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  • Articles  (6,622)
  • Polymer and Materials Science  (5,024)
  • Cell & Developmental Biology  (1,448)
  • Saccharomyces cerevisiae
  • 1990-1994  (6,516)
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  • 1925-1929  (106)
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  • 1994  (6,516)
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  • Articles  (6,622)
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  • 1990-1994  (6,516)
  • 1945-1949
  • 1940-1944
  • 1925-1929  (106)
  • 1920-1924
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  • 1
    Electronic Resource
    Electronic Resource
    Adaptation of a Saccharomyces cerevisiae strain to high copper concentrations (1994)
    Springer
    BioMetals 7 (1994), S. 221-226 
    Details
    ISSN: 1572-8773
    Keywords: catalase ; copper resistance ; pH-dependent growth ; Saccharomyces cerevisiae ; superoxide dismutase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A strain of Saccharomyces cerevisiae has been adapted to increasing concentrations of copper at two different pH values. The growth curve at pH 5.5 is characterized by a time generation increasing with the amount of added copper. A significant decrease of cell volume as compared with the control is also observed. At pH 3 the cells grow faster than at pH 5.5 and resist higher copper concentrations (3.8 against 1.2 mm). Experimental evidence indicates that, after copper treatment, the metal is not bound to the cell wall, but is localized intracellularly. A significant precipitation of copper salts in the medium was observed only at pH 5.5. Increased levels of superoxide dismutase (SOD) activity were observed in copper-treated cells and which persisted after 20 subsequent inocula in a medium without added metal. On the contrary, catalase activity was not stimulated by copper treatment and, hence, not correlated with SOD levels. The mechanism of copper resistance, therefore, probably involves a persistent induction of SOD, but not of catalase, and it is strongly pH-dependent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149552
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  • 2
    Electronic Resource
    Electronic Resource
    Chimeric evolution of the 2-μm genome in Saccharomyces cerevisiae (1994)
    Springer
    Journal of molecular evolution 38 (1994), S. 363-368 
    Details
    ISSN: 1432-1432
    Keywords: Saccharomyces cerevisiae ; 2-μm circle ; DNA sequencing ; Horizontal transmission ; Site-specific recombination ; Selfish DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We compared the nucleotide substitution pattern over the entire genome of two unique variants of the 6,300-bp selfish DNA (2 μm) plasmid in Saccharomyces cerevisiae. The DNA sequence of the left-unique region is identical among 2-μm variants, while the right-unique region shows substantial divergence. This chimeric pattern cannot be explained by neutral or Darwinian selection models. We propose that horizontal transmission of the 2-μm plasmid coupled with a directed, polarized gene conversion maintains the DNA sequence of the left-unique region, whereas the right-unique region is subject to random drift and Darwinian selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00163153
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  • 3
    Electronic Resource
    Electronic Resource
    Mistranslation of human phosphoglycerate kinase in yeast in the presence of paromomycin (1994)
    Springer
    Current genetics 26 (1994), S. 95-99 
    Details
    ISSN: 1432-0983
    Keywords: Translational fidelity ; Paromomycin ; Stuttering ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Missense errors in the translation of mRNAs in Saccharomyces cerevisiae were screened by looking for charge heterogeneity of proteins on two-dimensional gels resulting from the substitution of charged and neutral amino acids. No such mistranslation was detected in wild-type yeast strains grown in the presence of the translational error-inducing antibiotic paromomycin. However, paromomycin-induced mistranslation of a heterologous mRNA, encoding human phosphoglycerate kinase expressed in yeast, was seen. We suggest that the combination of error-prone translation of a heterologous mRNA, and growth in the presence of paromomycin, leads to an accumulation of mistranslated proteins that can be detected by two-dimensional gel electrophoresis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313794
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  • 4
    Electronic Resource
    Electronic Resource
    Saccharomyces cerevisiae YDR1, which encodes a member of the ATP-binding cassette (ABC) superfamily, is required for multidrug resistance (1994)
    Springer
    Current genetics 26 (1994), S. 285-294 
    Details
    ISSN: 1432-0983
    Keywords: ABC superfamily ; Multidrug resistance ; Saccharomyces cerevisiae ; YDR1 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A multidrug resistance gene, YDR1, of Saccharomyces cerevisiae, which encodes a 170-kDa protein of a member of the ABC superfamily, was identified. Disruption of YDR1 resulted in hypersensitivity to cycloheximide, cerulenin, compactin, staurosporine and fluphenazine, indicating that YDR1 is an important determinant of cross resistance to apparently-unrelated drugs. The Ydr1 protein bears the highest similarity to the S. cerevisiae Snq2 protein required for resistance to the mutagen 4-NQO. The drug-specificity analysis of YDR1 and SNQ2 by gene disruption, and its phenotypic suppression by the overexpressed genes, revealed overlapping, yet distinct, specificities. YDR1 was responsible for cycloheximide, cerulenin and compactin resistance, whereas, SNQ2 was responsible for 4-NQO resistance. The two genes had overlapping specificities toward staurosporine and fluphenazine. The transcription of YDR1 and SNQ2 was induced by various drugs, both relevant and irrelevant to the resistance caused by the gene, suggesting that drug specificity can be mainly attributed to the functional difference of the putative transporters. The transcription of these genes was also increased by heat shock. The yeast drug-resistance system provides a novel model for mammalian multidrug resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310491
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic effects of photoactivated psoralens during meiosis in DNA repair mutantpso3-1 ofSaccharomyces cerevisiae (1994)
    Springer
    Current genetics 25 (1994), S. 19-23 
    Details
    ISSN: 1432-0983
    Keywords: Psoralen ; DNA repair mutants ; Gene conversion ; Recombination ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of the DNA repair genePSO3 on photoactivated psoralen-induced meiotic recombination, gene conversion, reverse mutation, and on survival, was assayed in diploid strains ofSaccharomyces cerevisiae homozygous for the wild-type or thepso3-1 mutant allele. Sporulation was normal in thepso3-1 diploid. Wild-type and mutant strains had the same sensitivity to photoactivated monofunctional psoralen (3-CPs+UVA) in meiosis-uncommitted and meiosis-committed stages. The mutant showed higher sensitivity to photoactivated bifunctional psoralen (8-MOP+UVA) during all stages of the meiotic cycle. Mutation induction by 3-CPs+UVA or 8-MOP+UVA in meiosis-committed cells revealed no significant differences between wild-type and thepso3-1 mutant. The status of thePSO3 gene has no influence on the kinetics of induction of gene conversion and crossing-over after 3-CPs+UVA treatment in meiosis-committed cells: gene conversion was blocked while recombination was induced. After treatment with 8-MOP+UVA gene conversion was also blocked in both strains while crossing-over could only be observed in meiosis-committed wild-type cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712961
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  • 6
    Electronic Resource
    Electronic Resource
    New in-vivo cloning methods by homologous recombination in yeast (1994)
    Springer
    Current genetics 25 (1994), S. 180-183 
    Details
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; In-vivo cloning ; Non-replicative vectors ; Homologous recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have devised a new strategy to clone DNA sequences from an yeast autonomously-propagating plasmid into a non-autonomous integrative vector by in-vivo recombination. The method consists of a first step in which the replicative plasmid carrying the DNA fragment of interest forms a co-integrate with the non-replicative plasmid by an induced in-vivo reciprocal exchange accompanied by gene conversion. The dimeric plasmid obtained is then purified and cut with an appropriate restriction enzyme and ligated independently to obtain the two intact monomeric plasmids, the original autonomous plasmid plus the new non-autonomous plasmid carrying the subcloned DNA fragment. The dimeric co-integrate can also serve as substrate for a second in-vivo reciprocal exchange that produces new autonomous plasmids carrying the desired DNA fragment. The technique considerably expands the applications of in-vivo cloning in yeast by complementing three important characteristics of previously published methods: (1) it can be used to clone into non-propagating vectors; (2) co-transformation experiments are not required; and (3) the intermediate co-integrate can be used to generate new types of autonomously-propagating plasmids directly. These characteristics are independent of whether the DNA insert is flanked by appropriate restriction sites or whether it does, or does not, express a detectable phenotype in yeast. The method is particularly useful for the cloning of large DNA fragments and can be used for plasmids from organisms other than yeasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309546
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  • 7
    Electronic Resource
    Electronic Resource
    Expression of the Saccharomyces cerevisiae CYT2 gene, encoding cytochrome c1 heme lyase (1994)
    Springer
    Current genetics 25 (1994), S. 291-298 
    Details
    ISSN: 1432-0983
    Keywords: Cytochrome c 1 ; Cytochrome c 1 heme lyase ; GRF2p ; Glucose repression ; HAPp ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper we examine the expression of the Saccharomyces cerevisiae CYT2 gene, which encodes cytochrome c 1 heme lyase. This enzyme is required for covalent attachment of heme to apocytochrome c 1, a subunit of the mitochondrial respiratory chain. Transcription of the 1-kb CYT2 mRNA initiates at four prominent sites at a distance of 52–225 bp in front of the AUG start codon. The level of CYT2 mRNA is not influenced by the presence or absence of oxygen or of heme, but it is subject to carbonsource control. The concentration of the CYT2 mRNA is significantly reduced in glucose-grown cells as compared to cells grown under non-repressing conditions. Neither the HAPp activator proteins nor MIG1p, a repressor protein involved in glucose repression, seem to mediate this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351480
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  • 8
    Electronic Resource
    Electronic Resource
    The Escherichia coli recA gene increases UV-induced mitotic gene conversion in Saccharomyces cerevisiae (1994)
    Springer
    Current genetics 25 (1994), S. 472-474 
    Details
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; recA gene expression ; UV radiation ; Mitotic gene conversion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of the Escherichia coli RecA protein on mitotic recombination in the diploid D7 strain of Saccharomyces cerevisiae damaged by UV radiation was investigated. The D7 strain was transformed by two modified versions of the pNF2 plasmid: one, containing the ADH-1 promoter, and the other containing the recA gene tandemly arranged behind the ADH-1 promoter region. Immunological analysis proved the presence of the 38-kDa RecA protein in D7/pNF2ADHrecA transformants. We observed a positive effect of recA gene expression on mitotic gene conversion, mainly at higher doses of UV radiation. The results indicate that a RecA-like activity could participate in steps preceeding mitotic conversion events in yeast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351789
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  • 9
    Electronic Resource
    Electronic Resource
    ERV1 is involved in the cell-division cycle and the maintenance of mitochondrial genomes in Saccharomyces cerevisiae (1994)
    Springer
    Current genetics 26 (1994), S. 15-20 
    Details
    ISSN: 1432-0983
    Keywords: Cell-division cycle ; Mitochondrial genome ; Nuclear mutation ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In former studies it was found that the ERV1 gene is essential for cell viability and for the biogenesis of functional mitochondria. A temperature-sensitive nuclear mutant exhibits a severe reduction in all the mitochondrial transcripts. Elimination of the gene leads to growth arrest after a few cell divisions. The putative gene product bears the characteristics of a regulatory factor since it has low expression rate and a high content of charged amino acids. In this study it is further verified that the ERV1 gene alone is responsible for the observed cellular and mitochondrial defects. The 5′ region of the gene is analysed by DNA deletions and complementation studies. Expression of the gene under the control of the GAL1-10 promoter in a disruption strain of ERV1 allows a more detailed specification of its influence on mitochondrial and cellular functions. Immediate and complete loss of mitochondrial genomes is observed after the promoter has been shut off, whereas the yeast cells are still able to grow for a limited time under these conditions. Analysis of the cells by in-vivo DNA flurorescence demonstrates a specific arrest in the cell-division cycle as the terminal phenotype. To further characterize the temperature-sensitive allele of ERV1 the mutated gene has been isolated and sequenced. A single point mutation which leads to the exchange of a single amino acid is found in the reading frame.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326299
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  • 10
    Electronic Resource
    Electronic Resource
    The yeast nuclear gene MRP-L13 codes for a protein of the large subunit of the mitochondrial ribosome (1994)
    Springer
    Current genetics 26 (1994), S. 8-14 
    Details
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Nuclear gene ; Mitochondria ; Mitochondrial ribosomal protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear gene MRP-L13 of Saccharomyces cerevisiae, which codes for the mitochondrial ribosomal protein YmL13, has been cloned and characterized. It is a single-copy gene residing on chromosome XI. Its nucleotide sequence was found to be identical to that of the previously reported ORF YK105. A comparison of the predicted protein sequence of the MRP-L13 gene product and the actual N-terminal amino-acid sequence of the isolated YmL13 protein indicated that the mature protein is preceded by a mitochondrial signal peptide of 86 amino-acid residues, which is the longest among all known mitochondrial ribosomal proteins of S. cerevisiae. No sequence similarity was found to any other ribosomal protein in the current databases. The transcription of MRP-L13 was found to be repressed in the presence of glucose. Its protein product is not strictly essential for mitochondrial functions, but disruption of the gene by insertion of LEU2 noticeably affected cellular growth on non-fermentable carbon sources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326298
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  • 11
    Electronic Resource
    Electronic Resource
    Antisense RNA regulation of the ILV2 gene in yeast: a correction (1994)
    Springer
    Current genetics 25 (1994), S. 289-289 
    Details
    ISSN: 1432-0983
    Keywords: Saccharomyces cerevisiae ; Inducible antisense gene ; Acetolactate synthase ; Bradytrophic phenocopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A previous report of the use of antisense RNA to regulate gene expression in yeast is incorrect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357175
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  • 12
    Electronic Resource
    Electronic Resource
    Isolation and characterization of three mutants with increased sensitivity to photoactivated 3-carbethoxypsoralen in Saccharomyces cerevisiae (1994)
    Springer
    Current genetics 25 (1994), S. 407-411 
    Details
    ISSN: 1432-0983
    Keywords: Psoralen sensitivity ; Saccharomyces cerevisiae ; DNA repair ; Oxidative stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The complementation and genetical analysis of yeast mutants sensitive to photoactivated 3-carbethoxy-psoralen define three novel recessive mutant alleles pso-5-1, pso6-1, and pso7-1. Their cross-sensitivity to UV254nm, radiomimetic mutagens, and to chemicals enhancing oxidative stress suggest that these mutants are either impaired in metabolic steps protecting from oxidative stress or in mechanisms of the repair of oxygen-dependent DNA lesions. None of the three novel mutant alleles block the induction of reverse mutation by photoactivated mono- and bi-functional psoralens, nitrogen mustards, or UV254nm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351778
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  • 13
    Electronic Resource
    Electronic Resource
    Suppression of a mitochondrial point mutation in a tRNA gene can cast light on the mechanisms of 3′ end-processing (1994)
    Springer
    Current genetics 25 (1994), S. 451-455 
    Details
    ISSN: 1432-0983
    Keywords: tRNA processing ; Saccharomyces cerevisiae ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We used a genetic approach to study the nuclear factors involved in the biogenesis of mitochondrial tRNAs. A point mutation in the mitochondrial tRNAAsp gene of Saccharomyces cerevisiae had previously been shown to result in a temperature-sensitive respiratory-deficient phenotype as a result of the absence of 3′ end-processing of the tRNAAsp. Analysis of mitochondrial revertants has shown that all revertants sequenced have a G-A compensatory change at position 53, which restores the hydrogen-bond with the mutated nucleotide. We then searched for nuclear suppressors to identify the nuclear gene(s) involved in mitochondrial tRNA 3′ end-processing. One such suppressor mutation was further characterized: it restores tRNAAsp maturation and growth at 36°C on glycerol medium in heterozygous diploids, but leads to a defective growth phenotype in haploids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351785
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  • 14
    Electronic Resource
    Electronic Resource
    Stabilization of methionine-rich protein in Saccharomyces cerevisiae: targeting of BZN protein into the peroxisome (1994)
    Springer
    Current genetics 26 (1994), S. 390-397 
    Details
    ISSN: 1432-0983
    Keywords: Overexpression ; Peroxisomes ; Saccharomyces cerevisiae ; Stabilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have constructed a gene coding for the 12-kDa intermediate form of the 2s methionine-rich protein from Bertholletia excelsa seeds. This protein, expressed intracellularly in yeast, is characterised by a 20-min balf-life. By adding 11 amino acids corresponding to the peroxisome-targeting sequence (PTSc) of luciferase, we have significantly increased its half-life. This stabilization allowed accumulation of the BZN protein into the peroxisome as judged by cell fractionation. Accumulation of the 12-kDa protein results in a significant increase of the total methionine content in yeast cells (30%) indicating that such a microorganism could represent a practicable protected shuttl for an animal-feed additive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309924
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  • 15
    Electronic Resource
    Electronic Resource
    Sequence analysis of three deficient mutants of cytochrome oxidase subunit I of Saccharomyces cerevisiae and their revertants (1994)
    Springer
    Current genetics 26 (1994), S. 546-552 
    Details
    ISSN: 1432-0983
    Keywords: Cytochrome oxidase ; Revertant ; Mitochondria ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three respiratory-deficient mutants of cytochrome oxidase subunit I in the yeast mitochondrion have been sequenced. They are located in, or near, transmembrane segment VI, the catalytic core of the enzyme. Respiratory-competent revertants have been selected and studied. The mutant V244M was found to revert at the same site in valine (wild-type), isoleucine or threonine. The revertants of the mutant G251R were of three types: glycine (wild-type), serine and threonine at position 251. A search for second-site mutations was carried out but none were found. Among 60 revertants tested, the mutant K265M was found to revert only to the wild-type allele.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00309948
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  • 16
    Electronic Resource
    Electronic Resource
    Kinetic studies of killer toxin K1 binding to yeast cells indicate two receptor populations (1994)
    Springer
    Archives of microbiology 162 (1994), S. 211-214 
    Details
    ISSN: 1432-072X
    Keywords: Killer toxin ; Saccharomyces cerevisiae ; Toxin binding ; Cell wall receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A recently described new method for determination of killer toxin activity was used for kinetic measurenments of K1 toxin binding. The cells of the killer sensitive strain Saccharomyces cerevisiae S6 were shown to carry two classes of toxin binding sites differing widely in their half-saturation constants and maximum binding rates. The low-affinity and high-velocity binding component (K T1=2.6x109 L.U./ml, V max1=0.19 s-1) probably reflects diffusion-limited binding to cell wall receptors; the high-affinity and low-velocity component (K T2=3.2x107 L.U./ml, V max2=0.03 s-1) presumably indicates the binding of the toxin to plasma membrane receptors. Adsorption of most of the killer toxin K1 to the surface of sensitive cells occured within 1 min and was virtually complete within 5 min. The amount of toxin that saturated practically all cell receptors was about 600 lethal units (L.U.) per cell of S. cerevisiae S6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00314477
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  • 17
    Electronic Resource
    Electronic Resource
    Effect of the new fluorescent brightener Rylux BSU on morphology and biosynthesis of cell walls in Saccharomyces cerevisiae (1994)
    Springer
    Archives of microbiology 161 (1994), S. 340-344 
    Details
    ISSN: 1432-072X
    Keywords: Rylux BSU ; Fluorescent brightener ; Cell walls ; Chitin synthase ; Glucan synthase ; Yeast ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rylux BSU, a new fluorescent brightener from the family of 4,4′-diaminostilbene-2,2′disulfonic acid derivatives, inhibited growth and cytokinesis of the yeast Saccharomyces cerevisiae. In the presence of 0.1–1 mg/ml Rylux BSU the cells grew in clumps, had irregular shape and were larger than controls. They formed apparently normal primary septa but their secondary septa and lateral cell walls, especially those in older cells, were abnormally thick with large deposits of amorphous wall material in the periplasmic spaces all over the cell surface. Chitin content in the cell walls of cells grown in the presence of Rylux BSU was increased 2 to 5 times in comparison to that of the controls and glucan content was reduced by up to 30%. In the in vitro assays with particulate membrane fractions, Rylux BSU acted as a non-competitive inhibitor of β-1,3-glucan synthase with inhibitory constant K i=1.75 mg/ml whereas the chitin synthase was inhibited to a much lesser extent. From the difference of the effects of Rylux BSU on the synthesis of chitin in vivo and in vitro it is concluded that the brightener interacts with chitin synthase only indirectly, possibly by influencing the properties of integral plasma membrane.
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    URL: http://dx.doi.org/10.1007/BF00303590
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  • 18
    Electronic Resource
    Electronic Resource
    Kinetic studies of killer toxin K1 binding to yeast cells indicate two receptor populations (1994)
    Springer
    Archives of microbiology 162 (1994), S. 211-214 
    Details
    ISSN: 1432-072X
    Keywords: Key words     Killer toxin ; Saccharomyces cerevisiae ; Toxin binding ; Cell wall receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract      A recently described new method for determination of killer toxin activity was used for kinetic measurements of K1 toxin binding. The cells of the killer sensitive strain Saccharomyces cerevisiae S6 were shown to carry two classes of toxin binding sites differing widely in their half-saturation constants and maximum binding rates. The low-affinity and high-velocity binding component (K T1 = 2.6 × 109 L.U./ml, V max1 = 0.19 s– 1) probably reflects diffusion-limited binding to cell wall receptors; the high-affinity and low-velocity component (K T2 = 3.2 × 107 L.U./ml, V max2 = 0.03 s– 1) presumably indicates the binding of the toxin to plasma membrane receptors. Adsorption of most of the killer toxin K1 to the surface of sensitive cells occured within 1 min and was virtually complete within 5 min. The amount of toxin that saturated practically all cell receptors was about 600 lethal units (L.U.) per cell of S. cerevisiae S6.
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    URL: http://dx.doi.org/10.1007/BF00314477
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  • 19
    Electronic Resource
    Electronic Resource
    Phytate dephosphorylation by free and immobilized cells ofSaccharomyces cerevisiae (1994)
    Springer
    Journal of industrial microbiology and biotechnology 13 (1994), S. 30-34 
    Details
    ISSN: 1476-5535
    Keywords: Phytate ; Saccharomyces cerevisiae ; Polyacrylamide gel ; Inositol phosphates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Saccharomyces cerevisiae in the form of baker's yeast, cells cultivated on a yeast extract-peptone-glucose medium, as well as cells immobilized in 18% (w/v) polyacrylamide gel showed the ability to hydrolyze 1.727 mM sodium phytate solution at 45°C, pH 4.6, in a stirred tank reactor. Seventy percent yield of dephosphorylation was observed after 2 h using a baker's yeast concentration of 5.8 g dry matter per 100 ml. Hydrolytic activity at 1.8–2.0 μM Pi min−1 was observed between 1st and 3rd h of the reaction in cells cultured 24 or 48 h. No inhibition by the substrate was found at sodium phytate concentrations of 0.587–1.727 mM. After 1.5 h of hydrolysis a single, well distinguished peak ofmyo-inositol-triphosphate was the main product found. By means of immobilization the stability of the biocatalyst was enhanced 3.3-fold and reached its half-life at 64 ninety-minute runs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01569659
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  • 20
    Electronic Resource
    Electronic Resource
    Evolution of C6, C8 and C10 acids and their ethyl esters in cells and musts during fermentation with threeSaccharomyces cerevisiae races (1994)
    Springer
    Journal of industrial microbiology and biotechnology 13 (1994), S. 269-272 
    Details
    ISSN: 1476-5535
    Keywords: Wine ; Yeasts ; Fatty acids ; Ethyl esters ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The evolution of the cell and must contents of three short-chain fatty acids (C6, C8 and C10) and their ethyl esters during fermentations withSaccharomyces cerevisiae racescerevisiae, bayanus andcapensis were studied. The former is a fermentative yeast and the last two are ‘flor’ film yeasts. The acid concentrations in the musts increased throughout the alcoholic fermentations, and maximum cell concentrations of the fatty acids were reached after 48 h of fermentation. Maximum ester concentrations in the cells were attained after 48–72 h of fermentation. In the musts, ethyl octanoate and ethyl decanoate reached a peak also at this point, and ethyl hexanoate after 10 days. After 134 days,S. cerevisiae racecapensis formed a thick ‘flor’ film whileS. cerevisiae racebayanus developed a thin film andS. cerevisiae racecerevisiae formed no film. At this point, acid contents remained constant in the wines produced byS. cerevisiae racescerevisiae andbayanus, and decreased in those obtained with racecapensis. The ethyl ester contents tended to decrease with the exception of ethyl decanoate in the fermentations carried out byS. cerevisiae racescerevisiae andbayanus.
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    URL: http://dx.doi.org/10.1007/BF01569727
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  • 21
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    Electronic Resource
    Isolation and characterization of a multienzyme complex containing DNA replicative enzymes from mitochondria ofS. cerevisiae (1994)
    Springer
    Molecular biology reports 20 (1994), S. 135-141 
    Details
    ISSN: 1573-4978
    Keywords: mitochondria ; multienzyme complex ; replication ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A 40 S multienzyme complex containing mtDNA polymerase was isolated from mitochondria ofS. cerevisiae by density gradient centrifugation and by gel filtration chromatography. Besides DNA polymerase, RNA polymerase, primase, 3′→5′ exonuclease and an ATPase activities were found to be associated with it. The presence of some of these enzymes were confirmed by Western blot. This high molecular weight multienzyme complex containing DNA has most of the attributes of a putative replisome.
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    Cloning of an Arabidopsis thaliana cDNA coding for farnesyl diphosphate synthase by functional complementation in yeast (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1867-1873 
    Details
    ISSN: 1573-5028
    Keywords: Arabidopsis thaliana ; cDNA ; complementation ; erg20-2 yeast mutant ; farnesyl diphosphate synthase ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA encoding farnesyl diphosphate synthase, an enzyme that synthesizes C15 isoprenoid diphosphate from isopentenyl diphosphate and dimethylallyl diphosphate, was cloned from an Arabidopsis thaliana cDNA library by complementation of a mutant of Saccharomyces cerevisiae deficient in this enzyme. The A. thaliana cDNA was also able to complement the lethal phenotype of the erg20 deletion yeast mutant. As deduced from the full-length 1.22 kb cDNA nucleotide sequence, the polypeptide contains 343 amino acids and has a relative molecular mass of 39689. The predicted amino acid sequence presents about 50% identity with the yeast, rat and human FPP synthases. Southern blot analyses indicate that A. thaliana probably contains a single gene for farnesyl diphosphate synthase.
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    URL: http://dx.doi.org/10.1007/BF00019499
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    Cerulenin-resistant mutants of Saccharomyces cerevisiae with an altered fatty acid synthase gene (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 90-96 
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    ISSN: 1617-4623
    Keywords: Cerulenin ; Saccharomyces cerevisiae ; Fatty acid synthase ; β-Ketoacyl synthase ; Drug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cerulenin, an antifungal antibiotic produced by Cephalosporium caerulens, is a potent inhibitor of fatty acid synthase in various organisms, including Saccharomyces cerevisiae. The antibiotic inhibits the enzyme by binding covalently to the active center cysteine of the condensing enzyme domain. We isolated 12 cerulenin-resistant mutants of S. cerevisiae following treatment with ethyl methanesulfonate. The mechanism of cerulenin resistance in one of the mutants, KNCR-1, was studied. Growth of the mutant was over 20 times more resistant to cerulenin than that of the wild-type strain. Tetrad analysis suggested that all mutants mapped at the same locus, FAS2, the gene encoding the α subunit of the fatty acid synthase. The isolated fatty acid synthase, purified from the mutant KNCR-1, was highly resistant to cerulenin. The cerulenin concentration causing 50% inhibition (IC50) of the enzyme activity was measured to be 400 μM, whereas the IC50 value was 15 μM for the enzyme isolated from the wild-type strain, indicating a 30-fold increase in resistance to cerulenin. The FAS2 gene was cloned from the mutant. Sequence replacement experiments suggested that an 0.8 kb EcoRV-HindIII fragment closely correlated with cerulenin resistance. Sequence analysis of this region revealed that the GGT codon encoding Gly-1257 of the FAS2 gene was altered to AGT in the mutant, resulting in the codon for Ser. Furthermore, a recombinant FAS2 gene, in which the 0.8 Kb EcoRV-HindIII fragment of the wild-type FAS2 gene was replaced with the same region from the mutant, when introduced into FAS2-defective S. cerevisiae complemented the FAS2 pheno-type and showed cerulenin resistance. These data indicate that one amino acid substitution (Gly → Ser) in the α subunit of fatty acid synthase is responsible for the cerulenin resistance of the mutant KNCR-1.
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    Positive and negative transcriptional regulation by the yeast GAL11 protein depends on the structure of the promoter and a combination of cis elements (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 301-312 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Transcriptional regulation ; Chromatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract GAL11 was first identified as a gene required for full expression of some galactose-inducible genes that are activated by GAL4, and it was subsequently shown to be necessary for full expression of another set of genes activated by RAP1/GRFl/TUF. Genetic analysis suggests that GAL11 functions as a coactivator, mediating the interaction of sequence-specific activators with basal transcription factors. To test this hypothesis, we first tried to identify functional domains by deletion analysis and found that the 866–910 region is indispensable for function. Using reporters bearing various upstream activating sequences (UAS) and different core promoter structures, we show that the involvement of GAL11 in transcriptional activation varies with the target promoter and the particular combination of cis elements. Gel electrophoresis in the presence of chloroquine shows that GAL11 affects the chromatin structure of a circular plasmid. Based on these findings, the role of GAL 11 in regulation of transcription, including an alteration in chromatin structure, is discussed.
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    SCM2, a tryptophan permease in Saccharomyces cerevisiae, is important for cell growth (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 260-268 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Amino acid permeases ; Transport ; Tryptophan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract SCM2, a novel gene encoding a yeast tryptophan permease, was cloned as a high-copy-number suppressor of cse2-1. The cse2-1 mutation causes cold sensitivity, temperature sensitivity and chromosome missegregation. However, only the cold-sensitive phenotype of cse2-1 cells is suppressed by SCM2 at high copy. SCM2 is located on the left arm of yeast chromosome XV, adjacent to SUP3 and encodes a 65 kDa protein that is highly homologous to known amino acid permeases. Four out of five disrupted scm2 alleles (scm2Δ1-Δ4) cause slow growth, whereas one disrupted allele (scm2Δ5) is lethal. Cells with both the scm2Δ1 and trp1-Δ101 mutations exhibit a synthetic cold-sensitive phenotype and grow much more slowly at the permissive temperature than cells with a single scm2Δ1 or trp1-Δ101 mutation. A region of the predicted SCM2 protein is identical to the partial sequence recently reported for the yeast tryptophan permease TAP2, indicating that SCM2 and TAP2 probably encode the same protein.
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    The Saccharomyces cerevisiae SGE1 gene product: a novel drug-resistance protein within the major facilitator superfamily (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 287-294 
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    ISSN: 1617-4623
    Keywords: Drug sensitivity ; Saccharomyces cerevisiae ; Major facilitator superfamily ; Drug expulsion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several pleiotropic drug sensitivities have been described in yeast. Some involve the loss of putative drug efflux pumps analogous to mammalian P-glycoproteins, others are caused by defects in sterol synthesis resulting in higher plasma membrane permeability. We have constructed a Saccharomyces cerevisiae strain that exhibits a strong crystal violet-sensitive phenotype. By selecting cells of the supersensitive strain for normal sensitivity after transformation with a wild-type yeast genomic library, a complementing 10-kb DNA fragment was isolated, a 3.4-kb subfragment of which was sufficient for complementation. DNA sequence analysis revealed that the complementing fragment comprised the recently sequenced SGE1 gene, a partial multicopy suppressor of gal11 mutations. The supersensitive strain was found to be a sge1 null mutant. Overexpression of SGE1 on a high-copy-number plasmid increased the resistance of the supersensitive strain. Disruption of SGE1 in a wild-type strain increased the sensitivity of the strain. These features of the SGE1 phenotype, as well as sequence homologies of SGE1 at the amino acid level, confirm that the Sge1 protein is a member of the drug-resistance protein family within the major facilitator superfamily (MFS).
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    PDR3, a new yeast regulatory gene, is homologous toPDR1 and controls the multidrug resistance phenomenon (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 501-511 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Transcription factor ; Zinc finger ; Multidrug resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract TheSaccharomyces cerevisiae PDR3 gene, located near the centromere of chromosome II, has been completely sequenced and characterised. Mutationspdr3-1 andpdr3-2, which confer resistance to several antibiotics can be complemented by a wild-type allele of the PDR3 gene. The sequence of the wild-typePDR3 gene revealed the presence of a long open reading frame capable of encoding a 976-amino acid protein. The protein contains a single Zn(II)2Cys6 binuclear-type zinc finger homologous to the DNA-binding motifs of other transcriptional activators from lower eukaryotes. Evidence that the PDR3 protein is a transcriptional activator was provided by demonstrating that DNA-bound LexA-PDR3 fusion proteins stimulate expression of a nearby promoter containing LexA binding sites. The use of LexA-PDR3 fusions revealed that the protein contains two activation domains, one localised near the N-terminal, cysteine-rich domain and the other localised at the C-terminus. The salient feature of the PDR3 protein is its similarity to the protein coded byPDR1, a gene responsible forpleiotropicdrugresistance. The two proteins show 36% amino acid identity over their entire length and their zinc finger DNA-binding domains are highly conserved. The fact that the absence of both PDR1 and PDR3 (simultaneous disruption of the two genes) enhances multidrug sensitivity strongly suggests that the two transcriptional factors have closely related functions.
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    Two adjacent nuclear genes, ISF1 and NAM7/UPF1, cooperatively participate in mitochondrial functions in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 49-56 
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    ISSN: 1617-4623
    Keywords: Nuclear suppressor gene ; Mitochondrial functions ; Glucose repression ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We previously isolated a nuclear 5.7 kb genomic fragment carrying the NAM7/UPF1 gene, which is able to suppress mitochondrial splicing deficiency when present in multiple copies. We show here that an immediately adjacent gene ISF1 (Increasing Suppression Factor) increases the efficiency of the NAM7/UPF1 suppressor activity. The ISF1 gene has been independently isolated as the MBR3 gene and comparison of the ISF1 predicted protein sequence with data libraries revealed a significant similarity with the MBRI yeast protein. The ISF1 and NAM7 genes are transcribed in the same direction, and RNase mapping allowed the precise location of their termini within the intergenic region to be determined. The ISF1 gene is not essential for cell viability or respiratory growth. However as for many mitochondrial genes, ISF1 expression is sensitive to fermentative repression; in contrast expression of the NAM7 gene is unaffected by glucose. We propose that ISF1 could influence the NAM7/UPF1 function, possibly at the level of mRNA turnover, thus modulating the expression of nuclear genes involved in mitochondrial biogenesis.
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    Characterization of the Saccharomyces cerevisiae nuclear gene CYB3 encoding a cytochrome b polypeptide of respiratory complex II (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 708-716 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Mitochondria ; Cytochrome b ; Complex II ; HAP2/3/4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Computer-assisted structural analysis of the predicted product of the previously described open reading frame (ORF) YKL4 located on the left arm of chromosome XI of Saccharomyces cerevisiae revealed a high degree of similarity (〉50%) to bovine cytochrome b 560, the sdhC polypeptide of the Escherichia coli succinate dehydrogenase (SDH) complex and the protein specified by ORF137 located on the chloroplast DNA of Marchantia polymorpha. Disruption of the yeast gene severely impaired mitochondrial function, while Northern analysis showed it to be subject to catabolite repression. Deletion analysis of the CYB3 promoter identified a single HAP2/3/4-binding element that is necessary and sufficient for carbon source-dependent transcriptional regulation. These experiments also suggested the presence of additional, as yet unidentified, transcriptional control elements, both negative and positive. Taken together, these data lead us to conclude that the CYB3 gene encodes the yeast homolog of the bovine cytochrome b 560 component of complex II of the mitochondrial electron transport chain.
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    Functional analysis of the zinc cluster domain of the CYP1 (HAP1) complex regulator in heme-sufficient and heme-deficient yeast cells (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 699-707 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; CYP1(HAP1) protein ; Electron transport ; Oxygen and heme regulation ; Trans regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract CYP1 determines the expression of several genes whose transcription is heme-dependent in yeast. It exerts regulatory functions even in the absence of heme, usually considered to be its effector. It mediates both positive and negative effects, depending on the target gene and on the redox state of the cell. In the presence of heme, it binds through a cysteine-rich domain in which a histidine residue occupies the position of the sixth and essential cysteine of the otherwise classical zinc cluster DNA-binding domain exemplified by GAL4. We constructed specific missense mutations in the potential CYP1 zinc cluster domain by site-directed mutagenesis and looked for regulatory effects of the mutated proteins under specific physiological conditions. We show that CYP1 does belong to the zinc cluster regulatory family since a sixth essential cysteine residue is indeed present, albeit at a modified position when compared to the consensus sequence. We also show that the amino acid preceding the first cysteine residue of the DNA-binding domain critically affects the efficiency of regulation both in the presence and in the absence of heme: mutations known to affect DNA binding under heme-sufficient conditions also affect regulation under heme-deficient conditions. We therefore surmise that regulation under hemedeficient conditions is dependent upon DNA binding.
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    MBR1 and MBR3, two related yeast genes that can suppress the growth defect of hap2, hap3 and hap4 mutants (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 575-583 
    Details
    ISSN: 1617-4623
    Keywords: Multicopy suppressors ; HAP2/3/4 activation complex ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two new yeast genes, named MBR1 and MBR3, were isolated as multicopy suppressors of the growth defect of a strain lacking the HAP2 transcriptional activator. Both genes when overexpressed can also suppress the growth defect of hap3 and hap4 null mutants. However, overexpression of MBRI cannot substitute for the HAP2/3/4 complex in activation of the CYC1 gene. Nucleotide sequencing of MBR1 and MBR3 revealed that these two genes encode serine-rich, hydrophilic proteins with regions of significant homology. The functional importance of one of these conserved regions was shown by mutagenesis. Disruption of MBR1 leads to a partial growth defect on glycerol medium. Disruption of MBR3 has no major effect but the double disruptant shows a synthetic phenotype suggesting that the MBR1 and MBR3 gene products participate in common function.
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    Identification of a sporulation-specific promoter regulating divergent transcription of two novel sporulation genes in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 244 (1994), S. 661-672 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Meiosis Sporulation ; Divergent promoter ; Developmental regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Promoters that control gene expression in Saccharomyces cerevisiae only in a sporulation-specific manner have previously been isolated from a genomic yeast DNA library fused to a promoterless Escherichia coli lacZ gene. Two novel sporulation-specific genes, SPS18 and SPS19, were isolated using this technique. These genes are divergently controlled by the same promoter but with SPS18 expressed at four times the level of SPS19. Deletion analysis has shown that the promoter elements that exert sporulation control on each of the genes overlap, having a common 25 bp sequence located within the intergenic region. SPS18 encodes a 34-KDa protein of 300 amino acids that contains a putative zinc-binding domain and a region of highly basic residues that could target the protein to the nucleus. SPS19 encodes a 31-KDa protein of 295 amino acids, which has a peroxisomal targeting signal (SKL) at its C terminus; this protein belongs to the family of non-metallo short-chain alcohol dehydrogenases. A null mutation deleting the intergenic promoter prevented expression of both genes, and when homozygous in diploids, reduced the extent of sporulation four-fold; the spores that did form were viable, but failed to become resistant to ether, and were more sensitive to lytic enzymes. This phenotype reflects a defect in spore wall maturation, indicating that the product of at least one of the genes functions during the process of spore wall formation. Therefore these genes belong to the class of late sporulation-specific genes that are sequentially activated during the process of meiosis and spore formation.
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    Use of synthetic lethal mutants to clone and characterize a novel CTP synthetase gene in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 431-439 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Duplicate genes ; Synthetic lethal mutants ; CTP synthetase ; Pyrimidine biosynthetic pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the pyrimidine biosynthetic pathway, CTP synthetase catalyses the conversion of uridine 5′-triphosphate (UTP) to cytidine 5′-triphosphate (CTP). In the yeast Saccharomyces cerevisiae, the URA7 gene encoding this enzyme was previously shown to be nonessential for cell viability. The present paper describes the selection of synthetic lethal mutants in the CTP biosynthetic pathway that led us to clone a second gene, named URA8, which also encodes a CTP synthetase. Comparison of the predicted amino acid sequences of the products of URA7 and URA8 shows 78% identity. Deletion of the URA8 gene is viable in a haploid strain but simultaneous presence of null alleles both URA7 and URA8 is lethal. Based on the codon bias values for the two genes and the intracellular concentrations of CTP in strains deleted for one of the two genes, relative to the wild-type level, URA7 appears to be the major gene for CTP biosynthesis. Nevertheless, URA8 alone also allows yeast growth, at least under standard laboratory conditions.
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    Temperature-sensitive mutants of hsp82 of the budding yeast Saccharomyces cerevisiae (1994)
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    Molecular genetics and genomics 242 (1994), S. 517-527 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; HSP82 ; Random in vitro mutagenesis ; Temperature-sensitive mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The budding yeast Saccharomyces cerevisiae has two HSP90-related genes per haploid genome, HSP82 and HSC82. Random mutations were induced in vitro in the HSP82 gene by treatment of the plasmid with hydroxylamine. Four temperature-sensitive (ts) mutants and one simultaneously is and cold-sensitivie (cs) mutant were then selected in a yeast strain in which HSC82 had previously been disrupted. The mutants were found to have single base changes in the coding region, which caused single amino acid substitutions in the HSP82 protein. All of these mutations occurred in amino acid residues that are well conserved among HSP90-related proteins of various species from Escherichia coli to human. Various properties including cell morphology, macromolecular syntheses and thermosensitivity were examined in each mutant at both the permissive and nonpermissive temperatures. The mutations in HSP82 caused pleiotropic effects on these properties although the phenotypes exhibited at the nonpermissive temperature varied among the mutants.
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    The hypo-osmolarity-sensitive phenotype of the Saccharomyces cerevisiae hpo2 mutant is due to a mutation in PKC1, which regulates expression of β-glucanase (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 641-648 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cell wall ; Protein kinase C ; β-Glucanase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To obtain more information about the cell wall organization of Saccharomyces cerevisiae, we have developed a novel screening system to obtain cell wall-defective mutants, using a density gradient centrifugation method. Nine hypo-osmolarity-sensitive mutants were classified into two complementation groups, hpo1 and hpo2. Phase contrast microscopic observation showed that mutant cells bearing lesions at either locus became abnormally large. A gene that complemented the mutant phenotype of hpo2 was cloned and sequenced. This gene turned out to be identical to PKC1, which encodes the yeast homologue of mammalian protein kinase C. Complementation tests with pkc1Δ showed that hpo2 is allelic to pkc1. To study the reason for the fragility of hpo2 cells, cell wall was isolated and the glucan was analyzed. The amount of alkali, acid-insoluble glucan, which is responsible for the rigidity of the cell wall, was reduced to about 30% that of the wild-type cell and this may be the major cause of the fragility of the hpo2 mutant cell. Analysis of total wall proteins in hpo2 mutant cells on SDS-polyacrylamide gels revealed that a 33 kDa protein was overproduced two- to threefold relative to the wild-type level. This 33 kDa protein was identified as a β-glucanase, encoded by BGL2. Disruption of BGL2 in the hpo2 mutant partially rescued the growth rate defect. This suggests that the PKC1 kinase cascade regulates BGL2 expression negatively and overproduction of the β-glucanase is partially responsible for the growth defect. Since the bgl2 disruption did not rescue the hypo-osmolarty-sensitive phenotype of the hpo2 mutant, PKC1 must negatively regulate other enzymes involved in the biosynthesis and metabolism of the cell wall.
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    Polyubiquitin gene expression contributes to oxidative stress resistance in respiratory yeast (Saccharomyces cerevisiae) (1994)
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    Molecular genetics and genomics 243 (1994), S. 358-362 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Oxidative stress ; High temperature viability ; Ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract UBI4, the polyubiquitin gene of Saccharomyces cerevisiae, is expressed at a low level in vegetative cells, yet induced strongly in response to starvation, cadmium, DNA-damaging agents and heat shock. UBI4 is also expressed at a higher basal level in cells growing by respiration as compared to glucose-repressed cells growing by fermentation. This higher UBI4 expression of respiratory cultures probably helps to counteract the greater oxidative stress of respiratory growth. The effects of inactivating UBI4 on high temperature viability are more marked with respiratory cultures. Also loss of UBI4 leads to a considerably increased rate of killing of respiring cells by hydrogen peroxide, whereas the same gene inactivation has relatively little effect on the peroxide sensitivity of cells in which mitochondrial functions are repressed. This is the first study to reveal that ubiquitin levels in cells can influence their ability to withstand oxidative stress.
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    Open reading frames in the antisense strands of genes coding for glycolytic enzymes in Saccharomyces cerevisiae (1994)
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    Molecular genetics and genomics 243 (1994), S. 363-368 
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    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Glycolysis ; Phosphoglucose isomerase ; Antisense ; Double-strand coding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Open reading frames longer than 300 bases were observed in the antisense strands of the genes coding for the glycolytic enzymes phosphoglucose isomerase, phosphoglycerate mutase, pyruvate kinase and alcohol dehydrogenase I. The open reading frames on both strands are in codon register. It has been suggested that proteins coded in codon register by complementary DNA strands can bind to each other. Consequently, it was interesting to investigate whether the open reading frames in the antisense strands of glycolytic enzyme genes are functional. We used oligonucleotide-directed mutagenesis of the PGI1 phosphoglucose isomerase gene to introduce pairs of closely spaced base substitutions that resulted in stop codons in one strand and only silent replacements in the other. Introduction of the two stop codons into the PGI1 sense strand caused the same physiological defects as already observed for pgi1 deletion mutants. No detectable effects were caused by the two stop codons in the antisense strand. A deletion that removed a section from − 31 by to + 109 by of the PGI1 gene but left 83 bases of the 3′ region beyond the antisense open reading frame had the same phenotype as a deletion removing both reading frames. A similar pair of deletions of the PYK1 gene and its antisense reading frame showed identical defects. Our own Northern experiments and those reported by other authors using double-stranded probes detected only one transcript for each gene. These observations indicate that the antisense reading frames are not functional. On the other hand, evidence is provided to show that the rather long reading frames in the antisense strands of these glycolytic enzyme genes could arise from the strongly selective codon usage in highly expressed yeast genes, which reduces the frequency of stop codons in the antisense strand.
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    The archaebacterial membrane protein bacterio-opsin is expressed and N-terminally processed in the yeast Saccharomyces cerevisiae (1994)
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    Molecular genetics and genomics 244 (1994), S. 183-188 
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    ISSN: 1617-4623
    Keywords: Bacterio-opsin ; Expression ; Yeast ; Saccharomyces cerevisiae ; Membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bop gene codes for the membrane protein bacterio-opsin (BO), which on binding all-trans-retinal, constitutes the light-driven proton pump bacteriorhodopsin (BR) in the archaebacterium Halobacterium salinarium The designation H. salinarium instead of the former designation H. halobium is used throughout this paper following the classification of Tindall (1992) . This gene was cloned in a yeast multi-copy vector and expressed in Saccharomyces cerevisiae under the control of the constitutive ADH1 promoter. Both the authentic gene and a modified form lacking the precursor sequence were expressed in yeast. Both proteins are incorporated into the membrane in S. cerevisiae. The presequence is thus not required for membrane targeting and insertion of the archaebacterial protein in budding yeast, or in the fission yeast Schizosaccharomyces pombe, as has been shown previously. However, in contrast to S. pombe transformants, which take on a reddish colour when all-trans-retinal is added to the culture medium as a result of the in vivo regeneration of the pigment, S. cerevisiae cells expressing BO do not take on a red colour. The precursor of BO is processed to a protein identical in size to the mature BO found in the purple membrane of Halobacterium. The efficiency of processing in S. cerevisiae is dependent on growth phase, as well as on the composition of the medium and on the strain used. The efficiency of processing of BR is reduced in S. pombe and in a retinal-deficient strain of H. salinarium, when retinal is present in the medium.
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    Heterospecific cloning of Arabidopsis thaliana cDNAs by direct complementation of pyrimidine auxotrophic mutants of Saccharomyces cerevisiae. I. Cloning and sequence analysis of two cDNAs catalysing the second, fifth and sixth steps of the de novo pyrimidine biosynthesis pathway (1994)
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    Molecular genetics and genomics 244 (1994), S. 23-32 
    Details
    ISSN: 1617-4623
    Keywords: Arabidopsis thaliana ; Saccharomyces cerevisiae ; Complementation ; Aspartate transcarbamylase ; Orotate phosphoribosyl transferase ; Orotidine-5′-phosphate decarboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An Arabidopsis thaliana cDNA library was used to complement Saccharomyces cerevisiae pyrimidine auxotrophic mutants. Mutants in all but one (carbamylphosphate synthetase) of the six steps in the de novo pyrimidine biosynthetic pathway could be complemented. We report here the cloning, sequencing and computer analysis of two cDNAs encoding the aspartate transcarbamylase (ATCase; EC 2.1.3.2) and orotate phosphoribosyltransferase-orotidine-5′-phosphate decarboxylase (OPRTase-OMP-decase; EC 2.4.2.10, EC 4.1.1.23) enzymes. These results confirm the presence in A. thaliana of a bifunctional gene whose product catalyses the last two steps of the pyrimidine biosynthetic pathway, as previously suggested by biochemical studies. The ATCase encoding cDNA sequence (PYRB gene) shows an open reading frame (ORF) of 1173 by coding for 390 amino acids. The cDNA encoding OPRTase-OMPdecase (PYRE-F gene) shows an ORF of 1431 by coding for 476 amino acids. Computer analysis of the deduced amino acid sequences of both cDNAs shows the expected high similarity with the ATCase, ornithine transcarbamylase (OTCase; EC 2.1.3.3), OPRTase and OMPdecase families. This heterospecific cloning approach increases our understanding of the genetic organization and interspecific functional conservation of the pyrimidine biosynthetic pathway and underlines its usefulness as a model for evolutionary studies.
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    URL: http://dx.doi.org/10.1007/BF00280183
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    Sequence of the HAP3 transcription factor of Kluyveromyces lactis predicts the presence of a novel 4-cysteine zinc-finger motif (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 96-106 
    Details
    ISSN: 1617-4623
    Keywords: HAP3 ; Saccharomyces cerevisiae ; Kluyveromyces lactis ; Zinc finger ; Carbon source regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Kluyveromyces lactis homologue of the Saccharomyces cerevisiae HAP3 gene was isolated by functional complementation of the respiratory-deficient phenotype of the S. cerevisiae hap3::HIS4 strain SHY40. The KlHAP3 gene encodes a protein of 205 amino acids, of which the central B-domain of 90 residues is highly homologous to HAP3 counterparts of S. cerevisiae and higher eukaryotes. The protein contains a novel 4-cysteine zinc-finger motif and we propose by analogy that all other homologous HAP3 proteins contain the same motif, with the position containing the third cysteine being occupied by a serine residue. In contrast to the situation in S. cerevisiae, disruption of the KlHAP3 gene in K. lactis does not result in a respiratory-deficient phenotype and the growth of the null strain is indistinguishable from wild type. There is also no effect on the expression of the carbon source-regulated KlCYC1 gene, suggesting either a different role for the HAP2/3/4 complex, or the existence of a different mechanism of carbon source regulation. Sequence verification of the S. cerevisiae HAP3 locus reveals that, just as in K. lactis, a long open reading frame (ORF) is present upstream of the HAP3 gene. These highly homologous ORFs are predicted to have at least eight membrane-spanning fragments, but do not show significant homology to any known sequence present in databases. The ScORFX gene is transcribed in the opposite direction to ScHAP3, but, in contrast to an earlier report by Hahn et al. (1988), the transcripts of the two genes do not overlap. The model proposed by these authors, in which the ScHAP3 gene is regulated by an anti-sense non-coding mRNA, is therefore not correct.
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    URL: http://dx.doi.org/10.1007/BF00279755
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    Expression of human poly(ADP-ribose) polymerase in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 686-693 
    Details
    ISSN: 1617-4623
    Keywords: Yeast ; Saccharomyces cerevisiae ; Poly(ADP-ribose) polymerase ; DNA repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The coding sequence for human poly(ADP-ribose) polymerase was expressed inducibly in Saccharomyces cerevisiae from a low-copy-number plasmid vector. Cell free extracts of induced cells had poly(ADPribose) polymerase activity when assayed under standard conditions; activity could not be detected in non-induced cell extracts. Induced cells formed poly(ADP-ribose) in vivo, and levels of these polymers increased when cells were treated with the alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). The cytotoxicity of this agent was increased in induced cells, and in vivo labelling with [3H]adenine further decreased their viability. Increased levels of poly(ADP-ribose) found in cells treated with the alkylating agent were not accompanied by lowering of the NAD concentration.
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    A new yeast gene, HTR1, required for growth at high temperature, is needed for recovery from mating pheromone-induced G1 arrest (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 107-116 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; ts mutant ; Recovery ; HTR1 ; MCS1/SSD1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A new temperature-sensitive mutant of Saccharomyces cerevisiae was isolated. Arrested cells grown at the nonpermissive temperature were of dumb-bell shape and contained large vacuoles. A DNA fragment was cloned based on its ability to complement this temperature sensitivity. The HTR1 gene encodes a putative protein of 93 kDa without significant homology to any known proteins. The gene was mapped between ade5 and lys5 on the left arm of chromosome VII. The phenotype of the gene disruptant appeared to be strain-specific; disruption of the gene in strain W303 caused the cells to become temperature sensitive. The arrested phenotype here was similar to that of the original is mutant and cells in G2/M phase predominated at high temperature. Another disruptant in a strain YPH background grew slowly at high temperature due to slow progression through G2/M phase, and morphologically abnormal (elongated) cells accumulated. A single-copy suppressor that alleviated the temperature-sensitive defects in both strains was identified as MCS1/SSD1. The wild-type strains W303 and YPH are known to carry defective MCS1/SSD1 alleles; hence HTR1 may function redundantly with MCS1/SSD1 to suppress the temperature-sensitive phenotypes. In addition, based on a halo bioassay, the disruptant strains appeared to be defective in recovery from, or adaptive response to G1 arrest mediated by mating pheromone, even at the permissive temperature. Thus the gene has at least two functions and is designated HTR1 (required for high temperature growth and recovery from G1 arrest induced by mating pheromone).
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    Two subclasses of guanine exchange factor (GEF) domains revealed by comparison of activities of chimeric genes constructed from CDC25, SDC25 and BUD5 in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 167-176 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Cell cycle ; Bud site selection ; Guanine exchange factor ; Ras
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Guanine Exchange Factor (GEF) activity for Ras proteins has been associated with a conserved domain in Cdc25p, Sdc25p in Saccharomyces cerevisiae and several other proteins recently found in other eukaryotes. We have assessed the structure-function relationships between three different members of this family in S. cerevisiae, Cdc25p, Sdc25p and Bud5p. Cdc25p controls the Ras pathway, whereas Bud5p controls bud site localization. We demonstrate that the GEF domain of Sdc25p is closely related to that of Cdc25p. We first constructed a thermosensitive allele of SDC25 by specifically altering amino acid positions known to be changed in the cdc25-1 mutation. Secondly, we constructed three chimeric genes from CDC25 and SDC25, the products of which are as active in the Ras pathway as are the wild-type proteins. In contrast, similar chimeras made between CDC25 and BUD5 lead to proteins that are inactive both in the Ras and budding control pathways. This difference in the ability of chimeric proteins to retain activity allows us to define two subclasses of structurally different GEFs: Cdc25p and Sdc25p are Ras-specific GEFs, and Bud5p is a putative GEF for the Rsr1/Bud1 Rap-like protein.
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    Inactivation of SSM4, a new Saccharomyces cerevisiae gene, suppresses mRNA instability due to rna14 mutations (1994)
    Springer
    Molecular genetics and genomics 245 (1994), S. 323-333 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; mRNA decay Poly(A) tail ; Ty transposition ; SSM4 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Decay rates of mRNAs depend on many elements and among these, the role of the poly(A) tail is now well established. In the yeast Saccharomyces cerevisiae, thermosensitive mutations in two genes, RNA14 and RNA15, result in mRNAs having shorter poly(A) tails and reduced half-life. To identify other components interacting in the same process, we have used a genetic approach to isolate mutations that suppress the thermosensitivity of an rna14 mutant strain. Mutations in a single locus, named SSM4, not only suppress the cell growth phenotype but also the mRNA instability and extend the short mRNA poly(A) tails. The frequency of appearance and the recessive nature of these mutations suggested that the suppressor effect was probably due to a loss of function. We failed to clone the SSM4 gene directly by complementation, owing to its absence from gene banks; it later emerged that the gene is toxic to Escherichia coli, but we have nevertheless been able to clone the SSM4 sequence by Ty element transposition tagging. Disruption of the SSM4 gene does not affect cell viability and suppresses the rna14 mutant phenotypes. The protein encoded by the SSM4 gene has a calculated molecular mass of 151 kDa and does not contain any known motif or show homology with known proteins. The toxicity of the SSM4 gene in E. coli suggests that a direct biochemical activity is associated with the corresponding protein.
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    Genetic interaction between the Ras-CAMP pathway and the Dis2s1/Glc7 protein phosphatase in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 257-262 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Protein phosphatase ; Ras-cAMP pathway ; DIS2S1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Saccharomyces cerevisiae DIS2S1/GLC7 gene encodes a type 1 protein phosphatase indispensable for cell proliferation. We found that introduction of a multicopy DIS2S1 plasmid impaired growth of cells with reduced activity of the cAMP-dependent protein kinase. In order to understand further the interaction between the two enzymes, a temperature-sensitive mutation in the DIS2S1 gene was isolated. The mutant accumulated less glycogen than wild type at the permissive temperature, indicating that activity of the Dis2s1 protein phosphatase is attenuated by the mutation. Furthermore, the dis2s1 ts mutation was shown to be suppressed by a multicopy plasmid harboring PDE2, a gene for cAMP phosphodiesterase. These results indicate that the Ras-cAMP pathway interacts genetically with the DIS2S1/GLC7 gene.
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    Stress-induced transcriptional activation mediated by YAP1 and YAP2 genes that encode the Jun family of transcriptional activators in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 250-256 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Transcriptional activator ; AP-1 ; Stress response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Saccharomyces cerevisiae YAP2 gene encoding an AP-1-like transcriptional activator protein was cloned by selection for genes that confer pleiotropic drug resistance when present in high copy number. The novel YAP2 gene encodes a protein of 45827 daltons and is homologous in part to a known transcriptional activator protein encoded by YAP1/PDR4/SNQ3/PAR1. Homology was found only in both terminal regions. The N-terminal portion contains a region rich in basic amino acids, followed by a “leucine zipper” motif. Overexpression of YAP2 led to the induction of expression of an AP-1 recognition element (ARE)-dependent promoter. The yap1 disruptant has been shown to be sensitive to H2O2. In this study, we demonstrated that the yap1 disruptant is also unable to grow in medium containing 150 μM cadmium, whereas the yap2 disruptant exhibited no significant phenotypes. However, YAP2 in high copy number did suppress cadmium sensitivity, but not H2O2 sensitivity of the yap1 disruptant. YAP1 was able to mediate both cadmium- and H2O2-induced transcriptional activation of an ARE-dependent promoter. A high-copy-number plasmid bearing YAP2 mediated cadmium-induced transcriptional activation of this promoter. The inductions were prevented by the antioxidant N-acetyl-l-cysteine.
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    The 3′ → 5′ exonucleases of both DNA polymerases δ and ε participate in correcting errors of DNA replication in Saccharomyces cerevisiae (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 289-296 
    Details
    ISSN: 1617-4623
    Keywords: DNA polymerases ε and δ ; 3′ → 5′ Exonuclease ; Replication errors ; Spontaneous mutations ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA polymerases II (ε) and III(δ) are the only nuclear DNA polymerases known to possess an intrinsic 3′ → 5′ exonuclease in Saccharomyces cerevisiae. We have investigated the spontaneous mutator phenotypes of DNA polymerase δ and ε 3′ → 5′ exonuclease-deficient mutants, pol3-01 and pol2-4, respectively. pol3-01 and pol2-4 increased spontaneous mutation rates by factors of the order of 102 and 101, respectively, measured as URA3 forward mutation and his7-2 reversion. Surprisingly, a double mutant pol2-4 pol3-01 haploid was inviable. This was probably due to accumulation of unedited errors, since a pol2-4/pol2-4 pol3-01/pol3-01 diploid was viable, with the spontaneous his7-2 reversion rate increased by about 2 × 103-fold. Analysis of mutation rates of double mutants indicated that the 3′ → 5′ exonucleases of DNA polymerases δ and ε can act competitively and that, like the 3′ → 5′ exonuclease of DNA polymerase δ the 3′ → 5′ exonuclease of DNA polymerase ε acts in series with the PMS1 mismatch correction system. Mutational spectra at a URA3 gene placed in both orientations near to a defined replication origin provided evidence that the 3′ → 5′ exonucleases of DNA polymerases δ and ε act on opposite DNA strands, but were in sufficient to distinguish conclusively between different models of DNA replication.
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    URL: http://dx.doi.org/10.1007/BF00280418
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    A novel method for efficient expression cloning of fungal enzyme genes (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 253-260 
    Details
    ISSN: 1617-4623
    Keywords: Recombinant DNA ; Saccharomyces cerevisiae ; Endo-β-glucanase ; Endo-xylanase ; Heterologous expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have developed a method for fast and efficient isolation of enzyme genes from filamentous fungi by combining the ability of Saccharomyces cerevisiae to express heterologous genes with the utilisation of sensitive and reliable enzyme assays. A cDNA library from the fungus Humicola insolens was constructed in a S. cerevisiae/Escherichia coli shuttle vector in E. coli. Sub-pools of the library were subsequently screened for enzyme activity in S. cerevisiae. More than 130 clones were identified as positive in either an endo-β-glucanase or an endo-xylanase assay. Based on a partial characterization of the DNA sequence of the individual clones, they could be grouped into five distinct types of endo-β-glucanases and three types of endo-xylanases. A representative cDNA from each type was sub-cloned in an Aspergillus vector and expressed in A. oryzae. The new cloning method may be an important alternative to traditional cloning methods based on amino acid sequence information.
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    Efficient UV stimulation of yeast integrative transformation requires damage on both plasmid strands (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 308-314 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Integrative plasmids ; Recombinational structures ; UV irradiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nature of UV-induced pre-recombinational structures was studied using transformation of Saccharomyces cerevisiae cells with non-replicative plasmids. Transformation by double-stranded plasmids irradiated with UV was stimulated up to 50-fold, and both plasmid integration and conversion of the mutated chromosomal selective gene were found to be equally increased. The stimulation observed with such ‘totally’ irradiated plasmids was not found with plasmids bearing lesions in only one strand. This effect is attributed to the formation by excision repair of recombinogenic structures consisting of a pyrimidine dimer opposite a gap. When single-stranded integrative plasmids were irradiated, their transforming potential was decreased but the proportion of transformants that arose by gene conversion, rather than by plasmid integration, was increased from 8% to 49% as a function of the UV dose. Possible reasons why single-strand UV lesions favour gene conversion are discussed.
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    Shared control of maltose induction and catabolite repression of the MAL structural genes in Saccharomyces (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 622-630 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; Yeast Catabolite repression ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maltose utilization in yeast requires the presence of any one of the five unlinked, homologous MAL loci. Transcription of the two structural genes MALT (permease) and MALS (maltase) is induced by maltose and catabolite-repressed by glucose. MAL6T and MAL6S share a common 5′ intergenic sequence; deletion studies within this sequence revealed a bi-directionally functioning upstream activation sequence (UASM) consisting of four 11bp homologous sites. Activation of these sites by the MALR protein results in the coordinate expression of MAL6T and MAL6S. The basal promoter activates MALS expression to a greater extent than MALT and is located in a region that overlaps UASM. Deletion of several subsites within the UASM has an asymmetric effect on MAL gene expression, having a greater affect on MALT than on MALS. Catabolite repression of MAL6T and MAL6S by glucose is controlled at several levels. Using disruption mutants, the positively acting MAL1R protein was also found to play a role in catabolite repression of MAL6T and MAL6S.
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    RPK1, an essential yeast protein kinase involved in the regulation of the onset of mitosis, shows homology to mammalian dual-specificity kinases (1994)
    Springer
    Molecular genetics and genomics 243 (1994), S. 641-653 
    Details
    ISSN: 1617-4623
    Keywords: Saccharomyces cerevisiae ; RPK1 gene ; Protein kinase ; DNA replication ; Initiation of mitosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report here the sequence of RPK1 (for Regulatory cell Proliferation Kinase), a new Saccharomyces cerevisiae gene coding for a protein with sequence similarities to serine/threonine protein kinases. The protein sequence of 764 amino acids includes an amino-terminal domain (residues 1–410), which may be involved in regulation of the kinase domain (residues 411–764). The catalytic domain of Rpkl is not closely related to other known yeast protein kinases but exhibits strong homology to a newly discovered group of mammalian kinases (PYT, TTK, esk) with serine/threonine/tyrosine kinase activity. Null alleles of RPK1 are lethal and thus this gene belongs to the small group of yeast protein kinase genes that are essential for cell growth. In addition, eliminating the expression of RPK1 gives rise to the accumulation of non-viable cells with less than a 1 N DNA content suggesting that cells proceed into mitosis without completion of DNA synthesis. Therefore, the Rpkt kinase may function in a checkpoint control which couples DNA replication to mitosis. The level of the RPK1 transcript is extremely low and constant throughout the mitotic cycle. However it is regulated during cellular differentiation, being decreased in α-factor-treated a cells and increased late in meiosis in a/α diploids. Taken together, our results suggest that Rpk1 is involved in a pathway that coordinates cell proliferation and differentiation.
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    Image formation of alkyl-pendent aromatic polyimide by photocoupling with aromatic ketones (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 57-65 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Positive und negative Photostrukturen wurden in einem Polyimid (PI) aus 4,4′-Biphthalsäureanhydrid (BPA) und 4,4′-Diamino-3,3′-dimethyldiphenylmethan (DADMDPM), PI(BPA/DADMDPM) erzeugt, nachdem dieses mit Michlers Keton (MK) bzw. Benzophenon (BP) dotiert und einer ultravioletten Strahlung von 400 ± 50 nm ausgesetzt und naß entwickelt wurde. Das Prinzip der positiven Abbildung basiert auf dem Photokupplungseffekt von MK mit PI, der die Löslichkeit des Polyimids erhöht und so die Entwicklung eines Positivmusters ermöglicht. Die Erzeugung negativer Muster wird durch intermakromolekulare Wasserstoffbrücken zwischen der Carbonylgruppe des Imid-Rings und der Hydroxygruppe, die bei der photoinduzierten Kupplung von Benzophenon mit dem Polyimid gebildet wird, bewirkt. Die lithographische Auswertung zeigt, daß der mit MK dotierte, positive Polyimidfilm nicht in der Lage ist, brauchbare Muster zu erzeugen, da die UV-Wellenlängen von MK absorbiert werden, wodurch die Photokupplung in den tieferen Schichten des Films verhindert wird. Andererseits können in dem 0,6 μm dicken, mit Benzophenon dotierten Polyimidfilm sogar 2 μm schmale Linien aufgelöst werden.
    Notes: Positive and negative photostructures are formed after the polyimide (PI) of 4,4′-biphthalic anhydride (BPA) and 4,4′-diamino-3,3′-dimethyldiphenylmethane (DADMDPM), PI(BPA/DADMDPM) is doped with Michler′s ketone (MK) and benzophenone (BP), respectively, and is subjected to UV light (400 ± 50 nm) irradiation and solvent development. The principle of positive feature formation is based on the photocoupling of MK with PI, which increases PI solubility and thus enables a positive pattern to be developed. The phenomenon of negative photopatterning results from intermacromolecular H-bonding between the carbonyl group of the imide ring and the hydroxy group which is formed in the photoinduced coupling reaction between BP and PI. Lithographic evaluation shows that the MK-doped positive-acting PI film cannot form useful patterns because UV wavelengths are strongly absorbed by MK, which limits the depth of photocoupling in the film. On the other hand, 2-μm-wide lines can be resolved in the BP-doped negative-acting 0.6-μm-thick PI film.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052140106
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    Blends of polyamide 6 and poly(etheraroylhydrazide)s prepared concurrently with polyhydrazide polymerization (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 101-113 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polyhydrazid/Polyamid-Blends (PEHZ12/PA6) wurden durch Niedrigtemperatur-Polykondensation von 4,4′-Dichlorformyl-α,ω-diphenoxydodecan und Terephthaloyldihydrazid (TDH) zu Poly(etheraroylhydrazid) in Gegenwart von Polyamid 6 synthetisiert. Die DSC-Analysen lassen vermuten, daß die zwei Polymerkomponenten nicht wechselwirken. Bei der Extraktion des PA6-Anteils der Blends mit Ameisensäure zeigt die Charakterisierung des PEHZ12-Extraktionsrückstands aber, daß zumindest bei bestimmten Zusammensetzungen Wechselwirkungen zwischen den Komponenten auftreten. Modellreaktionen erlauben die Annahme, daß die PEHZ12-Polymerisation zwischen den Amino-Endgruppen des PA6 und den wachsenden PEHZ12-Polymerketten abläuft.
    Notes: Poly(etheraroylhydrazide) is synthesized in the presence of PA6 by means of low-temperature condensation polymerization of 4,4′-dichloroformyl-α,ω-diphenoxydodecane with terephthaloyl dihydrazide (TDH) in order to prepare polyhydrazide/poly-amide 6 (PEHZ12/PA6) blends. The thermal analysis of the blends by DSC seems to indicate that the two polymers are not interacting. Nevertheless, when the blends are subjected to an extraction process with formic acid in order to remove the PA6, the characterization of the residual PEHZ12 reveales that some interactions do occur between the constituent polymers, at least for selected compositions. Model experiments permit to hypothesize that the polymerization of PEHZ12 proceeds with a chemical interaction between amino end groups of PA6 and growing PEHZ12 chains.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052140110
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    Die kristallisation von polybutylenterephthalat (PBT) und polycarbonat (PC) im polymerblend PBT/PC (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 179-196 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The crystallization behavior of PBT as well as PC is changed in the controlled-processed blend due to intermolecular interactions between the different macromolecules in molten state.If the kinetics of the crystallization process prevents a crystallization-induced separation, the partial miscibility of the amorphous phases, measured by the glass transition temperatures, will lead to a decrease of the crystallinity of PBT. The crystallinity, normalized to the concentration of PBT in the blend, is independent from the concentration of PC at low coolling rates.At high cooling rates, PBT is crystallizing stepwise in the blend PBT/PC 40/60 wt.-%. The crystallization temperature in the anisothermic crystallization process is increased at low contents of PC due to a changed nucleation mechanism. The half-time of crystallization is increasing in blends with an increasing PC-content in isothermic crystallization experiments.The normally amorphous PC crystallizes considerably fast in presence of PBT in PC-rich blends. The crystallization or change in the state of order of PC was measured in situ by X-ray diffraction. Calorimetric experiments confirm this result and allow a quantitative estimation of the PC-crystallinity, which amounts to some 20% in the blend PBT/PC 5/95 wt.-%.
    Notes: Das Kristallisationsverhalten sowohl von PBT als auch von PC ist im definiert verarbeiteten Blend infolge intermolekularer Wechselwirkungen zwischen den unterschiedlichen Molekülen in der Schmelze verändert.Die über die Glasübergangstemperaturen gemessene teilweise Mischbarkeit der amorphen Phasen führt bei PBT zu einer Erniedrigung des Kristallinitätsgrades, wenn die kinetischen Bedingungen des Kristallisationsprozesses keine kristallisationsbedingte Entmischung zulassen. Der auf den PBT-Anteil normierte Kristallinitätsgrad ist bei kleinen Abkühlgeschwindigkeiten vom PC-Anteil unabhängüg.In der Mischung PBT/PC 40/60 Gew.-% kommt es bei hohen Kühlraten zu einer fraktionierten Kristallisation. Die Kristallisationstemperatur bei anisothermer Kristallisation ist bei geringen PC-Gehalten durch Änderung des Keimbildungsmechanismus erhöht. Bei isothermer Kristallisation steigt mit zunehmendem PC-Anteil die Kristallisationshalbwertszeit des PBT an.Das normalerweise amorphe PC kann in Gegenwart von PBT in den PC-reichen Mischungen besonders schnell kristallisieren, wobei der Kristallisations- bzw. Ordnungsprozeß des PC in situ mittels der Röntgenbeugung gemessen wurde. Kalorimetrische Untersuchungen bestätigen dieses Ergebnis und erlauben eine quantitative Abschätzung des PC-Kristallinitätsgrades zu ca. 20% im Blend PBT/PC 5/95 Gew.-%.
    Additional Material: 12 Ill.
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    Photoreactions in halogen-containing negative-tone novolac resists (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 197-210 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Elementaranalytische sowie NMR-, IR- und UV-spektroskopische Untersuchungen zeigen, daß die Photolyse von Halogenphenolnovolaken zur Substitution der Halogenatome durch Wasserstoff, der Bildung chinoider Gruppen und intermolekularen Vernetzung führt. Die Geschwindigkeit der Halogeneliminierung hängt von der Art des Halogens ab. Sie steigt in der Reihenfolge F 〈 Cl 〈 Br 〈 I. Die Chloreliminierung aus der 4-Position ist gegenüber der aus der 2- und 3-Position begünstigt. Außerdem verläuft die Abspaltung para-ständiger Chloratome aus Dimeren schneller als aus Trioder Tetrameren. ESR-Messungen bei 77 K sowie die Laserblitzphotolyse bei 296 K deuten auf die intermediäre Bildung von Phenoxyl- und Arylradikalen. Lithographische Tests belegen die hohe UV-Empfindlichkeit von Resisten auf der Basis von Halogenphenolnovolaken. Im Vergleich zu nichthalogenhaltigen Novolakresisten wird eine 6 - 10fache (System: 4-Chlorphenolnovolak/4,4′-Bisazidobiphenyl (5%)) bzw. eine ca. 25fache (System: 4-Chlorphenol-/m-Cresolnovolak/Hexamethoxymethylmelamin (5%)) Steigerung der Empfindlichkeit erreicht. Zur Interpretation wird ein Mechanismus postuliert, demzufolge die durch Halogenabspaltung hervorgerufene Sekundärradikalbildung zu einer zusätzlichen Vernetzung beiträgt. In den melaminhaltigen Resisten katalysiert der gebildete Halogenwasserstoff (Hal· + RH → H-Hal + R·) außerdem die Reaktion der Melaminverbindung mit der Novolakmatrix.
    Notes: The photolysis of halogenophenol novolacs is determined by the substitution of halogens by hydrogen and the formation of quinoid groups and intermolecular crosslinks. This is concluded from elemental analysis, NMR, IR and optical absorption measurements. The rate of halogen release depends on the chemical nature of the halogen. It increases in the order F 〈 Cl 〈 Br 〈 I. Chlorine elimination from 4-position is favored over that from 2- and 3-position. Moreover, dimers release chlorine from 4-position much more readily than trimers and tetramers. ESR measurements at 77 K and flash photolysis studies at 296 K yielded evidence for the intermediate existence of phenoxyl and aryl radicals. Lithographic tests demonstrated the high UV-sensitivity of resist formulations based on halogen-containing novolacs. The increase in sensitivity relative to that of formulations based on nonhalogenated novolacs is 6 to 10fold system: 4-chlorophenol novolac/4,4′-bisazidobiphenyl (5%) and ca. 25fold system: 4-chlorophenol/m-cresol novolac/hexamethoxymethylmelamine (5%). A postulated reactions mechanism concerning the sensitivity increase takes into account that halogen elimination results in the formation of additional radicals that accelerate the rate of crosslinking. Moreover, hydrogen halide generated by hydrogen abstraction of halogen radicals (Hal· + RH → H-Hal + R·) provides for the acid required to catalyze the reaction of the melamine compound with the novolac matrix.
    Additional Material: 6 Ill.
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    Crystallization behavior of polypropylene filled with calcium carbonate of various shape (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 11-24 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Calciumcarbonate unterschiedlicher Teilchenform (sphäarisch, kubisch und nadelfäormig) wurden mit Polypropylen (PP) in einer Zwei-Walzen-Mäuhle gemischt und anschließend zu Platten gepreßt. Der Einflußder Teilchenform auf das Kristallisationsverhalten der PP/CaCO3-Composite, d.h. Kristallisationspeaktemperatur (Tmax), Kristallisationsverlauf usw., wurde mittels Differentialkalorimetrie untersucht. Der Wert von Tmax häangt von der Größe der Gesamtoberfläache der CaCO3-Teilchen ab; Tmax ist bei nadelfäormigen Teilchen gräoßer als bei kubischen oder sphäarischen und hauangt in allen Fäallen der nicht-isothermen Kristallisation von der Abkäuhlgeschwindigkeit und der vorher erreichten maximalen Temperatur ab.
    Notes: Calcium carbonate of various particle shape (spheric, cubic, needle-shaped type) and polypropylene (PP) were mixed on a two roll mill and the mixture was pressed into plates. The effect of particle shape on the crystallization behavior of PP/CaCO3 composites, such as crystallization peak temperature (TMAX), crystallized pattern, etc., was investigated with differential scanning calorimetry measurements. The value of TMAX is explained by the total surface area of added CaCO3 particles; TMAX of needle-shaped series is larger than that of cubic or spheric ones. TMAX of various shaped CaCO3-filled PP totally depends on the cooling rate and maximum temperature in the non-isothermal crystallization, respectively.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052150102
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    Cationic polyelectrolytes, XIIPart. XI cf.8.. PEG-precursor for water-soluble cationic polymers with tertiary n-atoms in the main chain (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 107-119 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Polyaddition von Polyethylenglykol (PEG) Oligoglycidylethern (Mn (PEG): 396,587, 1437 und 3554) mit asymmetrischen Diaminen, wie N,N-Dimethylund N,N-Diethyl-1,3-diaminopropan, wurden wasserläosliche kationische Polymere erhalten. Die Eigenschaften der kationischen Polymeren sind vom urspräunglichen PEG-Molekulargewicht und der Diaminreaktivitäat abhäangig. PEG mit Mn = 396 zeigt das beste Verhalten. In verdäunnten wäassrigen Läosungen und in wäassrigen 2M NaCl-Läosungen der Polymeren wurde das Polyelektrolytverhalten veranschaulicht. Die Gegenwart der PEG Kette bestimmt das Polyelektrolytverhalten in den 2M NaCl Läosungen.
    Notes: Water-soluble cationic polymers were obtained by polyaddition of poly(ethylene glycol) (PEG) diglycidylethers (M̄n of PEG were 396, 587, 1437 and 3554, resp.) with asymmetrical diamines such as N,N-dimethyl-1,3-diaminopropane and N,N-diethyl-1,3-diaminopropane. The cationic polymer properties depend on the PEG initial molecular weight and on the diamine reactivity too. PEG with M̄n = 396 had the best behaviour in these reactions. The polyelectrolyte feature of cationic polymers was emphasized both in dilute aqueous solutions and in 2M aqueous NaCl solutions. The polyelectrolyte behaviour in 2M aqueous NaCl solution is determined by the PEG chain presence.
    Additional Material: 4 Ill.
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    Untersuchungen zur reaktion von o-kresol mit formaldehyd unter verwendung tertiärer amine (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 139-145 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Reaktion von o-Kresol mit Formaldehyd wurde unter Verwendung verschiedener tertiäarer Amine als Katalysatoren untersucht. Der Einfluß der Reaktionsparameter Basizitäat, Temperatur, Reaktionszeit und Formaldehydkonzentration wird diskutiert. Für die bevorzugte Bildung von 2,4-Bis(hydroxymethyl)-6-methylphenol wurden optimierte Synthesebedingungen erarbeitet. Die Bildung von Zwei-bzw. Mehrkernprodukten konnte nicht ausgeschlossen werden.
    Notes: The reaction between o-cresol and formaldehyde was investigated using various tertiary amines as catalysts. The influence of the reaction parameters basicity, temperature, reaction time and concentration of formaldehyde was discussed. To yield preferentially 2,4-bis(hydroxymethyl)-6-methylphenol the conditions of synthesis were optimized. The formation of bi- and polynuclear products cannot be avoided.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052150112
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    Effect of addition of cellulose powder on the viscometric behavior of liquid crystalline solutions of ethyl cellulose in m-cresol (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 189-200 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Scherviskositäat fläussigkristalliner Ethylcellulose, die mit Cellulosepulver unterschiedlicher Partikelgräoße gefäullt war, wurde bei konstantem Schergefäalle mit einem Kegel-Platte-Viskosimeter bestimmt. Der Einfluß des Cellulosepulvergehalts, des Läange/Breite-Verhäaltnisses der Pulverteilchen und der Temperatur auf das viskose Verhalten und die Phasenäubergäange wird diskutiert. Der Zusatz von Cellulosepulver erhäoht die Viskositäat und verringert die Aktivierungsenergie des Fließens(Ea), ohne jedoch die Phasenäubergäange zu beeinflussen. Die Viskositäat und die Aktivierungsenergie sind abhäangig vom Läange/Breite-Verhäaltnis der Pulverteilchen; mit zunehmender Gräoße dieses Verhäaltnisses wird die Viskositäatszunahme beschleunigt und die Aktivierungsenergie des Fließens erhäoht, wäahrend die Aktivierungsenergie mit steigendem Pulvergehalt abnimmt. Die Phasenumwandlungen sind unabhäangig von der Partikelform. Der Einfluß des Pulvergehalts auf Viskositäat und Aktivierungsenergie ist abhäangig von der Art der fläussigen Phase; in der anisotropen Phase ist der Einfluß geringer als in der isotropen Phase. Dies scheint von der Ausrichtung der Pulverteilchen und der stäabchenfäormigen Molekäule herzuräuhren.
    Notes: Steady-state shear viscosity for the liquid crystalline ethyl cellulose solution filled with cellulose powders was determined using a cone-plate-type viscometer and the effects of cellulose powder content, powder aspect ratio and temperature on the viscometric behavior and phase transformation were discussed. The addition of powder increased the viscosity and decreased the activation energy (Ea) for flow, but did not affect the phase transformation. The viscosity and Ea depended on the aspect ratio; with greater aspect ratio, the viscosity enhancement was accelerated and Ea as well as the decrease in Ea with powder content increased. The phase transformation did not depend on the aspect ratio, the dependences of viscosity and of Ea on powder content depended on the solution phase; the dependences for the anisotropic phase were smaller than those for the isotropic one. The findings appeared to originate from the alignments of powders and rod-like molecules.
    Additional Material: 4 Ill.
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    Oxygen uptake methods as a tool to determine the mechanism of action of hindered amine light stabilizers1Paper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 37-44 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The UV-degradation of an unstabilized and two HALS stabilized polyethylene (PE) films is described. The degradations are characterized by measuring the oxygen uptake, the formation of CO and CO2, the FT-IR spectra, the mechanical properties, the stabilizer concentration and the oxygen content of the film.The oxygen uptake of the unstabilized PE film led to the expected changes in the IR spectra and embrittlement of the film, while the oxygen uptake by the HALS stabilized films caused only minor changes. The differences between the results for the unstabilized and the HALS stabilized polymers are explained assuming that the initiation of the photodegradation of PE is due to charge transfer complexes.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052160103
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    Current of status of exploitation of radical scavenging stabilizers in advanced polymer stabilizationPaper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 135-146 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Principal chemical pathways characteristic of active participation of radical scavenging polymer stabilizers (phenols, aromatic, hydroaromatic and hindered aliphatic amines) are outlined. Pathways resulting in a partial depletion or distortion of activity of stabilizers, in formation of polymer discolouring products, or in interactions in bifunctional stabilizers are involved.
    Type of Medium: Electronic Resource
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    Poly(butyleneterephtalate) photolysis and photooxidation : Identification of the ir-absorbing productsPaper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 155-167 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Irradiations (λ≥300 nm) of poly(butyleneterphtalate) films were carried out in both vacum and air. Photoproducts were investigated by FTIR spectroscopy, chemical derivatization reactions and physical treatments. The repartition of photoproducts in the polymer was shown to be heterogeneous. A scheme accounting for the main routes of PBT photolysis was found on the basis of photoproducts identification. Most of oxidation products were analogous to vacum photolysis species; the mechanism of photooxidation proposed implied both pure photolytical processes and a photo-induced oxidation route.
    Additional Material: 8 Ill.
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    Photo- and radiation-induced degradation of synthetic polymers: Polymer structure and stabilityPaper presented at the “15th Annual International Conference on Advances in the Stabilization and Degradation of Polymers” in Luzern (Switzerland), June 2-4, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 216 (1994), S. 225-241 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of polymer density, processing conditions (quenching of annealing), degree of crystallinity, size of crystallite and mobility of polymer chains on the photo-and radiation-induced degradation and the polymer stability have been studied by UV, FTIR spectroscopic, viscosity and mechanical property measurements. Four kinds of annealed or quenched polyethylene (PE) films varying densities were used to the studies. Polystyrene (PSt) films were used to investigate the effect of chain mobility on polymer degradation. The following results were obtained. 1.In linear low density (LLD) PE, greater amounts of crosslinking (irradiated in vacuum) and chain scission (irradiated in air) were noticed than in mediun density (MD) PE and high density (HD) PE samples.2.Polyene formation is favored in the case of the irradiation in vacuum for LLDPE.3.Polymer stability evaluated by mechanical property such as elongation at break (%) is superior in LLDPE to MDPE and HDPE for annealed and quenched samples.4.Segmental motion of polymer chain also affects the polymer stability
    Additional Material: 19 Ill.
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    Eigenschaften von binären mischungen aus polyethylenen hoher dichte mit ultrahoher und normaler molmasse (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 217 (1994), S. 43-49 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The study is on two component blends of high density polyethylenes, having normal and ultra-high molecular weight. The polyethylenes were homogenized by two routes: in powder state or by rolling in melt, then pressed at temperatures in the range from 140°C to 220°C. Comparative studies showed that the way of homogenizing of the components does practically not affect the main mechanical properties of the blends when pressed at temperatures ≥ 160°C. Of special interest are the characteristics of those systems where ultra-high molecular weight polyethylene is the matrix component.
    Notes: Untersucht wurden binäre Mischungen von Polyethylenen hoher Dichte rnit normaler und ultrahochmolekularer Molmasse, die auf zweierlei Weise - in Pulverform oder durch Walzen im Schmelzezustand - homogenisiert und bei Temperaturen zwischen 140 und 220°C gepreßt waren.Es wurde festgestellt, daß die Art der Homogenisierung der Komponenten praktisch keinen Einfluß auf die Eigenschaften bei Preßtemperaturen ≥ 160°C hat. Von besonderem Interesse sind die Eigenschaften der Systeme, in welchen das ultrahochmolekulare Polyethylen die Rolle der Matrixkomponente spielt.
    Additional Material: 4 Ill.
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    Rôle des pigments dans une réaction de polymérisation sous lumière UV-visible (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 81-109 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Verhalten eines neuartigen photoinitiierenden Systems, das die Polymerisation von pigmenthaltigen Schichten großer Dicke in einem Reaktionsschritt gestattet, wird dargestellt. Die verschiedenen Wechselwirkungen, die in einem pigmenthaltigen System auftreten, werden qualitativ beschrieben, und der Anteil der von einem Photoinitiator absorbierten Lichtintensität wird berechnet. Neben dem Absorptions- und Reflexionsverhalten von verschiedenen Pigmentklassen werden die optischen Eigenschaften verschiedener Strahlungsquellen untersucht, um die Strahlungsbereiche zu finden, die am besten mit den optischen Parametern der Pigmente korrespondieren. Weiterhin wird die Beschleunigung von Polymerisationen durch die photokatalytische Wirkung einiger Pigmente behandelt.
    Notes: Ce travail sur le rôe des pigments définit le comportement d'un nouveau systeme photosensible qui permet de polymériser des milieux épais et pigmentés selon un procédé en une seule étape. Les différentes interactions présentes en milieu pigmenté sont décrites de façon qualitative, et la part de l'intensité lumineuse absorbée par un photo-amorceur dans un systéme pigmenté est evaluée. Les propriétés optiques telles que l'absorption et la réflectance des différentes familles chimiques de pigments sont déterminées, et, en paralléle, les propriétés optiques des différentes sources d'irradiation sont étudiées de manière à répondre au mieux aux fenêtres de transmission des pigments. L'effet photocatalytique de certains pigments est mentionné, ceci afin d'amkliorer la réaction de polymérisation.
    Additional Material: 18 Ill.
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    Molar mass distribution of polybutadiene synthesized with nickel-based Ziegler-Natta catalysts, I (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 153-162 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Herstellung von cis-1,4-Polybutadien erfolgte mittels Polymerisation von 1,3-Butadien mit einem Katalysatorsystem, das in einer zweistufigen Reaktion gebildet wird: (1) BF3 · O(C2H5)2 und Al(C2H5)3, (2) Ni(OOC8H15)2 und Al(C2H5)3, genannt in-situ-Katalysatorsystem.Die Molmassenverteilungen (MMD) der erhaltenen Polymeren sind mit der Größenausschlußchromatographie (SEC) untersucht worden. Sie lassen sich mit Summen aus Schulz-Flory-Funktionen (SFF) beschreiben. Veränderte Katalysatorformierungs- und Polymerisationsbedingungen beeinflussen die Parameter der SFF. Veränderte Peakflächen und Molmassenmittelwerte der Einzelpeaks zeigen, daß die Polymerisation über mehrere Arten aktiver Zentren verläuft.
    Notes: Cis-1,4-polybutadiene was produced by polymerization of 1,3-butadiene using a catalyst system formed by a two-step formation, Namely (1) BF3 . O(C2H5)2 and Al(C2H5)3, (2) Ni(OOC8H15)2 and Al(C2H5)3 named in-situ-catalyst.The molar mass distributions (MMD) of the polybutadienes are investigated by means of size exclusion chromatography (SEC). The MMD's were fitted by a sum of Schulz-Flory-Functions (SFF). Changed catalyst formation and polymerization conditions influenced the parameters of the SFF. Changed areas and changed molar mass averages indicate a polymerization with more than one peak maximum and kind of active species and lead to a better understanding of the polymerization.
    Additional Material: 9 Ill.
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    Synthesis and characterization of epoxy resins containing chromium acrylate (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 1-10 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Umsetzung von Chromacrylat mit Bisphenol A und einem Überschuß Epichlorhydrin wurden neuartige Epoxid-Harze hergestellt. Epoxy-Äquivalentgewicht, Gehalt an Hydroxygruppen und hydrolysierbarem Chlor sowie die Viskosität wurden bestimmt, und die Harze wurden mittels IR- und 1H-NMR-Spektroskopie charakterisiert. Die thermischen Eigenschaften der bei 30°C für 24 h mit Ciba Geigy HY 850 (aliphatisches Amin) gehärteten Harze wurden gemessen. Die Harze besitzen eine gute thermische und chemische Stabilität und eine gute elektrische Leitfähigkeit. Die Reaktion verläuft nach erster Ordnung; die Aktivierungsenergie beträgt 47 kJ mol-1 bzw. 34 kJ mol-1 mit bzw. ohne Chromacrylat. Aus spektroskopischen Untersuchungen wird geschlossen, daß das Chrom mit Bisphenol A einen Komplex bildet, der die Epoxidierung beschleunigt.
    Notes: Novel epoxy resins containing chromium acrylate have been synthesized by reacting chromium acrylate with bisphenol-A and excess epichlorohydrin. The quantities such as epoxy equivalent weight, hydroxy content, hydrolyzable chlorine content and viscosity have been determined. The resins have been characterized by IR and 1H NMR spectroscopy. The cured resins were evaluated for thermal properties. The curing of resins was carried out with Ciba Geigy HY 850 (aliphatic amine adduct) at 30°C for 24 h. The cured resins have excellent thermal and chemical resistance, in addition to an excellent electrical conductivity. The reaction follows first order kinetics with an activation energy of 47 kJ mol-1 and 34 kJ mol-1 in the presence and absence of chromium acrylate, respectively. The chromium forms a complex with bisphenol-A, as indicated by spectroscopic studies, which increases epoxidation.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052190101
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    Interpenetrating polymer networks based on liquid natural rubber. 1. Synthesis and effect of nco/oh ratio on physical and mechanical properties (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 67-76 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Interpenetrierende Polymernetzwerke (IPNs) aus Polystyrol und Polyurethan auf der Basis von hydroxyterminiertem Naturkautschuk mit unterschiedlichen NCO/OH-Verhältnissen wurden unter verschiedenen Reaktionsbedingungen hergestellt und zu widerstandsfähigen Filmen verarbeitet. Die IPNs wurden durch ihre physikalischen, mechanischen und morphologischen Eigenschaften wie Dichte, Shore-A-Härte, Vernetzungsdichte, Zugfestigkeit und Reißdehnung charakterisiert. Mit steigendem Polystyrolgehalt erhöhen sich auch Dichte, Shore-A-Härte und Zugfestigkeit, während die Reißdehnung abnimmt. Die Untersuchungen der Vernetzungsdichte lassen eine Phasenumkehr vermuten.
    Notes: Interpenetrating polymer networks (IPNs) of polyurethane based on hydroxyterminated natural rubber with varying NCO/OH ratios and polystyrene were synthesized under different experimental conditions. These IPNs were found to make tough films. The IPNs were characterized by their physical, mechanical and morphological properties like density, Shore-A hardness, crosslink density, tensile strength and elongation at break. The IPNs exhibited an increasing trend in density, Shore-A hardness and tensile strength with increasing polystyrene content, while elongation at break decreased with similar variation in polystyrene content. The crosslink density measurements indicated a possible phase inversion process.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052190106
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    Plasma treatment of polyethylene ultrafiltration membranes (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 117-124 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß einer Plasmabehandlung von Ultrafiltrationsmembranen aus Polyethylen auf die Fouling- und Reinigungseigenschaften bei der Filtration von Rinderserumalbumin werden diskutiert. Bei 2,45 GHz erzeugtes Luft-Plasma steigert die Hydrophilie der Membranoberfläche von 0 auf 60%. Der Durchfluß bleibt bei 90 bis 99%. Mit Plasma behandelte Membranen sind leichter zu reinigen als unbehandelte; dennoch sind sie anfälliger für die Ablagerung von Rinderserumalbumin.
    Notes: The effect of plasma treatment of polyethylene ultrafiltration membranes on fouling and cleaning phenomena during filtration of bovine serum albumin solutions is discussed. Air-plasma of 2.45 GHz raises the membrane surface hydrophilicity from 0 up to 60%. The flux is maintained at 90-99%. Plasma-treated membranes are easier to clean than untreated polyethylene membranes. Despite that, the plasma-modified membranes are susceptible to more intensive deposition of albumin.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052190110
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    Preparation and characteristics of immobilized glucose oxidase on membranes of photosensitive polymers (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 101-115 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Immobilisierung von Glucose-Oxidase in einer Poly(vinylalkohol) (PVAL)-Membran in Gegenwart von UV-Photoinitiatoren wurde untersucht. Enzym-Membranen wurden aus PVAL-Diazoharz- und PVAL-Photoinitiator-Systemen durch Vernetzung mit UV-Licht hergestellt. Mit diesen immobilisierten Glucose-Oxidase-Membranen wurde eine wirkungsvolle Enzymelektrode entwickelt, deren Eigenschaften untersucht wurden. Der Einfluß der Photoinitiatorkonzentration in Poly(vinylalkohol) und der UV-Bestrahlungsdauer auf den Grad der Unlöslichkeit sowie die Aktivitätsausbeute der Membran wurden mit Glucose als Substrat untersucht. Temperatur- und pH-Abhängigkeit der relativen Aktivität, Stabilität bei mehrmaligem Gebrauch, Lagerstabilität und Kalibrierungsdiagramme der Enzym-Membranen wurden ermittelt. Eine beim Erstgebrauch auftretende Instabilitätserscheinung der Membranen wurde ebenfalls untersucht.
    Notes: A study of the immobilization of glucose oxidase on a poly(vinyl alcohol) (PVAL) membrane in the presence of UV sensitizers was carried out. Enzyme membranes were prepared from PVAL-diazoresin and PVAL-sensitizer systems, crosslinked by means of UV irradiation. An effective enzyme electrode was developed by using the immobilized glucose oxidase membrane, and its characteristics were investigated. The effects of the concentration of sensitizers in poly(vinyl alcohol) and UV irradiation time on the degree of insolubility as well as the activity yield of the membrane were examined for the immobilized glucose oxidase using glucose as a substrate. Temperature and pH dependences of the relative activity, stability in repeated use, storage stability and calibration plots of the enzyme membranes were evaluated. The unstability phenomenon, found in the initial use of the immobilized glucose oxidase membrane, which was prepared from PVAL-sensitizer system, was also investigated.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052190109
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    Auswirkungen von Sterilisationsverfahren auf biologisch abbaubare Kunststoffe (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 11-26 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Biopol, Biocellat and Mater-Bi, three biologically decomposable plastics have been tested for their use in medical industries. Biopol did not loose its stress and stiffness under sterilisation, and was also resistant against temperature and alcohol. Mater-Bi and Biocellat, the two other materials, did not satisfy the test applications. Water vapor sterilisation, temperature up to 60°C, at higher temperatures this material will embrittle.
    Notes: Für den Einsatz biologisch abbaubarer Kunststoffe in der pharmazeutischen Industrie und Medizintechnik wurden Produkte verschiedener Hersteller, wie Biopol, Biocellat und Mater-Bi untersucht. Dabei zeigte vor allem Biopol das notwendige Anforderungsprofil, d.h. die Anwendbarkeit aller Sterilisationsverfahren ohne Festigkeitsbzw. Steifigkeitsverluste sowie Temperatur- und Alkoholbeständigkeit. Dagegen wiesen die Werkstoffe Mater-Bi und Biocellat einige Schwachstellen auf. Bei Mater-Bi lagen diese bei der Wasserdampfsterilisation sowie bei der geringen thermischen und Medienbeständigkeit. Biocellat versprödet dagegen durch die erhöhte Temperatur bei der Dampfsterilisation, d.h. daß ein Einsatz über 60°C nicht möglich wäre.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052190102
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    Polymers and copolymers based on vinyl tetrazoles, 2Part 1 cf.10.. Alkylation of poly(5-vinyl tetrazole) (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 219 (1994), S. 89-99 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Alkylierung von Poly(5-vinyltetrazol) mit Dimethylsulfat und tert-Butylalkohol sowie Alkylhalogeniden RHal (R=CH3, C2H5, CH2—CH=CH2, n-C4H9 und t-C4H9) und die Kinetik dieser Reaktion wurden untersucht, um eine neue Herstellungsmethode für tetrazolhaltige Polymere mit wertvollen Eigenschaften zu entwickeln. Die vergleichenden Untersuchungen über die isomere Zusammensetzung und die spektroskopischen Daten von Poly(N-alkyl-5-vinyltetrazol)en, die durch die Alkylierung von Poly(5-vinyltetrazol) sowie durch die Copolymerisation der entsprechenden Monomeren hergestellt wurden, wurden mit IR-, 1H-NMR- und 13C-NMR-Spektroskopie durchgeführt. Der Alkylierungsumsatz beträgt bis zu 99,8%; dadurch können polymere Produkte erhalten werden, deren Zusammensetzung, Struktur und Eigenschaften denen der Homo- und Copolymeren sehr ähnlich sind.
    Notes: Alkylation of poly(5-vinyl tetrazole) with dimethyl sulfate and tert-butyl alcohol as well as with alkyl halides RHal (R=CH3, C2H5, CH2—CH=CH2, n-C4H9, t-C4H9) has been studied under various conditions in order to develop a new method of synthesis of tetrazole-containing polymers having a complex of valuable properties. The kinetic study of the process and comparison of isomeric compositions and spectroscopic characteristics (IR, 1H NMR and 13C NMR) of poly(N-alkyl-5-vinyl tetrazole)s synthesized by alkylation of poly(5-vinyl tetrazole) and of those prepared by (co)polymerization of the corresponding vinyl tetrazoles have been carried out. The alkylation is found to proceed to high conversion extents (up to 99.8%) and enables to obtain a wide variety of polymeric products having the composition, structure and properties very similar to those of homo- and copolymers.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052190108
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    Dyes for nonlinear optics prepared from 2-hydroxyethyl methacrylate. Nonlinear properties of the resulting copolymers (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 220 (1994), S. 75-87 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Farbstoffe mit nichtlinearen optischen Eigenschaften wurden in einer zweistufigen Synthese aus 2-Hydroxyethylmethacrylat (HEMA), 4-Carboxybenzaldehyd und verschiedenen Anilinderivaten hergestellt. Die Farbstoffe (aromatische Iminester von HEMA) wurden mit Styrol copolymerisiert, die erhaltenen Copolymere wurden mit DSC sowie IR-, 1H NMR- und UV-VIS-Spektroskopie charakterisiert, und ihre nichtlinearen Eigenschaften wurden untersucht. Es zeigte sich, daß die nichtlinearen Koeffizienten d31 und d33 vom Farbstoffgehalt der Copolymeren und der Art der elektronenspendenden Gruppen abhängig sind.
    Notes: Dyes for nonlinear optics have been synthesized in two steps from 2-hydroxyethyl methacrylate (HEMA), 4-carboxybenzaldehyde and various substituted anilines. The obtained dyes (aromatic imine esters of HEMA) have been copolymerized with styrene, the copolymers characterized by DSC as well as IR, 1H NMR and UV-VIS spectroscopy, and studied for their nonlinear properties. The d31 and d33 nonlinear coefficients proved to be dependent on the dye content of the copolymers and on the nature of electrondonating groups.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052200107
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    Viscosity behaviour of multivalent metal ion-containing carboxymethyl cellulose solutions (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 220 (1994), S. 123-132 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Einfluß von Ca2+-bzw. Al3+-Ionen auf das Viskositätsverhalten (Salzverträglichkeit) wäßriger Lösungen von Natriumcarboxymethylcellulose (CMC) sowohl mit unterschiedlichem Polymerisationsgrad (DP) als auch mit unterschiedlichem Substitutionsgrad (DS) und verschiedenartiger Substitutentenverteilung wurde untersucht. Aus Viskositätsmessungen mit einem Rotationsviskosimeter bei einer Scherrate von 500 s-1 geht hervor, daß die relative Abnahme der Viskosität im Ergebnis des Zusatzes der mehrwertigen Metallkationen unabhängig vom DP (im Bereich von 160 bis 900) der CMC ist. Homogen hergestellte CMC-Proben 2 mit einem größeren Gehalt an 2,3,6-Tri-O-carboxymethylglucose-Einheiten in der Polymerkette weisen im Vergleich zu heterogen hergestellten CMCs 1 bei gleichem Gesamt-DS eine höhere Salzverträglichkeit auf.
    Notes: The influence of Ca2+-and Al3+-ions, respectively, upon the viscosity behaviour (so-called salt tolerance) of aqueous solutions of sodium carboxymethyl cellulose (CMC) with different degree of polymerization (DP) and, on the other hand, with both different degree of substitution (DS) and distribution of substituents, was investigated. Viscosimetry by means of a rotational rheometer at a shear rate of 500 s-1 shows that the relative drop in viscosity as a result of addition of the multivalent metal cations is independent of DP (ranging from 160 to 900) of the CMC samples. Homogeneously synthesized CMCs (2) with a higher content of 2,3,6-tri-O-carboxymethyl glucose units in the polymer chain possess a significantly higher salt tolerance than those (1) prepared under heterogeneous reaction conditions at comparable total DS values.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052200111
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    Modification of melamine-formaldehyde moulding compounds with ethylene/vinyl acetate copolymers (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 222 (1994), S. 61-87 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Melamin-Formaldehyd-Harz-Formmassen (MF) wurden durch mechanisches Mischen mit Ethylen-Vinylacetat-Copolymeren (EVA) und teilverseiftem EVA modifiziert, wobei Etherbindungen zwischen dem hydrolysierten EVA und dem MF-Harz nachgewiesen werden konnten, die die mechanischen Eigenschaften von spritzgepreßten Formteilen im Vergleich zur Modifizierung mit EVA verbessern. Der Zusatz solcher Modifikatoren erhöht die Duktilität und verringert im Falle von EVA die Nachschwindung der überaus steifen MF-Matrix, solange der Modifikatoranteil gering bleibt. Dagegen werden die Steifigkeit und die Wärmeformbeständigkeit verschlechtert. Die durch solche unvernetzten Polymeren erreichbare Steigerung der Schlagzähigkeit bleibt allerdings unzureichend.
    Notes: Melamine-formaldehyde moulding compounds (MF) were modified by mechanical mixing with ethylene/vinyl acetate copolymers (EVA) and with partially hydrolysed EVA. Ether linkages between the hydrolysed material and the MF resin improve the mechanical properties of the transfer moulded parts containing the hydrolysed material compared to those made with EVA. The use of both modifying polymers improves the ductility and, in case of the partially hydrolysed material, the postshrinkage of the extremely rigid MF matrix, as long as the modification polymer content is kept low. On the contrary, Young's modulus and the heat deflection temperature are deteriorated. The improvement in impact strength by use of those uncrosslinked polymers is still insufficient.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052220106
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    Synthesis and properties of biodegradable copolyesteramides: Nylon 6,6/∊-caprolactone copolymers, 1 (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 222 (1994), S. 111-123 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine Reihe von Copolyesteramiden mit Molekulargewichten zwischen 1000 und 7000 (GPC, NMR) wurden aus Adipinsäure/1,6-Hexandiamin/∊-Caprolacton bzw. Nylon 6,6-Salz/∊-Caprolacton hergestellt. Die thermischen Eigenschaften der synthetisierten Polymeren (Glasübergangs-, Schmelz-, und Zersetzungstemperaturen, Schmelzenthalpien) wurden durch DSC- und TGA-Messungen bestimmt und in Bezug auf das Comonomerverhältnis in der Ausgangsmischung diskutiert. Die Übereinstimmung der Copolymerzusammensetzung mit dem Ausgangscomonomerverhältnis wurde mit FT-IR- und NMR-Spektroskopie untersucht. Die Bioabbaubarkeit der Copolyesteramide wurde durch enzymatische Hydrolyse geprüft.
    Notes: A series of copolyesteramides based on adipic acid/1,6-hexane diamine/∊-caprolactone and Nylon 6,6 salt/∊-caprolactone were synthesized. Their molecular weights, determined by gel permeation chromatography and NMR spectroscopy, were found to lie within the range from 1000 up to 7000. Their thermal properties (glass transitions, melting points and heats of melting, and decomposition temperatures) were recorded with diferential scanning calorimetry and thermogravimetry, respectively, and correlated to the comonomer feed composition. The FT-IR and NMR spectra were also recorded in order to confirm the composition of the copolyesteramides and to compare them with that of the comonomer feed. The biodegradability of the synthesized copolymers was tested by enzymatic hydrolysis.
    Additional Material: 4 Ill.
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    Study of the condensation products of abietic acid with formaldehyde at high temperatures (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 222 (1994), S. 165-174 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch sulfonsäurekatalysierte Umsetzung von Abietinsäure und Paraformaldehyd bei hohen Temperaturen wurden neuartige Kondensationsprodukte erhalten. Als Nebenprodukte der Polykondensation werden eine Ketoverbindung sowie Wasser und Kohlendioxid gebildet. Die Carboxygruppen der Abietinsäure sind an der Kondensationsreaktion beteiligt. In Abwesenheit von Paraformaldehyd wurde das Abietinsäure/Sulfonsäurekatalysator-System untersucht, um zusätzliche Informationen über die Reaktion zu erhalten. Der Reaktionsverlauf hängt von der Temperatur und der chemischen Struktur des Katalysators ab. Ein möglicher Reaktionsmechanismus der Kondensation wird diskutiert.
    Notes: New condensation products have been synthesized by heating abietic acid and formaldehyde at high temperatures in the presence of sulfonic-type acid catalysts. The main polycondensation reaction is associated with a secondary one which leads to a ketonic compound, carbon dioxide and water. The carboxylic groups of abietic acid participate in this condensation reaction. The behaviour of the abietic acid-sulfonic acid catalyst system was studied in absence of formaldehyde to acquire additional information about the reaction. The process is defined by the reaction temperature and chemical nature of the catalyst. A possible mechanism of the condensation reaction is discussed on the basis of the obtained results.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052220112
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    Tailored polymers by cationic ring-opening polymerization (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 1-11 
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    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: After a general classification of the cationic ring-opening polymerizations (CROP's) according to their polymerization mechanism, a number of examples of tailored polymers based on CROP are presented. The monomers used for the synthesis of these tailored structures are tetrahydrofuran (THF), N-tert-butyl aziridine (TBA), 2-methyl-1,3-oxazoline (MeOX) and 1,3-dioxolane (DXL).The polymer structures include different block and graft copolymers, macromonomers, star-shaped polymers, polymer networks and interpenetrating polymer networks (IPNs).
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052230101
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    Massgeschneiderte PolymereVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Fortschritte in der Polymersynthese” in Bad Nauheim, 21.-22. März 1994. Synthesestrategien für Telechele, Makromonomere, Block- und Pfropfcopolymere (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 29-46 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In diesem Beitrag wird ein überblick über neuere Entwicklungen auf dem Gebiet der Synthese von Telechelen, Makromonomeren, Block- und Pfropfcopolymeren gegeben. Synthesestrategien aus den Bereichen der Polykondensation, der radikalischen, anionischen und kationischen Polymerisation, der Kettenspaltung sowie der Criss-Cross-Cycloaddition werden diskutiert.
    Notes: New developments in the synthesis of telechelics, macromonomers, block- and graftcopolymers are presented. Synthetic strategies for them are demonstrated with examples from different fields such as polycondensation, radical, anionic, and cationic polymerization, chain cleavage and criss-cross-cycloaddition.
    Additional Material: 1 Tab.
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    Alkane als initiatoren zur radikalischen polymerizationHerrn Professor Dr. rer. nat. Dr.-Ing. E.h. Hansjörg Sinn mit den besten Wünschen zum 65. Geburtstag gewidmet (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 69-79 
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    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Alkanes with highly substituted carbon-carbon bonds can be cleaved in free radicals by homolytic dissociation under the influence of thermal energy. The energy of dissociation is mainly determined by the type and size of the respective substituents. For tetraarylbutane dinitriles the temperatures of decomposition are in the range of other technically used initiators. But nevertheless, these compounds are up to now rather seldom used to initiate free radical polymerizations. This is connected with the special mechanism of initiation: the formed highly substituted alkyl radicals are relatively stable and show only a rather low reactivity against the usually used monomers. Therefore, in the beginning of the polymerization the radical concentration is rather high which leads not only to addition to monomers but also to a pronounced primary radical termination. In some cases this termination process is reversible which results in an unusual polymerization kinetics. Depending on the type of monomer and the degree of reversibility of the primary radical termination, either a period of “dead-end” polymerization follows or the cleavage of the oligomers at the chain end results in a re-initiation process with a “normal” polymerization with increased rate. The reaction mechanism, kinetics and some possible applications of such initiating alkanes are reported.
    Additional Material: 3 Ill.
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    Cycloolefin-copolymere: Eine neue klasse transparenter thermoplasteHerrn Prof. Dr. H. Sinn zum 65. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 121-133 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Untersuchungen wesentlicher Aspekte der Polymerisation und der Eigenschaftsmodifikation auf Metallocen-Katalyse basierender Cycloolefin-Copolymere (COC) zeigen, daß mit dieser Monomer-Katalysator-Kombination eine neue Klasse transparenter Thermoplasten zugänglich gemacht wird. COC können mit Metallocenen in beliebiger zusammensetzung und mit kontrollierter Mikrostruktur hergestellt werden. Die somit erreichte und durch zusätzliche Modifikationen noch erweiterbare Breite des Eigenschaftsspektrums ermöglicht vielfältige Anwendungen dieser neuen Polymerklasse. Die wichtigsten Schlüsselfaktoren im rohstofflich-technologischen Bereich, die diese Struktur- und Eigenschaftsvielfalt ergeben, werden beispielhaft beschrieben.
    Notes: Investigation of the polymerization process and property modification of metallocene-based cycloolefin copolymers (COC) shows that this monomer-catalyst combination enables synthesis of a new class of transparent thermoplastic polymers. Metallocene catalysis offers much opportunity to vary the composition and microstructure of the copolymers. The breadth of the polymer spectrum which can be further widened by polymer modification enables many applications for this new class of thermoplastics. The key parameters that control structure and properties in the COC family are discussed in this paper.
    Additional Material: 6 Ill.
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    Funktionalisierte Kammpolymere: Synthesen, modifizierung und anwendungen (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 165-175 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The present paper deals with the synthesis and modification of functionalized polymers characterized by a special molecular architecture. The reactivity of a functionalized polymer with comb-like structure can be controlled in a significant manner by the crystalline order of the side chains. In contrast, photocrosslinking of comblike polymers containing cinnamic components in the side chains influences the crystallization process. The air drying process of a modified polybutadiene system with comb-like structure was shown to depend sensitively on the side chain order. Enzymatic synthesis of new monomers and polymers is briefly reviewed. The complexing capability of cyclodextrines were used to synthesize polyrotaxanes. Finally, the synthesis of a chiral polymerizable dendrimer containing eight estergroups in the monomer unit is presented.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052230112
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    Intramolekular vernetzte poly(organosiloxan)partikel (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 223 (1994), S. 203-216 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Intramolecularly crosslinked poly(organosiloxane) particles are prepared by means of emulsion polycondensation or emulsion polymerization of alkoxysilanes or cyclic organic siloxanes. Starting from these intramolecularly crosslinked poly(organosiloxane) particles, graft copolymers are obtained by free-radical emulsion polymerization of unsaturated olefinic monomers (e.g. acrylates, styrene) in the presence of (functionalized) organosiloxanes. Intramolecularly crosslinked poly(siloxane) particles and their graft copolymers are characterized by means of light scattering (in dispersion), electron microscopy and thermal analyses (DSC, DMTA).
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052230115
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    Study on poly(2,6-dimethyl-1,4-phenylene oxide)/SBS triblock copolymer blends (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 153-167 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Zusammenhang zwischen der Mischbarkeit und den physikalischen Eigenschaften von Polymerblends aus Poly(2,6-dimethyl-1,4-phenylenoxid) (PPO), die in unterschiedlichen Zusammensetzungen in einem Doppelschneckenextruder mit Polystyrol, schlagzähem Polystyrol oder Styrol-Butadien-Copolymeren hergestellt wurden, wird diskutiert. Die Verträglichkeit der Komponenten wurde mittels DSC und DMA, die Morphologie der Blends mittels SEM untersucht. Mit abnehmendem Polystyrolanteil wurde eine schlechtere Mischbarkeit bei den Blends beobachtet, deren Kerbschlagempfindlichkeit sich erhöhte. Die Untersuchungsergebnisse werden mit dem Micellmodell interpretiert.
    Notes: The relationship between the miscibility and the physical properties of polymer blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene (PS), high-impact polystyrene (IPS) and poly(styrene-block-butadiene-block-styrene) (SBS), which are blended in different compositions by a twin-screw extruder is discussed. The three types of SBS that were used are SBS1, SBS2 and SBS3 having different styrene/butadiene ratios. Dynamic mechanical analysis and differential scanning calorimetry were used to study the miscibility. The morphology was examined by SEM. The miscibility of the blends decreases with decreasing PS content. The notch sensitivity is improved by blending. Finally, the micelle model was used to explain the testing phenomena.
    Additional Material: 8 Ill.
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    Water-soluble polyamides as potential drug carriers, VIIPresented in part at the Symposium on Water-soluble Polymers, 198th National Meeting Am. Chem. Soc., Miami Beach, Florida, 10-16 September 1989. For Part VI, cf1.. Synthesis of polymers containing intrachain- or extrachain-type amine ligands by interfacial polymerization (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 137-152 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Aliphatische Polyamide mit Poly(ethylenoxid)-Kettensegmenten unterschiedlicher Länge wurden durch Grenzflächenpolymerisation aus Succinylchlorid und Jeffamine ED-900 (O,O'-Bis(2-aminopropyl)poly(ethylenglykol) 800) bzw. Jeffamine ED-2001 (O,O'-Bis(2-aminopropyl)poly(ethylenglykol) 1900) zur Verwendung als Trägersubstanzen für Medikamente synthetisiert. Copolyamide mit kurzkettigen Diamin- und Jeffamine-Segmenten sowie Polyamide aus Cystin und Diamineinheiten wurden auf die gleiche Weise hergestellt. Die Polymerisationen wurden im zweiphasigen System Dichlormethan/Wasser bei Temperaturen um 0°C durchgeführt. Die Polymerprodukte wurden durch stufenweise Dialyse in wäßriger Phase bis zu einem Molekulargewicht von 25000 fraktioniert, nach Gefriertrocknung als wasserlösliche Harze oder Feststoffe erhalten und durch Mikroanalyse sowie 1H NMR-Spektroskopie charakterisiert. Die inhärenten Viskositäten liegen im Bereich von 10-20 ml/g. Die Eignung eines repräsentativen Zielmoleküls zur Bindung von Medikamenten wurde durch eine kovalente Verankerung einer als Medikamentmodell fungierenden Ferrocen-Verbindung untersucht. Dabei wurde ein wasserlösliches Polymer-Ferrocen-Konjugat erhalten.
    Notes: Aliphatic polyamides comprising poly(ethylene oxide) chain segments of various lengths, designed for use as drug carriers, are synthesized by interfacial polymerization of succinyl chloride with the two Jeffamine types ED-900 and ED-2001, formally described by the supplier as O,O'-bis(2-aminopropyl)poly(ethylene glycol) 800 and O,O'-bis(2-aminopropyl)poly(ethylene glycol) 1900. Copolyamides comprising both short-chain diamine and Jeffamine segments are similarly prepared, as are polyamides made up of cystine and diamine segments. The polymerizations are performed in a two-phase methylene chloride-water system at temperatures near or below 0°C. The product polymers, crudely fractionated by staged aqueous-phase dialysis at an ultimate molecular-mass cut-off of 25000, are collected after freeze-drying as water-soluble resins or solids and are characterized microanalytically and by 1H NMR spectroscopy. Inherent viscosities are in the range of 10-20 ml g-1. The drug-binding potential of a representative target polymer is probed by the covalent anchoring of a ferrocene compound used as a drug model, giving a water-soluble polymer-ferrocene conjugate.
    Additional Material: 2 Tab.
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    Studies on vinyl ester resin and its urethane derivative as coating materials (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 211-216 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Über die Anwendung von Vinylesterharzen aus dem Diglycidylether von Bisphenol A sowie dessen Urethanderivat als Beschichtungsmaterial wird berichtet. Die mit den Harzen beschichteten Flußstahlplatten wurden auf Oberflächenglanz, Kratzfestigkeit und Chemikalienbeständigkeit untersucht. Harze mit Styrolanteil zeigen deutlich verbesserte Beschichtungseigenschaften.
    Notes: The present paper is concerned with the coating applications of a vinyl ester resin derived from diglycidyl ether of bisphenol-A and its urethane derivative. The mild steel panels coated with the synthesized resins were evaluated for their gloss on the surface, scratch hardness and chemical resistance. The incorporation of styrene in the resin systems improves the properties of coatings remarkably.
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    URL: http://dx.doi.org/10.1002/apmc.1994.052140118
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    Silica gel supported zirconocene dichloride/methylalumoxane catalysts for ethylene polymerization: Effects of heterogenation on activity, polymer microstructure and product morphology (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 47-57 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Katalysatorsystem Zirkonocendichlorid/Methylalumoxan wurde auf Siliciumdioxid aufgebracht, um Katalysatoren fur die Suspensions- order Gasphasenpolymerisation von Ethylen herzustellen. Die häochste Aktivitäat wurde für eine sandwichartige, dreilagige Verankerung von Zirkonzentren auf der Träageroberfläache gefunden. Dieneuen Katalysatorsysteme besitzen eine im Vergleich zu den entsprechenden homogenen Katalysatoren geringere Aktivitäat. Die Immobilisierung der aktiven Katalysatorzentren führt zu einer deutlichen Erhäohung der Polymermolmassen. Dabei bleibt die enge Molekulargewichtsverteilung der Polymerprodukte nahezu erhalten. Solche auf Träager aufgebrachte Metallocen-Katalysatoren käonnten für die Herstellung von Polyethylenen mit kontrollierter Rheologie Anwendung finden.
    Notes: The system zirconocene dichloride/methylalumoxane was supported on silica in order to provide ethylene polymerization catalysts for suspension or gas phase processes. Highest activity was found for a sandwich-like, three layer anchoring of the zirconium centers on the support surface. The new catalyst systems show a decrease of activity compared to polymerization experiments in homogeneous phase. However, the molecular weights are increased and the weight distributions remain narrow by immobilization of the active catalyst sites. Those supported metallocene catalysts could find application for the synthesis of polyethylene materials with controlled rheology.
    Additional Material: 3 Ill.
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    Evaluation of poly(butyl acrylate-co-ethylene glycol dimethacrylate) sorbents for chromatographic separation of biomolecules (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 215 (1994), S. 129-138 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Vernetzte Copolmere aus Butylacrylat (BA) und Ethylenglycol-dimethacrylat (EGDMA) wurden auf ihre Eignung als stationäare Phase für die Chromatographie untersucht. Es wurde festgestellt, daß gering vernetzte Copolymere (〈 30 Gew.-% EGDMA) nicht poräos sind, wäahrend Matrices mit mehr als 40 Gew.-% EGDMA eine konstante Porositäat aufweisen. Eine Erhäohung des Vernetzergehaltes beeinflußt hauptsäachlich die Hydrophobie der Oberfläache. Zwei Meßmethoden für diese Eigenschaft werden diskutiert: Die Absorption von Alkylalkoholen und von Aminosäauren. Für letztere wurde aus der Steigung der Beziehung zwischen der Sälenkapazitäat und dem Hydrophobie-Parameter der Aminosäauren ein Matrix-Hydrophobie-Index berechnet und dieser mit den bekannten Energien der Wechselwirkung von Alkylalkohol—CH2 Gruppen mit der Polymermatrix verglichen. Die Vorteile der Verwendung des Hydrophobie-Indexes bei der Bewertung von polymeren Sorbentien werden aufgezeigt.
    Notes: Copolymers of butyl acrylate (BA) crosslinked with ethylene glycol dimethacrylate (EGDMA) were evaluated as potential chromatographic packings. It was found that slightly crosslinked copolymers (up to 30 wt.-% EGDMA) did not provide porous material, while for matrices which exceeded 40 wt.-% of EGDMA the porous structure remained unchangeable. The increase of crosslinker content mostly affected the surface hydrophobicity. Two methods of measurement of this property were discussed: Sorption of alkyl alcohols and amino acids. Taking the latter for testing, a polymer matrix hydrophobicity index was calculated as the slope of dependence of column capacity vs. amino acid hydrophobicity parameter. The indices were verified against well-established interaction energies of —CH2— groups of alkyl alcohols and polymer surfaces. Some benefits of the use of the hydrophobicity index in evaluation of polymer sorbents were demonstrated.
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    Epoxysiloxane resins by the condensation of 3-glycidyloxypropyltrimethoxysilane with diphenylsilanediolDedicvated to Prof. Dr. Dr.-Ing. E. h. Hansjörg Sinn on the occasion of his 65th birthday (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 111-126 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Kondensation von 3-Glycidyloxypropyltrimethoxysilan I mit Diphenylsilandiol II wurde untersucht. Abhängig von Lösungsmittel, Temperatur und Katalysator werden unterschiedliche Primärprodukte erhalten. Die Reaktion in Masse bei 120°C mit Titan(IV)-isopropylat als Katalysator liefert ein transparentes Harz A. Das eduktfreie Produkt wurde IR-, 1H- und 13C-NMR-spektroskopisch charakterisiert und chromatographisch mit GPC und HPLC untersucht. Die trimeren und tetrameren Siloxane bestehen aus Diphenylsilan- und 3-Glycidyloxypropylmethoxysilaneinheiten. Das Verhältnis von cyclischen zu linearen Molekülen beträgt 2:1. Höhermolekulare Verbindungen entstehen nur in geringen Mengen. Das Epoxysiloxangemisch löst sich in unterschiedlichen organischen Lösungsmitteln und ist mit kommerziell verfügbaren Epoxiden mischbar. Die Zeitabhs̈ngigkeit von Viskosität und Epoxidwert bei der Lagerung unter Normalbedingungen wurden gemessen und mit HPLC verfolgt . Die Lagerstabilität wurde durch eine zusätzliche thermische Behandlung verbessert.
    Notes: Condensation of 3-glycidyloxypropyltrimethoxysilane I with diphenylsilanediol II was investigated. Depending on solvent, temperature and catalyst, different products were obtained. Bulk reaction at 120°C using titanium(IV)-isopropylate as a catalyst provided the transparent resin A. A was characterised by IR, 1H- and 13C-NMR spectroscopy and contained no reactants. GPC and HPLC studies revealed that A consists of trimer and tetramer siloxanes of pertinent diphenylsilane and 3-glycidyloxypropylmethoxysilane moieties. The proportion of cyclic to linear molecules was evaluated 2:1. Only small amounts of high-molecular-weight compounds were observed. The epoxysiloxane product proved to be miscible with various organic solvents and with commercial epoxy resins. Time dependence of viscosity and epoxy content were recorded during ambient storage and monitored by HPLC. Pot-life was improved by a subsequent thermal procedure.
    Additional Material: 7 Ill.
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    Molar mass distribution of polybutadiene synthesized with nickel-based Ziegler-Natta catalysts, IIPart I cf.14. (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 163-170 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Cis-1,4-Polybutadien wurde durch Polymerisation von 1,3-Butadien mit Katalysatorsystemen hergestellt, die Ni(OOC8H15)2 und Al(C2H5)3 sowie die Lewissäuren BF3 · O(C2H5)2 oder TiCl4 enthalten. Die Molmassenverteilungen (MMD) der erhaltenen Polybutadiene wurden mit der Größenausschlußchromatographie (SEC) untersucht. Sie lassen sich mit Summen aus Schulz-Flory-Funktionen (SFF) beschreiben. Da eine Art aktiver Zentren eine SFF ergibt, die durch Molmassenmittelwerte definiert ist, lassen sich verschiedene Molmassenverteilungen nach Bandentrennung auf gleiche und verschiedene Arten aktiver Zentren untersuchen. In den untersuchten Systemen lassen sich zwei vergleichbare und eine unterscheidbare Art aktiver Zentren zuordnen. Auf diese Weise wurde das Kettenwachstum in Abhängigkeit von den Komponenten und Katalysatorformierungsbedingungen untersucht.
    Notes: Cis-1,4-polybutadiene was produced by polymerization of 1,3-butadiene using a catalyst system containing Ni(OOC8H15)2 and Al(C2H5)3 and the Lewis acids BF3 · O(C2H5)2 or TiCl4. The molar mass distributions (MMD) of the polybutadienes are investigated by means of size exclusion chromatography (SEC). The MMD's were fitted by a sum of Schulz-Flory-Functions (SFF). Taking into account that one kind of active species gives one SFF defined by molar mass averages, one comparable active species in both systems and one different were found. This way it was tried to find a relationship between the grown up of the active species depending on components and reactions conditions.
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    Molecular dynamics simulation of oligosaccharides containing N-acetyl neuraminic acid (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 11-20 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: αD-N-acetyl neuraminic acid (Neu5Ac, sialic acid) is a commonly occurring carbohydrate residue in various cell surface glycolipids and glycoproteins. This residue is linked terminally or internally to Gal residues via an α(2 → 3) or α(2 → 6) linkage. In the cell surface receptor, sialyl-LewisX, a terminal α(2 → 3) linkage is present. Previous studies from our laboratory have shown that in solution LewisX adopts a relatively rigid structure. In order to model the Neu5Ac residue, vacuum molecular dynamics of this monosaccharide were compared with simulations that explicitly include solvent water. The dynamical average of the monosaccharide conformation obtained from the two simulations was similar. Vacuum calculations for the disaccharide Neu5Ac α(2 → 3) Gal β-O-methyl show that a number of low energy minima are accessible to this disaccharide. Molecular dynamics simulations starting from the low energy minima show conformational transitions with a time scale of 10-50 ps among several of the minima while large barriers between other minima prevent transitions on the time scale studied. Simulations of this disaccharide in the presence of solvent show fewer conformational transitions, illustrating a dampening effect of the solvent that has been observed in some other studies. Our results are most consistent with an equilibrium among multiple conformations for the Neu5Ac α(2 → 3) Gal β linkage. © 1994 John Wiley & Sons, Inc.
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    The effect of the L-azetidine-2-carboxylic acid residue on protein conformation. IV. Local substitutions in the collagen triple helix (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 51-60 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The properties of collagen are affected by the replacement of Pro by imino acid analogues. The structural effect of the low-level local substitution of L-azetidine-2-carboxylic acid (Aze) has been analyzed by computing the energy of CH3CO-(Gly-Pro-Pro)4-NHCH3 triple helices in which a single residue of one strand has been replaced by Aze. When Aze is in position Y of a (Gly-X-Y) unit, low-energy local deformations are introduced in the triple helix, i.e., it becomes more flexible. On the other hand, the flexibility of the triple helix is not increased with Aze in position X. The energy of the triple helix to coil transition is not changed significantly by this amount of substitution. In an earlier study, we have demonstrated that the regular substitution of Aze in every tripeptide distorts or destabilizes the triple helix to a large extent [A. Zagari, G. Némethy, & H. A. Scheraga (1990) Biopolymers, Vol. 30, pp. 967-974 ]. Thus, it appears that a high level of substitution is required to cause the observed chemical and biological effects of Aze on collagen. © 1994 John Wiley & Sons, Inc.
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    Microwave dielectric study on bound water of globule proteins in aqueous solution (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 357-364 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dielectric relaxation peak due to bound water of globule proteins in aqueous solution was observed at first by the use of a time domain reflectometry. This peak locates around 100 MHz as well as that of the aqueous DNA solution and the moist collagen, and has a relaxation strength in proportion to surface of the globule protein except for trypsin and pepsin of hydrolase. It is suggested that this peak is caused by orientation of bound water molecules on the protein surface. The number of bound water molecules estimated is in good agreement with that obtained by other method such as x-ray analysis. The solution exhibits another peak below 100 MHz, which is caused by the rotation of globule protein supplemented by migration of the counterion. Its relaxation time is completely proportional to the molecular weight of the protein. © 1994 John Wiley & Sons, Inc.
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    Microcalorimetric investigations of the interactions of small ions with arterial elastin (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 393-401 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enthalpies of interactions of porcine arterial elastin with alkali metal and alkali earth halides and sulphates were investigated by means of flow microcalorimetry and the stoichiometry measured using radiotracer techniques. In aqueous solutions, all alkali earth halides interacted exothermically at concentrations ranging from 0.01 to 2.5M. All the alkali metal halides, particularly NaCl, exhibited complex concentration-dependent interactions, exothermic at low concentrations and endothermic at high concentrations. Both the anion and cation contributed to the response, although the anion seemed to dominate. SO42- interacted most strongly of the anions tested. All interactions were reversible in the sense that repeat experiments gave identical results, but the enthalpy of “adsorption” was generally different from that of “desorption.” The enthalpy of interaction depended on the conformation of the elastin in a salt-specific manner. For example, CaCl2 and MgCl2 interacted similarly in water but very differently in 1 : 1 water : methanol. © 1994 John Wiley & Sons, Inc.
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    Photophysical behavior of poly(L-lysine) carrying porphyrin and naphthyl chromophores (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 435-442 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photophysical behavior of protoporphyrin IX (P) and 1-naphthylacetic acid (N), covalently bound to ε-amino groups of poly (L-lysine) (PL), was investigated by steady-state and time-resolved fluorescence as a function of pH. Within the whole range of pH explored, i.e., 7-11, exciplex emission is minor and nearly pH independent. Fluorescence quantum yields, decay time measurements, and transient absorption spectra suggest that quenching of the excited naphthyl chromophore chiefly occurs by interconversion to the triplet state when the sample is randomly coiled and by intramolecular electron transfer (ET) from ground-state porphyrin when the polypeptide is in α-helical conformation. The kinetic law, based on a two-state model for the polymeric matrix, is presented. The specific rate constant of photoinduced ET is 3.1 · 107 s-1 (25°C), in excellent agreement with that obtained by taking simply into account the lifetimes of naphthalene fluorescence in α-helical PNPL and NPL (pH 11). The relaxation time of the helix-coil transition was found to be definitely shorter than 20 ns. © 1994 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bip.360340314
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  • 96
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    Filipin and its interaction with cholesterol in aqueous media studied using static and dynamic light scattering (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 447-456 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aggregation of filipin in aqueous medium and filipin-induced changes in cholesterol micelles have been studied using intensity and dynamic light scattering. The dependencies of filipin aggregate dimensions on concentration, solvent, and temperature were studied, and revealed that the aggregates do not have a well-defined geometry, i.e., a critical micelle concentration cannot be detected and stable structures are not formed. The aggregates are of size Rg ≈ 110 nm and Rh ≈ 63 nm, referring to the radius of gyration and hydrodynamic radius, respectively. In the concentration range studied (1 μM 〈 C 〈 30 μM), a low molecular weight species (monomer/dimer) is always present together with the aggregates. In ethanol/ water mixtures, large (Rg ≈ 500 nm), narrow distribution aggregates are formed in the water volume fraction range 0.45 〈 ΦH2O 〈 0.65. Aggregation also occurs on changing the temperature; In the range 7-37°C, smaller aggregates (10-30 nm) form and the process is only partially reversible.No pronounced effect of filipin on the structure of the cholesterol micelles was observed (a small increase in Rg and Rh is noted). These results rule out any “specificity” for the filipin interactions with cholesterol, which has been considered a key event in the filipin biochemical mode of action. A reevaluatiori Of this question is suggested and some alternatives are advanced. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360340402
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  • 97
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    Electronic Resource
    Folding polypeptide α-carbon backbones by distance geometry methods (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 489-505 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polypeptide α-carbon backbones were modeled as freely rotating chains made up of spherical monomers. The monomers were assigned an abstract binary “hydrophobicity” property that could be either present or absent. Under the assumption that “hydrophobic” residues tend to cluster together, away from the polar solvent, three-dimensional conformations of random copolymers of “hydrophobic” and “hydrophilic” monomers were calculated by a novel algorithm based on distance geometry techniques. The simulated molecules were globular and compact, in shape, and possessed distinct hydrophobic cores, indicating that our method was capable of reproducing some of the important global features of real polypeptides. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360340406
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  • 98
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    Electronic Resource
    Coupling constants as restraints in ensemble distance driven dynamics (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 559-563 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360340411
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  • 99
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    Nmr and molecular modeling investigations of the neuropeptide bradykinin in three different solvent systems: DMSO, 9 : 1 dioxane/water, and in the presence of 7.4 mM lyso phosphatidylcholine micelles (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 611-623 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The linear nonapeptide hormone bradykinin (Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9) is involved, either directly or indirectly, in a wide variety of physiological processes, particularly pain and hyperanalgesia. Additional evidence suggests that bradykinin also plays a major role in inflammatory response, asthma, sepsis, and symptoms associated with the rhinoviral infection. It has long been speculated that a β-turn at the C-terminus of bradykinin plays a major role in the biological activity of the neuropeptide. The β-turn forming potential of bradykinin in three vastly different local chemical environments, DMSO, 9 : 1 dioxane/water, and in the presence of 7.4 mM lyso phosphatidylcholine micelles, was investigated using two-dimensional homonuclear nmr experiments coupled with simulated annealing calculations. The results of these investigations show that in all three systems residues 6-9 of the C-terminus adopt very similar β-turn like structures. These results suggest that the β-turn at the C-terminus of bradykinin is an important secondary structural feature for receptor recognition and binding. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360340504
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  • 100
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    Electronic Resource
    Solution structure and dynamics of DNA topoisomers: Dynamic light scattering studies and Monte Carlo simulations (1994)
    New York : Wiley-Blackwell
    Biopolymers 34 (1994), S. 639-646 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using dynamic light scattering (DLS), we have measured the diffusion coefficient and internal motions of narrow topoisomer distributions of pUCl8 DNA (2687 base pairs) as a function of linking number. The topoisomer distributions were prepared by C-18 reversed phase high performance liquid chromatography separation of topoisomerase I/ethidium-generated topoisomer families. The measured diffusion coefficients agree well with those predicted by a Monte Carlo model for the generation of equilibrium ensembles of DNA topoisomers of defined linking number. The only parameters used in the model were the bending persistence length, torsional rigidity, and hydrodynamic radius of DNA known independently from other techniques. Two different values for the torsional rigidity, α = 4 · 10-12 and 8.8 · 10-12 dyn cm, were used. Intrachain interactions in the DNA were taken into account by using an “effective DNA radius,” which was varied between rDNA = 1-8 nm. The best agreement between the measured and calculated values was obtained for α = 4 · 10-12 dyn cm, rDNA = 4 nm. The internal motions of the DNA topoisomers were characterized by the amplitude of the fast relaxation of the DLS autocorrelation function. Our earlier result that supercoiling leads to a decrease in the amplitude of internal motion was confirmed. In addition, we see a characteristic maximum of the internal motion amplitude at a superhelix density of σ = -0.03. The maximum occurs in the same range as a structural transition in pUC8 dimers previously described by L. Song et al. (1990 J. Mol. Biol. 214, 307-326). © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360340506
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