetic suppression and synthetic lethality studies demonstrate that these gene products interact to ensure accurate chromosome segregation. We also describe new mutant alleles of CSE1 and analyze a new temperature-sensitive allele of CSE1, cse1-2. This allele causes high levels of chromosome missegregation and cell cycle arrest during mitosis at the nonpermissive temperature.
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    URL: http://dx.doi.org/10.1007/s004380050022
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    Cat8p, the activator of gluconeogenic genes in Saccharomyces cerevisiae, regulates carbon source-dependent expression of NADP-dependent cytosolic isocitrate dehydrogenase (Idp2p) and lactate permease (Jen1p) (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 869-875 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsCAT8 ; Transcriptional regulation ; IDP2 ; JEN1 ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yeast transcriptional activator Cat8p has been identified as a factor that is essential for the derepression of genes involved in gluconeogenesis (like FBP1, PCK1, ACR1, ICL1 and MLS1) when only non-fermentable carbon sources are provided. Cat8p-dependent expression is mediated by cis-acting elements in the respective promoters, which are named UAS/CSREs (upstream activating sequence/carbon source responsive element). To establish whether the function of Cat8p is restricted to the activation of gluconeogenesis or is also involved in the regulation of a greater variety of genes, we investigated the transcriptional regulation of two genes, IDP2 and JEN1, which exhibit a similar expression pattern to gluconeogenic genes, although IDP2 at least is not linked directly to the gluconeogenic pathway. We identified functional UAS/CSRE elements in the promoters of both genes. Expression studies revealed that JEN1 is regulated negatively by the repressors Mig1p and Mig2p, and that Cat8p is needed for full derepression of the gene under non-fermentative growth conditions. Furthermore, we showed that Mig2p is also involved in the repression of CAT8 itself. The results presented in this study support a model in which Cat8p-dependent gene activation is not restricted to gluconeogenesis, but targets a wide variety of genes which are strongly derepressed under non-fermentative growth conditions.
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    URL: http://dx.doi.org/10.1007/s004380051152
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    Yeast genes GIS1–4: multicopy suppressors of the Gal− phenotype of snf1 mig1 srb8/10/11 cells (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 589-599 
    Details
    ISSN: 1617-4623
    Keywords: Key words Ras/cAMP pathway ; Saccharomyces cerevisiae ; Snf1 ; Mig1 ; Mediator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyclin C and the cyclin C-dependent protein kinase are associated with the RNA polymerase II Mediator complex, which regulates initiation of transcription in response to signals from activators and repressors bound to upstream promoter elements. Disruption of the corresponding genes, SRB11 and SRB10, in budding yeast causes a reduction in expression of the GAL genes, which is particularly pronounced in a mig1 snf1 background. We have screened two yeast genomic libraries for genes that can suppress this phenotype when overexpressed. Seven suppressor genes were identified, GIS1–7. GIS1 encodes one of two related zinc-finger proteins, which also share two other highly conserved domains present in several eukaryotic transcription factors. GIS2 encodes a homologue of the mammalian CNBP and fission yeast Byr3 proteins. GIS3 and GIS4 predict proteins with no obvious similarities to any known proteins. GIS5–7 are identical to the previously described genes PDE2, SGE1 and TUB3, respectively. None of the suppressor genes seem to be involved in Mediator function. Instead, we find that the GIS1, GIS2 and GIS4 genes interact with the CDC25 gene, indicating a possible involvement of these genes in the RAS/cAMP signaling pathway.
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    URL: http://dx.doi.org/10.1007/s004380051121
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    Galactose induction in yeast involves association of Gal80p with Gal1p or Gal3p (1999)
    Springer
    Molecular genetics and genomics 261 (1999), S. 495-507 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsKluyveromyces lactis ; Saccharomyces cerevisiae ; GAL1 ; GAL80 ; Protein interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gal1p carries out two functions in the galactose pathway of yeast. It activates Gal4p by interacting with Gal80p – a function that can also served by Gal3p – and it catalyzes the formation of galactose-1-phosphate. Recently, we and others have presented biochemical evidence for complex formation between Gal1p and Gal80p. Here, we extend these data and present genetic evidence for an interaction between Gal1p and Gal80p in vivo, using a two-hybrid assay. Interaction between Gal1p and Gal80p depends on the presence of galactose, but not on the catalytic activity of Gal1p. A new class of Kluyveromyces lactis mutants was isolated, designated Klgal1-m, which have lost the derepressing activity but retain galactokinase activity, indicating that the two Gal1p activities are functionally independent. The KlGal1-m proteins are defective in their ability to interact with Gal80p in a two-hybrid assay. The locations of gal1-m mutations identify putative interaction sites in Gal1p and Gal80p. A dominant mutation, KlGAL1-d, leads to a high level of constitutive expression of genes of the galactose pathway. The behavior of chimeric proteins consisting of Gal3p and KlGal1p sequences indicates that both the N-terminal and C-terminal halves of KlGal1p are involved in specific interaction with KlGal80p.
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    URL: http://dx.doi.org/10.1007/s004380050993
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    Genetic evidence for interaction between components of the yeast 26S proteasome: combination of a mutation in RPN12 (a lid component gene) with mutations in RPT1 (an ATPase gene) causes synthetic lethality (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 145-153 
    Details
    ISSN: 1617-4623
    Keywords: Key words Proteasome ; Synthetic lethality ; Saccharomyces cerevisiae ; AAA-ATPase ; 19S Regulatory particle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 19S regulatory particle of the yeast 26S proteasome consists of six related ATPases (Rpt proteins) and at least 11 non-ATPase proteins (Rpn proteins). RPN12 (formerly NIN1) encodes an Rpn component of the 19S regulatory particle and is essential for growth. To determine which subunit(s) of the 26S proteasome interact(s) with Rpn12, we attempted to screen for mutations that cause synthetic lethality in the presence of the rpn12-1 (formerly nin1-1) mutation. Among the candidates recovered was a new allele of RPT1 (formerly CIM5). This mutant allele was designated rpt1-2; on its own this mutation caused no phenotypic change, whereas the rpn12-1 rpt1-2 double mutant was lethal, suggesting a strong interaction between Rpn12 and Rpt1. The site of the rpt1-2 mutation was determined by DNA sequencing of the RPT1 locus retrieved from the mutant, and a single nucleotide alteration was found. This changes amino acid 446 of the RPT1 product from alanine to valine. The alanine residue is conserved in all Rpt proteins, except Rpt5, but no function has yet been assigned to the region that contains it. We propose that this region is necessary for Rpt1 to interact with Rpn12. The terminal phenotype of the rpn12-1 rpt1-2 double mutant was not cell cycle specific, suggesting that in the double mutant cells the function of the 26S proteasome is completely eliminated, thereby inducing multiple defects in cellular functions.
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    URL: http://dx.doi.org/10.1007/s004380051069
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    The Saccharomyces cerevisiae LEP1/SAC3 gene is associated with leucine transport (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 332-341 
    Details
    ISSN: 1617-4623
    Keywords: Key words Leucine transport ; Saccharomyces cerevisiae ; Trifluoroleucine resistance ; LEP1 ; SAC3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leucine uptake by Saccharomyces cerevisiae is mediated by three transport systems, the general amino acid transport system (GAP), encoded by GAP1, and two group-specific systems (S1 and S2), which also transport isoleucine and valine. A new mutant defective in both group-specific transport activities was isolated by employing a gap1 leu4 strain and selecting for trifluoroleucine-resistant mutants which also showed greatly reduced ability to utilize l-leucine as sole nitrogen source and very low levels of [14C]l-leucine uptake. A multicopy plasmid containing a DNA fragment which complemented the leucine transport defect was isolated by selecting for transformants that grew normally on minimal medium containing leucine as nitrogen source and subsequently assaying [14C]l-leucine uptake. Transformation of one such mutant, lep1, restored sensitivity to trifluoroleucine. The complementing gene, designated LEP1, was subcloned and sequenced. The LEP1 ORF encodes a large protein that lacks characteristics of a transporter or permease (i.e., lacks hydrophobic domains necessary for membrane association). Instead, Lep1p is a very basic protein (pI of 9.2) that contains a putative bipartite signal sequence for targeting to the nucleus, suggesting that it might be a DNA-binding protein. A database search revealed that LEP1 encodes a polypeptide that is identical to Sac3p except for an N-terminal truncation. The original identification of SAC3 was based on the isolation of a mutant allele, sac3-1, that suppresses the temperature-sensitive growth defect of an actin mutant containing the allele act1-1. Sac3p has been previously shown to be localized in the nucleus. When a lep1 mutant was crossed with a sac3 deletion mutant, no complementation was observed, indicating that the two mutations are functionally allelic.
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    URL: http://dx.doi.org/10.1007/s004380051091
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