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Sample records for saccharomyces uvarum pt

  1. Microsatellite analysis of Saccharomyces uvarum diversity.

    PubMed

    Masneuf-Pomarede, Isabelle; Salin, Franck; Börlin, Marine; Coton, Emmanuel; Coton, Monika; Jeune, Christine Le; Legras, Jean-Luc

    2016-03-01

    Considered as a sister species of Saccharomyces cerevisiae, S. uvarum is, to a lesser extent, an interesting species for fundamental and applied research studies. Despite its potential interest as a new gene pool for fermenting agents, the intraspecific molecular genetic diversity of this species is still poorly investigated. In this study, we report the use of nine microsatellite markers to describe S. uvarum genetic diversity and population structure among 108 isolates from various geographical and substrate origins (wine, cider and natural sources). Our combined microsatellite markers set allowed differentiating 89 genotypes. In contrast to S. cerevisiae genetic diversity, wild and human origin isolates were intertwined. A total of 75% of strains were proven to be homozygotes and estimated heterozygosity suggests a selfing rate above 0.95 for the different population tested here. From this point of view, the S. uvarum life cycle appears to be more closely related to S. paradoxus or S. cerevisiae of natural resources than S. cerevisiae wine isolates. Population structure could not be correlated to distinct geographic or technological origins, suggesting lower differentiation that may result from a large exchange between human and natural populations mediated by insects or human activities. PMID:26772797

  2. Interaction between Hanseniaspora uvarum and Saccharomyces cerevisiae during alcoholic fermentation.

    PubMed

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2015-08-01

    During wine fermentation, Saccharomyces clearly dominate over non-Saccharomyces wine yeasts, and several factors could be related to this dominance. However, the main factor causing the reduction of cultivable non-Saccharomyces populations has not yet been fully established. In the present study, various single and mixed fermentations were performed to evaluate some of the factors likely responsible for the interaction between Saccharomyces cerevisiae and Hanseniaspora uvarum. Alcoholic fermentation was performed in compartmented experimental set ups with ratios of 1:1 and 1:9 and the cultivable population of both species was followed. The cultivable H. uvarum population decreased sharply at late stages when S. cerevisiae was present in the other compartment, similarly to alcoholic fermentations in non-compartmented vessels. Thus, cell-to-cell contact did not seem to be the main cause for the lack of cultivability of H. uvarum. Other compounds related to fermentation performance (such as sugar and ethanol) and/or certain metabolites secreted by S. cerevisiae could be related to the sharp decrease in H. uvarum cultivability. When these factors were analyzed, it was confirmed that metabolites from S. cerevisiae induced lack of cultivability in H. uvarum, however ethanol and other possible compounds did not seem to induce this effect but played some role during the process. This study contributes to a new understanding of the lack of cultivability of H. uvarum populations during the late stages of wine fermentation. PMID:25956738

  3. Saccharomyces eubayanus and Saccharomyces uvarum associated with the fermentation of Araucaria araucana seeds in Patagonia.

    PubMed

    Rodríguez, M Eugenia; Pérez-Través, Laura; Sangorrín, Marcela P; Barrio, Eladio; Lopes, Christian A

    2014-09-01

    Mudai is a traditional fermented beverage, made from the seeds of the Araucaria araucana tree by Mapuche communities. The main goal of the present study was to identify and characterize the yeast microbiota responsible of Mudai fermentation as well as from A. araucana seeds and bark from different locations in Northern Patagonia. Only Hanseniaspora uvarum and a commercial bakery strain of Saccharomyces cerevisiae were isolated from Mudai and all Saccharomyces isolates recovered from A. araucana seed and bark samples belonged to the cryotolerant species Saccharomyces eubayanus and Saccharomyces uvarum. These two species were already reported in Nothofagus trees from Patagonia; however, this is the first time that they were isolated from A. araucana, which extends their ecological distribution. The presence of these species in A. araucana seeds and bark samples, led us to postulate a potential role for them as the original yeasts responsible for the elaboration of Mudai before the introduction of commercial S. cerevisiae cultures. The molecular and genetic characterization of the S. uvarum and S. eubayanus isolates and their comparison with European S. uvarum strains and S. eubayanus hybrids (S. bayanus and S. pastorianus), allowed their ecology and evolution us to be examined. PMID:25041507

  4. New family of pectinase genes PGU1b-PGU3b of the pectinolytic yeast Saccharomyces bayanus var. uvarum.

    PubMed

    Naumov, G I; Shalamitskiy, M Yu; Naumova, E S

    2016-03-01

    Using yeast genome databases and literature data, we have conducted a phylogenetic analysis of pectinase PGU genes from Saccharomyces strains assigned to the biological species S. arboricola, S. bayanus (var. uvarum), S. cariocanus, S. cerevisiae, S. kudriavzevii, S. mikatae, S. paradoxus, and hybrid taxon S. pastorianus (syn. S. carlsbergensis). Single PGU genes were observed in all Saccharomyces species, except S. bayanus. The superfamily of divergent PGU genes has been documented in S. bayanus var. uvarum for the first time. Chromosomal localization of new PGU1b, PGU2b, and PGU3b genes in the yeast S. bayanus var. uvarum has been determined by molecular karyotyping and Southern hybridization. PMID:27193705

  5. A Gondwanan imprint on global diversity and domestication of wine and cider yeast Saccharomyces uvarum

    NASA Astrophysics Data System (ADS)

    Almeida, Pedro; Gonçalves, Carla; Teixeira, Sara; Libkind, Diego; Bontrager, Martin; Masneuf-Pomarède, Isabelle; Albertin, Warren; Durrens, Pascal; Sherman, David James; Marullo, Philippe; Todd Hittinger, Chris; Gonçalves, Paula; Sampaio, José Paulo

    2014-06-01

    In addition to Saccharomyces cerevisiae, the cryotolerant yeast species S. uvarum is also used for wine and cider fermentation but nothing is known about its natural history. Here we use a population genomics approach to investigate its global phylogeography and domestication fingerprints using a collection of isolates obtained from fermented beverages and from natural environments on five continents. South American isolates contain more genetic diversity than that found in the Northern Hemisphere. Moreover, coalescence analyses suggest that a Patagonian sub-population gave rise to the Holarctic population through a recent bottleneck. Holarctic strains display multiple introgressions from other Saccharomyces species, those from S. eubayanus being prevalent in European strains associated with human-driven fermentations. These introgressions are absent in the large majority of wild strains and gene ontology analyses indicate that several gene categories relevant for wine fermentation are overrepresented. Such findings constitute a first indication of domestication in S. uvarum.

  6. Biosorption of water-soluble dyes on magnetically modified Saccharomyces cerevisiae subsp. uvarum cells.

    PubMed

    Safaríková, M; Ptácková, L; Kibriková, I; Safarík, I

    2005-05-01

    Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized with perchloric acid. Magnetically modified yeast cells efficiently adsorbed various water soluble dyes. The dyes adsorption can be described by the Langmuir adsorption model. The maximum adsorption capacity of the magnetic cells differed substantially for individual dyes; the highest value was found for aniline blue (approx. 220 mg per g of dried magnetic adsorbent). PMID:15811411

  7. Saccharomyces kudriavzevii and Saccharomyces uvarum differ from Saccharomyces cerevisiae during the production of aroma-active higher alcohols and acetate esters using their amino acidic precursors.

    PubMed

    Stribny, Jiri; Gamero, Amparo; Pérez-Torrado, Roberto; Querol, Amparo

    2015-07-16

    Higher alcohols and acetate esters are important flavour and aroma components in the food industry. In alcoholic beverages these compounds are produced by yeast during fermentation. Although Saccharomyces cerevisiae is one of the most extensively used species, other species of the Saccharomyces genus have become common in fermentation processes. This study analyses and compares the production of higher alcohols and acetate esters from their amino acidic precursors in three Saccharomyces species: Saccharomyces kudriavzevii, Saccharomyces uvarum and S. cerevisiae. The global volatile compound analysis revealed that S. kudriavzevii produced large amounts of higher alcohols, whereas S. uvarum excelled in the production of acetate esters. Particularly from phenylalanine, S. uvarum produced the largest amounts of 2-phenylethyl acetate, while S. kudriavzevii obtained the greatest 2-phenylethanol formation from this precursor. The present data indicate differences in the amino acid metabolism and subsequent production of flavour-active higher alcohols and acetate esters among the closely related Saccharomyces species. This knowledge will prove useful for developing new enhanced processes in fragrance, flavour, and food industries. PMID:25886016

  8. Volatile flavour profile of reduced alcohol wines fermented with the non-conventional yeast species Metschnikowia pulcherrima and Saccharomyces uvarum.

    PubMed

    Varela, C; Sengler, F; Solomon, M; Curtin, C

    2016-10-15

    Production of quality wines with decreased alcohol concentration continues to be one of the major challenges facing wine producers. Therefore, there is considerable interest in the isolation or generation of wine yeasts less efficient at transforming grape sugars into ethanol. We recently demonstrated that Metschnikowia pulcherrima AWRI1149 and Saccharomyces uvarum AWRI2846 were both able to produce reduced alcohol wine when used in sequential inoculation with Saccharomyces cerevisiae. This effect is additive when both strains are co-inoculated in grape must. Here we describe the volatile flavour profile of Chardonnay and Shiraz wines produced with these two strains. Wines fermented with M. pulcherrima showed concentrations of ethyl acetate likely to affect negatively wine aroma. Wines fermented with S. uvarum and with a combination of M. pulcherrima and S. uvarum were characterised by increased concentrations of 2-phenyl ethanol and 2-phenylethyl acetate, both associated with positive sensory attributes. PMID:27173534

  9. The Oenological Potential of Hanseniaspora uvarum in Simultaneous and Sequential Co-fermentation with Saccharomyces cerevisiae for Industrial Wine Production.

    PubMed

    Tristezza, Mariana; Tufariello, Maria; Capozzi, Vittorio; Spano, Giuseppe; Mita, Giovanni; Grieco, Francesco

    2016-01-01

    In oenology, the utilization of mixed starter cultures composed by Saccharomyces and non-Saccharomyces yeasts is an approach of growing importance for winemakers in order to enhance sensory quality and complexity of the final product without compromising the general quality and safety of the oenological products. In fact, several non-Saccharomyces yeasts are already commercialized as oenological starter cultures to be used in combination with Saccharomyces cerevisiae, while several others are the subject of various studies to evaluate their application. Our aim, in this study was to assess, for the first time, the oenological potential of H. uvarum in mixed cultures (co-inoculation) and sequential inoculation with S. cerevisiae for industrial wine production. Three previously characterized H. uvarum strains were separately used as multi-starter together with an autochthonous S. cerevisiae starter culture in lab-scale micro-vinification trials. On the basis of microbial development, fermentation kinetics and secondary compounds formation, the strain H. uvarum ITEM8795 was further selected and it was co- and sequentially inoculated, jointly with the S. cerevisiae starter, in a pilot scale wine production. The fermentation course and the quality of final product indicated that the co-inoculation was the better performing modality of inoculum. The above results were finally validated by performing an industrial scale vinification The mixed starter was able to successfully dominate the different stages of the fermentation process and the H. uvarum strain ITEM8795 contributed to increasing the wine organoleptic quality and to simultaneously reduce the volatile acidity. At the best of our knowledge, the present report is the first study regarding the utilization of a selected H. uvarum strain in multi-starter inoculation with S. cerevisiae for the industrial production of a wine. In addition, we demonstrated, at an industrial scale, the importance of non-Saccharomyces in

  10. The Oenological Potential of Hanseniaspora uvarum in Simultaneous and Sequential Co-fermentation with Saccharomyces cerevisiae for Industrial Wine Production

    PubMed Central

    Tristezza, Mariana; Tufariello, Maria; Capozzi, Vittorio; Spano, Giuseppe; Mita, Giovanni; Grieco, Francesco

    2016-01-01

    In oenology, the utilization of mixed starter cultures composed by Saccharomyces and non-Saccharomyces yeasts is an approach of growing importance for winemakers in order to enhance sensory quality and complexity of the final product without compromising the general quality and safety of the oenological products. In fact, several non-Saccharomyces yeasts are already commercialized as oenological starter cultures to be used in combination with Saccharomyces cerevisiae, while several others are the subject of various studies to evaluate their application. Our aim, in this study was to assess, for the first time, the oenological potential of H. uvarum in mixed cultures (co-inoculation) and sequential inoculation with S. cerevisiae for industrial wine production. Three previously characterized H. uvarum strains were separately used as multi-starter together with an autochthonous S. cerevisiae starter culture in lab-scale micro-vinification trials. On the basis of microbial development, fermentation kinetics and secondary compounds formation, the strain H. uvarum ITEM8795 was further selected and it was co- and sequentially inoculated, jointly with the S. cerevisiae starter, in a pilot scale wine production. The fermentation course and the quality of final product indicated that the co-inoculation was the better performing modality of inoculum. The above results were finally validated by performing an industrial scale vinification The mixed starter was able to successfully dominate the different stages of the fermentation process and the H. uvarum strain ITEM8795 contributed to increasing the wine organoleptic quality and to simultaneously reduce the volatile acidity. At the best of our knowledge, the present report is the first study regarding the utilization of a selected H. uvarum strain in multi-starter inoculation with S. cerevisiae for the industrial production of a wine. In addition, we demonstrated, at an industrial scale, the importance of non-Saccharomyces in

  11. Differences in Enzymatic Properties of the Saccharomyces kudriavzevii and Saccharomyces uvarum Alcohol Acetyltransferases and Their Impact on Aroma-Active Compounds Production

    PubMed Central

    Stribny, Jiri; Querol, Amparo; Pérez-Torrado, Roberto

    2016-01-01

    Higher alcohols and acetate esters belong to the most important yeast secondary metabolites that significantly contribute to the overall flavor and aroma profile of fermented products. In Saccharomyces cerevisiae, esterification of higher alcohols is catalyzed mainly by the alcohol acetyltransferases encoded by genes ATF1 and ATF2. Previous investigation has shown other Saccharomyces species, e.g., S. kudriavzevii and S. uvarum, to vary in aroma-active higher alcohols and acetate esters formation when compared to S. cerevisiae. Here, we aimed to analyze the enzymes encoded by the ATF1 and ATF2 genes from S. kudriavzevii (SkATF1, SkATF2) and S. uvarum (SuATF1, SuATF2). The heterologous expression of the individual ATF1 and ATF2 genes in a host S. cerevisiae resulted in the enhanced production of several higher alcohols and acetate esters. Particularly, an increase of 2-phenylethyl acetate production by the strains that harbored ATF1 and ATF2 genes from S. kudriavzevii and S. uvarum was observed. When grown with individual amino acids as the nitrogen source, the strain that harbored SkATF1 showed particularly high 2-phenylethyl acetate production and the strains with introduced SkATF2 or SuATF2 revealed increased production of isobutyl acetate, isoamyl acetate, and 2-phenylethyl acetate compared to the reference strains with endogenous ATF genes. The alcohol acetyltransferase activities of the individual Atf1 and Atf2 enzymes measured in the cell extracts of the S. cerevisiae atf1 atf2 iah1 triple-null strain were detected for all the measured substrates. This indicated that S. kudriavzevii and S. uvarum Atf enzymes had broad range substrate specificity as S. cerevisiae Atf enzymes. Individual Atf1 enzymes exhibited markedly different kinetic properties since SkAtf1p showed c. twofold higher and SuAtf1p c. threefold higher Km for isoamyl alcohol than ScAtf1p. Together these results indicated that the differences found among the three Saccharomyces species during the

  12. Analysis of temperature-mediated changes in the wine yeast Saccharomyces bayanus var uvarum. An oenological study of how the protein content influences wine quality.

    PubMed

    Muñoz-Bernal, Eugenia; Deery, Michael J; Rodríguez, María Esther; Cantoral, Jesús M; Howard, Julie; Feret, Renata; Natera, Ramón; Lilley, Kathryn S; Fernández-Acero, Francisco Javier

    2016-02-01

    Saccharomyces bayanus var. uvarum plays an important role in the fermentation of red wine from the D.O. Ribera del Duero. This is due to the special organoleptic taste that this yeast gives the wines and their ability to ferment at low temperature. To determine the molecular factors involved in the fermentation process at low temperature, a differential proteomic approach was performed by using 2D-DIGE, comparing, qualitatively and quantitatively, the profiles obtained at 13 and 25°C. A total of 152 protein spots were identified. We detected proteins upregulated at 13°C that were shown to be related to temperature stress, the production of aromatic compounds involved in the metabolism of amino acids, and the production of fusel alcohols and their derivatives, each of which is directly related to the quality of the wines. To check the temperature effects, an aromatic analysis by GC-MS was performed. The proteomic and "aromatomic" results are discussed in relation to the oenological properties of S. bayanus var. uvarum. PMID:26621492

  13. Hanseniaspora uvarum from Winemaking Environments Show Spatial and Temporal Genetic Clustering.

    PubMed

    Albertin, Warren; Setati, Mathabatha E; Miot-Sertier, Cécile; Mostert, Talitha T; Colonna-Ceccaldi, Benoit; Coulon, Joana; Girard, Patrick; Moine, Virginie; Pillet, Myriam; Salin, Franck; Bely, Marina; Divol, Benoit; Masneuf-Pomarede, Isabelle

    2015-01-01

    Hanseniaspora uvarum is one of the most abundant yeast species found on grapes and in grape must, at least before the onset of alcoholic fermentation (AF) which is usually performed by Saccharomyces species. The aim of this study was to characterize the genetic and phenotypic variability within the H. uvarum species. One hundred and fifteen strains isolated from winemaking environments in different geographical origins were analyzed using 11 microsatellite markers and a subset of 47 strains were analyzed by AFLP. H. uvarum isolates clustered mainly on the basis of their geographical localization as revealed by microsatellites. In addition, a strong clustering based on year of isolation was evidenced, indicating that the genetic diversity of H. uvarum isolates was related to both spatial and temporal variations. Conversely, clustering analysis based on AFLP data provided a different picture with groups showing no particular characteristics, but provided higher strain discrimination. This result indicated that AFLP approaches are inadequate to establish the genetic relationship between individuals, but allowed good strain discrimination. At the phenotypic level, several extracellular enzymatic activities of enological relevance (pectinase, chitinase, protease, β-glucosidase) were measured but showed low diversity. The impact of environmental factors of enological interest (temperature, anaerobia, and copper addition) on growth was also assessed and showed poor variation. Altogether, this work provided both new analytical tool (microsatellites) and new insights into the genetic and phenotypic diversity of H. uvarum, a yeast species that has previously been identified as a potential candidate for co-inoculation in grape must, but whose intraspecific variability had never been fully assessed. PMID:26834719

  14. Hanseniaspora uvarum from Winemaking Environments Show Spatial and Temporal Genetic Clustering

    PubMed Central

    Albertin, Warren; Setati, Mathabatha E.; Miot-Sertier, Cécile; Mostert, Talitha T.; Colonna-Ceccaldi, Benoit; Coulon, Joana; Girard, Patrick; Moine, Virginie; Pillet, Myriam; Salin, Franck; Bely, Marina; Divol, Benoit; Masneuf-Pomarede, Isabelle

    2016-01-01

    Hanseniaspora uvarum is one of the most abundant yeast species found on grapes and in grape must, at least before the onset of alcoholic fermentation (AF) which is usually performed by Saccharomyces species. The aim of this study was to characterize the genetic and phenotypic variability within the H. uvarum species. One hundred and fifteen strains isolated from winemaking environments in different geographical origins were analyzed using 11 microsatellite markers and a subset of 47 strains were analyzed by AFLP. H. uvarum isolates clustered mainly on the basis of their geographical localization as revealed by microsatellites. In addition, a strong clustering based on year of isolation was evidenced, indicating that the genetic diversity of H. uvarum isolates was related to both spatial and temporal variations. Conversely, clustering analysis based on AFLP data provided a different picture with groups showing no particular characteristics, but provided higher strain discrimination. This result indicated that AFLP approaches are inadequate to establish the genetic relationship between individuals, but allowed good strain discrimination. At the phenotypic level, several extracellular enzymatic activities of enological relevance (pectinase, chitinase, protease, β-glucosidase) were measured but showed low diversity. The impact of environmental factors of enological interest (temperature, anaerobia, and copper addition) on growth was also assessed and showed poor variation. Altogether, this work provided both new analytical tool (microsatellites) and new insights into the genetic and phenotypic diversity of H. uvarum, a yeast species that has previously been identified as a potential candidate for co-inoculation in grape must, but whose intraspecific variability had never been fully assessed. PMID:26834719

  15. Saccharomyces boulardii

    MedlinePlus

    ... believed to be a strain of Saccharomyces cerevisiae (baker's yeast). Saccharomyces boulardii is used as medicine. Saccharomyces boulardii ... Hansen CBS 5926), Probiotic, Probiotique, Saccharomyces, Saccharomyces boulardii, Saccharomyces Cerevisiae, S. Boulardii.

  16. Viability of Hanseniaspora uvarum yeast preserved by lyophilization and cryopreservation.

    PubMed

    de Arruda Moura Pietrowski, Giovana; Grochoski, Mayara; Sartori, Gabriela Felkl; Gomes, Tatiane Aparecida; Wosiacki, Gilvan; Nogueira, Alessandro

    2015-08-01

    Hanseniaspora yeasts are known to produce volatile compounds that give fruity aromas in wine and fermented fruit. This study aimed to verify the feasibility of the Hanseniaspora uvarum strain that had been isolated and identified during a previous study and preserved by lyophilization and freezing at -80 °C (cryopreservation). This strain was assessed in relation to its macroscopic and microscopic morphology and for its ability to ferment apple must. After having been subjected to lyophilization and cryopreservation, viability was assessed in relation to these characteristics during 12 months of storage. The strain showed stable colonial features and its microscopic appearance was unchanged during all recoveries. The plate count results showed consistency in both processes. Regarding the fermentative capacity, the kinetic results showed 100% viability for the strain subjected to lyophilization, as well as for those preserved at -80 °C. These results demonstrate that the preservation methods used are compatible with the maintenance of the relevant characteristics of the strain for the period of evaluation of this study (12 months). PMID:26095929

  17. Pure and mixed genetic lines of Saccharomyces bayanus and Saccharomyces pastorianus and their contribution to the lager brewing strain genome.

    PubMed

    Rainieri, Sandra; Kodama, Yukiko; Kaneko, Yoshinobu; Mikata, Kozaburo; Nakao, Yoshihiro; Ashikari, Toshihiko

    2006-06-01

    The yeast species Saccharomyces bayanus and Saccharomyces pastorianus are of industrial importance since they are involved in the production process of common beverages such as wine and lager beer; however, they contain strains whose variability has been neither fully investigated nor exploited in genetic improvement programs. We evaluated this variability by using PCR-restriction fragment length polymorphism analysis of 48 genes and partial sequences of 16. Within these two species, we identified "pure" strains containing a single type of genome and "hybrid" strains that contained portions of the genomes from the "pure" lines, as well as alleles termed "Lager" that represent a third genome commonly associated with lager brewing strains. The two pure lines represent S. uvarum and S. bayanus, the latter a novel group of strains that may be of use in strain improvement programs. Hybrid lines identified include (i) S. cerevisiae/S. bayanus/Lager, (ii) S. bayanus/S. uvarum/Lager, and (iii) S. cerevisiae/S. bayanus/S. uvarum/Lager. The genome of the lager strains may have resulted from chromosomal loss, replacement, or rearrangement within the hybrid genetic lines. This study identifies brewing strains that could be used as novel genetic sources in strain improvement programs and provides data that can be used to generate a model of how naturally occurring and industrial hybrid strains may have evolved. PMID:16751504

  18. Hybridization within Saccharomyces Genus Results in Homoeostasis and Phenotypic Novelty in Winemaking Conditions.

    PubMed

    da Silva, Telma; Albertin, Warren; Dillmann, Christine; Bely, Marina; la Guerche, Stéphane; Giraud, Christophe; Huet, Sylvie; Sicard, Delphine; Masneuf-Pomarede, Isabelle; de Vienne, Dominique; Marullo, Philippe

    2015-01-01

    Despite its biotechnological interest, hybridization, which can result in hybrid vigor, has not commonly been studied or exploited in the yeast genus. From a diallel design including 55 intra- and interspecific hybrids between Saccharomyces cerevisiae and S. uvarum grown at two temperatures in enological conditions, we analyzed as many as 35 fermentation traits with original statistical and modeling tools. We first showed that, depending on the types of trait--kinetics parameters, life-history traits, enological parameters and aromas -, the sources of variation (strain, temperature and strain * temperature effects) differed in a large extent. Then we compared globally three groups of hybrids and their parents at two growth temperatures: intraspecific hybrids S. cerevisiae * S. cerevisiae, intraspecific hybrids S. uvarum * S. uvarum and interspecific hybrids S. cerevisiae * S. uvarum. We found that hybridization could generate multi-trait phenotypes with improved oenological performances and better homeostasis with respect to temperature. These results could explain why interspecific hybridization is so common in natural and domesticated yeast, and open the way to applications for wine-making. PMID:25946464

  19. Molecular genetic study of introgression between Saccharomyces bayanus and S. cerevisiae.

    PubMed

    Naumova, Elena S; Naumov, Gennadi I; Masneuf-Pomarède, Isabelle; Aigle, Michel; Dubourdieu, Denis

    2005-10-30

    The genomic constitution of different S. bayanus strains and natural interspecific Saccharomyces hybrids has been studied by genetic and molecular methods. Unlike S. bayanus var. uvarum, some S. bayanus var. bayanus strains (the type culture CBS 380, CBS 378, CBS 425, CBS 1548) harbour a number of S. cerevisiae subtelomeric sequences: Y', pEL50, SUC, RTM and MAL. The two varieties, having 86-100% nDNA-nDNA reassociation, are partly genetically isolated from one another but completely isolated from S. cerevisiae. Genetic and molecular data support the maintaining of var. bayanus and var. uvarum strains in the species S. bayanus. Using Southern hybridization with species-specific molecular markers, RFLP of the MET2 gene and flow cytometry analysis, we showed that the non-S. cerevisiae parents are different in lager brewing yeasts and in wine hybrid strains. Our results suggest that S. pastorianus is a hybrid between S. cerevisiae and S. bayanus var. bayanus, while S. bayanus var. uvarum contributed to the formation of the wine hybrids S6U and CID1. According to the partial sequence of ACT1 gene and flow cytometry analysis, strain CID1 is a triple hybrid between S. cerevisiae, S. kudriavzevii and S. bayanus var. uvarum. PMID:16240458

  20. Hybridization within Saccharomyces Genus Results in Homoeostasis and Phenotypic Novelty in Winemaking Conditions

    PubMed Central

    Dillmann, Christine; Bely, Marina; la Guerche, Stéphane; Giraud, Christophe; Huet, Sylvie; Sicard, Delphine; Masneuf-Pomarede, Isabelle; de Vienne, Dominique; Marullo, Philippe

    2015-01-01

    Despite its biotechnological interest, hybridization, which can result in hybrid vigor, has not commonly been studied or exploited in the yeast genus. From a diallel design including 55 intra- and interspecific hybrids between Saccharomyces cerevisiae and S. uvarum grown at two temperatures in enological conditions, we analyzed as many as 35 fermentation traits with original statistical and modeling tools. We first showed that, depending on the types of trait – kinetics parameters, life-history traits, enological parameters and aromas –, the sources of variation (strain, temperature and strain * temperature effects) differed in a large extent. Then we compared globally three groups of hybrids and their parents at two growth temperatures: intraspecific hybrids S. cerevisiae * S. cerevisiae, intraspecific hybrids S. uvarum * S. uvarum and interspecific hybrids S. cerevisiae * S. uvarum. We found that hybridization could generate multi-trait phenotypes with improved oenological performances and better homeostasis with respect to temperature. These results could explain why interspecific hybridization is so common in natural and domesticated yeast, and open the way to applications for wine-making. PMID:25946464

  1. The Interaction between Saccharomyces cerevisiae and Non-Saccharomyces Yeast during Alcoholic Fermentation Is Species and Strain Specific

    PubMed Central

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2016-01-01

    The present study analyzes the lack of culturability of different non-Saccharomyces strains due to interaction with Saccharomyces cerevisiae during alcoholic fermentation. Interaction was followed in mixed fermentations with 1:1 inoculation of S. cerevisiae and ten non-Saccharomyces strains. Starmerella bacillaris, and Torulaspora delbrueckii indicated longer coexistence in mixed fermentations compared with Hanseniaspora uvarum and Metschnikowia pulcherrima. Strain differences in culturability and nutrient consumption (glucose, alanine, ammonium, arginine, or glutamine) were found within each species in mixed fermentation with S. cerevisiae. The interaction was further analyzed using cell-free supernatant from S. cerevisiae and synthetic media mimicking both single fermentations with S. cerevisiae and using mixed fermentations with the corresponding non-Saccharomyces species. Cell-free S. cerevisiae supernatants induced faster culturability loss than synthetic media corresponding to the same fermentation stage. This demonstrated that some metabolites produced by S. cerevisiae played the main role in the decreased culturability of the other non-Saccharomyces yeasts. However, changes in the concentrations of main metabolites had also an effect. Culturability differences were observed among species and strains in culture assays and thus showed distinct tolerance to S. cerevisiae metabolites and fermentation environment. Viability kit and recovery analyses on non-culturable cells verified the existence of viable but not-culturable status. These findings are discussed in the context of interaction between non-Saccharomyces and S. cerevisiae. PMID:27148191

  2. The Interaction between Saccharomyces cerevisiae and Non-Saccharomyces Yeast during Alcoholic Fermentation Is Species and Strain Specific.

    PubMed

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2016-01-01

    The present study analyzes the lack of culturability of different non-Saccharomyces strains due to interaction with Saccharomyces cerevisiae during alcoholic fermentation. Interaction was followed in mixed fermentations with 1:1 inoculation of S. cerevisiae and ten non-Saccharomyces strains. Starmerella bacillaris, and Torulaspora delbrueckii indicated longer coexistence in mixed fermentations compared with Hanseniaspora uvarum and Metschnikowia pulcherrima. Strain differences in culturability and nutrient consumption (glucose, alanine, ammonium, arginine, or glutamine) were found within each species in mixed fermentation with S. cerevisiae. The interaction was further analyzed using cell-free supernatant from S. cerevisiae and synthetic media mimicking both single fermentations with S. cerevisiae and using mixed fermentations with the corresponding non-Saccharomyces species. Cell-free S. cerevisiae supernatants induced faster culturability loss than synthetic media corresponding to the same fermentation stage. This demonstrated that some metabolites produced by S. cerevisiae played the main role in the decreased culturability of the other non-Saccharomyces yeasts. However, changes in the concentrations of main metabolites had also an effect. Culturability differences were observed among species and strains in culture assays and thus showed distinct tolerance to S. cerevisiae metabolites and fermentation environment. Viability kit and recovery analyses on non-culturable cells verified the existence of viable but not-culturable status. These findings are discussed in the context of interaction between non-Saccharomyces and S. cerevisiae. PMID:27148191

  3. Efficient engineering of marker-free synthetic allotetraploids of Saccharomyces.

    PubMed

    Alexander, William G; Peris, David; Pfannenstiel, Brandon T; Opulente, Dana A; Kuang, Meihua; Hittinger, Chris Todd

    2016-04-01

    Saccharomyces interspecies hybrids are critical biocatalysts in the fermented beverage industry, including in the production of lager beers, Belgian ales, ciders, and cold-fermented wines. Current methods for making synthetic interspecies hybrids are cumbersome and/or require genome modifications. We have developed a simple, robust, and efficient method for generating allotetraploid strains of prototrophic Saccharomyces without sporulation or nuclear genome manipulation. S. cerevisiae×S. eubayanus, S. cerevisiae×S. kudriavzevii, and S. cerevisiae×S. uvarum designer hybrid strains were created as synthetic lager, Belgian, and cider strains, respectively. The ploidy and hybrid nature of the strains were confirmed using flow cytometry and PCR-RFLP analysis, respectively. This method provides an efficient means for producing novel synthetic hybrids for beverage and biofuel production, as well as for constructing tetraploids to be used for basic research in evolutionary genetics and genome stability. PMID:26555931

  4. Potential of Glycosidase from Non-Saccharomyces Isolates for Enhancement of Wine Aroma.

    PubMed

    Hu, Kai; Qin, Yi; Tao, Yong-Sheng; Zhu, Xiao-Lin; Peng, Chuan-Tao; Ullah, Niamat

    2016-04-01

    The aim of this work was to rapidly screen indigenous yeasts with high levels of β-glucosidase activity and assess the potential of glycosidase extracts for aroma enhancement in winemaking. A semiquantitative colorimetric assay was applied using 96-well plates to screen yeasts from 3 different regions of China. Isolates with high β-glucosidase activity were confirmed by the commonly used pNP assay. Among 493 non-Saccharomyces isolates belonging to 8 generas, 3 isolates were selected for their high levels of β-glucosidase activity and were identified as Hanseniaspora uvarum, Pichia membranifaciens, and Rhodotorula mucilaginosa by sequence analysis of the 26S rDNA D1/D2 domain. β-Glucosidase in the glycosidase extract from H. uvarum strain showed the highest activity in winemaking conditions among the selected isolates. For aroma enhancement in winemaking, the glycosidase extract from H. uvarum strain exhibited catalytic specificity for aromatic glycosides of C13 -norisoprenoids and some terpenes, enhancing fresh floral, sweet, berry, and nutty aroma characteristics in wine. PMID:26954887

  5. Sequential Fermentation with Selected Immobilized Non-Saccharomyces Yeast for Reduction of Ethanol Content in Wine.

    PubMed

    Canonico, Laura; Comitini, Francesca; Oro, Lucia; Ciani, Maurizio

    2016-01-01

    The average ethanol content of wine has increased over the last two decades. This increase was due to consumer preference, and also to climate change that resulted in increased grape maturity at harvest. In the present study, to reduce ethanol content in wine, a microbiological approach was investigated, using immobilized selected strains of non-Saccharomyces yeasts namely Starmerella bombicola, Metschnikowia pulcherrima, Hanseniaspora osmophila, and Hanseniaspora uvarum to start fermentation, followed by inoculation of free Saccharomyces cerevisiae cells. The immobilization procedures, determining high reaction rates, led a feasible sequential inoculation management avoiding possible contamination under actual winemaking. Under these conditions, the immobilized cells metabolized almost 50% of the sugar in 3 days, while S. cerevisiae inoculation completed all of fermentation. The S. bombicola and M. pulcherrima initial fermentations showed the best reductions in the final ethanol content (1.6 and 1.4% v/v, respectively). Resulting wines did not have any negative fermentation products with the exception of H. uvarum sequential fermentation that showed significant amount of ethyl acetate. On the other hand, there were increases in desirable compounds such as glycerol and succinic acid for S. bombicola, geraniol for M. pulcherrima and isoamyl acetate and isoamyl alcohol for H. osmophila sequential fermentations. The overall results indicated that a promising ethanol reduction could be obtained using sequential fermentation of immobilized selected non-Saccharomyces strains. In this way, a suitable timing of second inoculation and an enhancement of analytical profile of wine were obtained. PMID:27014203

  6. Sequential Fermentation with Selected Immobilized Non-Saccharomyces Yeast for Reduction of Ethanol Content in Wine

    PubMed Central

    Canonico, Laura; Comitini, Francesca; Oro, Lucia; Ciani, Maurizio

    2016-01-01

    The average ethanol content of wine has increased over the last two decades. This increase was due to consumer preference, and also to climate change that resulted in increased grape maturity at harvest. In the present study, to reduce ethanol content in wine, a microbiological approach was investigated, using immobilized selected strains of non-Saccharomyces yeasts namely Starmerella bombicola, Metschnikowia pulcherrima, Hanseniaspora osmophila, and Hanseniaspora uvarum to start fermentation, followed by inoculation of free Saccharomyces cerevisiae cells. The immobilization procedures, determining high reaction rates, led a feasible sequential inoculation management avoiding possible contamination under actual winemaking. Under these conditions, the immobilized cells metabolized almost 50% of the sugar in 3 days, while S. cerevisiae inoculation completed all of fermentation. The S. bombicola and M. pulcherrima initial fermentations showed the best reductions in the final ethanol content (1.6 and 1.4% v/v, respectively). Resulting wines did not have any negative fermentation products with the exception of H. uvarum sequential fermentation that showed significant amount of ethyl acetate. On the other hand, there were increases in desirable compounds such as glycerol and succinic acid for S. bombicola, geraniol for M. pulcherrima and isoamyl acetate and isoamyl alcohol for H. osmophila sequential fermentations. The overall results indicated that a promising ethanol reduction could be obtained using sequential fermentation of immobilized selected non-Saccharomyces strains. In this way, a suitable timing of second inoculation and an enhancement of analytical profile of wine were obtained. PMID:27014203

  7. Saccharomyces boulardii

    MedlinePlus

    ... colitis), Lyme disease, a bowel disorder called relapsing Clostridium difficile colitis, and bacterial overgrowth in short bowel syndrome. ... appearance of acne. Diarrhea caused by the bacteria Clostridium difficile. Taking Saccharomyces boulardii by mouth along with the ...

  8. "Hanseniaspora uvarum" the ultrastructural morphology of a rare ascomycete, isolated from oral thrush.

    PubMed

    Emmanouil-Nikoloussi, E; Kanellaki-Kyparissi, M; Papavassiliou, P; Koliakos, K; Dermentzopoulou, M; Foroglou, C

    1994-01-01

    Superficial fungal infections, including oral thrush, often affect aged full denture wearers and many individuals over 65 years old. The aim of this study was to examine the ultrastructural morphology of a very rare yeast, named Hanseniaspora uvarum/guillermondi, member of the Ascomycetes family, whose pathogenesis and behaviour is not widely known. The yeast was isolated from whitish lesions of the buccal mucosa of an 70 years old woman. The specimen was collected with a mouth swab and cultured in Sabourauds-Dextrose agar. The identification of the organism was performed on the Api 20C Aux system. The yeast colonies, after fixation in glutaraldehyde 3% for 1 hour were immersed in OsO4 1% solution for 1 hour and were "in tissue" stained with uranyl acetate. Ultrathin sections, were observed with TEM Jeol C x 100. Our ultrastructural observations showed that this yeast had a thick cell wall in which the outer surface appeared fuzzy. In some yeasts we observed multilayered intracytoplasmic membrane a figure which is not described as far as we know in any yeast. Many vacuoles were frequently observed in the cytoplasm and especially in the center of the oval shaped cells. Bilateral budding which form ascospores is identical for the morphology of this yeast. PMID:7994154

  9. Povalibacter uvarum gen. nov., sp. nov., a polyvinyl-alcohol-degrading bacterium isolated from grapes.

    PubMed

    Nogi, Yuichi; Yoshizumi, Masaki; Hamana, Koei; Miyazaki, Masayuki; Horikoshi, Koki

    2014-08-01

    Polyvinyl-alcohol-degrading bacteria were isolated from the fruit of a grape in Yokosuka, Japan. The isolated strain, Zumi 37(T), was a Gram-stain-negative, rod-shaped, motile, non-spore-forming and strictly aerobic chemo-organotroph, showing optimal growth at pH 7.5, 30 °C and 0.1% (w/v) NaCl. The major respiratory quinone was Q-8. The predominant fatty acids were iso-C(15 : 0), C(16 : 0) and C(16 : 1)ω7c. The major polyamines were homospermidine and putrescine. The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content of the novel strain was 64.2 mol%. 16S rRNA gene sequence comparison revealed that strain Zumi 37(T) belongs to the family Sinobacteraceae within the class Gammaproteobacteria. Steroidobacter denitrificans DSM 18526(T) was the most closely related species with a validly published name, with 98.0% similarity based on 16S rRNA gene sequence comparison (and showed less than 87.5% sequence similarity to members of the genera Alkanibacter, Fontimonas, Hydrocarboniphaga, Nevskia and Solimonas with known 16S rRNA gene sequences). Phenotypes for growth under aerobic conditions and on complex media and major fatty acid composition, differed greatly from those of with comparatively high 16S rRNA gene sequence similarity. Based on phylogenetic, phenotypic and chemotaxonomic evidence, it is proposed that strain Zumi 37(T) represents a novel species in a new genus for which the name Povalibacter uvarum gen. nov., sp. nov. is proposed. The type strain of the type species is Zumi 37(T) ( = JCM 18749(T) = DSM 26723(T)). PMID:24844263

  10. On the Complexity of the Saccharomyces bayanus Taxon: Hybridization and Potential Hybrid Speciation

    PubMed Central

    Pérez-Través, Laura; Lopes, Christian A.; Querol, Amparo; Barrio, Eladio

    2014-01-01

    Although the genus Saccharomyces has been thoroughly studied, some species in the genus has not yet been accurately resolved; an example is S. bayanus, a taxon that includes genetically diverse lineages of pure and hybrid strains. This diversity makes the assignation and classification of strains belonging to this species unclear and controversial. They have been subdivided by some authors into two varieties (bayanus and uvarum), which have been raised to the species level by others. In this work, we evaluate the complexity of 46 different strains included in the S. bayanus taxon by means of PCR-RFLP analysis and by sequencing of 34 gene regions and one mitochondrial gene. Using the sequence data, and based on the S. bayanus var. bayanus reference strain NBRC 1948, a hypothetical pure S. bayanus was reconstructed for these genes that showed alleles with similarity values lower than 97% with the S. bayanus var. uvarum strain CBS 7001, and of 99–100% with the non S. cerevisiae portion in S. pastorianus Weihenstephan 34/70 and with the new species S. eubayanus. Among the S. bayanus strains under study, different levels of homozygosity, hybridization and introgression were found; however, no pure S. bayanus var. bayanus strain was identified. These S. bayanus hybrids can be classified into two types: homozygous (type I) and heterozygous hybrids (type II), indicating that they have been originated by different hybridization processes. Therefore, a putative evolutionary scenario involving two different hybridization events between a S. bayanus var. uvarum and unknown European S. eubayanus-like strains can be postulated to explain the genomic diversity observed in our S. bayanus var. bayanus strains. PMID:24705561

  11. On the complexity of the Saccharomyces bayanus taxon: hybridization and potential hybrid speciation.

    PubMed

    Pérez-Través, Laura; Lopes, Christian A; Querol, Amparo; Barrio, Eladio

    2014-01-01

    Although the genus Saccharomyces has been thoroughly studied, some species in the genus has not yet been accurately resolved; an example is S. bayanus, a taxon that includes genetically diverse lineages of pure and hybrid strains. This diversity makes the assignation and classification of strains belonging to this species unclear and controversial. They have been subdivided by some authors into two varieties (bayanus and uvarum), which have been raised to the species level by others. In this work, we evaluate the complexity of 46 different strains included in the S. bayanus taxon by means of PCR-RFLP analysis and by sequencing of 34 gene regions and one mitochondrial gene. Using the sequence data, and based on the S. bayanus var. bayanus reference strain NBRC 1948, a hypothetical pure S. bayanus was reconstructed for these genes that showed alleles with similarity values lower than 97% with the S. bayanus var. uvarum strain CBS 7001, and of 99-100% with the non S. cerevisiae portion in S. pastorianus Weihenstephan 34/70 and with the new species S. eubayanus. Among the S. bayanus strains under study, different levels of homozygosity, hybridization and introgression were found; however, no pure S. bayanus var. bayanus strain was identified. These S. bayanus hybrids can be classified into two types: homozygous (type I) and heterozygous hybrids (type II), indicating that they have been originated by different hybridization processes. Therefore, a putative evolutionary scenario involving two different hybridization events between a S. bayanus var. uvarum and unknown European S. eubayanus-like strains can be postulated to explain the genomic diversity observed in our S. bayanus var. bayanus strains. PMID:24705561

  12. Deciphering the Hybridisation History Leading to the Lager Lineage Based on the Mosaic Genomes of Saccharomyces bayanus Strains NBRC1948 and CBS380T

    PubMed Central

    Nguyen, Huu-Vang; Legras, Jean-Luc; Neuvéglise, Cécile; Gaillardin, Claude

    2011-01-01

    Saccharomyces bayanus is a yeast species described as one of the two parents of the hybrid brewing yeast S. pastorianus. Strains CBS380T and NBRC1948 have been retained successively as pure-line representatives of S. bayanus. In the present study, sequence analyses confirmed and upgraded our previous finding: S. bayanus type strain CBS380T harbours a mosaic genome. The genome of strain NBRC1948 was also revealed to be mosaic. Both genomes were characterized by amplification and sequencing of different markers, including genes involved in maltotriose utilization or genes detected by array-CGH mapping. Sequence comparisons with public Saccharomyces spp. nucleotide sequences revealed that the CBS380T and NBRC1948 genomes are composed of: a predominant non-cerevisiae genetic background belonging to S. uvarum, a second unidentified species provisionally named S. lagerae, and several introgressed S. cerevisiae fragments. The largest cerevisiae-introgressed DNA common to both genomes totals 70kb in length and is distributed in three contigs, cA, cB and cC. These vary in terms of length and presence of MAL31 or MTY1 (maltotriose-transporter gene). In NBRC1948, two additional cerevisiae-contigs, cD and cE, totaling 12kb in length, as well as several smaller cerevisiae fragments were identified. All of these contigs were partially detected in the genomes of S. pastorianus lager strains CBS1503 (S. monacensis) and CBS1513 (S. carlsbergensis) explaining the noticeable common ability of S. bayanus and S. pastorianus to metabolize maltotriose. NBRC1948 was shown to be inter-fertile with S. uvarum CBS7001. The cross involving these two strains produced F1 segregants resembling the strains CBS380T or NRRLY-1551. This demonstrates that these S. bayanus strains were the offspring of a cross between S. uvarum and a strain similar to NBRC1948. Phylogenies established with selected cerevisiae and non-cerevisiae genes allowed us to decipher the complex hybridisation events linking S

  13. Deciphering the hybridisation history leading to the Lager lineage based on the mosaic genomes of Saccharomyces bayanus strains NBRC1948 and CBS380.

    PubMed

    Nguyen, Huu-Vang; Legras, Jean-Luc; Neuvéglise, Cécile; Gaillardin, Claude

    2011-01-01

    Saccharomyces bayanus is a yeast species described as one of the two parents of the hybrid brewing yeast S. pastorianus. Strains CBS380(T) and NBRC1948 have been retained successively as pure-line representatives of S. bayanus. In the present study, sequence analyses confirmed and upgraded our previous finding: S. bayanus type strain CBS380(T) harbours a mosaic genome. The genome of strain NBRC1948 was also revealed to be mosaic. Both genomes were characterized by amplification and sequencing of different markers, including genes involved in maltotriose utilization or genes detected by array-CGH mapping. Sequence comparisons with public Saccharomyces spp. nucleotide sequences revealed that the CBS380(T) and NBRC1948 genomes are composed of: a predominant non-cerevisiae genetic background belonging to S. uvarum, a second unidentified species provisionally named S. lagerae, and several introgressed S. cerevisiae fragments. The largest cerevisiae-introgressed DNA common to both genomes totals 70kb in length and is distributed in three contigs, cA, cB and cC. These vary in terms of length and presence of MAL31 or MTY1 (maltotriose-transporter gene). In NBRC1948, two additional cerevisiae-contigs, cD and cE, totaling 12kb in length, as well as several smaller cerevisiae fragments were identified. All of these contigs were partially detected in the genomes of S. pastorianus lager strains CBS1503 (S. monacensis) and CBS1513 (S. carlsbergensis) explaining the noticeable common ability of S. bayanus and S. pastorianus to metabolize maltotriose. NBRC1948 was shown to be inter-fertile with S. uvarum CBS7001. The cross involving these two strains produced F1 segregants resembling the strains CBS380(T) or NRRLY-1551. This demonstrates that these S. bayanus strains were the offspring of a cross between S. uvarum and a strain similar to NBRC1948. Phylogenies established with selected cerevisiae and non-cerevisiae genes allowed us to decipher the complex hybridisation events

  14. Alternative Glycerol Balance Strategies among Saccharomyces Species in Response to Winemaking Stress

    PubMed Central

    Pérez-Torrado, Roberto; Oliveira, Bruno M.; Zemančíková, Jana; Sychrová, Hana; Querol, Amparo

    2016-01-01

    Production and balance of glycerol is essential for the survival of yeast cells in certain stressful conditions as hyperosmotic or cold shock that occur during industrial processes as winemaking. These stress responses are well-known in S. cerevisiae, however, little is known in other phylogenetically close related Saccharomyces species associated with natural or fermentation environments such as S. uvarum, S. paradoxus or S. kudriavzevii. In this work we have investigated the expression of four genes (GPD1, GPD2, STL1, and FPS1) crucial in the glycerol pool balance in the four species with a biotechnological potential (S. cerevisiae; S. paradoxus; S. uvarum; and S. kudriavzevii), and the ability of strains to grow under osmotic and cold stresses. The results show different pattern and level of expression among the different species, especially for STL1. We also studied the function of Stl1 glycerol symporter in the survival to osmotic changes and cell growth capacity in winemaking environments. These experiments also revealed a different functionality of the glycerol transporters among the different species studied. All these data point to different strategies to handle glycerol accumulation in response to winemaking stresses as hyperosmotic or cold-hyperosmotic stress in the different species, with variable emphasis in the production, influx, or efflux of glycerol. PMID:27064588

  15. Persistence of Two Non-Saccharomyces Yeasts (Hanseniaspora and Starmerella) in the Cellar

    PubMed Central

    Grangeteau, Cédric; Gerhards, Daniel; von Wallbrunn, Christian; Alexandre, Hervé; Rousseaux, Sandrine; Guilloux-Benatier, Michèle

    2016-01-01

    Different genera and/or species of yeasts present on grape berries, in musts and wines are widely described. Nevertheless, the community of non-Saccharomyces yeasts present in the cellar is still given little attention. Thus it is not known if the cellar is a real ecological niche for these yeasts or if it is merely a transient habitat for populations brought in by grape berries during the winemaking period. This study focused on three species of non-Saccharomyces yeasts commonly encountered during vinification: Starmerella bacillaris (synonymy with Candida zemplinina), Hanseniaspora guilliermondii and Hanseniaspora uvarum. More than 1200 isolates were identified at the strain level by FT-IR spectroscopy (207 different FTIR strain pattern). Only a small proportion of non-Saccharomyces yeasts present in musts came directly from grape berries for the three species studied. Some strains were found in the must in two consecutive years and some of them were also found in the cellar environment before the arrival of the harvest of second vintage. This study demonstrates for the first time the persistence of non-Saccharomyces yeast strains from year to year in the cellar. Sulfur dioxide can affect yeast populations in the must and therefore their persistence in the cellar environment. PMID:27014199

  16. Enological characterization of Spanish Saccharomyces kudriavzevii strains, one of the closest relatives to parental strains of winemaking and brewing Saccharomyces cerevisiae × S. kudriavzevii hybrids.

    PubMed

    Peris, D; Pérez-Través, L; Belloch, C; Querol, A

    2016-02-01

    Wine fermentation and innovation have focused mostly on Saccharomyces cerevisiae strains. However, recent studies have shown that other Saccharomyces species can also be involved in wine fermentation or are useful for wine bouquet, such as Saccharomyces uvarum and Saccharomyces paradoxus. Many interspecies hybrids have also been isolated from wine fermentation, such as S. cerevisiae × Saccharomyces kudriavzevii hybrids. In this study, we explored the genetic diversity and fermentation performance of Spanish S. kudriavzevii strains, which we compared to other S. kudriavzevii strains. Fermentations of red and white grape musts were performed, and the phenotypic differences between Spanish S. kudriavzevii strains under different temperature conditions were examined. An ANOVA analysis suggested striking similarity between strains for glycerol and ethanol production, although a high diversity of aromatic profiles among fermentations was found. The sources of these phenotypic differences are not well understood and require further investigation. Although the Spanish S. kudriavzevii strains showed desirable properties, particularly must fermentations, the quality of their wines was no better than those produced with a commercial S. cerevisiae. We suggest hybridization or directed evolution as methods to improve and innovate wine. PMID:26678127

  17. Functional toxicity and tolerance patterns of bioavailable Pd(II), Pt(II), and Rh(III) on suspended Saccharomyces cerevisiae cells assayed in tandem by a respirometric biosensor.

    PubMed

    Frazzoli, Chiara; Dragone, Roberto; Mantovani, Alberto; Massimi, Cristiana; Campanella, Luigi

    2007-12-01

    Toxicological implications of exposure to bioavailable platinum group metals, here Pd, Pt, and Rh, are still to be clarified. This study obtained by a biosensor-based method preliminary information on potential effects on cellular metabolism as well as on possible tolerance mechanisms. Aerobic respiration was taken as the toxicological end point to perform tandem tests, namely functional toxicity test and tolerance test. Cells were suspended in the absence of essential constituents for growth. The dose-response curves obtained by exposure (2 h) to the metals (nanogram per gram range) suggested the same mechanisms of action, with Rh showing the greatest curve steepness and the lowest EC50 value. Conservative (95% lower confidence interval) EC10 values were 187, 85 and 51 ng g(-1) for Pt, Pd, and Rh respectively. Tolerance patterns were tested during the same runs. The full tolerance obtained after 12 h of exposure to each metal suggested mitochondrial inhibition of aerobic respiration as a target effect. The hazard rating of the metals in the tolerance test changed in the Rh EC50 range, where Rh showed the lowest toxicity. The observed tolerance might suggest a protective mechanism such as metallothionein induction at concentrations around the EC50 values. The performance of the bioassay was satisfactory, in terms of the limit of detection, repeatability, reproducibility, roboustness, sensibility, and stability; the method's critical uncertainty sources were identified for improvements. PMID:17960368

  18. Fermentative capabilities and volatile compounds produced by Kloeckera/Hanseniaspora and Saccharomyces yeast strains in pure and mixed cultures during Agave tequilana juice fermentation.

    PubMed

    González-Robles, Ivonne Wendolyne; Estarrón-Espinosa, Mirna; Díaz-Montaño, Dulce María

    2015-09-01

    The fermentative and aromatic capabilities of Kloeckera africana/Hanseniaspora vineae K1, K. apiculata/H. uvarum K2, and Saccharomyces cerevisiae S1 and S2 were studied in pure and mixed culture fermentations using Agave tequila juice as the culture medium. In pure and mixed cultures, Kloeckera/Hanseniaspora strains showed limited growth and sugar consumption, as well as low ethanol yield and productivity, compared to S. cerevisiae, which yielded more biomass, ethanol and viable cell concentrations. In pure and mixed cultures, S. cerevisiae presented a similar behaviour reaching high biomass production, completely consuming the sugar, leading to high ethanol production. Furthermore, the presence of S. cerevisiae strains in the mixed cultures promoted the production of higher alcohols, acetaldehyde and ethyl esters, whereas Kloeckera/Hanseniaspora strains stimulated the production of ethyl acetate and 2-phenyl ethyl acetate compounds. PMID:26108494

  19. A New System for Comparative Functional Genomics of Saccharomyces Yeasts

    PubMed Central

    Caudy, Amy A.; Guan, Yuanfang; Jia, Yue; Hansen, Christina; DeSevo, Chris; Hayes, Alicia P.; Agee, Joy; Alvarez-Dominguez, Juan R.; Arellano, Hugo; Barrett, Daniel; Bauerle, Cynthia; Bisaria, Namita; Bradley, Patrick H.; Breunig, J. Scott; Bush, Erin; Cappel, David; Capra, Emily; Chen, Walter; Clore, John; Combs, Peter A.; Doucette, Christopher; Demuren, Olukunle; Fellowes, Peter; Freeman, Sam; Frenkel, Evgeni; Gadala-Maria, Daniel; Gawande, Richa; Glass, David; Grossberg, Samuel; Gupta, Anita; Hammonds-Odie, Latanya; Hoisos, Aaron; Hsi, Jenny; Hsu, Yu-Han Huang; Inukai, Sachi; Karczewski, Konrad J.; Ke, Xiaobo; Kojima, Mina; Leachman, Samuel; Lieber, Danny; Liebowitz, Anna; Liu, Julia; Liu, Yufei; Martin, Trevor; Mena, Jose; Mendoza, Rosa; Myhrvold, Cameron; Millian, Christian; Pfau, Sarah; Raj, Sandeep; Rich, Matt; Rokicki, Joe; Rounds, William; Salazar, Michael; Salesi, Matthew; Sharma, Rajani; Silverman, Sanford; Singer, Cara; Sinha, Sandhya; Staller, Max; Stern, Philip; Tang, Hanlin; Weeks, Sharon; Weidmann, Maxwell; Wolf, Ashley; Young, Carmen; Yuan, Jie; Crutchfield, Christopher; McClean, Megan; Murphy, Coleen T.; Llinás, Manuel; Botstein, David; Troyanskaya, Olga G.; Dunham, Maitreya J.

    2013-01-01

    Whole-genome sequencing, particularly in fungi, has progressed at a tremendous rate. More difficult, however, is experimental testing of the inferences about gene function that can be drawn from comparative sequence analysis alone. We present a genome-wide functional characterization of a sequenced but experimentally understudied budding yeast, Saccharomyces bayanus var. uvarum (henceforth referred to as S. bayanus), allowing us to map changes over the 20 million years that separate this organism from S. cerevisiae. We first created a suite of genetic tools to facilitate work in S. bayanus. Next, we measured the gene-expression response of S. bayanus to a diverse set of perturbations optimized using a computational approach to cover a diverse array of functionally relevant biological responses. The resulting data set reveals that gene-expression patterns are largely conserved, but significant changes may exist in regulatory networks such as carbohydrate utilization and meiosis. In addition to regulatory changes, our approach identified gene functions that have diverged. The functions of genes in core pathways are highly conserved, but we observed many changes in which genes are involved in osmotic stress, peroxisome biogenesis, and autophagy. A surprising number of genes specific to S. bayanus respond to oxidative stress, suggesting the organism may have evolved under different selection pressures than S. cerevisiae. This work expands the scope of genome-scale evolutionary studies from sequence-based analysis to rapid experimental characterization and could be adopted for functional mapping in any lineage of interest. Furthermore, our detailed characterization of S. bayanus provides a valuable resource for comparative functional genomics studies in yeast. PMID:23852385

  20. Aroma Profile of Montepulciano d'Abruzzo Wine Fermented by Single and Co-culture Starters of Autochthonous Saccharomyces and Non-saccharomyces Yeasts.

    PubMed

    Tofalo, Rosanna; Patrignani, Francesca; Lanciotti, Rosalba; Perpetuini, Giorgia; Schirone, Maria; Di Gianvito, Paola; Pizzoni, Daniel; Arfelli, Giuseppe; Suzzi, Giovanna

    2016-01-01

    Montepulciano d'Abruzzo is a native grape variety of Vitis vinifera L., grown in central Italy and used for production of high quality red wines. Limited studies have been carried out to improve its enological characteristics through the use of indigenous strains of Saccharomyces cerevisiae. The main objective of the present work was to test two indigenous strains of S. cerevisiae (SRS1, RT73), a strain of Starmerella bacillaris (STS12), one of Hanseniaspora uvarum (STS45) and a co-culture of S. cerevisiae (SRS1) and S. bacillaris (STS12), in an experimental cellar to evaluate their role in the sensory characteristic of Montepulciano d'Abruzzo wine. A S. cerevisiae commercial strain was used. Fermentations were conducted under routine Montepulciano d'Abruzzo wine production, in which the main variables were the yeast strains used for fermentation. Basic winemaking parameters, some key chemical analysis and aroma compounds were considered. S. cerevisiae strain dynamics during fermentation were determined by molecular methods. The musts inoculated with the co-culture were characterized by a faster fermentation start and a higher content of glycerol after 3 days of fermentation, as well as the musts added with strains S. bacillaris (STS12) and H. uvarum (STS45). At the end of fermentation the parameters studied were quite similar in all the wines. Total biogenic amines (BA) content of all the wines was low. Ethanolamine was the predominant BA, with a concentration ranging from 21 to 24 mg/l. Wines were characterized by esters and alcohols. In particular, 2-phenylethanol, 3-methylbut-1-yl methanoate, and ethyl ethanoate were the major aroma volatile compounds in all wines. Statistical analysis highlighted the different role played by aroma compounds in the differentiation of wines, even if it was impossible to select a single class of compounds as the most important for a specific yeast. The present study represents a further step toward the use of tailored

  1. Aroma Profile of Montepulciano d'Abruzzo Wine Fermented by Single and Co-culture Starters of Autochthonous Saccharomyces and Non-saccharomyces Yeasts

    PubMed Central

    Tofalo, Rosanna; Patrignani, Francesca; Lanciotti, Rosalba; Perpetuini, Giorgia; Schirone, Maria; Di Gianvito, Paola; Pizzoni, Daniel; Arfelli, Giuseppe; Suzzi, Giovanna

    2016-01-01

    Montepulciano d'Abruzzo is a native grape variety of Vitis vinifera L., grown in central Italy and used for production of high quality red wines. Limited studies have been carried out to improve its enological characteristics through the use of indigenous strains of Saccharomyces cerevisiae. The main objective of the present work was to test two indigenous strains of S. cerevisiae (SRS1, RT73), a strain of Starmerella bacillaris (STS12), one of Hanseniaspora uvarum (STS45) and a co-culture of S. cerevisiae (SRS1) and S. bacillaris (STS12), in an experimental cellar to evaluate their role in the sensory characteristic of Montepulciano d'Abruzzo wine. A S. cerevisiae commercial strain was used. Fermentations were conducted under routine Montepulciano d'Abruzzo wine production, in which the main variables were the yeast strains used for fermentation. Basic winemaking parameters, some key chemical analysis and aroma compounds were considered. S. cerevisiae strain dynamics during fermentation were determined by molecular methods. The musts inoculated with the co-culture were characterized by a faster fermentation start and a higher content of glycerol after 3 days of fermentation, as well as the musts added with strains S. bacillaris (STS12) and H. uvarum (STS45). At the end of fermentation the parameters studied were quite similar in all the wines. Total biogenic amines (BA) content of all the wines was low. Ethanolamine was the predominant BA, with a concentration ranging from 21 to 24 mg/l. Wines were characterized by esters and alcohols. In particular, 2-phenylethanol, 3-methylbut-1-yl methanoate, and ethyl ethanoate were the major aroma volatile compounds in all wines. Statistical analysis highlighted the different role played by aroma compounds in the differentiation of wines, even if it was impossible to select a single class of compounds as the most important for a specific yeast. The present study represents a further step toward the use of tailored

  2. Screening of β-Glucosidase and β-Xylosidase Activities in Four Non-Saccharomyces Yeast Isolates.

    PubMed

    López, María Consuelo; Mateo, José Juan; Maicas, Sergi

    2015-08-01

    The finding of new isolates of non-Saccharomyces yeasts, showing beneficial enzymes (such as β-glucosidase and β-xylosidase), can contribute to the production of quality wines. In a selection and characterization program, we have studied 114 isolates of non-Saccharomyces yeasts. Four isolates were selected because of their both high β-glucosidase and β-xylosidase activities. The ribosomal D1/D2 regions were sequenced to identify them as Pichia membranifaciens Pm7, Hanseniaspora vineae Hv3, H. uvarum Hu8, and Wickerhamomyces anomalus Wa1. The induction process was optimized to be carried on YNB-medium supplemented with 4% xylan, inoculated with 106 cfu/mL and incubated 48 h at 28 °C without agitation. Most of the strains had a pH optimum of 5.0 to 6.0 for both the β-glucosidase and β-xylosidase activities. The effect of sugars was different for each isolate and activity. Each isolate showed a characteristic set of inhibition, enhancement or null effect for β-glucosidase and β-xylosidase. The volatile compounds liberated from wine incubated with each of the 4 yeasts were also studied, showing an overall terpene increase (1.1 to 1.3-folds) when wines were treated with non-Saccharomyces isolates. In detail, terpineol, 4-vinyl-phenol and 2-methoxy-4-vinylphenol increased after the addition of Hanseniaspora isolates. Wines treated with Hanseniaspora, Wickerhamomyces, or Pichia produced more 2-phenyl ethanol than those inoculated with other yeasts. PMID:26126488

  3. Enhancing the Bioconversion of Winery and Olive Mill Waste Mixtures into Lignocellulolytic Enzymes and Animal Feed by Aspergillus uvarum Using a Packed-Bed Bioreactor.

    PubMed

    Salgado, José Manuel; Abrunhosa, Luís; Venâncio, Armando; Domínguez, José Manuel; Belo, Isabel

    2015-10-28

    Wineries and olive oil industries are dominant agro-industrial activities in southern European regions. Olive pomace, exhausted grape marc, and vine shoot trimmings are lignocellulosic residues generated by these industries, which could be valued biotechnologically. In the present work these residues were used as substrate to produce cellulases and xylanases through solid-state fermentation using Aspergillus uvarum MUM 08.01. For that, two factorial designs (3(2)) were first planned to optimize substrate composition, temperature, and initial moisture level. Subsequently, the kinectics of cellulolytic enzyme production, fungal growth, and fermented solid were characterized. Finally, the process was performed in a packed-bed bioreactor. The results showed that cellulase activity improved with the optimization processes, reaching 33.56 U/g, and with the packed-bed bioreactor aeration of 0.2 L/min, reaching 38.51 U/g. The composition of fermented solids indicated their potential use for animal feed because cellulose, hemicellulose, lignin, and phenolic compounds were partially degraded 28.08, 10.78, 13.3, and 28.32%, respectively, crude protein was increased from 8.47 to 17.08%, and the mineral contents meet the requirements of main livestock. PMID:26165254

  4. Analysis of the Saccharomyces cerevisiae pan-genome reveals a pool of copy number variants distributed in diverse yeast strains from differing industrial environments

    PubMed Central

    Dunn, Barbara; Richter, Chandra; Kvitek, Daniel J.; Pugh, Tom; Sherlock, Gavin

    2012-01-01

    Although the budding yeast Saccharomyces cerevisiae is arguably one of the most well-studied organisms on earth, the genome-wide variation within this species—i.e., its “pan-genome”—has been less explored. We created a multispecies microarray platform containing probes covering the genomes of several Saccharomyces species: S. cerevisiae, including regions not found in the standard laboratory S288c strain, as well as the mitochondrial and 2-μm circle genomes–plus S. paradoxus, S. mikatae, S. kudriavzevii, S. uvarum, S. kluyveri, and S. castellii. We performed array-Comparative Genomic Hybridization (aCGH) on 83 different S. cerevisiae strains collected across a wide range of habitats; of these, 69 were commercial wine strains, while the remaining 14 were from a diverse set of other industrial and natural environments. We observed interspecific hybridization events, introgression events, and pervasive copy number variation (CNV) in all but a few of the strains. These CNVs were distributed throughout the strains such that they did not produce any clear phylogeny, suggesting extensive mating in both industrial and wild strains. To validate our results and to determine whether apparently similar introgressions and CNVs were identical by descent or recurrent, we also performed whole-genome sequencing on nine of these strains. These data may help pinpoint genomic regions involved in adaptation to different industrial milieus, as well as shed light on the course of domestication of S. cerevisiae. PMID:22369888

  5. Actin from Saccharomyces cerevisiae.

    PubMed Central

    Greer, C; Schekman, R

    1982-01-01

    Inhibition of DNase I activity has been used as an assay to purify actin from Saccharomyces cerevisiae (yeast actin). The final fraction, obtained after a 300-fold purification, is approximately 97% pure as judged by sodium dodecyl sulfate-gel electrophoresis. Like rabbit skeletal muscle actin, yeast actin has a molecular weight of about 43,000, forms 7-nm-diameter filaments when polymerization is induced by KCl or Mg2+, and can be decorated with a proteolytic fragment of muscle myosin (heavy meromyosin). Although heavy meromyosin ATPase activity is stimulated by rabbit muscle and yeast actins to approximately the same Vmax (2 mmol of Pi per min per mumol of heavy meromyosin), half-maximal activation (Kapp) is obtained with 14 micro M muscle actin, but requires approximately 135 micro M yeast actin. This difference suggests a low affinity of yeast actin for muscle myosin. Yeast and muscle filamentous actin respond similarly to cytochalasin and phalloidin, although the drugs have no effect on S. cerevisiae cell growth. Images PMID:6217414

  6. Prothrombin time (PT)

    MedlinePlus

    PT; Pro-time; Anticoagulant-prothrombin time; Clotting time: protime; INR; International normalized ratio ... PT is measured in seconds. Most of the time, results are given as what is called INR ( ...

  7. PT -symmetry Wave Chaos

    NASA Astrophysics Data System (ADS)

    West, Carl T.; Kottos, Tsampikos; Prosen, Tomaz

    2010-03-01

    We study a new class of chaotic systems with dynamical localization, where gain/loss processes break the hermiticity, while allowing for parity-time PT symmetry. For a value γPT of the gain/loss parameter the spectrum undergoes a spontaneous phase transition from real (exact phase) to complex values (broken phase). We develop a one parameter scaling theory for γPT, and show that chaos assists the exact PT-phase. Our results will have applications to the design of optical elements with PT-symmetry.

  8. Peptidase activities in Saccharomyces cerevisiae.

    PubMed Central

    Rose, B; Becker, J M; Naider, F

    1979-01-01

    At least four distinct aminopeptidase activities and a single dipeptidase activity were found in cell extracts of a leucine-lysine auxotroph of Saccharomyces cerevisiae. The assay for peptidase activity involved polyacrylamide gel electrophoresis followed by an enzyme-coupled activity staining procedure. The aminopeptidases had largely overlapping specificities but could be distinguished from one another by their electrophoretic mobilities and activities toward different peptide substrates. Substrates tested included both free and blocked di- and tripeptides and amino acid derivatives. Images PMID:378955

  9. Selected non-Saccharomyces wine yeasts in controlled multistarter fermentations with Saccharomyces cerevisiae.

    PubMed

    Comitini, Francesca; Gobbi, Mirko; Domizio, Paola; Romani, Cristina; Lencioni, Livio; Mannazzu, Ilaria; Ciani, Maurizio

    2011-08-01

    Non-Saccharomyces yeasts are metabolically active during spontaneous and inoculated must fermentations, and by producing a plethora of by-products, they can contribute to the definition of the wine aroma. Thus, use of Saccharomyces and non-Saccharomyces yeasts as mixed starter cultures for inoculation of wine fermentations is of increasing interest for quality enhancement and improved complexity of wines. We initially characterized 34 non-Saccharomyces yeasts of the genera Candida, Lachancea (Kluyveromyces), Metschnikowia and Torulaspora, and evaluated their enological potential. This confirmed that non-Saccharomyces yeasts from wine-related environments represent a rich sink of unexplored biodiversity for the winemaking industry. From these, we selected four non-Saccharomyces yeasts to combine with starter cultures of Saccharomyces cerevisiae in mixed fermentation trials. The kinetics of growth and fermentation, and the analytical profiles of the wines produced indicate that these non-Saccharomyces strains can be used with S. cerevisiae starter cultures to increase polysaccharide, glycerol and volatile compound production, to reduce volatile acidity, and to increase or reduce the total acidity of the final wines, depending on yeast species and inoculum ratio used. The overall effects of the non-Saccharomyces yeasts on fermentation and wine quality were strictly dependent on the Saccharomyces/non-Saccharomyces inoculum ratio that mimicked the differences of fermentation conditions (natural or simultaneous inoculated fermentation). PMID:21569929

  10. Cadmium biosorption by Saccharomyces cerevisiae

    SciTech Connect

    Volesky, B.; May, H.; Holan, Z.R. )

    1993-04-01

    Cadmium uptake by nonliving and resting cells of Saccharomyces cerevisiae obtained from aerobic or anaerobic cultures from pure cadmium-bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal-sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min.

  11. PT-symmetric strings

    SciTech Connect

    Amore, Paolo; Fernández, Francisco M.; Garcia, Javier; Gutierrez, German

    2014-04-15

    We study both analytically and numerically the spectrum of inhomogeneous strings with PT-symmetric density. We discuss an exactly solvable model of PT-symmetric string which is isospectral to the uniform string; for more general strings, we calculate exactly the sum rules Z(p)≡∑{sub n=1}{sup ∞}1/E{sub n}{sup p}, with p=1,2,… and find explicit expressions which can be used to obtain bounds on the lowest eigenvalue. A detailed numerical calculation is carried out for two non-solvable models depending on a parameter, obtaining precise estimates of the critical values where pair of real eigenvalues become complex. -- Highlights: •PT-symmetric Hamiltonians exhibit real eigenvalues when PT symmetry is unbroken. •We study PT-symmetric strings with complex density. •They exhibit regions of unbroken PT symmetry. •We calculate the critical parameters at the boundaries of those regions. •There are exact real sum rules for some particular complex densities.

  12. Methionine catabolism in Saccharomyces cerevisiae.

    PubMed

    Perpète, Philippe; Duthoit, Olivier; De Maeyer, Simon; Imray, Louise; Lawton, Andrew I; Stavropoulos, Konstantinos E; Gitonga, Virginia W; Hewlins, Michael J E; Dickinson, J Richard

    2006-01-01

    The catabolism of methionine to methionol and methanethiol in Saccharomyces cerevisiae was studied using (13)C NMR spectroscopy, GC-MS, enzyme assays and a number of mutants. Methionine is first transaminated to alpha-keto-gamma-(methylthio)butyrate. Methionol is formed by a decarboxylation reaction, which yields methional, followed by reduction. The decarboxylation is effected specifically by Ydr380wp. Methanethiol is formed from both methionine and alpha-keto-gamma-(methylthio)butyrate by a demethiolase activity. In all except one strain examined, demethiolase was induced by the presence of methionine in the growth medium. This pathway results in the production of alpha-ketobutyrate, a carbon skeleton, which can be re-utilized. Hence, methionine catabolism is more complex and economical than the other amino acid catabolic pathways in yeast, which use the Ehrlich pathway and result solely in the formation of a fusel alcohol. PMID:16423070

  13. Glucose repression in Saccharomyces cerevisiae.

    PubMed

    Kayikci, Ömur; Nielsen, Jens

    2015-09-01

    Glucose is the primary source of energy for the budding yeast Saccharomyces cerevisiae. Although yeast cells can utilize a wide range of carbon sources, presence of glucose suppresses molecular activities involved in the use of alternate carbon sources as well as it represses respiration and gluconeogenesis. This dominant effect of glucose on yeast carbon metabolism is coordinated by several signaling and metabolic interactions that mainly regulate transcriptional activity but are also effective at post-transcriptional and post-translational levels. This review describes effects of glucose repression on yeast carbon metabolism with a focus on roles of the Snf3/Rgt2 glucose-sensing pathway and Snf1 signal transduction in establishment and relief of glucose repression. PMID:26205245

  14. Glucose repression in Saccharomyces cerevisiae

    PubMed Central

    Kayikci, Ömur; Nielsen, Jens

    2015-01-01

    Glucose is the primary source of energy for the budding yeast Saccharomyces cerevisiae. Although yeast cells can utilize a wide range of carbon sources, presence of glucose suppresses molecular activities involved in the use of alternate carbon sources as well as it represses respiration and gluconeogenesis. This dominant effect of glucose on yeast carbon metabolism is coordinated by several signaling and metabolic interactions that mainly regulate transcriptional activity but are also effective at post-transcriptional and post-translational levels. This review describes effects of glucose repression on yeast carbon metabolism with a focus on roles of the Snf3/Rgt2 glucose-sensing pathway and Snf1 signal transduction in establishment and relief of glucose repression. PMID:26205245

  15. Metabolic Engineering of Saccharomyces cerevisiae

    PubMed Central

    Ostergaard, Simon; Olsson, Lisbeth; Nielsen, Jens

    2000-01-01

    Comprehensive knowledge regarding Saccharomyces cerevisiae has accumulated over time, and today S. cerevisiae serves as a widley used biotechnological production organism as well as a eukaryotic model system. The high transformation efficiency, in addition to the availability of the complete yeast genome sequence, has facilitated genetic manipulation of this microorganism, and new approaches are constantly being taken to metabolicially engineer this organism in order to suit specific needs. In this paper, strategies and concepts for metabolic engineering are discussed and several examples based upon selected studies involving S. cerevisiae are reviewed. The many different studies of metabolic engineering using this organism illustrate all the categories of this multidisciplinary field: extension of substrate range, improvements of producitivity and yield, elimination of byproduct formation, improvement of process performance, improvements of cellular properties, and extension of product range including heterologous protein production. PMID:10704473

  16. Postreplication repair in Saccharomyces cerevisiae

    SciTech Connect

    Resnick, M.A.; Boyce, J.; Cox, B.

    1981-04-01

    Postreplication events in logarithmically growing excision-defective mutants of Saccharomyces cerevisiae were examined after low doses of ultraviolet light. Pulse-labeled deoxyribonucleic acid had interruptions, and when the cells were chased, the interruptions were no longer detected. Since the loss of interruptions was not associated with an exchange of pyrimidine dimers at a detection level of 10 to 20% of the induced dimers, it was concluded that postreplication repair in excision-defective mutants does not involve molecular recombination. Pyrimidine dimers were assayed by utilizing the ultraviolet-endonuclease activity in extracts of Micrococcus luteus and newly developed alkaline sucrose gradient techniques, which yielded chromosomal-size deoxyribonucleic acid after treatment of irradiated cells.

  17. PT quantum mechanics.

    PubMed

    Bender, Carl M; DeKieviet, Maarten; Klevansky, S P

    2013-04-28

    PT-symmetric quantum mechanics (PTQM) has become a hot area of research and investigation. Since its beginnings in 1998, there have been over 1000 published papers and more than 15 international conferences entirely devoted to this research topic. Originally, PTQM was studied at a highly mathematical level and the techniques of complex variables, asymptotics, differential equations and perturbation theory were used to understand the subtleties associated with the analytic continuation of eigenvalue problems. However, as experiments on PT-symmetric physical systems have been performed, a simple and beautiful physical picture has emerged, and a PT-symmetric system can be understood as one that has a balanced loss and gain. Furthermore, the PT phase transition can now be understood intuitively without resorting to sophisticated mathematics. Research on PTQM is following two different paths: at a fundamental level, physicists are attempting to understand the underlying mathematical structure of these theories with the long-range objective of applying the techniques of PTQM to understanding some of the outstanding problems in physics today, such as the nature of the Higgs particle, the properties of dark matter, the matter-antimatter asymmetry in the universe, neutrino oscillations and the cosmological constant; at an applied level, new kinds of PT-synthetic materials are being developed, and the PT phase transition is being observed in many physical contexts, such as lasers, optical wave guides, microwave cavities, superconducting wires and electronic circuits. The purpose of this Theme Issue is to acquaint the reader with the latest developments in PTQM. The articles in this volume are written in the style of mini-reviews and address diverse areas of the emerging and exciting new area of PT-symmetric quantum mechanics. PMID:23509390

  18. Xe adsorption site distributions on Pt(111), Pt(221) and Pt(531)

    NASA Astrophysics Data System (ADS)

    Gellman, Andrew J.; Baker, L.; Holsclaw, B. S.

    2016-04-01

    The ideal structures of the Pt(111), Pt(221) and Pt(531) surfaces expose adsorption sites that can be qualitatively described as terrace sites on Pt(111), both step and terrace sites on Pt(221), and kink sites on Pt(531). The real surface structures of these surfaces can be complicated by imperfections such as misorientation, reconstruction and thermal roughening, all of which will influence their distributions of adsorption sites. Xe adsorption sites on the Pt(111), Pt(221) and Pt(531) surfaces have been probed using both photoemission of adsorbed Xe (PAX) and temperature programmed desorption (TPD) of Xe. Both PAX and Xe TPD are sensitive to the adsorption sites of the Xe and serve as complementary means of assessing the distributions of adsorption sites on these three Pt surfaces. The adsorption of Xe is sufficiently sensitive to detect the presence of residual steps on the Pt(111) surface at a density of ~ 1.5% step atoms per Pt atom. On the Pt(221) surface, PAX and Xe TPD reveal adsorption at both terrace and step sites simultaneously. Although the ideal structure of the Pt(531) surface has no well-defined steps or terraces, Xe adsorption indicates that its adsorption sites are best described as a distribution of both step and kink sites with roughly twice as many steps sites as kinks.

  19. PET genes of Saccharomyces cerevisiae.

    PubMed Central

    Tzagoloff, A; Dieckmann, C L

    1990-01-01

    We describe a collection of nuclear respiratory-defective mutants (pet mutants) of Saccharomyces cerevisiae consisting of 215 complementation groups. This set of mutants probably represents a substantial fraction of the total genetic information of the nucleus required for the maintenance of functional mitochondria in S. cerevisiae. The biochemical lesions of mutants in approximately 50 complementation groups have been related to single enzymes or biosynthetic pathways, and the corresponding wild-type genes have been cloned and their structures have been determined. The genes defined by an additional 20 complementation groups were identified by allelism tests with mutants characterized in other laboratories. Mutants representative of the remaining complementation groups have been assigned to one of the following five phenotypic classes: (i) deficiency in cytochrome oxidase, (ii) deficiency in coenzyme QH2-cytochrome c reductase, (iii) deficiency in mitochondrial ATPase, (iv) absence of mitochondrial protein synthesis, and (v) normal composition of respiratory-chain complexes and of oligomycin-sensitive ATPase. In addition to the genes identified through biochemical and genetic analyses of the pet mutants, we have cataloged PET genes not matched to complementation groups in the mutant collection and other genes whose products function in the mitochondria but are not necessary for respiration. Together, this information provides an up-to-date list of the known genes coding for mitochondrial constituents and for proteins whose expression is vital for the respiratory competence of S. cerevisiae. PMID:2215420

  20. Proteomics of Saccharomyces cerevisiae Organelles*

    PubMed Central

    Wiederhold, Elena; Veenhoff, Liesbeth M.; Poolman, Bert; Slotboom, Dirk Jan

    2010-01-01

    Knowledge of the subcellular localization of proteins is indispensable to understand their physiological roles. In the past decade, 18 studies have been performed to analyze the protein content of isolated organelles from Saccharomyces cerevisiae. Here, we integrate the data sets and compare them with other large scale studies on protein localization and abundance. We evaluate the completeness and reliability of the organelle proteomics studies. Reliability depends on the purity of the organelle preparations, which unavoidably contain (small) amounts of contaminants from different locations. Quantitative proteomics methods can be used to distinguish between true organellar constituents and contaminants. Completeness is compromised when loosely or dynamically associated proteins are lost during organelle preparation and also depends on the sensitivity of the analytical methods for protein detection. There is a clear trend in the data from the 18 organelle proteomics studies showing that proteins of low abundance frequently escape detection. Proteins with unknown function or cellular abundance are also infrequently detected, indicating that these proteins may not be expressed under the conditions used. We discuss that the yeast organelle proteomics studies provide powerful lead data for further detailed studies and that methodological advances in organelle preparation and in protein detection may help to improve the completeness and reliability of the data. PMID:19955081

  1. PT-symmetric kinks

    SciTech Connect

    Souza Dutra, A. de; Santos, V. G. C. S. dos; Amaro de Faria, A. C. Jr.

    2007-06-15

    Some kinks for non-Hermitian quantum field theories in 1+1 dimensions are constructed. A class of models where the soliton energies are stable and real are found. Although these kinks are not Hermitian, they are symmetric under PT transformations.

  2. Pt, Co-Pt and Fe-Pt alloy nanoclusters encapsulated in virus capsids

    NASA Astrophysics Data System (ADS)

    Okuda, M.; Eloi, J.-C.; Jones, S. E. Ward; Verwegen, M.; Cornelissen, J. J. L. M.; Schwarzacher, W.

    2016-03-01

    Nanostructured Pt-based alloys show great promise, not only for catalysis but also in medical and magnetic applications. To extend the properties of this class of materials, we have developed a means of synthesizing Pt and Pt-based alloy nanoclusters in the capsid of a virus. Pure Pt and Pt-alloy nanoclusters are formed through the chemical reduction of [PtCl4]- by NaBH4 with/without additional metal ions (Co or Fe). The opening and closing of the ion channels in the virus capsid were controlled by changing the pH and ionic strength of the solution. The size of the nanoclusters is limited to 18 nm by the internal diameter of the capsid. Their magnetic properties suggest potential applications in hyperthermia for the Co-Pt and Fe-Pt magnetic alloy nanoclusters. This study introduces a new way to fabricate size-restricted nanoclusters using virus capsid.

  3. PT-Symmetric Wave Chaos

    NASA Astrophysics Data System (ADS)

    West, Carl T.; Kottos, Tsampikos; Prosen, Tomaž

    2010-02-01

    We study a new class of chaotic systems with dynamical localization, where gain or loss mechanisms break the Hermiticity, while allowing for parity-time (PT) symmetry. For a value γPT of the gain or loss parameter the spectrum undergoes a spontaneous phase transition from real (exact phase) to complex values (broken phase). We develop a one parameter scaling theory for γPT, and show that chaos assists the exact PT phase. Our results have applications to the design of optical elements with PT symmetry.

  4. The permanent electric dipole moment of PtO, PtS, PtN, and PtC

    SciTech Connect

    Steimle, T.C.; Jung, K.Y.; Li, B.

    1995-08-01

    The permanent electric dipole moments of the ground, and the low-lying excited electronic states of platinum monocarbide, PtC, platinum monoxide, PtO, and platinum monosulfide, PtS, were measured using a molecular beam optical Stark spectroscopic scheme. The determined values were (in Debye): PtO({ital X} {sup 3}{Sigma}{sup {minus}}) 2.77(2); PtO({ital A} {sup 1}{Sigma}{sup +}) 1.15(4); PtS[{ital X}({Omega}=0)] 1.78(2); PtS[{ital B}({Omega}=0)] 0.54(6); PtC({ital X} {sup 1}{Sigma}{sup +}) 0.99(5); and PtC({ital A} {sup 1}{Pi}) 2.454(3). These results, along with the previous results for PtN({ital X} {sup 2}{Pi}{sub 1/2}) 1.977(9); PtN({ital d} {sup 4}{Pi}{sub 1/2}) 1.05(9) [J. Chem. Phys. {bold 102}, 643 (1995)], are used as a basis for a discussion of the nature of the electronic states. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  5. Enzymatic activities produced by mixed Saccharomyces and non-Saccharomyces cultures: relationship with wine volatile composition.

    PubMed

    Maturano, Yolanda Paola; Assof, Mariela; Fabani, María Paula; Nally, María Cristina; Jofré, Viviana; Rodríguez Assaf, Leticia Anahí; Toro, María Eugenia; Castellanos de Figueroa, Lucía Inés; Vazquez, Fabio

    2015-11-01

    During certain wine fermentation processes, yeasts, and mainly non-Saccharomyces strains, produce and secrete enzymes such as β-glucosidases, proteases, pectinases, xylanases and amylases. The effects of enzyme activity on the aromatic quality of wines during grape juice fermentation, using different co-inoculation strategies of non-Saccharomyces and Saccharomyces cerevisiae yeasts, were assessed in the current study. Three strains with appropriate enological performance and high enzymatic activities, BSc562 (S. cerevisiae), BDv566 (Debaryomyces vanrijiae) and BCs403 (Candida sake), were assayed in pure and mixed Saccharomyces/non-Saccharomyces cultures. β-Glucosidase, pectinase, protease, xylanase and amylase activities were quantified during fermentations. The aromatic profile of pure and mixed cultures was determined at the end of each fermentation. In mixed cultures, non-Saccharomyces species were detected until day 4-5 of the fermentation process, and highest populations were observed in MSD2 (10% S. cerevisiae/90% D. vanrijiae) and MSC1 (1% S. cerevisiae/99% C. sake). According to correlation and multivariate analysis, MSD2 presented the highest concentrations of terpenes and higher alcohols which were associated with pectinase, amylase and xylanase activities. On the other hand, MSC1 high levels of β-glucosidase, proteolytic and xylanolytic activities were correlated to esters and fatty acids. Our study contributes to a better understanding of the effect of enzymatic activities by yeasts on compound transformations that occur during wine fermentation. PMID:26386703

  6. PT symmetry in optics

    NASA Astrophysics Data System (ADS)

    Christodoulides, Demetrios

    2015-03-01

    Interest in complex Hamiltonians has been rekindled after the realization that a wide class of non-Hermitian Hamiltonians can have entirely real spectra as long as they simultaneously respect parity and time reversal operators. In non-relativistic quantum mechanics, governed by the Schrödinger equation, a necessary but not sufficient condition for PT symmetry to hold is that the complex potential should involve real and imaginary parts which are even and odd functions of position respectively. As recently indicated, optics provides a fertile ground to observe and utilize notions of PT symmetry. In optics, the refractive index and gain/loss profiles play the role of the real and imaginary parts of the aforementioned complex potentials. As it has been demonstrated in several studies, PT-symmetric optical structures can exhibit peculiar properties that are otherwise unattainable in traditional Hermitian (conservative) optical settings. Among them, is the possibility for breaking this symmetry through an abrupt phase transition, band merging effects and unidirectional invisibility. Here we review recent developments in the field of -symmetric optics.

  7. Asymmetrical division of Saccharomyces cerevisiae.

    PubMed Central

    Lord, P G; Wheals, A E

    1980-01-01

    The unequal division model proposed for budding yeast (L. H. Hartwell and M. W. Unger, J. Cell Biol. 75:422-435, 1977) was tested by bud scar analyses of steady-state exponential batch cultures of Saccharomyces cerevisiae growing at 30 degrees C at 19 different rates, which were obtained by altering the carbon source. The analyses involved counting the number of bud scars, determining the presence or absence of buds on at least 1,000 cells, and independently measuring the doubling times (gamma) by cell number increase. A number of assumptions in the model were tested and found to be in good agreement with the model. Maximum likelihood estimates of daughter cycle time (D), parent cycle time (P), and the budded phase (B) were obtained, and we concluded that asymmetrical division occurred at all growth rates tested (gamma, 75 to 250 min). D, P, and B are all linearly related to gamma, and D, P, and gamma converge to equality (symmetrical division) at gamma = 65 min. Expressions for the genealogical age distribution for asymmetrically dividing yeast cells were derived. The fraction of daughter cells in steady-state populations is e-alpha P, and the fraction of parent cells of age n (where n is the number of buds that a cell has produced) is (e-alpha P)n-1(1-e-alpha P)2, where alpha = IN2/gamma; thus, the distribution changes with growth rate. The frequency of cells with different numbers of bud scars (i.e., different genealogical ages) was determined for all growth rates, and the observed distribution changed with the growth rate in the manner predicted. In this haploid strain new buds formed adjacent to the previous buds in a regular pattern, but at slower growth rates the pattern was more irregular. The median volume of the cells and the volume at start in the cell cycle both increased at faster growth rates. The implications of these findings for the control of the cell cycle are discussed. PMID:6991494

  8. Thermodynamic Modeling of the Pt-Te and Pt-Sb-Te Systems

    NASA Astrophysics Data System (ADS)

    Guo, Cuiping; Huang, Liang; Li, Changrong; Shang, Shunli; Du, Zhenmin

    2015-08-01

    The Pt-Te and the Pt-Sb-Te systems are modeled using the calculation of phase diagram (CALPHAD) technique. In the Pt-Te system, the liquid phase is modeled as (Pt, PtTe2, Te) using the associate model, and four intermediates, PtTe2, Pt2Te3, Pt3Te4 and PtTe, are treated as stoichiometric compounds and their enthalpies of formation are obtained by means of first-principles calculations. The solution phases, fcc(Pt) and hex(Te), are described as substitutional solutions. Combined with the thermodynamic models of the liquid phase in the Pt-Sb and Sb-Te systems in the literature, the liquid phase of the Pt-Sb-Te ternary system is modeled as (Pt, Sb, Te, Sb2Te3, PtTe2) also using the associate model. The compounds, PtTe2, Pt2Te3, Pt3Te4 and PtTe in the Pt-Te system and PtSb2, PtSb, Pt3Sb2 and Pt7Sb in the Pt-Sb system are treated as line compounds Pt m (Sb,Te) n in the Pt-Sb-Te system, and the compound Pt5Sb is treated as (Pt,Sb)5(Pt,Sb,Te). A set of self-consistent thermodynamic parameters is obtained. Using these thermodynamic parameters, the experimental Pt-Te phase diagram, the experimental heat capacities of PtTe and PtTe2, the enthalpies of formation from first-principles calculations for PtTe2, Pt2Te3, Pt3Te4, and PtTe, and the ternary isothermal sections at 873 K, 923 K, 1073 K and 1273 K are well reproduced.

  9. Mechanisms of Ethanol Tolerance in Saccharomyces cerevisiae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Saccharomyces cerevisiae is a superb ethanol producer, yet is also sensitive to higher ethanol concentrations especially under high gravity or very high gravity fermentation conditions. Ethanol tolerance is associated with interplay of complex networks at the genome level. Although significant eff...

  10. Fatal Saccharomyces Cerevisiae Aortic Graft Infection

    NASA Technical Reports Server (NTRS)

    Meyer, Michael (Technical Monitor); Smith, Davey; Metzgar, David; Wills, Christopher; Fierer, Joshua

    2002-01-01

    Saccharomyces cerevisiae is a yeast commonly used in baking and a frequent colonizer of human mucosal surfaces. It is considered relatively nonpathogenic in immunocompetent adults. We present a case of S. cerevisiae fungemia and aortic graft infection in an immunocompetent adult. This is the first reported case of S. cerevisiue fungemia where the identity of the pathogen was confirmed by rRNA sequencing.

  11. MEL gene polymorphism in the genus Saccharomyces.

    PubMed Central

    Turakainen, H; Aho, S; Korhola, M

    1993-01-01

    In Saccharomyces spp. the ability to use melibiose depends on the presence of a MEL gene encoding alpha-galactosidase. We used two cloned MEL genes as probes to characterize the physical structure and chromosomal location of the MEL genes in several industrial and natural Mel+ strains of Saccharomyces cerevisiae, Saccharomyces pastorianus, and Saccharomyces bayanus. Electrokaryotyping showed that all of the S. pastorianus strains and most of the S. bayanus strains studied had one MEL locus. The MEL gene in S. bayanus strains was similar but not identical to the S. pastorianus MEL gene. Mel+ S. cerevisiae strains had one to seven loci containing MEL sequences. The MEL genes of these strains could be divided into two categories on the basis of hybridization to MEL1, one group exhibiting strong hybridization to MEL1 and the other group exhibiting weak hybridization to MEL1. In S. pastorianus and S. bayanus strains, the MEL gene was expressed as a single 1.5-kb transcript, and the expression was galactose inducible. In some S. cerevisiae strains, the MEL genes were expressed even without induction at fairly high levels. Expression was usually further induced by galactose. In two strains, CBS 5378 and CBS 4903, expression of the MEL genes was at the same level without induction as it was in most other strains with induction. In all S. cerevisiae strains, irrespective of the number of MEL genes, mRNA of only one size (1.6 kb) was observed. Images PMID:8396384

  12. Saccharomyces cerevisiae osteomyelitis in an immunocompetent baker.

    PubMed

    Seng, Piseth; Cerlier, Alexandre; Cassagne, Carole; Coulange, Mathieu; Legré, Regis; Stein, Andreas

    2016-01-01

    Invasive infection caused by Saccharomyces cerevisiae is rare. We report the first case of osteomyelitis caused by S. cerevisiae (baker's yeast) in a post-traumatic patient. The clinical outcome was favorable after surgical debridement, prolonged antifungal treatment and hyperbaric oxygen therapy. PMID:27347482

  13. Tangential Ultrafiltration of Aqueous "Saccharomyces Cerevisiae" Suspensions

    ERIC Educational Resources Information Center

    Silva, Carlos M.; Neves, Patricia S.; Da Silva, Francisco A.; Xavier, Ana M. R. B.; Eusebio, M. F. J.

    2008-01-01

    Experimental work on ultrafiltration is presented to illustrate the practical and theoretical principles of this separation technique. The laboratory exercise comprises experiments with pure water and with aqueous "Saccharomyces cerevisiae" (from commercial Baker's yeast) suspensions. With this work students detect the characteristic phenomena…

  14. Pt and Pt/(Cu) Carbonyl clusters synthesized by radiolysis

    NASA Astrophysics Data System (ADS)

    Le Gratiet, B.; Remita, H.; Picq, G.; Delcourt, M. O.

    1996-02-01

    In the mixed solvent: 50/50% v/v water/2-propanol, [Pt 3(CO) 6] n2- clusters with n = 3-10 have been obtained by irradiating solutions containing K 2PtCl 4 under 1 atm CO. n is deduced from the very typical UV-visible and IR absorption spectra. The reduction occurs by a combined effect of CO and of the radicals produced by radiolysis (radiocatalysis). The synthesis is selective: the nuclearity n can be chosen by adjusting the dose (high doses yield low n values). Increasing the Pt salt concentration leads to CO-stabilized subcolloid particles. Intermetallic cluster compounds are expected from solutions containing two metal salts: bimetallic Pt/Cu carbonyl clusters have been obtained. Two distinct compounds have been characterized by their UV-visible spectra. Attempts with Pt/Ru and Pt/Sn systems were unsuccessful.

  15. Characterization of azo dyes on Pt and Pt/polyaniline/dispersed Pt electrodes

    NASA Astrophysics Data System (ADS)

    Molina, J.; Fernández, J.; del Río, A. I.; Bonastre, J.; Cases, F.

    2012-06-01

    The electrochemical characterization of two organic dyes (amaranth and procion orange MX-2R) has been performed on Pt electrodes and Pt electrodes coated with polyaniline and dispersed Pt. Electrodes with different Pt loads have been synthesized and characterized obtaining that a load of 300 μg cm-2 was the optimum one. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) was employed to observe the distribution and morphology of the Pt nanoparticles. The electroactivity of the electrodes has also been characterized by means of scanning electrochemical microscopy (SECM). The chemical characterization of Pt dispersed Pani coated Pt electrodes (Pt-Pani-Pt) was performed by means of X-ray photoelectron spectroscopy (XPS). The electrochemical characterization of the dyes has been performed by means of cyclic voltammetry. Voltammograms have shown that the presence of the dyes diminishes characteristic Pt oxidation and reduction peaks. However, redox processes due to the dyes, appeared in the voltammograms. The different species responsible of these redox processes were generated in the vicinity of the electrode and were not adsorbed on the electrode surface since after stirring, the different redox processes disappeared. Characterization with different scan rates showed that redox processes of both dyes were controlled by diffusion.

  16. Saccharomyces Fungemia Associated with Esophageal Disease Identified by D1/D2 Ribosomal RNA Gene Sequence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Disseminated Saccharomyces infection has been reported in immunosuppressed patients treated with probiotics, but disseminated Saccharomyces cerevisiae infection associated with underlying esophageal disease is not previously described. Saccharomyces cerevisiae (which occasionally colonizes the gast...

  17. Surface-layered ordered alloy (Pt/Pt3Mn) on Pt(111)

    NASA Astrophysics Data System (ADS)

    Gallego, S.; Ocal, C.; Muñoz, M. C.; Soria, F.

    1997-11-01

    A Mn-Pt layered intermetallic compound formed by alternated planes of Pt(111) and Pt3Mn(111) composition has been stabilized in a controlled way by two different mechanisms, which confirm the great stability of the final system. The surface exhibits a 2×2 superstructure due to chemical order underneath a Pt topmost layer. The structural analysis by low-energy electron diffraction gives a Pendry reliability factor (R-factor) of RP=0.17. The hybridization of the Pt and Mn atomic levels leads to atomic magnetic moments of 3.17μB and ~0.10μB at the Mn and Pt sites of the topmost layers, respectively.

  18. Genomic Insights into the Saccharomyces sensu stricto Complex

    PubMed Central

    Borneman, Anthony R.; Pretorius, Isak S.

    2015-01-01

    The Saccharomyces sensu stricto group encompasses species ranging from the industrially ubiquitous yeast Saccharomyces cerevisiae to those that are confined to geographically limited environmental niches. The wealth of genomic data that are now available for the Saccharomyces genus is providing unprecedented insights into the genomic processes that can drive speciation and evolution, both in the natural environment and in response to human-driven selective forces during the historical “domestication” of these yeasts for baking, brewing, and winemaking. PMID:25657346

  19. Comparison of Properties of Pt/PZT/Pt and Ru/PZT/Pt Ferroelectric Capacitors

    NASA Astrophysics Data System (ADS)

    Jia, Ze; Ren, Tian-Ling; Liu, Tian-Zhi; Hu, Hong; Zhang, Zhi-Gang; Xie, Dan; Liu, Li-Tian

    2006-04-01

    Pb(Zr0.4Ti0.6)O3 film prepared by sol-gel spin coating on a Pt/Ti/SiO2/Si substrate is applied to ferroelectric capacitors with Pt or Ru as the top electrode. For the Pt/PZT/Pt and Ru/PZT/Pt ferroelectric capacitors, although with the same ferroelectric film, different top electrode materials incur different properties of PZT capacitors, such as fatigue, leakage, remanent and saturated polarization, except the similar crystal orientations of the PZT film. After 1010 switch cycles, the remanent polarizations of the Ru/PZT/Pt and Pt/PZT/Pt capacitors decrease to 70% and 84%, respectively. The leakage current density of the latter increases obviously at positive bias after 108 switch cycles, compared with the former. Different materials for the top electrode bring different conditions at the PZT/top electrode interface. The influence of oxygen-vacancy concentration at the PZT/electrode interface and the influence of oxides of the electrode material at the PZT/electrode interface to charge injection can explain the difference of properties of the PZT capacitors with Pt or Ru as the top electrodes.

  20. The Saccharomyces Genome Database Variant Viewer.

    PubMed

    Sheppard, Travis K; Hitz, Benjamin C; Engel, Stacia R; Song, Giltae; Balakrishnan, Rama; Binkley, Gail; Costanzo, Maria C; Dalusag, Kyla S; Demeter, Janos; Hellerstedt, Sage T; Karra, Kalpana; Nash, Robert S; Paskov, Kelley M; Skrzypek, Marek S; Weng, Shuai; Wong, Edith D; Cherry, J Michael

    2016-01-01

    The Saccharomyces Genome Database (SGD; http://www.yeastgenome.org) is the authoritative community resource for the Saccharomyces cerevisiae reference genome sequence and its annotation. In recent years, we have moved toward increased representation of sequence variation and allelic differences within S. cerevisiae. The publication of numerous additional genomes has motivated the creation of new tools for their annotation and analysis. Here we present the Variant Viewer: a dynamic open-source web application for the visualization of genomic and proteomic differences. Multiple sequence alignments have been constructed across high quality genome sequences from 11 different S. cerevisiae strains and stored in the SGD. The alignments and summaries are encoded in JSON and used to create a two-tiered dynamic view of the budding yeast pan-genome, available at http://www.yeastgenome.org/variant-viewer. PMID:26578556

  1. Homogeneous Pt-bimetallic Electrocatalysts

    SciTech Connect

    Wang, Chao; Chi, Miaofang; More, Karren Leslie; Markovic, Nenad; Stamenkovic, Vojislav

    2011-01-01

    Alloying has shown enormous potential for tailoring the atomic and electronic structures, and improving the performance of catalytic materials. Systematic studies of alloy catalysts are, however, often compromised by inhomogeneous distribution of alloying components. Here we introduce a general approach for the synthesis of monodispersed and highly homogeneous Pt-bimetallic alloy nanocatalysts. Pt{sub 3}M (where M = Fe, Ni, or Co) nanoparticles were prepared by an organic solvothermal method and then supported on high surface area carbon. These catalysts attained a homogeneous distribution of elements, as demonstrated by atomic-scale elemental analysis using scanning transmission electron microscopy. They also exhibited high catalytic activities for the oxygen reduction reaction (ORR), with improvement factors of 2-3 versus conventional Pt/carbon catalysts. The measured ORR catalytic activities for Pt{sub 3}M nanocatalysts validated the volcano curve established on extended surfaces, with Pt{sub 3}Co being the most active alloy.

  2. The ecology and evolution of non-domesticated Saccharomyces species

    PubMed Central

    Boynton, Primrose J; Greig, Duncan

    2014-01-01

    Yeast researchers need model systems for ecology and evolution, but the model yeast Saccharomyces cerevisiae is not ideal because its evolution has been affected by domestication. Instead, ecologists and evolutionary biologists are focusing on close relatives of S. cerevisiae, the seven species in the genus Saccharomyces. The best-studied Saccharomyces yeast, after S. cerevisiae, is S. paradoxus, an oak tree resident throughout the northern hemisphere. In addition, several more members of the genus Saccharomyces have recently been discovered. Some Saccharomyces species are only found in nature, while others include both wild and domesticated strains. Comparisons between domesticated and wild yeasts have pinpointed hybridization, introgression and high phenotypic diversity as signatures of domestication. But studies of wild Saccharomyces natural history, biogeography and ecology are only beginning. Much remains to be understood about wild yeasts' ecological interactions and life cycles in nature. We encourage researchers to continue to investigate Saccharomyces yeasts in nature, both to place S. cerevisiae biology into its ecological context and to develop the genus Saccharomyces as a model clade for ecology and evolution. © 2014 The Authors. Yeast published by John Wiley & Sons Ltd. PMID:25242436

  3. Saccharomyces eubayanus and Saccharomyces arboricola reside in North Island native New Zealand forests.

    PubMed

    Gayevskiy, Velimir; Goddard, Matthew R

    2016-04-01

    Saccharomyces is one of the best-studied microbial genera, but our understanding of the global distributions and evolutionary histories of its members is relatively poor. Recent studies have altered our view of Saccharomyces' origin, but a lack of sampling from the vast majority of the world precludes a holistic perspective. We evaluate alternate Gondwanan and Far East Asian hypotheses concerning the origin of these yeasts. Being part of Gondwana, and only colonized by humans in the last ∼1000 years, New Zealand represents a unique environment for testing these ideas. Genotyping and ribosomal sequencing of samples from North Island native forest parks identified a widespread population of Saccharomyces. Whole genome sequencing identified the presence of S. arboricola and S. eubayanus in New Zealand, which is the first report of S. arboricola outside Far East Asia, and also expands S. eubayanus' known distribution to include the Oceanic region. Phylogenomic approaches place the S. arboricola population as significantly diverged from the only other sequenced Chinese isolate but indicate that S. eubayanus might be a recent migrant from South America. These data tend to support the Far East Asian origin of the Saccharomyces, but the history of this group is still far from clear. PMID:26522264

  4. Lifetime measurements in 180Pt

    NASA Astrophysics Data System (ADS)

    Chen, Q. M.; Wu, X. G.; Chen, Y. S.; Li, C. B.; Gao, Z. C.; Li, G. S.; Chen, F. Q.; He, C. Y.; Zheng, Y.; Hu, S. P.; Zhong, J.; Wu, Y. H.; Li, H. W.; Luo, P. W.

    2016-04-01

    Lifetimes of the yrast states in 180Pt have been measured from 4+ to 8+ using the recoil distance Doppler-shift technique in the coincidence mode. These states were populated by the reaction 156Gd(28Si,4 n )180Pt at a beam energy of 144 MeV. The differential decay curve method was applied to determine the lifetimes from experimental coincidence data. The B (E 2 ) values extracted from lifetimes increase with increasing spin, implying rotor behavior, but do not show the typical shape coexistence where the B (E 2 ) values present a rapid increase at very low spins. Calculations based on the triaxial projected shell model were performed for the yrast states in 180Pt and the results of both energies and E 2 transition probabilities reproduce the experimental data very well. The result also shows that a better description of the yrast band in 180Pt requires consideration of the γ degree of freedom.

  5. Preparation of Saccharomyces cerevisiae expression plasmids.

    PubMed

    Drew, David; Kim, Hyun

    2012-01-01

    Expression plasmids for Saccharomyces cerevisiae offer a wide choice of vector copy number, promoters of varying strength and selection markers. These expression plasmids are usually shuttle vectors that can be propagated both in yeast and bacteria, making them useful in gene cloning. For heterologous production of membrane proteins, we used the green fluorescent protein (GFP) fusion technology which was previously developed in the Escherichia coli system. We designed an expression plasmid carrying an inducible GAL1 promoter, a gene encoding a membrane protein of interest and the GFP-octa-histidine sequence. Here we describe construction of multi-copy yeast expression plasmids by homologous recombination in S. cerevisiae. PMID:22454112

  6. Fermentation studies using Saccharomyces diastaticus yeast strains

    SciTech Connect

    Erratt, J.A.; Stewart, G.G.

    1981-01-01

    The yeast species, Saccharomyces diastaticus, has the ability to ferment starch and dextrin, because of the extracellular enzyme, glucoamylase, which hydrolyzes the starch/dextrin to glucose. A number of nonallelic genes--DEX 1, DEX 2, and dextrinase B which is allelic to STA 3--have been isolated, which impart to the yeast the ability to ferment dextrin. Various diploid yeast strains were constructed, each being either heterozygous or homozygous for the individual dextrinase genes. Using 12 (sup 0) plato hopped wort (30% corn adjunct) under agitated conditions, the fermentation rates of the various diploid yeast strains were monitored. A gene-dosage effect was exhibited by yeast strains containing DEX 1 or DEX 2, however, not with yeast strains containing dextrinase B (STA 3). The fermentation and growth rates and extents were determined under static conditions at 14.4 C and 21 C. With all yeast strains containing the dextrinase genes, both fermentation and growth were increased at the higher incubation temperature. Using 30-liter fermentors, beer was produced with the various yeast strains containing the dextrinase genes and the physical and organoleptic characteristics of the products were determined. The concentration of glucose in the beer was found to increase during a 3-mo storage period at 21 C, indicating that the glucoamylase from Saccharomyces diastaticus is not inactivated by pasteurization. (Refs. 36).

  7. Biocuration at the Saccharomyces genome database.

    PubMed

    Skrzypek, Marek S; Nash, Robert S

    2015-08-01

    Saccharomyces Genome Database is an online resource dedicated to managing information about the biology and genetics of the model organism, yeast (Saccharomyces cerevisiae). This information is derived primarily from scientific publications through a process of human curation that involves manual extraction of data and their organization into a comprehensive system of knowledge. This system provides a foundation for further analysis of experimental data coming from research on yeast as well as other organisms. In this review we will demonstrate how biocuration and biocurators add a key component, the biological context, to our understanding of how genes, proteins, genomes and cells function and interact. We will explain the role biocurators play in sifting through the wealth of biological data to incorporate and connect key information. We will also discuss the many ways we assist researchers with their various research needs. We hope to convince the reader that manual curation is vital in converting the flood of data into organized and interconnected knowledge, and that biocurators play an essential role in the integration of scientific information into a coherent model of the cell. PMID:25997651

  8. Metabolic Engineering of Probiotic Saccharomyces boulardii.

    PubMed

    Liu, Jing-Jing; Kong, In Iok; Zhang, Guo-Chang; Jayakody, Lahiru N; Kim, Heejin; Xia, Peng-Fei; Kwak, Suryang; Sung, Bong Hyun; Sohn, Jung-Hoon; Walukiewicz, Hanna E; Rao, Christopher V; Jin, Yong-Su

    2016-04-01

    Saccharomyces boulardiiis a probiotic yeast that has been used for promoting gut health as well as preventing diarrheal diseases. This yeast not only exhibits beneficial phenotypes for gut health but also can stay longer in the gut than Saccharomyces cerevisiae Therefore, S. boulardiiis an attractive host for metabolic engineering to produce biomolecules of interest in the gut. However, the lack of auxotrophic strains with defined genetic backgrounds has hampered the use of this strain for metabolic engineering. Here, we report the development of well-defined auxotrophic mutants (leu2,ura3,his3, and trp1) through clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9-based genome editing. The resulting auxotrophic mutants can be used as a host for introducing various genetic perturbations, such as overexpression or deletion of a target gene, using existing genetic tools forS. cerevisiae We demonstrated the overexpression of a heterologous gene (lacZ), the correct localization of a target protein (red fluorescent protein) into mitochondria by using a protein localization signal, and the introduction of a heterologous metabolic pathway (xylose-assimilating pathway) in the genome ofS. boulardii We further demonstrated that human lysozyme, which is beneficial for human gut health, could be secreted by S. boulardii Our results suggest that more sophisticated genetic perturbations to improveS. boulardii can be performed without using a drug resistance marker, which is a prerequisite for in vivo applications using engineeredS. boulardii. PMID:26850302

  9. Biocuration at the Saccharomyces Genome Database

    PubMed Central

    Skrzypek, Marek S.; Nash, Robert S.

    2015-01-01

    Saccharomyces Genome Database is an online resource dedicated to managing information about the biology and genetics of the model organism, yeast (Saccharomyces cerevisiae). This information is derived primarily from scientific publications through a process of human curation that involves manual extraction of data and their organization into a comprehensive system of knowledge. This system provides a foundation for further analysis of experimental data coming from research on yeast as well as other organisms. In this review we will demonstrate how biocuration and biocurators add a key component, the biological context, to our understanding of how genes, proteins, genomes and cells function and interact. We will explain the role biocurators play in sifting through the wealth of biological data to incorporate and connect key information. We will also discuss the many ways we assist researchers with their various research needs. We hope to convince the reader that manual curation is vital in converting the flood of data into organized and interconnected knowledge, and that biocurators play an essential role in the integration of scientific information into a coherent model of the cell. PMID:25997651

  10. PT quantum mechanics - Recent results

    NASA Astrophysics Data System (ADS)

    Bender, Carl M.

    2012-09-01

    Most quantum physicists believe that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under matrix transposition and complex conjugation) to be sure that the energy eigenvalues are real and that time evolution is unitary. However, the non-Dirac-hermitian Hamiltonian H = p2+ix3 has a real positive discrete spectrum and generates unitary time evolution and defines a fully consistent and physical quantum theory. Evidently, Dirac Hermiticity is too restrictive. While H = p2+ix3 is not Dirac Hermitian, it is PT symmetric (invariant under combined space reflection P and time reversal T). Another PT-symmetric Hamiltonian whose energy levels are real, positive and discrete is H = p2-x4, which contains an upside-down potential. The quantum mechanics defined by a PT-symmetric Hamiltonian is a complex generalization of ordinary quantum mechanics. When quantum mechanics and quantum field theory are extended into the complex domain, new kinds of theories having strange and remarkable properties emerge. In the past two years some of these properties have been verified in laboratory experiments. Here, we first discuss PT-symmetric Hamiltonians at a simple intuitive level and explain why the energy levels of such Hamiltonians may be real, positive, and discrete. Second, we describe a recent experiment in which the PT phase transition was observed. Third, we briefly mention that PT-symmetric theories can be useful at a fundamental level. While the double-scaling limit of an O(N)-symmetric gφ4 quantum field theory appears to be inconsistent because the critical value of g is negative, this limit is in fact not inconsistent because the critical theory is PT symmetric.

  11. Segmented Pt/Ru, Pt/Ni, and Pt/RuNi nanorods as model bifunctional catalysts for methanol oxidation.

    PubMed

    Liu, Fang; Lee, Jim Yang; Zhou, Wei Jiang

    2006-01-01

    Five-segment (Pt-Ru-Pt-Ru-Pt, Pt-Ni-Pt-Ni-Pt, and Pt-RuNi-Pt-RuNi-Pt) nanorods with the same overall rod length and the same total Pt segment length were prepared by sequential electrodeposition of the metals into the pores of commercially available anodic aluminum oxide (AAO) membranes. Field-emission scanning electron microscopy (FESEM) showed that the nanorods were about 210 nm in diameter and about 1.5 microm in length. The alternating Pt and oxophilic metal(s) segments could be easily differentiated in backscattered-electron images. X-ray diffraction (XRD) analysis of the nanorods indicated that Pt and Ni were polycrystalline with fcc structures, Ru was hcp, and the co-deposited RuNi adopted the nickel fcc structure with some negative shifts in the Bragg angles. The chemical states of Pt, Ru, and Ni on the nanorod surface were assayed by X-ray photoelectron spectroscopy (XPS), and the presence of Pt(0), Pt(II), Pt(IV), Ru(0), Ru(VI), Ni(0), and Ni(II) was observed. The nanorods were catalytically active for the room-temperature electrooxidation of methanol in acidic solutions. The relative rates of reaction showed the Pt-RuNi pair sites as having the lowest overpotential to dissociate water, the highest catalytic activity in methanol oxidation, and the strongest CO-tolerance in the potential window employed. The use of segmented nanorods with identifiable Pt-oxophilic metal(s) interfaces removes many of the ambiguities in the interpretation of experimental data from conventional alloy catalysts, thereby enabling a direct comparison of the activities of various types of pair sites in methanol oxidation. PMID:17193567

  12. Gains and Losses of Transcription Factor Binding Sites in Saccharomyces cerevisiae and Saccharomyces paradoxus.

    PubMed

    Schaefke, Bernhard; Wang, Tzi-Yuan; Wang, Chuen-Yi; Li, Wen-Hsiung

    2015-08-01

    Gene expression evolution occurs through changes in cis- or trans-regulatory elements or both. Interactions between transcription factors (TFs) and their binding sites (TFBSs) constitute one of the most important points where these two regulatory components intersect. In this study, we investigated the evolution of TFBSs in the promoter regions of different Saccharomyces strains and species. We divided the promoter of a gene into the proximal region and the distal region, which are defined, respectively, as the 200-bp region upstream of the transcription starting site and as the 200-bp region upstream of the proximal region. We found that the predicted TFBSs in the proximal promoter regions tend to be evolutionarily more conserved than those in the distal promoter regions. Additionally, Saccharomyces cerevisiae strains used in the fermentation of alcoholic drinks have experienced more TFBS losses than gains compared with strains from other environments (wild strains, laboratory strains, and clinical strains). We also showed that differences in TFBSs correlate with the cis component of gene expression evolution between species (comparing S. cerevisiae and its sister species Saccharomyces paradoxus) and within species (comparing two closely related S. cerevisiae strains). PMID:26220934

  13. Thermotolerant Kluyveromyces marxianus and Saccharomyces cerevisiae strains representing potentials for bioethanol production from Jerusalem artichoke by consolidated bioprocessing.

    PubMed

    Hu, Nan; Yuan, Bo; Sun, Juan; Wang, Shi-An; Li, Fu-Li

    2012-09-01

    Thermotolerant inulin-utilizing yeast strains are desirable for ethanol production from Jerusalem artichoke tubers by consolidated bioprocessing (CBP). To obtain such strains, 21 naturally occurring yeast strains isolated by using an enrichment method and 65 previously isolated Saccharomyces cerevisiae strains were investigated in inulin utilization, extracellular inulinase activity, and ethanol fermentation from inulin and Jerusalem artichoke tuber flour at 40 °C. The strains Kluyveromyces marxianus PT-1 (CGMCC AS2.4515) and S. cerevisiae JZ1C (CGMCC AS2.3878) presented the highest extracellular inulinase activity and ethanol yield in this study. The highest ethanol concentration in Jerusalem artichoke tuber flour fermentation (200 g L(-1)) at 40 °C achieved by K. marxianus PT-1 and S. cerevisiae JZ1C was 73.6 and 65.2 g L(-1), which corresponded to the theoretical ethanol yield of 90.0 and 79.7 %, respectively. In the range of 30 to 40 °C, temperature did not have a significant effect on ethanol production for both strains. This study displayed the distinctive superiority of K. marxianus PT-1 and S. cerevisiae JZ1C in the thermotolerance and utilization of inulin-type oligosaccharides reserved in Jerusalem artichoke tubers. It is proposed that both K. marxianus and S. cerevisiae have considerable potential in ethanol production from Jerusalem artichoke tubers by a high temperature CBP. PMID:22760784

  14. Social wasps are a Saccharomyces mating nest.

    PubMed

    Stefanini, Irene; Dapporto, Leonardo; Berná, Luisa; Polsinelli, Mario; Turillazzi, Stefano; Cavalieri, Duccio

    2016-02-23

    The reproductive ecology of Saccharomyces cerevisiae is still largely unknown. Recent evidence of interspecific hybridization, high levels of strain heterozygosity, and prion transmission suggest that outbreeding occurs frequently in yeasts. Nevertheless, the place where yeasts mate and recombine in the wild has not been identified. We found that the intestine of social wasps hosts highly outbred S. cerevisiae strains as well as a rare S. cerevisiae×S. paradoxus hybrid. We show that the intestine of Polistes dominula social wasps favors the mating of S. cerevisiae strains among themselves and with S. paradoxus cells by providing a succession of environmental conditions prompting cell sporulation and spores germination. In addition, we prove that heterospecific mating is the only option for European S. paradoxus strains to survive in the gut. Taken together, these findings unveil the best hidden secret of yeast ecology, introducing the insect gut as an environmental alcove in which crosses occur, maintaining and generating the diversity of the ascomycetes. PMID:26787874

  15. Sporulation in the Budding Yeast Saccharomyces cerevisiae

    PubMed Central

    Neiman, Aaron M.

    2011-01-01

    In response to nitrogen starvation in the presence of a poor carbon source, diploid cells of the yeast Saccharomyces cerevisiae undergo meiosis and package the haploid nuclei produced in meiosis into spores. The formation of spores requires an unusual cell division event in which daughter cells are formed within the cytoplasm of the mother cell. This process involves the de novo generation of two different cellular structures: novel membrane compartments within the cell cytoplasm that give rise to the spore plasma membrane and an extensive spore wall that protects the spore from environmental insults. This article summarizes what is known about the molecular mechanisms controlling spore assembly with particular attention to how constitutive cellular functions are modified to create novel behaviors during this developmental process. Key regulatory points on the sporulation pathway are also discussed as well as the possible role of sporulation in the natural ecology of S. cerevisiae. PMID:22084423

  16. [Urinary infection by Saccharomyces cerevisiae: Emerging yeast?].

    PubMed

    Elkhihal, B; Elhalimi, M; Ghfir, B; Mostachi, A; Lyagoubi, M; Aoufi, S

    2015-12-01

    Saccharomyces cerevisiae is a commensal yeast of the digestive, respiratory and genito-urinary tract. It is widely used as a probiotic for the treatment of post-antibiotic diarrhea. It most often occurs in immunocompromised patients frequently causing fungemia. We report the case of an adult diabetic patient who had a urinary tract infection due to S. cerevisiae. The disease started with urination associated with urinary frequency burns without fever. The diagnosis was established by the presence of yeasts on direct examination and positivity of culture on Sabouraud-chloramphenicol three times. The auxanogramme gallery (Auxacolor BioRad(®)) allowed the identification of S. cerevisiae. The patient was put on fluconazole with good outcome. This observation points out that this is an opportunistic yeast in immunocompromised patients. PMID:26522963

  17. Synchronization of the Budding Yeast Saccharomyces cerevisiae.

    PubMed

    Foltman, Magdalena; Molist, Iago; Sanchez-Diaz, Alberto

    2016-01-01

    A number of model organisms have provided the basis for our understanding of the eukaryotic cell cycle. These model organisms are generally much easier to manipulate than mammalian cells and as such provide amenable tools for extensive genetic and biochemical analysis. One of the most common model organisms used to study the cell cycle is the budding yeast Saccharomyces cerevisiae. This model provides the ability to synchronise cells efficiently at different stages of the cell cycle, which in turn opens up the possibility for extensive and detailed study of mechanisms regulating the eukaryotic cell cycle. Here, we describe methods in which budding yeast cells are arrested at a particular phase of the cell cycle and then released from the block, permitting the study of molecular mechanisms that drive the progression through the cell cycle. PMID:26519319

  18. Transcriptional Regulatory Networks in Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Lee, Tong Ihn; Rinaldi, Nicola J.; Robert, François; Odom, Duncan T.; Bar-Joseph, Ziv; Gerber, Georg K.; Hannett, Nancy M.; Harbison, Christopher T.; Thompson, Craig M.; Simon, Itamar; Zeitlinger, Julia; Jennings, Ezra G.; Murray, Heather L.; Gordon, D. Benjamin; Ren, Bing; Wyrick, John J.; Tagne, Jean-Bosco; Volkert, Thomas L.; Fraenkel, Ernest; Gifford, David K.; Young, Richard A.

    2002-10-01

    We have determined how most of the transcriptional regulators encoded in the eukaryote Saccharomyces cerevisiae associate with genes across the genome in living cells. Just as maps of metabolic networks describe the potential pathways that may be used by a cell to accomplish metabolic processes, this network of regulator-gene interactions describes potential pathways yeast cells can use to regulate global gene expression programs. We use this information to identify network motifs, the simplest units of network architecture, and demonstrate that an automated process can use motifs to assemble a transcriptional regulatory network structure. Our results reveal that eukaryotic cellular functions are highly connected through networks of transcriptional regulators that regulate other transcriptional regulators.

  19. Social wasps are a Saccharomyces mating nest

    PubMed Central

    Stefanini, Irene; Dapporto, Leonardo; Berná, Luisa; Polsinelli, Mario; Turillazzi, Stefano; Cavalieri, Duccio

    2016-01-01

    The reproductive ecology of Saccharomyces cerevisiae is still largely unknown. Recent evidence of interspecific hybridization, high levels of strain heterozygosity, and prion transmission suggest that outbreeding occurs frequently in yeasts. Nevertheless, the place where yeasts mate and recombine in the wild has not been identified. We found that the intestine of social wasps hosts highly outbred S. cerevisiae strains as well as a rare S. cerevisiae×S. paradoxus hybrid. We show that the intestine of Polistes dominula social wasps favors the mating of S. cerevisiae strains among themselves and with S. paradoxus cells by providing a succession of environmental conditions prompting cell sporulation and spores germination. In addition, we prove that heterospecific mating is the only option for European S. paradoxus strains to survive in the gut. Taken together, these findings unveil the best hidden secret of yeast ecology, introducing the insect gut as an environmental alcove in which crosses occur, maintaining and generating the diversity of the ascomycetes. PMID:26787874

  20. Glycerol production of various strains of saccharomyces

    SciTech Connect

    Radler, F.; Schuetz, H.

    1982-01-01

    The quantity of glycerol as principal by-product of the alcoholic fermentation depends to a large extent on the yeast strain. Different strains of Saccharomyces cerevisiae were found to form amounts of glycerol varying between 4.2 to 10.4 g/L. The formation of glycerol is regarded as a result of the competition between alcohol dehydrogenase and glycerol-3-phosphate dehydrogenase that compete for the reduced coenzyme NADH/sub 2/. High and low glycerol forming yeast strains showed large differences in the activity of glycerol-3-phosphate dehydrogenase and only small variation in the activity of alcohol dehydrogenase. The total amount of glycerol formed was also influenced by amino acids. In thiamine deficient media a decrease in glycerol formation was observed. Experiments indicate a correlation between the formation of acetaldehyde and glycerol and the production of cell mass that may be of practical interest. (Refs. 12).

  1. Characterization of NiPt, FePt, and NiFePt nanoparticles

    NASA Astrophysics Data System (ADS)

    Sutherland, Greg; Wood, Darren; Jackson, Amy; Warren, Andrew; Coffey, Kevin; Vanfleet, Richard

    2012-10-01

    Many metal alloys can form in chemically ordered structures, often resulting in significant changes in properties. The ordered structures are preferred at low temperatures and will go through an order-disorder phase transition at a critical temperature. The formation and stability of these ordered structures in alloy nanoparticles is not well understood but may give insight into the role size plays in phase transitions. To this end we are studying FePt, NiPt, and FeNiPt alloy nanoparticles. We will focus this presentation on the characterization of these nanoparticles in a Transmission Electron Microscope (TEM) for composition, size, and structure. These nanoparticles are made by co-sputtering the constituents and annealing at different temperatures in various gas mixtures. The nanoparticle samples are prepared for TEM viewing by wedge polishing. We find FePt to be ``well behaved'' meaning this alloy forms particles, retains the as deposited composition, and chemically orders as expected. However, the order-disorder temperature is too high for the desired further studies. NiPt, which has a lower order-disorder temperature, is not ``well behaved'' in that the nanoparticle compositions are not good matches to the as deposited conditions and no chemical ordering has been achieved even under conditions that should be sufficient based on bulk processing. We will discuss these results and possible implications.

  2. Prediction of Saccharomyces cerevisiae replication origins

    PubMed Central

    Breier, Adam M; Chatterji, Sourav; Cozzarelli, Nicholas R

    2004-01-01

    Background Autonomously replicating sequences (ARSs) function as replication origins in Saccharomyces cerevisiae. ARSs contain the 17 bp ARS consensus sequence (ACS), which binds the origin recognition complex. The yeast genome contains more than 10,000 ACS matches, but there are only a few hundred origins, and little flanking sequence similarity has been found. Thus, identification of origins by sequence alone has not been possible. Results We developed an algorithm, Oriscan, to predict yeast origins using similarity to 26 characterized origins. Oriscan used 268 bp of sequence, including the T-rich ACS and a 3' A-rich region. The predictions identified the exact location of the ACS. A total of 84 of the top 100 Oriscan predictions, and 56% of the top 350, matched known ARSs or replication protein binding sites. The true accuracy was even higher because we tested 25 discrepancies, and 15 were in fact ARSs. Thus, 94% of the top 100 predictions and an estimated 70% of the top 350 were correct. We compared the predictions to corresponding sequences in related Saccharomyces species and found that the ACSs of experimentally supported predictions show significant conservation. Conclusions The high accuracy of the predictions indicates that we have defined near-sufficient conditions for ARS activity, the A-rich region is a recognizable feature of ARS elements with a probable role in replication initiation, and nucleotide sequence is a reliable predictor of yeast origins. Oriscan detected most origins in the genome, demonstrating previously unrecognized generality in yeast replication origins and significant discriminatory power in the algorithm. PMID:15059255

  3. The Mitochondrial Genome Impacts Respiration but Not Fermentation in Interspecific Saccharomyces Hybrids

    PubMed Central

    Rigoulet, Michel; Salin, Benedicte; Masneuf-Pomarede, Isabelle; de Vienne, Dominique; Sicard, Delphine; Bely, Marina; Marullo, Philippe

    2013-01-01

    In eukaryotes, mitochondrial DNA (mtDNA) has high rate of nucleotide substitution leading to different mitochondrial haplotypes called mitotypes. However, the impact of mitochondrial genetic variant on phenotypic variation has been poorly considered in microorganisms because mtDNA encodes very few genes compared to nuclear DNA, and also because mitochondrial inheritance is not uniparental. Here we propose original material to unravel mitotype impact on phenotype: we produced interspecific hybrids between S. cerevisiae and S. uvarum species, using fully homozygous diploid parental strains. For two different interspecific crosses involving different parental strains, we recovered 10 independent hybrids per cross, and allowed mtDNA fixation after around 80 generations. We developed PCR-based markers for the rapid discrimination of S. cerevisiae and S. uvarum mitochondrial DNA. For both crosses, we were able to isolate fully isogenic hybrids at the nuclear level, yet possessing either S. cerevisiae mtDNA (Sc-mtDNA) or S. uvarum mtDNA (Su-mtDNA). Under fermentative conditions, the mitotype has no phenotypic impact on fermentation kinetics and products, which was expected since mtDNA are not necessary for fermentative metabolism. Alternatively, under respiratory conditions, hybrids with Sc-mtDNA have higher population growth performance, associated with higher respiratory rate. Indeed, far from the hypothesis that mtDNA variation is neutral, our work shows that mitochondrial polymorphism can have a strong impact on fitness components and hence on the evolutionary fate of the yeast populations. We hypothesize that under fermentative conditions, hybrids may fix stochastically one or the other mt-DNA, while respiratory environments may increase the probability to fix Sc-mtDNA. PMID:24086452

  4. PT-symmetric quantum theory

    NASA Astrophysics Data System (ADS)

    Bender, Carl M.

    2015-07-01

    The average quantum physicist on the street would say that a quantum-mechanical Hamiltonian must be Dirac Hermitian (invariant under combined matrix transposition and complex conjugation) in order to guarantee that the energy eigenvalues are real and that time evolution is unitary. However, the Hamiltonian H = p2 + ix3, which is obviously not Dirac Hermitian, has a positive real discrete spectrum and generates unitary time evolution, and thus it defines a fully consistent and physical quantum theory. Evidently, the axiom of Dirac Hermiticity is too restrictive. While H = p2 + ix3 is not Dirac Hermitian, it is PT symmetric; that is, invariant under combined parity P (space reflection) and time reversal T. The quantum mechanics defined by a PT-symmetric Hamiltonian is a complex generalization of ordinary quantum mechanics. When quantum mechanics is extended into the complex domain, new kinds of theories having strange and remarkable properties emerge. In the past few years, some of these properties have been verified in laboratory experiments. A particularly interesting PT-symmetric Hamiltonian is H = p2 - x4, which contains an upside-down potential. This potential is discussed in detail, and it is explained in intuitive as well as in rigorous terms why the energy levels of this potential are real, positive, and discrete. Applications of PT-symmetry in quantum field theory are also discussed.

  5. Lessons Learned from PT3

    ERIC Educational Resources Information Center

    Duffield, Judith A.; Moore, Julie A.

    2006-01-01

    Technology integration is a three-pronged effort. Not only do teachers, no matter the level, need to know how to use technology, they need to know how to integrate it into their curriculum. These two prongs were a consistent theme throughout the Preparing Tomorrow's Teachers to Use Technology (PT3) projects. Add access to technology to these and…

  6. PT3. [SITE 2002 Section].

    ERIC Educational Resources Information Center

    Thompson, Mary, Ed.; Price, Jerry, Ed.

    This document contains 142 papers on PT3 (Preparing Tomorrow's Teachers to use Technology) from the SITE (Society for Information Technology & Teacher Education) 2002 conference. Topics covered include: a technology in urban education summit; student professional development; meeting NCATE (National Council of Teachers of English) standards;…

  7. Force Sensitivity in Saccharomyces cerevisiae Flocculins

    PubMed Central

    Chan, Cho X. J.; El-Kirat-Chatel, Sofiane; Joseph, Ivor G.; Jackson, Desmond N.; Ramsook, Caleen B.; Dufrêne, Yves F.

    2016-01-01

    ABSTRACT Many fungal adhesins have short, β-aggregation-prone sequences that play important functional roles, and in the Candida albicans adhesin Als5p, these sequences cluster the adhesins after exposure to shear force. Here, we report that Saccharomyces cerevisiae flocculins Flo11p and Flo1p have similar β-aggregation-prone sequences and are similarly stimulated by shear force, despite being nonhomologous. Shear from vortex mixing induced the formation of small flocs in cells expressing either adhesin. After the addition of Ca2+, yeast cells from vortex-sheared populations showed greatly enhanced flocculation and displayed more pronounced thioflavin-bright surface nanodomains. At high concentrations, amyloidophilic dyes inhibited Flo1p- and Flo11p-mediated agar invasion and the shear-induced increase in flocculation. Consistent with these results, atomic force microscopy of Flo11p showed successive force-distance peaks characteristic of sequentially unfolding tandem repeat domains, like Flo1p and Als5p. Flo11p-expressing cells bound together through homophilic interactions with adhesion forces of up to 700 pN and rupture lengths of up to 600 nm. These results are consistent with the potentiation of yeast flocculation by shear-induced formation of high-avidity domains of clustered adhesins at the cell surface, similar to the activation of Candida albicans adhesin Als5p. Thus, yeast adhesins from three independent gene families use similar force-dependent interactions to drive cell adhesion. IMPORTANCE The Saccharomyces cerevisiae flocculins mediate the formation of cellular aggregates and biofilm-like mats, useful in clearing yeast from fermentations. An important property of fungal adhesion proteins, including flocculins, is the ability to form catch bonds, i.e., bonds that strengthen under tension. This strengthening is based, at least in part, on increased avidity of binding due to clustering of adhesins in cell surface nanodomains. This clustering depends

  8. Force Sensitivity in Saccharomyces cerevisiae Flocculins.

    PubMed

    Chan, Cho X J; El-Kirat-Chatel, Sofiane; Joseph, Ivor G; Jackson, Desmond N; Ramsook, Caleen B; Dufrêne, Yves F; Lipke, Peter N

    2016-01-01

    Many fungal adhesins have short, β-aggregation-prone sequences that play important functional roles, and in the Candida albicans adhesin Als5p, these sequences cluster the adhesins after exposure to shear force. Here, we report that Saccharomyces cerevisiae flocculins Flo11p and Flo1p have similar β-aggregation-prone sequences and are similarly stimulated by shear force, despite being nonhomologous. Shear from vortex mixing induced the formation of small flocs in cells expressing either adhesin. After the addition of Ca(2+), yeast cells from vortex-sheared populations showed greatly enhanced flocculation and displayed more pronounced thioflavin-bright surface nanodomains. At high concentrations, amyloidophilic dyes inhibited Flo1p- and Flo11p-mediated agar invasion and the shear-induced increase in flocculation. Consistent with these results, atomic force microscopy of Flo11p showed successive force-distance peaks characteristic of sequentially unfolding tandem repeat domains, like Flo1p and Als5p. Flo11p-expressing cells bound together through homophilic interactions with adhesion forces of up to 700 pN and rupture lengths of up to 600 nm. These results are consistent with the potentiation of yeast flocculation by shear-induced formation of high-avidity domains of clustered adhesins at the cell surface, similar to the activation of Candida albicans adhesin Als5p. Thus, yeast adhesins from three independent gene families use similar force-dependent interactions to drive cell adhesion. IMPORTANCE The Saccharomyces cerevisiae flocculins mediate the formation of cellular aggregates and biofilm-like mats, useful in clearing yeast from fermentations. An important property of fungal adhesion proteins, including flocculins, is the ability to form catch bonds, i.e., bonds that strengthen under tension. This strengthening is based, at least in part, on increased avidity of binding due to clustering of adhesins in cell surface nanodomains. This clustering depends on

  9. Effect of Pt layers on chemical ordering in FePt thin films

    NASA Astrophysics Data System (ADS)

    Gupta, R.; Medwal, R.; Sharma, P.; Mahapatro, A. K.; Annapoorni, S.

    2013-12-01

    The tunability in the structural and magnetic phases present in RF-sputtered Fe3Pt thin films over Si (1 0 0) substrates have been studied by introducing thin films of platinum (Pt) as an underlayer and/or overlayers. Annealing of the Fe3Pt thin films with Pt underlayers (Pt/Fe3Pt) structures at 600 °C for 1 h, indicates well organized nanostructured grains as imaged through an atomic force microscope (AFM). The evolution of superstructure peaks as well as the preferred orientation along (0 0 1) plane observed in the X-ray diffraction (XRD) study is well supported by the magnetic measurements. These annealed Pt/Fe3Pt structures show high magnetocrystalline anisotropy and the presence of hard phase with a coercivity of 8.5 kOe. Here, the annealing process allows the adjacent Pt atoms to diffuse into the Fe3Pt unit cells and triggers the structural transformation to chemically ordered L10 phase. An additional L12 phase is observed in the annealed Fe3Pt thin films with Pt overlayer and underlayer (Pt/Fe3Pt/Pt) tri-layered structures.

  10. Calcium control of Saccharomyces cerevisiae actin assembly.

    PubMed Central

    Greer, C; Schekman, R

    1982-01-01

    Low levels of Ca2+ dramatically influence the polymerization of Saccharomyces cerevisiae actin in KCl. The apparent critical concentration for polymerization (C infinity) increases eightfold in the presence of 0.1 mM Ca2+. This effect is rapidly reversed by the addition of ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid or of 0.1 mM Mg2+. Furthermore, the addition of Ca2+ to polymerized actin causes a reversible increase in the apparent C infinity. In the presence of Ca2+, at actin concentrations below the apparent C infinity, particles of 15 to 50 nm in diameter are seen instead of filaments. These particles are separated from soluble actin when Ca2+-treated filamentous actin is sedimented at high speed; both the soluble and particulate fractions retain Ca2+-sensitive polymerization. The Ca2+ effect is S. cerevisiae actin-specific: the C infinity for rabbit muscle actin is not affected by the presence of Ca2+ and S. cerevisiae actin. Ca2+ may act directly on S. cerevisiae actin to control the assembly state in vivo. Images PMID:6757718

  11. Killer systems of the yeast Saccharomyces cerevisiae

    SciTech Connect

    Nesterova, G.F.

    1989-01-01

    The killer systems of Saccharomyces cerevisiae are an unusual class of cytoplasmic symbionts of primitive eukaryotes. The genetic material of these symbionts is double-stranded RNA. They are characterized by the linearity of the genome, its fragmentation into a major and a minor fraction, which replicate separately, and their ability to control the synthesis of secretory mycocin proteins possessing a toxic action on closely related strains. The secretion of mycocins at the same time ensures acquiring of resistance to them. Strains containing killer symbionts are toxigenic and resistant to the action of their own toxin, but strains that are free of killer double-stranded RNAs are sensitive to the action of mycocins. The killer systems of S. cerevisiae have retained features relating them to viruses and are apparently the result of evolution of infectious viruses. The occurrences of such systems among monocellular eukaryotic organisms is an example of complication of the genome by means of its assembly from virus-like components. We discuss the unusual features of replication and the expression of killer systems and their utilization in the construction of vector molecules.

  12. Regulation of Phosphatidylcholine Biosynthesis in Saccharomyces cerevisiae

    PubMed Central

    Waechter, Charles J.; Lester, Robert L.

    1971-01-01

    Evidence is presented which indicates that the biosynthesis of phosphatidylcholine by the methylation pathway in growing cultures of Saccharomyces cerevisiae is repressed by the presence of choline in the growth medium. This result, obtained previously for glucose-grown cells, was also observed for lactate-grown cells, of which half of the phosphatidylcholine is mitochondrial. A respiration-deficient mutant of the parent wild-type strain has been studied, and its inability to form functional mitochondria cannot be due to an impaired methylation pathway, as it has been shown to incorporate 14C-CH3-methionine into all of the methylated glycerophosphatides. The incorporation rate is depressed by the inclusion of 1 mm choline in the growth medium, suggesting a regulatory effect similar to that demonstrated for the wild-type strain. The effects of choline on the glycerophospholipid composition of lactate and glucose-grown cells is presented. The repressive effects of the two related bases, mono- and dimethylethanolamine, were examined, and reduced levels of 14C-CH3-methionine incorporation were found for cells grown in the presence of these bases. The effect of choline on the methylation rates is reversible and glucosegrown cells regain the nonrepressed level of methylation activity in 60 to 80 min after removal of choline from the growth medium. Images PMID:5547992

  13. Inositol-Requiring Mutants of SACCHAROMYCES CEREVISIAE

    PubMed Central

    Culbertson, Michael R.; Henry, Susan A.

    1975-01-01

    Fifty-two inositol-requiring mutants of Saccharomyces cerevisiae were isolated following mutagenesis with ethyl methanesulfonate. Complementation and tetrad analysis revealed ten major complementation classes, representing ten independently segregating loci (designated ino1 through ino10) which recombined freely with their respective centromeres. Members of any given complementation class segregated as alleles of a single locus. Thirteen complementation subclasses were identified among thirty-six mutants which behaved as alleles of the ino1 locus. The complementation map for these mutants was circular.—Dramatic cell viability losses indicative of unbalanced growth were observed in liquid cultures of representative mutants under conditions of inositol starvation. Investigation of the timing, kinetics, and extent of cell death revealed that losses in cell viability in the range of 2-4 log orders could be prevented by the addition of inositol to the medium or by disruption of protein synthesis with cycloheximide. Mutants defective in nine of the ten loci identified in this study displayed these unusual characteristics. The results suggest an important physiological role for inositol that may be related to its cellular localization and function in membrane phospholipids. The possibility is discussed that inositol deficiency initiates the process of unbalanced growth leading to cell death through the loss of normal assembly, function, or integrity of biomembranes.—Part of this work has been reported in preliminary form (Culbertson and Henry 1974). PMID:1093935

  14. Filamentation of Metabolic Enzymes in Saccharomyces cerevisiae.

    PubMed

    Shen, Qing-Ji; Kassim, Hakimi; Huang, Yong; Li, Hui; Zhang, Jing; Li, Guang; Wang, Peng-Ye; Yan, Jun; Ye, Fangfu; Liu, Ji-Long

    2016-06-20

    Compartmentation via filamentation has recently emerged as a novel mechanism for metabolic regulation. In order to identify filament-forming metabolic enzymes systematically, we performed a genome-wide screening of all strains available from an open reading frame-GFP collection in Saccharomyces cerevisiae. We discovered nine novel filament-forming proteins and also confirmed those identified previously. From the 4159 strains, we found 23 proteins, mostly metabolic enzymes, which are capable of forming filaments in vivo. In silico protein-protein interaction analysis suggests that these filament-forming proteins can be clustered into several groups, including translational initiation machinery and glucose and nitrogen metabolic pathways. Using glutamine-utilising enzymes as examples, we found that the culture conditions affect the occurrence and length of the metabolic filaments. Furthermore, we found that two CTP synthases (Ura7p and Ura8p) and two asparagine synthetases (Asn1p and Asn2p) form filaments both in the cytoplasm and in the nucleus. Live imaging analyses suggest that metabolic filaments undergo sub-diffusion. Taken together, our genome-wide screening identifies additional filament-forming proteins in S. cerevisiae and suggests that filamentation of metabolic enzymes is more general than currently appreciated. PMID:27312010

  15. Progress in Metabolic Engineering of Saccharomyces cerevisiae

    PubMed Central

    Nevoigt, Elke

    2008-01-01

    Summary: The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic engineering, evolutionary engineering, and global transcription machinery engineering, in yeast strain improvement. It also summarizes existing tools for fine-tuning and regulating enzyme activities and thus metabolic pathways. Recent examples of yeast metabolic engineering for food, beverage, and industrial biotechnology (bioethanol and bulk and fine chemicals) follow. S. cerevisiae currently enjoys increasing popularity as a production organism in industrial (“white”) biotechnology due to its inherent tolerance of low pH values and high ethanol and inhibitor concentrations and its ability to grow anaerobically. Attention is paid to utilizing lignocellulosic biomass as a potential substrate. PMID:18772282

  16. Biosorption of heavy metals by Saccharomyces cerevisiae.

    PubMed

    Volesky, B; May-Phillips, H A

    1995-01-01

    Abundant and common yeast biomass has been examined for its capacity to sequester heavy metals from dilute aqueous solutions. Live and non-living biomass of Saccharomyces cerevisiae differs in the uptake of uranium, zinc and copper at the optimum pH 4-5. Culture growth conditions can influence the biosorbent metal uptake capacity which normally was: living and non-living brewer's yeast: U > Zn > Cd > Cu; non-living baker's yeast: Zn > (Cd) > U > Cu; living baker's yeast: Zn > Cu approximately (Cd) > U. Non-living brewer's yeast biomass accumulated 0.58 mmol U/g. The best biosorbent of zinc was non-living baker's yeast (approximately 0.56 mmol Zn/g). Dead cells of S. cerevisiae removed approximately 40% more uranium or zinc than the corresponding live cultures. Biosorption of uranium by S. cerevisiae was a rapid process reaching 60% of the final uptake value within the first 15 min of contact. Its deposition differing from that of other heavy metals more associated with the cell wall, uranium was deposited as fine needle-like crystals both on the inside and outside of the S. cerevisiae cells. PMID:7765919

  17. Stationary phase in the yeast Saccharomyces cerevisiae.

    PubMed Central

    Werner-Washburne, M; Braun, E; Johnston, G C; Singer, R A

    1993-01-01

    Growth and proliferation of microorganisms such as the yeast Saccharomyces cerevisiae are controlled in part by the availability of nutrients. When proliferating yeast cells exhaust available nutrients, they enter a stationary phase characterized by cell cycle arrest and specific physiological, biochemical, and morphological changes. These changes include thickening of the cell wall, accumulation of reserve carbohydrates, and acquisition of thermotolerance. Recent characterization of mutant cells that are conditionally defective only for the resumption of proliferation from stationary phase provides evidence that stationary phase is a unique developmental state. Strains with mutations affecting entry into and survival during stationary phase have also been isolated, and the mutations have been shown to affect at least seven different cellular processes: (i) signal transduction, (ii) protein synthesis, (iii) protein N-terminal acetylation, (iv) protein turnover, (v) protein secretion, (vi) membrane biosynthesis, and (vii) cell polarity. The exact nature of the relationship between these processes and survival during stationary phase remains to be elucidated. We propose that cell cycle arrest coordinated with the ability to remain viable in the absence of additional nutrients provides a good operational definition of starvation-induced stationary phase. PMID:8393130

  18. Synthesis of Morphinan Alkaloids in Saccharomyces cerevisiae

    PubMed Central

    Fossati, Elena; Narcross, Lauren; Ekins, Andrew; Falgueyret, Jean-Pierre; Martin, Vincent J. J.

    2015-01-01

    Morphinan alkaloids are the most powerful narcotic analgesics currently used to treat moderate to severe and chronic pain. The feasibility of morphinan synthesis in recombinant Saccharomyces cerevisiae starting from the precursor (R,S)-norlaudanosoline was investigated. Chiral analysis of the reticuline produced by the expression of opium poppy methyltransferases showed strict enantioselectivity for (S)-reticuline starting from (R,S)-norlaudanosoline. In addition, the P. somniferum enzymes salutaridine synthase (PsSAS), salutaridine reductase (PsSAR) and salutaridinol acetyltransferase (PsSAT) were functionally co-expressed in S. cerevisiae and optimization of the pH conditions allowed for productive spontaneous rearrangement of salutaridinol-7-O-acetate and synthesis of thebaine from (R)-reticuline. Finally, we reconstituted a 7-gene pathway for the production of codeine and morphine from (R)-reticuline. Yeast cell feeding assays using (R)-reticuline, salutaridine or codeine as substrates showed that all enzymes were functionally co-expressed in yeast and that activity of salutaridine reductase and codeine-O-demethylase likely limit flux to morphine synthesis. The results of this study describe a significant advance for the synthesis of morphinans in S. cerevisiae and pave the way for their complete synthesis in recombinant microbes. PMID:25905794

  19. Myo-inositol transport in Saccharomyces cerevisiae.

    PubMed

    Nikawa, J; Nagumo, T; Yamashita, S

    1982-05-01

    myo-Inositol uptake in Saccharomyces cerevisiae was dependent on temperature, time, and substrate concentration. The transport obeyed saturation kinetics with an apparent Km for myo-inositol of 0.1 mM, myo-Inositol analogs, such as scyllo-inositol, 2-inosose, mannitol, and 1,2-cyclohexanediol, had no effect on myo-inositol uptake, myo-Inositol uptake required metabolic energy. Removal of D-glucose resulted in a loss of activity, and azide and cyanide ions were inhibitory. In the presence of D-glucose, myo-inositol was accumulated in the cells against a concentration gradient. A myo-inositol transport mutant was isolated from UV-mutagenized S. cerevisiae cells using the replica-printing technique. The defect in myo-inositol uptake was due to a single nuclear gene mutation. The activities of L-serine and D-glucose transport were not affected by the mutation. Thus it was shown that S. cerevisiae grown under the present culture conditions possessed a single and specific myo-inositol transport system. myo-Inositol transport activity was reduced by the addition of myo-inositol to the culture medium. The activity was reversibly restored by the removal of myo-inositol from the medium. This restoration of activity was completely abolished by cycloheximide. PMID:7040334

  20. Synthesis of Morphinan Alkaloids in Saccharomyces cerevisiae.

    PubMed

    Fossati, Elena; Narcross, Lauren; Ekins, Andrew; Falgueyret, Jean-Pierre; Martin, Vincent J J

    2015-01-01

    Morphinan alkaloids are the most powerful narcotic analgesics currently used to treat moderate to severe and chronic pain. The feasibility of morphinan synthesis in recombinant Saccharomyces cerevisiae starting from the precursor (R,S)-norlaudanosoline was investigated. Chiral analysis of the reticuline produced by the expression of opium poppy methyltransferases showed strict enantioselectivity for (S)-reticuline starting from (R,S)-norlaudanosoline. In addition, the P. somniferum enzymes salutaridine synthase (PsSAS), salutaridine reductase (PsSAR) and salutaridinol acetyltransferase (PsSAT) were functionally co-expressed in S. cerevisiae and optimization of the pH conditions allowed for productive spontaneous rearrangement of salutaridinol-7-O-acetate and synthesis of thebaine from (R)-reticuline. Finally, we reconstituted a 7-gene pathway for the production of codeine and morphine from (R)-reticuline. Yeast cell feeding assays using (R)-reticuline, salutaridine or codeine as substrates showed that all enzymes were functionally co-expressed in yeast and that activity of salutaridine reductase and codeine-O-demethylase likely limit flux to morphine synthesis. The results of this study describe a significant advance for the synthesis of morphinans in S. cerevisiae and pave the way for their complete synthesis in recombinant microbes. PMID:25905794

  1. Genetic variation of the repeated MAL loci in natural populations of Saccharomyces cerevisiae and Saccharomyces paradoxus.

    PubMed

    Naumov, G I; Naumova, E S; Michels, C A

    1994-03-01

    In Saccharomyces cerevisiae, the gene functions required to ferment the disaccharide maltose are encoded by the MAL loci. Any one of five highly sequence homologous MAL loci identified in various S. cerevisiae strains (called MAL1, 2, 3, 4 and 6) is sufficient to ferment maltose. Each is a complex of three genes encoding maltose permease, maltase and a transcription activator. This family of loci maps to telomere-linked positions on different chromosomes and most natural strains contain more than one MAL locus. A number of naturally occurring, mutant alleles of MAL1 and MAL3 have been characterized which lack one or more of the gene functions encoded by the fully functional MAL loci. Loss of these gene functions appears to have resulted from mutation and/or rearrangement within the locus. Studies to date concentrated on the standard maltose fermenting strains of S. cerevisiae available from the Berkeley Yeast Stock Center collection. In this report we extend our genetic analysis of the MAL loci to a number of maltose fermenting and nonfermenting natural strains of S. cerevisiae and Saccharomyces paradoxus. No new MAL loci were discovered but several new mutant alleles of MAL1 were identified. The evolution of this gene family is discussed. PMID:8005435

  2. PT AND PT/NI "NEEDLE" ELETROCATALYSTS ON CARBON NANOTUBES WITH HIGH ACTIVITY FOR THE ORR

    SciTech Connect

    Colon-Mercado, H.

    2011-11-10

    Platinum and platinum/nickel alloy electrocatalysts supported on graphitized (gCNT) or nitrogen doped carbon nanotubes (nCNT) are prepared and characterized. Pt deposition onto carbon nanotubes results in Pt 'needle' formations that are 3.5 nm in diameter and {approx}100 nm in length. Subsequent Ni deposition and heat treatment results in PtNi 'needles' with an increased diameter. All Pt and Pt/Ni materials were tested as electrocatalysts for the oxygen reduction reaction (ORR). The Pt and Pt/Ni catalysts showed excellent performance for the ORR, with the heat treated PtNi/gCNT (1.06 mA/cm{sup 2}) and PtNi/nCNT (0.664 mA/cm{sup 2}) showing the highest activity.

  3. The Role of Pt Complex on the Synthesis of FePt by Polyol Process

    SciTech Connect

    Aizawa, S.; Tohji, K.; Jeyadevan, B.

    2008-02-25

    Target materials in this experiment were FePt alloy nanoparticles with face-centered tetragonal structure, narrow size distribution, and the size of 6-8 nm. This type of materials was expected to have high recording-density of 1 Tbit/inch{sup 2} with high magnetic anisotropy. In this study, a detailed investigation was carried out to understand the reduction characteristics of Pt complexes, and FePt alloy nanoparticles with diameters larger than 6 nm was try to synthesize. For the synthesis of Pt nanoparticles by using polyol process, three kinds of Pt complexes, namely, H{sub 2}PtCl{sub 6}, Pt(EDTA), and Pt(acac){sub 2} was used. The size of Pt metal nanoparticles was only few nm in the case of single Pt complex, while it was increased to 7-10 nm in the case of mixed Pt complex and adjusting the reaction temperature increasing ratio. FePt alloy nanoparticles with the diameter of 7-8 nm, distorted shape, and narrow size distribution were successfully synthesized. However, composition ratio of the particle was Fe{sub 12-21}Pt{sub 79-88}, nevertheless the ratio of a Fe:Pt in the original solution was 2:1.

  4. Low Pt content direct methanol fuel cell anode catalyst: nanophase PtRuNiZr

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram R. (Inventor); Whitacre, Jay F. (Inventor)

    2010-01-01

    A method for the preparation of a metallic material having catalytic activity that includes synthesizing a material composition comprising a metal content with a lower Pt content than a binary alloy containing Pt but that displays at least a comparable catalytic activity on a per mole Pt basis as the binary alloy containing Pt; and evaluating a representative sample of the material composition to ensure that the material composition displays a property of at least a comparable catalytic activity on a per mole Pt basis as a representative binary alloy containing Pt. Furthermore, metallic compositions are disclosed that possess substantial resistance to corrosive acids.

  5. Organization of the SUC gene family in Saccharomyces.

    PubMed Central

    Carlson, M; Botstein, D

    1983-01-01

    The SUC gene family of yeast (Saccharomyces) includes six structural genes for invertase (SUC1 through SUC5 and SUC7) found at unlinked chromosomal loci. A given yeast strain does not usually carry SUC+ alleles at all six loci; the natural negative alleles are called suc0 alleles. Cloned SUC2 DNA probes were used to investigate the physical structure of the SUC gene family in laboratory strains, commercial wine strains, and different Saccharomyces species. The active SUC+ genes are homologous. The suc0 allele at the SUC2 locus (suc2(0) in some strains is a silent gene or pseudogene. Other SUC loci carrying suc0 alleles appear to lack SUC DNA sequences. These findings imply that SUC genes have transposed to different chromosomal locations in closely related Saccharomyces strains. Images PMID:6843548

  6. Direct Determination of the Ionization Energies of PtC, PtO, and PtO2 with VUVRadiation

    SciTech Connect

    Citir, Murat; Metz, Ricardo B.; Belau, Leonid; Ahmed, Musahid

    2008-07-21

    Photoionization efficiency curves were measured for gas-phase PtC, PtO, and PtO2 using tunable vacuum ultraviolet (VUV) radiation at the Advanced Light Source. The molecules were prepared by laser ablation of a platinum tube, followed by reaction with CH4 or N2O and supersonic expansion. These measurements providethe first directly measured ionization energy for PtC, IE(PtC) = 9.45 +- 0.05 eV. The direct measurement also gives greatly improved ionization energies for the platinum oxides, IE(PtO) = 10.0 +- 0.1 eV and IE(PtO2) = 11.35 +- 0.05 eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to greatly improved 0 K bond dissociation energies for the neutrals: D0(Pt-C) = 5.95 +- 0.07 eV, D0(Pt-O)= 4.30 +- 0.12 eV, and D0(OPt-O) = 4.41 +- 0.13 eV, as well as enthalpies of formation for the gas-phase molecules Delta H0 f,0(PtC(g)) = 701 +- 7 kJ/mol, Delta H0f,0(PtO(g)) = 396 +- 12 kJ/mol, and Delta H0f,0(PtO2(g)) = 218 +- 11 kJ/mol. Much of the error in previous Knudsen cell measurements of platinum oxide bond dissociation energies is due to the use of thermodynamic second law extrapolations. Third law values calculated using statistical mechanical thermodynamic functions are in much better agreement with values obtained from ionization energies and ion energetics. These experiments demonstrate that laser ablation production with direct VUV ionization measurements is a versatile tool to measure ionization energies and bond dissociation energies for catalytically interesting species such as metal oxides and carbides.

  7. Regulation of Cation Balance in Saccharomyces cerevisiae

    PubMed Central

    Cyert, Martha S.; Philpott, Caroline C.

    2013-01-01

    All living organisms require nutrient minerals for growth and have developed mechanisms to acquire, utilize, and store nutrient minerals effectively. In the aqueous cellular environment, these elements exist as charged ions that, together with protons and hydroxide ions, facilitate biochemical reactions and establish the electrochemical gradients across membranes that drive cellular processes such as transport and ATP synthesis. Metal ions serve as essential enzyme cofactors and perform both structural and signaling roles within cells. However, because these ions can also be toxic, cells have developed sophisticated homeostatic mechanisms to regulate their levels and avoid toxicity. Studies in Saccharomyces cerevisiae have characterized many of the gene products and processes responsible for acquiring, utilizing, storing, and regulating levels of these ions. Findings in this model organism have often allowed the corresponding machinery in humans to be identified and have provided insights into diseases that result from defects in ion homeostasis. This review summarizes our current understanding of how cation balance is achieved and modulated in baker’s yeast. Control of intracellular pH is discussed, as well as uptake, storage, and efflux mechanisms for the alkali metal cations, Na+ and K+, the divalent cations, Ca2+ and Mg2+, and the trace metal ions, Fe2+, Zn2+, Cu2+, and Mn2+. Signal transduction pathways that are regulated by pH and Ca2+ are reviewed, as well as the mechanisms that allow cells to maintain appropriate intracellular cation concentrations when challenged by extreme conditions, i.e., either limited availability or toxic levels in the environment. PMID:23463800

  8. Combinatorial Cis-regulation in Saccharomyces Species

    PubMed Central

    Spivak, Aaron T.; Stormo, Gary D.

    2016-01-01

    Transcriptional control of gene expression requires interactions between the cis-regulatory elements (CREs) controlling gene promoters. We developed a sensitive computational method to identify CRE combinations with conserved spacing that does not require genome alignments. When applied to seven sensu stricto and sensu lato Saccharomyces species, 80% of the predicted interactions displayed some evidence of combinatorial transcriptional behavior in several existing datasets including: (1) chromatin immunoprecipitation data for colocalization of transcription factors, (2) gene expression data for coexpression of predicted regulatory targets, and (3) gene ontology databases for common pathway membership of predicted regulatory targets. We tested several predicted CRE interactions with chromatin immunoprecipitation experiments in a wild-type strain and strains in which a predicted cofactor was deleted. Our experiments confirmed that transcription factor (TF) occupancy at the promoters of the CRE combination target genes depends on the predicted cofactor while occupancy of other promoters is independent of the predicted cofactor. Our method has the additional advantage of identifying regulatory differences between species. By analyzing the S. cerevisiae and S. bayanus genomes, we identified differences in combinatorial cis-regulation between the species and showed that the predicted changes in gene regulation explain several of the species-specific differences seen in gene expression datasets. In some instances, the same CRE combinations appear to regulate genes involved in distinct biological processes in the two different species. The results of this research demonstrate that (1) combinatorial cis-regulation can be inferred by multi-genome analysis and (2) combinatorial cis-regulation can explain differences in gene expression between species. PMID:26772747

  9. Combinatorial Cis-regulation in Saccharomyces Species.

    PubMed

    Spivak, Aaron T; Stormo, Gary D

    2016-01-01

    Transcriptional control of gene expression requires interactions between the cis-regulatory elements (CREs) controlling gene promoters. We developed a sensitive computational method to identify CRE combinations with conserved spacing that does not require genome alignments. When applied to seven sensu stricto and sensu lato Saccharomyces species, 80% of the predicted interactions displayed some evidence of combinatorial transcriptional behavior in several existing datasets including: (1) chromatin immunoprecipitation data for colocalization of transcription factors, (2) gene expression data for coexpression of predicted regulatory targets, and (3) gene ontology databases for common pathway membership of predicted regulatory targets. We tested several predicted CRE interactions with chromatin immunoprecipitation experiments in a wild-type strain and strains in which a predicted cofactor was deleted. Our experiments confirmed that transcription factor (TF) occupancy at the promoters of the CRE combination target genes depends on the predicted cofactor while occupancy of other promoters is independent of the predicted cofactor. Our method has the additional advantage of identifying regulatory differences between species. By analyzing the S. cerevisiae and S. bayanus genomes, we identified differences in combinatorial cis-regulation between the species and showed that the predicted changes in gene regulation explain several of the species-specific differences seen in gene expression datasets. In some instances, the same CRE combinations appear to regulate genes involved in distinct biological processes in the two different species. The results of this research demonstrate that (1) combinatorial cis-regulation can be inferred by multi-genome analysis and (2) combinatorial cis-regulation can explain differences in gene expression between species. PMID:26772747

  10. Spin-flipping in Pt and at Co/Pt interfaces

    NASA Astrophysics Data System (ADS)

    Nguyen, H. Y. T.; Pratt, W. P.; Bass, J.

    2014-06-01

    There has been recent controversy about the magnitude of spin-flipping in the heavy metal Pt, characterized by the spin-diffusion length lsfPt. We propose a resolution of this controversy, and also present evidence for the importance of a phenomenon neglected in prior studies of transport across sputtered Ferromagnet/Pt (F/Pt) interfaces, spin-flipping at the interface. The latter is characterized by an interface spin-flipping parameter, δCo/Pt, that specifies the probability P=[1-exp(-δ)] of a conduction electron flipping its spin direction as it traverses a Co/Pt interface. From studies of the Current-Perpendicular-to-Plane (CPP) Resistances and Magnetoresistances of sputtered ferromagnetically coupled Co/Pt multilayers by themselves, and embedded within Py-based Double Exchange-biased Spin-Valves, we derive values at 4.2 K of δCo/Pt=0.9-0.2+0.5, interface specific resistance, ARCo/Pt*=0.74±0.15 fΩ m2, and interface spin-scattering asymmetry, γCo/Pt=0.53±0.12. This value of δCo/Pt is much larger than ones previously found for five other interfaces involving Co but not Pt. To derive δ requires knowledge of lsfPt for our sputtered Pt, which we obtain from separate measurements. Combining our results with those from others, we find that lsfPt for Pt is approximately proportional to the inverse resistivity, 1/ρPt.

  11. Analysis of the Saccharomyces cerevisiae proteome with PeptideAtlas

    PubMed Central

    King, Nichole L; Deutsch, Eric W; Ranish, Jeffrey A; Nesvizhskii, Alexey I; Eddes, James S; Mallick, Parag; Eng, Jimmy; Desiere, Frank; Flory, Mark; Martin, Daniel B; Kim, Bong; Lee, Hookeun; Raught, Brian; Aebersold, Ruedi

    2006-01-01

    We present the Saccharomyces cerevisiae PeptideAtlas composed from 47 diverse experiments and 4.9 million tandem mass spectra. The observed peptides align to 61% of Saccharomyces Genome Database (SGD) open reading frames (ORFs), 49% of the uncharacterized SGD ORFs, 54% of S. cerevisiae ORFs with a Gene Ontology annotation of 'molecular function unknown', and 76% of ORFs with Gene names. We highlight the use of this resource for data mining, construction of high quality lists for targeted proteomics, validation of proteins, and software development. PMID:17101051

  12. Guiding SPPs with PT-symmetry

    PubMed Central

    Yang, Fan; Lei Mei, Zhong

    2015-01-01

    The concept of parity-time (PT) symmetry in SPPs is proposed and confirmed for the first time in this work. By introducing periodic modulation of the effective refractive index in SPP system, the asymmetric propagation is theoretically predicted and numerically demonstrated. After validation of this concept, we apply it in two applications: PT-waveguide and PT-cloak. Both two applications further illustrate the wide applicability of this concept in SPP system. PMID:26446520

  13. Pt{sub 3}Au and PtAu clusters: Electronic states and potential energy surfaces

    SciTech Connect

    Dai, D.; Balasubramanian, K.

    1994-03-15

    We carried out complete active space multiconfiguration self-consistent-field calculations followed by multireference singles+doubles configuration interaction with the Davidson correction which included up to 3.55 million configurations employing relativistic effective core potentials on Pt{sub 3}+Au and PtAu clusters. Four low-lying electronic states were identified for Pt{sub 3}+Au. The {sup 2}{ital A}{sub 2} electronic state ({ital C}{sub 3{ital v}}) was found to be the ground state of Pt{sub 3}Au. Spin--orbit effects were found to be significant. We also computed six low-lying electronic states of PtAu and four low-lying electronic states of PtAu{sup +}. The 5/2 ({sup 2}{Delta}) and 0{sup +}({sup 1}{Sigma}{sup +}) states were found to be the ground states of PtAu and PtAu{sup +}, respectively.

  14. Physics of YbBiPt

    SciTech Connect

    Thompson, J.D.; Canfield, P.C.; Lacerda, A.; Hundley, M.F.; Fisk, Z. ); Ott, H.R.; Felder, E.; Chernikov, M. ); Maple, M.B.; Visani, P.; Seaman, C.L.; Lopez de la Torre, M.A. ); Aeppli, G. )

    1992-09-15

    YbBiPt has a low temperature linear specific heat coefficient of 8J/mole-Yb K{sup 2} and a small specific-heat anomaly at 0.4K. We discuss new experiments on specific-heat of diluted YbBiPt, and magnetic field dependent effects and electrical resistivity in pure YbBiPt. We argue that in this material the Kondo and crystal-field energy scales are small and of comparable magnitude, placing YbBiPt in the same class as many Uranium heavy-electron compounds.

  15. Magnetic properties and microstructure of FePtB, FePt(B-Ag) granular films

    NASA Astrophysics Data System (ADS)

    Tsai, Jai-Lin; Huang, Jian-Chiang; Tai, Hsueh-Wei; Tsai, Wen-Chieh; Lin, Yi-Cheng

    2013-03-01

    Multilayers [FePt(1 nm)/B(t nm)]10 (t=0.05-0.6) were alternately deposited on a glass substrate and subsequently annealed by the rapid thermal process (RTP) at 800 °C for 3 min. After RTP, FePt and B layers intermix to form the FePtB film with (0 0 1) texture. The ordering degree of FePt was slightly increased with doped B. The (Fe-Pt)100-xBx (x=0, 5, 10) films show perpendicular magnetization and the minor FeB phase was indexed in isotropic (Fe-Pt)100-xBx (x=30, 40, 60) films. By adding Ag into (Fe-Pt)95B5 film, the ordering degree was slightly increased in (Fe-Pt)95(B0.9Ag0.1)5 film. In (Fe-Pt)100-xBx (x=5, 10) and (Fe-Pt)95(B0.9Ag0.1)5 granular films, the intermixed B or Ag atoms were diffused among FePt grain boundaries to isolate and refine FePt grains uniformly with average grain sizes of 20, 15, and 6.7 nm, respectively.

  16. Bulk structures of PtO and PtO2 from density functional calculations

    NASA Astrophysics Data System (ADS)

    Nomiyama, Ricardo K.; Piotrowski, Maurício J.; da Silva, Juarez L. F.

    2011-09-01

    Platinum plays an important role in catalysis and electrochemistry, and it is known that the direct interaction of oxygen with Pt surfaces can lead to the formation of platinum oxides (PtOx), which can affect the reactivity. To contribute to the atomistic understanding of the atomic structure of PtOx, we report a density functional theory study of the atomic structure of bulk PtOx (1≤x≤2). From our calculations, we identified a lowest-energy structure (GeS type, space group Pnma) for PtO, which is 0.181 eV lower in energy than the structure suggested by W. J. Moore and L. Pauling [J. Am. Chem. Soc. 10.1021/ja01850a07463, 1392 (1941)] (PtS type). Furthermore, two atomic structures were identified for PtO2, which are almost degenerate in energy with the lowest-energy structure reported so far for PtO2 (CaCl2 type). Based on our results and analysis, we suggest that Pt and O atoms tend to form octahedron motifs in PtOx even at lower O composition by the formation of Pt-Pt bonds.

  17. Synthesis of ribosomes in Saccharomyces cerevisiae.

    PubMed Central

    Warner, J R

    1989-01-01

    The assembly of a eucaryotic ribosome requires the synthesis of four ribosomal ribonucleic acid (RNA) molecules and more than 75 ribosomal proteins. It utilizes all three RNA polymerases; it requires the cooperation of the nucleus and the cytoplasm, the processing of RNA, and the specific interaction of RNA and protein molecules. It is carried out efficiently and is exquisitely sensitive to the needs of the cell. Our current understanding of this process in the genetically tractable yeast Saccharomyces cerevisiae is reviewed. The ribosomal RNA genes are arranged in a tandem array of 100 to 200 copies. This tandem array has led to unique ways of carrying out a number of functions. Replication is asymmetric and does not initiate from every autonomously replicating sequence. Recombination is suppressed. Transcription of the major ribosomal RNA appears to involve coupling between adjacent transcription units, which are separated by the 5S RNA transcription unit. Genes for many ribosomal proteins have been cloned and sequenced. Few are linked; most are duplicated; most have an intron. There is extensive homology between yeast ribosomal proteins and those of other species. Most, but not all, of the ribosomal protein genes have one or two sites that are essential for their transcription and that bind a common transcription factor. This factor binds also to many other places in the genome, including the telomeres. There is coordinated transcription of the ribosomal protein genes under a variety of conditions. However, the cell seems to possess no mechanism for regulating the transcription of individual ribosomal protein genes in response either to a deficiency or an excess of a particular ribosomal protein. A deficiency causes slow growth. Any excess ribosomal protein is degraded very rapidly, with a half-life of 1 to 5 min. Unlike most types of cells, yeast cells appear not to regulate the translation of ribosomal proteins. However, in the case of ribosomal protein L32

  18. Thermal resistance of Saccharomyces yeast ascospores in beers.

    PubMed

    Milani, Elham A; Gardner, Richard C; Silva, Filipa V M

    2015-08-01

    The industrial production of beer ends with a process of thermal pasteurization. Saccharomyces cerevisiae and Saccharomyces pastorianus are yeasts used to produce top and bottom fermenting beers, respectively. In this research, first the sporulation rate of 12 Saccharomyces strains was studied. Then, the thermal resistance of ascospores of three S. cerevisiae strains (DSMZ 1848, DSMZ 70487, Ethanol Red(®)) and one strain of S. pastorianus (ATCC 9080) was determined in 4% (v/v) ethanol lager beer. D60 °C-values of 11.2, 7.5, 4.6, and 6.0 min and z-values of 11.7, 14.3, 12.4, and 12.7 °C were determined for DSMZ 1848, DSMZ 70487, ATCC 9080, and Ethanol Red(®), respectively. Lastly, experiments with 0 and 7% (v/v) beers were carried out to investigate the effect of ethanol content on the thermal resistance of S. cerevisiae (DSMZ 1848). D55 °C-values of 34.2 and 15.3 min were obtained for 0 and 7% beers, respectively, indicating lower thermal resistance in the more alcoholic beer. These results demonstrate similar spore thermal resistance for different Saccharomyces strains and will assist in the design of appropriate thermal pasteurization conditions for preserving beers with different alcohol contents. PMID:25996521

  19. Social wasps promote social behavior in Saccharomyces spp.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This commentary provides background and an evaluation of a paper to be published in the Proceedings of the National Academy of Sciences in which social wasps were found to harbor significant populations of two species of the yeast genus Saccharomyces. Apparently, the yeasts were acquired during feed...

  20. Analysis of the RNA Content of the Yeast "Saccharomyces Cerevisiae"

    ERIC Educational Resources Information Center

    Deutch, Charles E.; Marshall, Pamela A.

    2008-01-01

    In this article, the authors describe an interconnected set of relatively simple laboratory experiments in which students determine the RNA content of yeast cells and use agarose gel electrophoresis to separate and analyze the major species of cellular RNA. This set of experiments focuses on RNAs from the yeast "Saccharomyces cerevisiae", a…

  1. Improving biomass sugar utilization by engineered Saccharomyces cerevisiae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The efficient utilization of all available sugars in lignocellulosic biomass, which is more abundant than available commodity crops and starch, represents one of the most difficult technological challenges for the production of bioethanol. The well-studied yeast Saccharomyces cerevisiae has played a...

  2. Molecular mechanisms of ethanol tolerance in Saccharomyces cerevisiae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The yeast Saccharomyces cerevisiae is a superb ethanol producer, yet sensitive to ethanol at higher concentrations especially under high gravity or very high gravity fermentation conditions. Although significant efforts have been made to study ethanol-stress response in past decades, molecular mecha...

  3. Saccharomyces cerevisiae boulardii transient fungemia after intravenous self-inoculation.

    PubMed

    Cohen, Lola; Ranque, Stéphane; Raoult, Didier

    2013-02-14

    We report the case of a young psychotic intravenous drug user injecting herself with Saccharomyces cervisiae (boulardii). She experienced a 24 h fever, resolving spontaneously confirming, quasi experimentally, the inocuity of this yeast in a non-immunocompromised host. PMID:24432219

  4. Nonlinear waves in PT -symmetric systems

    NASA Astrophysics Data System (ADS)

    Konotop, Vladimir V.; Yang, Jianke; Zezyulin, Dmitry A.

    2016-07-01

    Recent progress on nonlinear properties of parity-time (PT )-symmetric systems is comprehensively reviewed in this article. PT symmetry started out in non-Hermitian quantum mechanics, where complex potentials obeying PT symmetry could exhibit all-real spectra. This concept later spread out to optics, Bose-Einstein condensates, electronic circuits, and many other physical fields, where a judicious balancing of gain and loss constitutes a PT -symmetric system. The natural inclusion of nonlinearity into these PT systems then gave rise to a wide array of new phenomena which have no counterparts in traditional dissipative systems. Examples include the existence of continuous families of nonlinear modes and integrals of motion, stabilization of nonlinear modes above PT -symmetry phase transition, symmetry breaking of nonlinear modes, distinctive soliton dynamics, and many others. In this article, nonlinear PT -symmetric systems arising from various physical disciplines are presented, nonlinear properties of these systems are thoroughly elucidated, and relevant experimental results are described. In addition, emerging applications of PT symmetry are pointed out.

  5. Linearization of Pt resistance temperature measurement circuit

    NASA Astrophysics Data System (ADS)

    Li, Chuan-xiang

    2001-09-01

    A correction method for non-linear Pt resistance temperature measurement based on the principle of A/D conversion is introduced. The design principle of Pt resistance linear temperature measurement is analyzed and a new method for interfacing A/D converter with single chip computer 89c52 is provided together with the experimental data.

  6. Shape-Controlled Synthesis of Pt Nanopeanuts.

    PubMed

    Zhang, Xuemei; Xia, Zengzilu; Huang, Yingzhou; Jia, Yunpeng; Sun, Xiaonan; Li, Yu; Li, Xueming; Wu, Rui; Liu, Anping; Qi, Xueqiang; Wang, Shuxia; Wen, Weijia

    2016-01-01

    Exploring the novel shape of Pt nanoparticles is one of the most useful ways to improve the electrocatalytic performance of Pt in fuel cells. In this work, the Pt nanopeanuts consisting of two nanospheres grown together have been fabricated through a two-step polyol method. The high resolution scanning electron microscope (SEM) images and energy dispersive x-ray (EDX) spectrum collected at adjacent part point out the Pt nanopeanut is apparently different from the two physical attached nanospheres. To understand the growth mechanism of this nanopeanut, the final products in different synthesis situations are studied. The results indicate the interesting morphology of Pt nanopeanuts mainly benefit from the chemical reagent (FeCl3) while the size and homogeneity are greatly affected by the temperature. Furthermore, the electrocatalytic activity of the Pt nanopeanuts has also been demonstrated here. Our two-step synthesis of Pt nanopeanuts not only enlarges the group of Pt nanoparticles, but also provides a beneficial strategy for the synthesis of novel metal nanoparticles. PMID:27528078

  7. AN ANIMAL MODEL OF PLATINUM (PT) HYPERSENSITIVITY

    EPA Science Inventory

    Exposure to Pt salts has been associated with occupational asthma. Pt, the most active component and widely used metal in catalytic converters, is released in automobile exhaust and is a proposed diesel fuel additive. Thus, with the potential for widespread environmental distrib...

  8. Shape-Controlled Synthesis of Pt Nanopeanuts

    PubMed Central

    Zhang, Xuemei; Xia, Zengzilu; Huang, Yingzhou; Jia, Yunpeng; Sun, Xiaonan; Li, Yu; Li, Xueming; Wu, Rui; Liu, Anping; Qi, Xueqiang; Wang, Shuxia; Wen, Weijia

    2016-01-01

    Exploring the novel shape of Pt nanoparticles is one of the most useful ways to improve the electrocatalytic performance of Pt in fuel cells. In this work, the Pt nanopeanuts consisting of two nanospheres grown together have been fabricated through a two-step polyol method. The high resolution scanning electron microscope (SEM) images and energy dispersive x-ray (EDX) spectrum collected at adjacent part point out the Pt nanopeanut is apparently different from the two physical attached nanospheres. To understand the growth mechanism of this nanopeanut, the final products in different synthesis situations are studied. The results indicate the interesting morphology of Pt nanopeanuts mainly benefit from the chemical reagent (FeCl3) while the size and homogeneity are greatly affected by the temperature. Furthermore, the electrocatalytic activity of the Pt nanopeanuts has also been demonstrated here. Our two-step synthesis of Pt nanopeanuts not only enlarges the group of Pt nanoparticles, but also provides a beneficial strategy for the synthesis of novel metal nanoparticles. PMID:27528078

  9. Introducing a New Breed of Wine Yeast: Interspecific Hybridisation between a Commercial Saccharomyces cerevisiae Wine Yeast and Saccharomyces mikatae

    PubMed Central

    Bellon, Jennifer R.; Schmid, Frank; Capone, Dimitra L.; Dunn, Barbara L.; Chambers, Paul J.

    2013-01-01

    Interspecific hybrids are commonplace in agriculture and horticulture; bread wheat and grapefruit are but two examples. The benefits derived from interspecific hybridisation include the potential of generating advantageous transgressive phenotypes. This paper describes the generation of a new breed of wine yeast by interspecific hybridisation between a commercial Saccharomyces cerevisiae wine yeast strain and Saccharomyces mikatae, a species hitherto not associated with industrial fermentation environs. While commercially available wine yeast strains provide consistent and reliable fermentations, wines produced using single inocula are thought to lack the sensory complexity and rounded palate structure obtained from spontaneous fermentations. In contrast, interspecific yeast hybrids have the potential to deliver increased complexity to wine sensory properties and alternative wine styles through the formation of novel, and wider ranging, yeast volatile fermentation metabolite profiles, whilst maintaining the robustness of the wine yeast parent. Screening of newly generated hybrids from a cross between a S. cerevisiae wine yeast and S. mikatae (closely-related but ecologically distant members of the Saccharomyces sensu stricto clade), has identified progeny with robust fermentation properties and winemaking potential. Chemical analysis showed that, relative to the S. cerevisiae wine yeast parent, hybrids produced wines with different concentrations of volatile metabolites that are known to contribute to wine flavour and aroma, including flavour compounds associated with non-Saccharomyces species. The new S. cerevisiae x S. mikatae hybrids have the potential to produce complex wines akin to products of spontaneous fermentation while giving winemakers the safeguard of an inoculated ferment. PMID:23614011

  10. PT-Symmetric Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Bender, Carl M.

    2011-09-01

    In 1998 it was discovered that the requirement that a Hamiltonian be Dirac Hermitian (H = H†) can be weakened and generalized to the requirement that a Hamiltonian be PT symmetric ([H,PT] = 0); that is, invariant under combined space reflection and time reversal. Weakening the constraint of Hermiticity allows one to consider new kinds of physically acceptable Hamiltonians and, in effect, it amounts to extending quantum mechanics from the real (Hermitian) domain into the complex domain. Much work has been done on the analysis of various PT-symmetric quantum-mechanical models. However, only very little analysis has been done on PT-symmetric quantum-field-theoretic models. Here, we describe some of what has been done in the context of PT-symmetric quantum field theory and describe some possible fundamental applications.

  11. Reduction of Pt2+ species in model Pt-CeO2 fuel cell catalysts upon reaction with methanol

    NASA Astrophysics Data System (ADS)

    Neitzel, Armin; Johánek, Viktor; Lykhach, Yaroslava; Skála, Tomáš; Tsud, Nataliya; Vorokhta, Mykhailo; Matolín, Vladimír; Libuda, Jörg

    2016-11-01

    The stability of atomically dispersed Pt2+ species on the surface of nanostructured CeO2 films during the reaction with methanol has been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy. The isolated Pt2+ species were prepared at low Pt concentration in Pt-CeO2 film. Additionally, Pt2+ species coexisting with metallic Pt particles were prepared at high Pt concentration. We found that adsorption of methanol yields similar decomposition products regardless of Pt concentration in Pt-CeO2 films. A small number of oxygen vacancies formed during the methanol decomposition can be replenished in the Pt-CeO2 film with low Pt concentration by diffusion of oxygen from the bulk. In the presence of supported Pt particles, a higher number of oxygen vacancies leads to a partial reduction of the Pt2+ species. The isolated Pt2+ species are reduced under rather strongly reducing conditions only, i.e. during annealing under continuous exposure to methanol. Reduction of isolated Pt2+ species results in the formation of ultra-small Pt particles containing around 25 atoms per particle or less. Such ultra-small Pt particles demonstrate excellent stability against sintering during annealing of Pt-CeO2 film with low Pt concentration under reducing conditions.

  12. Architecturally designed Pt-MoS2 and Pt-graphene composites for electrocatalytic methanol oxidation.

    PubMed

    Patil, Sagar H; Anothumakkool, Bihag; Sathaye, Shivaram D; Patil, Kashinath R

    2015-10-21

    Thin films consisting of platinum nanoparticles (Pt NPs) with uniform size and distribution have been successfully prepared at a liquid-liquid interface. Apart from the usual substrates like glass, Si etc. the films were also deposited on the surfaces of MoS2 thin films and graphene nanosheets (GNS) respectively, by using a layer-by-layer (LbL) deposition technique to form Pt-MoS2 and Pt-GNS composites. The loading concentration of Pt NPs on MoS2 and GNS can be adjusted by selecting the number and sequence of the component layers during LbL deposition. The Pt thin films, Pt-MoS2 and Pt-GNS nanocomposite thin films are characterized using transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). TEM results of the composites show that Pt NPs with sizes in the range of 1 to 3 nm are uniformly dispersed on the MoS2/GNS surface. The catalytic activities of Pt and Pt-composites for the reaction of methanol oxidation are studied using cyclic voltammetry and chronoamperometry. Electrochemical studies reveal that both the Pt-MoS2 and Pt-GNS nanocomposites show excellent electrocatalytic activity towards methanol oxidation. Pt-MoS2 and Pt-GNS nanocomposite electrodes show excellent stability for reuse of the catalyst. A probable mechanism of catalysis has been discussed. We propose that the similar architecture reported here would be promising for the synthesis of high performance catalysts for fuel cells, gas phase reactions, and other applications such as sensors. PMID:26377752

  13. Highly Active Pt(3)Pb and Core-Shell Pt(3)Pb-Pt Electrocatalysts for Formic Acid Oxidation

    SciTech Connect

    Kang Y.; Stach E.; Qi L.; Li M.; Diaz R.E.; Su D.; Adzic R.R.; Li J.; Murray C.B.

    2012-03-27

    Formic acid is a promising chemical fuel for fuel cell applications. However, due to the dominance of the indirect reaction pathway and strong poisoning effects, the development of direct formic acid fuel cells has been impeded by the low activity of existing electrocatalysts at desirable operating voltage. We report the first synthesis of Pt{sub 3}Pb nanocrystals through solution phase synthesis and show they are highly efficient formic acid oxidation electrocatalysts. The activity can be further improved by manipulating the Pt{sub 3}Pb-Pt core-shell structure. Combined experimental and theoretical studies suggest that the high activity from Pt{sub 3}Pb and the Pt-Pb core-shell nanocrystals results from the elimination of CO poisoning and decreased barriers for the dehydrogenation steps. Therefore, the Pt{sub 3}Pb and Pt-Pb core-shell nanocrystals can improve the performance of direct formic acid fuel cells at desired operating voltage to enable their practical application.

  14. Outlining a future for non-Saccharomyces yeasts: selection of putative spoilage wine strains to be used in association with Saccharomyces cerevisiae for grape juice fermentation.

    PubMed

    Domizio, Paola; Romani, Cristina; Lencioni, Livio; Comitini, Francesca; Gobbi, Mirko; Mannazzu, Ilaria; Ciani, Maurizio

    2011-06-30

    The use of non-Saccharomyces yeasts that are generally considered as spoilage yeasts, in association with Saccharomyces cerevisiae for grape must fermentation was here evaluated. Analysis of the main oenological characteristics of pure cultures of 55 yeasts belonging to the genera Hanseniaspora, Pichia, Saccharomycodes and Zygosaccharomyces revealed wide biodiversity within each genus. Moreover, many of these non-Saccharomyces strains had interesting oenological properties in terms of fermentation purity, and ethanol and secondary metabolite production. The use of four non-Saccharomyces yeasts (one per genus) in mixed cultures with a commercial S. cerevisiae strain at different S. cerevisiae/non-Saccharomyces inoculum ratios was investigated. This revealed that most of the compounds normally produced at high concentrations by pure cultures of non-Saccharomyces, and which are considered detrimental to wine quality, do not reach threshold taste levels in these mixed fermentations. On the other hand, the analytical profiles of the wines produced by these mixed cultures indicated that depending on the yeast species and the S. cerevisiae/non-Saccharomyces inoculum ratio, these non-Saccharomyces yeasts can be used to increase production of polysaccharides and to modulate the final concentrations of acetic acid and volatile compounds, such as ethyl acetate, phenyl-ethyl acetate, 2-phenyl ethanol, and 2-methyl 1-butanol. PMID:21531033

  15. Experimental and theoretical studies of ammonia decomposition activity on Fe-Pt, Co-Pt, and Cu-Pt bimetallic surfaces

    NASA Astrophysics Data System (ADS)

    Hansgen, Danielle A.; Thomanek, Lisa M.; Chen, Jingguang G.; Vlachos, Dionisios G.

    2011-05-01

    We investigate the decomposition of ammonia on bimetallic surfaces prepared by the deposition of a monolayer of Fe, Co, or Cu on a Pt(111) surface computationally and experimentally. We explore the correlation between predicted activities based on the nitrogen binding energies with experimental decomposition activity on these bimetallic and corresponding monometallic surfaces. Through density functional theory calculations and microkinetic modeling, it is predicted that the Fe-Pt-Pt(111) and Co-Pt-Pt(111) surfaces, with a monolayer of Fe or Co on top of Pt(111), are active toward decomposing ammonia. In contrast, the corresponding subsurface configurations, Pt-Fe-Pt(111) and Pt-Co-Pt(111) are inactive. These predictions were confirmed experimentally through temperature programmed desorption experiments. Decomposition was seen at temperatures below 350 K for the Fe-Pt-Pt(111) and Co-Pt-Pt(111) surfaces. For the Cu/Pt(111) system, the surface, subsurface and parent metals were each predicted to be inactive, consistent with experiments, further validating the model predictions. The stability of these bimetallic surfaces in the presence of adsorbed nitrogen is also discussed.

  16. Microstructure and electronic behavior of PtPd@Pt core-shell nanowires

    SciTech Connect

    Han, Wei-Qiang; Su, Dong; Murphy, Michael; Ward, Matthew; Sham, Tsun-Kong; Wu, Lijun; Zhu, Yimei; Hu, Yongfeng; Aoki, Toshihiro

    2010-07-19

    PtPd{at}Pt core-shell ultrathin nanowires were prepared using a one-step phase-transfer approach. The diameters of the nanowires range from 2 to 3 nm, and their lengths are up to hundreds of nanometers. Line scanning electron energy loss spectra showed that PtPd bimetallic nanowires have a core-shell structure, with a PtPd alloy core and a Pt monolayer shell. X-ray absorption near edge structure (XANES) spectra reveal that a strong Pt-Pd interaction exists in this nanowire system in that there is PtPd alloying and/or interfacial interaction. Extended x-ray absorption fine structures (EXAFS) further confirms the PtPd@Pt core-shell structure. The bimetallic nanowires were determined to be face-centered cubic structures. The long-chain organic molecules of n-dodecyl trimethylammonium bromide and octadecylamine, used as surfactants during synthesis, were clearly observed using aberration-corrected TEM operated at 80 KV. The interaction of Pt and surfactants was also revealed by EXAFS.

  17. \\cal{PT} -symmetry in Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Ziauddin; Chuang, You-Lin; Lee, Ray-Kuang

    2016-07-01

    We propose a scheme to realize parity-time ( {PT} )-symmetry in an ensemble of strongly interacting Rydberg atoms, which act as superatoms due to the dipole blockade mechanism. We show that Rydberg-dressed 87Rb atoms in a four-level inverted Y-type configuration is highly efficient to generate the refractive index for a probe field, with a symmetric (antisymmetric) profile spatially in the corresponding real (imaginary) part. Comparing with earlier investigations, the present scheme provides a versatile platform to control the system from {PT} -symmetry to non-PT -symmetry via different external parameters, i.e., coupling field detuning, probe field intensity and control field intensity.

  18. Genome annotation of a Saccharomyces sp. lager brewer's yeast.

    PubMed

    De León-Medina, Patricia Marcela; Elizondo-González, Ramiro; Damas-Buenrostro, Luis Cástulo; Geertman, Jan-Maarten; Van den Broek, Marcel; Galán-Wong, Luis Jesús; Ortiz-López, Rocío; Pereyra-Alférez, Benito

    2016-09-01

    The genome of lager brewer's yeast is a hybrid, with Saccharomyces eubayanus and Saccharomyces cerevisiae as sub-genomes. Due to their specific use in the beer industry, relatively little information is available. The genome of brewing yeast was sequenced and annotated in this study. We obtained a genome size of 22.7 Mbp that consisted of 133 scaffolds, with 65 scaffolds larger than 10 kbp. With respect to the annotation, 9939 genes were obtained, and when they were submitted to a local alignment, we found that 53.93% of these genes corresponded to S. cerevisiae, while another 42.86% originated from S. eubayanus. Our results confirm that our strain is a hybrid of at least two different genomes. PMID:27330999

  19. Bioethanol production from sweet potato using Saccharomyces diastaticus

    NASA Astrophysics Data System (ADS)

    Abdullah, Suryani, Irma; Pradia Paundradewa, J.

    2015-12-01

    Sweet potato contains about 16 to 40% dry matter and about 70-90% of the dry matter is a carbohydrate made up of starch, sugar, cellulose, hemicellulose and pectin so suitable for used as raw material for bioethanol. In this study focused on the manufacture of bioethanol with changes in temperature and concentration variations of yeast with sweet potato raw materials used yeast Saccharomyces diastaticus. Operating variables used are at a temperature of 30°C; 31,475°C; 35°C; 38,525°C; and 40°C with a yeast concentration of 25.9%; 30%; 40%; 50% and 54.1%. The experimental results obtained, the optimum conditions of ethanol fermentation with yeast Saccharomyces diastaticus on 36,67 °C temperature and yeast concentration of 43,43 % v / v.

  20. The reference genome sequence of Saccharomyces cerevisiae: then and now.

    PubMed

    Engel, Stacia R; Dietrich, Fred S; Fisk, Dianna G; Binkley, Gail; Balakrishnan, Rama; Costanzo, Maria C; Dwight, Selina S; Hitz, Benjamin C; Karra, Kalpana; Nash, Robert S; Weng, Shuai; Wong, Edith D; Lloyd, Paul; Skrzypek, Marek S; Miyasato, Stuart R; Simison, Matt; Cherry, J Michael

    2014-03-01

    The genome of the budding yeast Saccharomyces cerevisiae was the first completely sequenced from a eukaryote. It was released in 1996 as the work of a worldwide effort of hundreds of researchers. In the time since, the yeast genome has been intensively studied by geneticists, molecular biologists, and computational scientists all over the world. Maintenance and annotation of the genome sequence have long been provided by the Saccharomyces Genome Database, one of the original model organism databases. To deepen our understanding of the eukaryotic genome, the S. cerevisiae strain S288C reference genome sequence was updated recently in its first major update since 1996. The new version, called "S288C 2010," was determined from a single yeast colony using modern sequencing technologies and serves as the anchor for further innovations in yeast genomic science. PMID:24374639

  1. Saccharomyces cerevisiae: a sexy yeast with a prion problem.

    PubMed

    Kelly, Amy C; Wickner, Reed B

    2013-01-01

    Yeast prions are infectious proteins that spread exclusively by mating. The frequency of prions in the wild therefore largely reflects the rate of spread by mating counterbalanced by prion growth slowing effects in the host. We recently showed that the frequency of outcross mating is about 1% of mitotic doublings with 23-46% of total matings being outcrosses. These findings imply that even the mildest forms of the [PSI+], [URE3] and [PIN+] prions impart > 1% growth/survival detriment on their hosts. Our estimate of outcrossing suggests that Saccharomyces cerevisiae is far more sexual than previously thought and would therefore be more responsive to the adaptive effects of natural selection compared with a strictly asexual yeast. Further, given its large effective population size, a growth/survival detriment of > 1% for yeast prions should strongly select against prion-infected strains in wild populations of Saccharomyces cerevisiae. PMID:23764836

  2. The Reference Genome Sequence of Saccharomyces cerevisiae: Then and Now

    PubMed Central

    Engel, Stacia R.; Dietrich, Fred S.; Fisk, Dianna G.; Binkley, Gail; Balakrishnan, Rama; Costanzo, Maria C.; Dwight, Selina S.; Hitz, Benjamin C.; Karra, Kalpana; Nash, Robert S.; Weng, Shuai; Wong, Edith D.; Lloyd, Paul; Skrzypek, Marek S.; Miyasato, Stuart R.; Simison, Matt; Cherry, J. Michael

    2014-01-01

    The genome of the budding yeast Saccharomyces cerevisiae was the first completely sequenced from a eukaryote. It was released in 1996 as the work of a worldwide effort of hundreds of researchers. In the time since, the yeast genome has been intensively studied by geneticists, molecular biologists, and computational scientists all over the world. Maintenance and annotation of the genome sequence have long been provided by the Saccharomyces Genome Database, one of the original model organism databases. To deepen our understanding of the eukaryotic genome, the S. cerevisiae strain S288C reference genome sequence was updated recently in its first major update since 1996. The new version, called “S288C 2010,” was determined from a single yeast colony using modern sequencing technologies and serves as the anchor for further innovations in yeast genomic science. PMID:24374639

  3. A Saccharomyces cerevisiae Internet protein resource now available.

    PubMed

    Latter, G I; Boutell, T; Monardo, P J; Kobayashi, R; Futcher, B; Mclaughlin, C S; Garrels, J I

    1995-07-01

    The QUEST Protein Database Center is now making available two Saccharomyces cerevisiae protein databases via the Internet. The yeast electrophoretic protein database (YEPD) is a database of approximately one hundred protein identifications on two-dimensional gels. The yeast protein database (YPD) is a database of gene names and properties of over 3500 yeast proteins of known sequence. These databases can be accessed via a World-Wide Web (WWW) server (URL http:@siva.cshl.org). YPD is available via public ftp (isis.cshl.org) as well, in a spreadsheet format, and in ASCII format. When accessed via WWW, both of these databases have hypertext links to other biological data, such as the SWISS-PROT protein sequence database and the Saccharomyces Genome Database (SacchDB), and to each other. PMID:7498160

  4. Expression of bacterial mercuric ion reductase in Saccharomyces cerevisiae.

    PubMed Central

    Rensing, C; Kües, U; Stahl, U; Nies, D H; Friedrich, B

    1992-01-01

    The gene merA coding for bacterial mercuric ion reductase was cloned under the control of the yeast promoter for alcohol dehydrogenase I in the yeast-Escherichia coli shuttle plasmid pADH040-2 and transformed into Saccharomyces cerevisiae AH22. The resulting transformant harbored stable copies of the merA-containing hybrid plasmid, displayed a fivefold increase in the MIC of mercuric chloride, and synthesized mercuric ion reductase activity. Images PMID:1735719

  5. Invasive Saccharomyces cerevisiae infection: a friend turning foe?

    PubMed

    Pillai, Unnikrishnan; Devasahayam, Joe; Kurup, Aparna Narayana; Lacasse, Alexandre

    2014-11-01

    We report a very rare case of acute pyelonephritis in a 51-year-old female with a history of chronic kidney disease (CKD) and diabetes caused by a normally benign and a well-known human commensal organism, Saccharomyces cerevisiae that is very often prescribed as a probiotic in modern medical practice. The causal role of S. cerevisiae was confirmed by its isolation in blood, urine, stool as well as vaginal swabs thus proving its virulent nature in suitable situations. PMID:25394448

  6. A global topology map of the Saccharomyces cerevisiae membrane proteome

    NASA Astrophysics Data System (ADS)

    Kim, Hyun; Melén, Karin; Österberg, Marie; von Heijne, Gunnar

    2006-07-01

    The yeast Saccharomyces cerevisiae is, arguably, the best understood eukaryotic model organism, yet comparatively little is known about its membrane proteome. Here, we report the cloning and expression of 617 S. cerevisiae membrane proteins as fusions to a C-terminal topology reporter and present experimentally constrained topology models for 546 proteins. By homology, the experimental topology information can be extended to 15,000 membrane proteins from 38 fully sequenced eukaryotic genomes. membrane proteins | membrane proteomics | yeast

  7. [Lyophilized Saccharomyces boulardii: example of a probiotic medicine].

    PubMed

    Buts, Jean-Paul

    2005-01-01

    Saccharomyces boulardii is a natural yeast without genetic modification isolated from the bark of the litchi tree in Indochina. In its lyophilized form is an example of the called probiotic medicine. The probiotic denomination is in relation to that itself assets in the gastrointestinal tract in interrelation to that biologic environment. And is labelled as medicine because the lyophilized form has a clinical and pharmaceutical expedient included in the regulation of medicinal products in almost 100 countries. PMID:16021204

  8. Horizontal Transfer of Genetic Material among Saccharomyces Yeasts

    PubMed Central

    Marinoni, Gaelle; Manuel, Martine; Petersen, Randi Føns; Hvidtfeldt, Jeanne; Sulo, Pavol; Piškur, Jure

    1999-01-01

    The genus Saccharomyces consists of several species divided into the sensu stricto and the sensu lato groups. The genomes of these species differ in the number and organization of nuclear chromosomes and in the size and organization of mitochondrial DNA (mtDNA). In the present experiments we examined whether these yeasts can exchange DNA and thereby create novel combinations of genetic material. Several putative haploid, heterothallic yeast strains were isolated from different Saccharomyces species. All of these strains secreted an a- or α-like pheromone recognized by S. cerevisiae tester strains. When interspecific crosses were performed by mass mating between these strains, hybrid zygotes were often detected. In general, the less related the two parental species were, the fewer hybrids they gave. For some crosses, viable hybrids could be obtained by selection on minimal medium and their nuclear chromosomes and mtDNA were examined. Often the frequency of viable hybrids was very low. Sometimes putative hybrids could not be propagated at all. In the case of sensu stricto yeasts, stable viable hybrids were obtained. These contained both parental sets of chromosomes but mtDNA from only one parent. In the case of sensu lato hybrids, during genetic stabilization one set of the parental chromosomes was partially or completely lost and the stable mtDNA originated from the same parent as the majority of the nuclear chromosomes. Apparently, the interspecific hybrid genome was genetically more or less stable when the genetic material originated from phylogenetically relatively closely related parents; both sets of nuclear genetic material could be transmitted and preserved in the progeny. In the case of more distantly related parents, only one parental set, and perhaps some fragments of the other one, could be found in genetically stabilized hybrid lines. The results obtained indicate that Saccharomyces yeasts have a potential to exchange genetic material. If Saccharomyces

  9. Integrated X-ray photoelectron spectroscopy and DFT characterization of benzene adsorption on Pt(111), Pt(355) and Pt(322) surfaces.

    PubMed

    Zhang, Renqin; Hensley, Alyssa J; McEwen, Jean-Sabin; Wickert, Sandra; Darlatt, Erik; Fischer, Kristina; Schöppke, Matthias; Denecke, Reinhard; Streber, Regine; Lorenz, Michael; Papp, Christian; Steinrück, Hans-Peter

    2013-12-21

    We systematically investigate the adsorption of benzene on Pt(111), Pt(355) and Pt(322) surfaces by high-resolution X-ray photoelectron spectroscopy (XPS) and first-principle calculations based on density functional theory (DFT), including van der Waals corrections. By comparing the adsorption energies at 1/9, 1/16 and 1/25 ML on Pt(111), we find significant lateral interactions exist between the benzene molecules at 1/9 ML. The adsorption behavior on Pt(355) and Pt(322) is very different. While on Pt(355) a step species is clearly identified in the C 1s spectra at low coverages followed by occupation of a terrace species at high coverages, no evidence for a step species is found on Pt(322). These different adsorption sites are confirmed by extensive DFT calculations, where the most favorable adsorption configurations on Pt(355) and Pt(322) are also found to vary: a highly distorted across the step molecule is found on Pt(355) while a less distorted configuration adjacent to the step molecule is deduced for Pt(322). The theoretically proposed C 1s core level binding energy shifts between these most favorable configurations and the terrace species are found to correlate well with experiment: for Pt(355), two adsorbate states are found, separated by ~0.4 eV in XPS and 0.3 eV in the calculations, in contrast to only one state on Pt(322). PMID:24189500

  10. Stress Evolution Behavior in CoCrPt Alloy Thin Films with varying Pt Concentration

    SciTech Connect

    Im, M.-Y.; Jeong, J.-R.; Shin, S.-C.

    2007-11-01

    CoCrPt alloy thin film is one of the most promising candidates for ultrahigh density magnetic recording media. One of interesting issues for an application of ferromagnetic thin film to high density magnetic recording media is to investigate growth stress, since stress inevitably generated during thin film fabrication drastically alters magnetic properties as well as mechanical properties due to film fracture and buckling [1]. However, sufficient studies have not been addressed on in situ experimental investigation on stress evolution during film growth of magnetic thin film and its correlation with directly observed film growth structure. We have investigated in situ stress evolution of 400-{angstrom} (Co{sub 82}Cr{sub 18}){sub 100-x}Pt{sub x}/1100-{angstrom} Ti alloy films with varying Pt concentration by means of an ultrahigh vacuum (UHV) chamber equipped with a highly sensitive optical deflection-detecting system [2]. Interestingly enough, the stress evolution patterns during the film deposition are remarkably changed with varying the Pt concentration. CoCrPt alloy films with lower Pt concentration (6 {le} x {le} 13) grow through compressive, tensile, and again compressive stress during film deposition, while CoCrPt alloy films with higher Pt concentration (21 {le} x {le} 28) develop with compressive and relaxed compressive stress without tensile stress generation. In situ stress-evolution behavior for 400-{angstrom} (Co{sub 82}Cr{sub 18}){sub 100-x}Pt{sub x}/1100-{angstrom} Ti alloy films with the Pt concentrations of (a) 6, (b) 13, (c) 21, and (d) 28 at.% are demonstrated in Fig.1. Here, the positive slope corresponds to tensile stress, while the negative slope implies compressive stress. The microstructural studies at the stress transition region reveal that film growth structure plays a major role in considerable change of stress evolution pattern in CoCrPt alloy films with the increase of Pt concentration.

  11. Synthesis and optical property characterization of elongated AuPt and Pt@Au metal nanoframes

    NASA Astrophysics Data System (ADS)

    Lee, Sangji; Jang, Hee-Jeong; Jang, Ho Young; Hong, Soonchang; Moh, Sang Hyun; Park, Sungho

    2016-02-01

    We report a facile method to synthesize elongated nanoframes consisting of Pt and Au in solution. Pentagonal Au nanorods served as templates and successfully led to an elongated AuPt nanoframe after etching the core Au. Subsequently, the coating of Au around Pt ridges resulted in Pt@Au metal nanoframes. The resulting elongated nanostructure exhibited 5 well-defined ridges continuously connected along the long axis. During the shape evolution from pure Au nanorods to elongated Pt@Au metal nanoframes, their corresponding localized surface plasmon resonance bands were monitored. Especially, unique surface plasmon features were observed for elongated Pt@Au nanoframes where the short-axis oscillation of surface free electrons is strongly coupled but the long-axis oscillation is not coupled among the ridges.We report a facile method to synthesize elongated nanoframes consisting of Pt and Au in solution. Pentagonal Au nanorods served as templates and successfully led to an elongated AuPt nanoframe after etching the core Au. Subsequently, the coating of Au around Pt ridges resulted in Pt@Au metal nanoframes. The resulting elongated nanostructure exhibited 5 well-defined ridges continuously connected along the long axis. During the shape evolution from pure Au nanorods to elongated Pt@Au metal nanoframes, their corresponding localized surface plasmon resonance bands were monitored. Especially, unique surface plasmon features were observed for elongated Pt@Au nanoframes where the short-axis oscillation of surface free electrons is strongly coupled but the long-axis oscillation is not coupled among the ridges. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08200e

  12. Nanosecond Dynamics in Pt Nanoparticles

    NASA Astrophysics Data System (ADS)

    Vila, F. D.; Moore, J. M.; Rehr, J. J.

    2014-03-01

    Understanding the physical and chemical behavior of supported catalysts is of fundamental and technological importance. However, due to the complex nature of their structure and dynamics at operando temperatures, their nanoscale behavior remains poorly understood. We have shown that DFT/MD calculations provide fundamental insight into the few ps dynamic structure of the nanoparticles, but such methods can be very computationally intensive.[2,3] In order to examine relaxation dynamics in the ns regime here we present finite temperature MD simulations based on a modified Sutton-Chen (SC) model potential, supplemented with Lennard-Jones potentials for the interaction with the support. We find that bulk SC parameters tend to produce nanoparticles with less fluxional dynamics than those in ab initio simulations. To address this issue, we have determined modified SC parameters that capture the DFT dynamics. Nanosecond simulations reveal regimes controlled by internal particle melting and activation of surface mobility. The approach is illustrated for nano-catalysts of Pt/ γ-alumina and compared with ab initio DFT/MD results. Supported in part by DOE grant DE-FG02-03ER15476 (F.D.V and J.J.R) and by NSF grant PHY-1262811, REU Site: University of Washington Physics (J.M.M.), with computer support from DOE - NERSC.

  13. Consistency of PT-symmetric quantum mechanics

    NASA Astrophysics Data System (ADS)

    Brody, Dorje C.

    2016-03-01

    In recent reports, suggestions have been put forward to the effect that parity and time-reversal (PT) symmetry in quantum mechanics is incompatible with causality. It is shown here, in contrast, that PT-symmetric quantum mechanics is fully consistent with standard quantum mechanics. This follows from the surprising fact that the much-discussed metric operator on Hilbert space is not physically observable. In particular, for closed quantum systems in finite dimensions there is no statistical test that one can perform on the outcomes of measurements to determine whether the Hamiltonian is Hermitian in the conventional sense, or PT-symmetric—the two theories are indistinguishable. Nontrivial physical effects arising as a consequence of PT symmetry are expected to be observed, nevertheless, for open quantum systems with balanced gain and loss.

  14. Heavy Lift & Propulsion Technology (HL&PT)

    NASA Video Gallery

    Cris Guidi delivers a presentation from the Heavy Lift & Propulsion Technology (HL&PT) study team on May 25, 2010, at the NASA Exploration Enterprise Workshop held in Galveston, TX. The purpose of ...

  15. Exchange coupled L10-FePt/fcc-FePt nanomagnets: Synthesis, characterization and magnetic properties

    NASA Astrophysics Data System (ADS)

    Srivastava, Sachchidanand; Gajbhiye, Namdeo S.

    2016-03-01

    We report synthesis, characterization and magnetic properties of exchange-coupled L10-FePt/fcc-FePt nanomagnets. Structural and morphological characterization of exchange-coupled L10-FePt/fcc-FePt was carried out by powder X-ray diffraction, Mössbauer spectroscopy and transmission electron microscopy. Rietveld refinement of powder X-ray diffraction pattern has been used to quantify L10-FePt and fcc-FePt phases present in samples. Room temperature Mössbauer spectroscopy showed sextets of both L10-FePt and fcc-FePt phases with their respective hyperfine interaction parameters. Transmission electron microscopic (TEM and HRTEM) images confirmed nanocrystalline nature of exchange-coupled nanomagnets with particle size ranges from 15 nm to 50 nm after annealing for different time at 700 °C. Room temperature magnetic studies showed ferromagnetic nature of nanomagnets and maximum energy product (BH)max~10.92 MGOe was obtained for sample containing 89.0% volume fraction of L10-FePt phase.

  16. Suspended core-shell Pt-PtOx nanostructure for ultrasensitive hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Basu, Palash Kr.; Kallatt, Sangeeth; Anumol, Erumpukuthickal A.; Bhat, Navakanta

    2015-06-01

    High sensitivity gas sensors are typically realized using metal catalysts and nanostructured materials, utilizing non-conventional synthesis and processing techniques, incompatible with on-chip integration of sensor arrays. In this work, we report a new device architecture, suspended core-shell Pt-PtOx nanostructure that is fully CMOS-compatible. The device consists of a metal gate core, embedded within a partially suspended semiconductor shell with source and drain contacts in the anchored region. The reduced work function in suspended region, coupled with built-in electric field of metal-semiconductor junction, enables the modulation of drain current, due to room temperature Redox reactions on exposure to gas. The device architecture is validated using Pt-PtO2 suspended nanostructure for sensing H2 down to 200 ppb under room temperature. By exploiting catalytic activity of PtO2, in conjunction with its p-type semiconducting behavior, we demonstrate about two orders of magnitude improvement in sensitivity and limit of detection, compared to the sensors reported in recent literature. Pt thin film, deposited on SiO2, is lithographically patterned and converted into suspended Pt-PtO2 sensor, in a single step isotropic SiO2 etching. An optimum design space for the sensor is elucidated with the initial Pt film thickness ranging between 10 nm and 30 nm, for low power (<5 μW), room temperature operation.

  17. Scattering properties of PT-symmetric objects

    NASA Astrophysics Data System (ADS)

    Miri, Mohammad-Ali; Eftekhar, Mohammad Amin; Facao, Margarida; Abouraddy, Ayman F.; Bakry, Ahmed; Razvi, Mir A. N.; Alshahrie, Ahmed; Alù, Andrea; Christodoulides, Demetrios N.

    2016-07-01

    We investigate the scattering response of parity-time (PT) symmetric structures. We show that, due to the local flow of energy between gain and loss regions, such systems can deflect light in unusual ways, as a function of the gain/loss contrast. Such structures are highly anisotropic and their scattering patterns can drastically change as a function of the angle of incidence. In addition, we derive a modified optical theorem for PT-symmetric scattering systems, and discuss its ramifications.

  18. The CO/Pt(111) Puzzle

    SciTech Connect

    FEIBELMAN,PETER J.; HAMMER,B.; NORSHOV,J.K.; WAGNER,F.; SCHEFFLER,M.; STUMPF,R.; DUMESIC,J.; WATWE,R.

    2000-07-12

    Notwithstanding half a dozen theoretical publications, well-converged density-functional calculations, whether based on a local or generalized-gradient exchange-correlation potential, whether all-electron or employing pseudopotentials underestimate CO's preference for low-coordination binding sites on Pt(111) and vicinals to it. For example, they imply that CO should prefer hollow- to atop-site adsorption on Pt(111), in apparent contradiction to a host of low temperature experimental studies.

  19. Saccharomyces cerevisiae and non-Saccharomyces yeasts in grape varieties of the São Francisco Valley.

    PubMed

    de Ponzzes-Gomes, Camila M P B S; de Mélo, Dângelly L F M; Santana, Caroline A; Pereira, Giuliano E; Mendonça, Michelle O C; Gomes, Fátima C O; Oliveira, Evelyn S; Barbosa, Antonio M; Trindade, Rita C; Rosa, Carlos A

    2014-01-01

    The aims of this work was to characterise indigenous Saccharomyces cerevisiae strains in the naturally fermented juice of grape varieties Cabernet Sauvignon, Grenache, Tempranillo, Sauvignon Blanc and Verdejo used in the São Francisco River Valley, northeastern Brazil. In this study, 155 S. cerevisiae and 60 non-Saccharomyces yeasts were isolated and identified using physiological tests and sequencing of the D1/D2 domains of the large subunit of the rRNA gene. Among the non-Saccharomyces species, Rhodotorula mucilaginosa was the most common species, followed by Pichia kudriavzevii, Candida parapsilosis, Meyerozyma guilliermondii, Wickerhamomyces anomalus, Kloeckera apis, P. manshurica, C. orthopsilosis and C. zemplinina. The population counts of these yeasts ranged among 1.0 to 19 × 10(5) cfu/mL. A total of 155 isolates of S. cerevisiae were compared by mitochondrial DNA restriction analysis, and five molecular mitochondrial DNA restriction profiles were detected. Indigenous strains of S. cerevisiae isolated from grapes of the São Francisco Valley can be further tested as potential starters for wine production. PMID:25242923

  20. Coating Pt-Ni Octahedra with Ultrathin Pt Shells to Enhance the Durability without Compromising the Activity toward Oxygen Reduction.

    PubMed

    Park, Jinho; Liu, Jingyue; Peng, Hsin-Chieh; Figueroa-Cosme, Legna; Miao, Shu; Choi, Sang-Il; Bao, Shixiong; Yang, Xuan; Xia, Younan

    2016-08-23

    We describe a new strategy to enhance the catalytic durability of Pt-Ni octahedral nanocrystals in the oxygen reduction reaction (ORR) by conformally depositing an ultrathin Pt shell on the surface. The Pt-Ni octahedra were synthesized according to a protocol reported previously and then employed directly as seeds for the conformal deposition of ultrathin Pt shells by introducing a Pt precursor dropwise at 200 °C. The amount of Pt precursor was adjusted relative to the number of Pt-Ni octahedra involved to obtain Pt-Ni@Pt1.5L octahedra of 12 nm in edge length for the systematic evaluation of their chemical stability and catalytic durability compared to Pt-Ni octahedra. Specifically, we compared the elemental compositions of the octahedra before and after treatment with acetic and sulfuric acids. We also examined their electrocatalytic stability toward the ORR through an accelerated durability test by using a rotating disk electrode method. Even after treatment with sulfuric acid for 24 h, the Pt-Ni@Pt1.5L octahedra maintained their original Ni content, whereas 11 % of the Ni was lost from the Pt-Ni octahedra. After 10 000 cycles of ORR, the mass activity of the Pt-Ni octahedra decreased by 75 %, whereas the Pt-Ni@Pt1.5L octahedra only showed a 25 % reduction. PMID:27460459

  1. Interface structures in FePt/Fe3Pt hard-soft exchange-coupled magnetic nanocomposites

    NASA Astrophysics Data System (ADS)

    Li, Jing; Wang, Zhong Lin; Zeng, Hao; Sun, Shouheng; Ping Liu, J.

    2003-05-01

    Self-assembly of FePt and Fe3O4 nanoparticles of different sizes led to various FePt-Fe3O4 nanocomposites. Annealing the composite under reducing atmosphere at 650 and 700 °C induced magnetically hard FePt phase and magnetically soft Fe3Pt phase. The FePt and Fe3Pt phases were either linked by a common interface or coexisted within one grain as domains with sizes <10 nm. This ensures the effective exchange coupling of magnetically hard and soft phases. High-resolution transmission electron microscopy studies provide detailed structural characterization for the FePt based nanocomposites.

  2. Unipolar resistance switching and abnormal reset behaviors in Pt/CuO/Pt and Cu/CuO/Pt structures

    NASA Astrophysics Data System (ADS)

    Wu, Liang; Li, Xiaomin; Gao, Xiangdong; Zheng, Renkui; Zhang, Feng; Liu, Xinjun; Wang, Qun

    2012-07-01

    The effects of Pt and Cu top electrodes on resistance switching properties were investigated for CuO thin films with Pt/CuO/Pt and Cu/CuO/Pt sandwich structures. Typical unipolar resistance switching (URS) behaviors and two different kinds of resistance changes in the reset process were observed in both structures. When voltages were applied to the film, the low-resistance state (LRS) with relatively low resistance value (<30 Ω) was switched to the high-resistance state (HRS), exhibiting normal reset behavior. For LRS with relatively high resistance value (>50 Ω), the resistance first decreased then increased to HRS, showing abnormal reset behavior. The former variation of LRS could be ascribed to the decrease in filament size induced by Joule heating, while the latter one could be ascribed to the growth of disconnected filaments induced by high electric fields. This study indicates that the switching modes and the abnormal reset behaviors in CuO thin films are not due to Pt and Cu top electrodes, but the intrinsic properties of CuO film.

  3. Copper dusting effects on perpendicular magnetic anisotropy in Pt/Co/Pt tri-layers

    NASA Astrophysics Data System (ADS)

    Parakkat, Vineeth Mohanan; Ganesh, K. R.; Anil Kumar, P. S.

    2016-05-01

    The effect of Cu dusting on perpendicular magnetic anisotropy of sputter grown Pt/Co/Pt stack in which the Cu layer is in proximity with that of Co is investigated in this work. We used magneto optic Kerr effect microscopy measurements to study the variation in the reversal mechanisms in films with Co thicknesses below 0.8nm by systematically varying their perpendicular magnetic anisotropy using controlled Cu dusting. Cu dusting was done separately above and below the cobalt layer in order to understand the role of bottom and top Pt layers in magnetization reversal mechanisms of sputtered Pt/Co/Pt stack. The introduction of even 0.3nm thick Cu layer below the cobalt layer drastically affected the perpendicular magnetic anisotropy as evident from the nucleation behavior. On the contrary, even a 4nm thick top Cu layer had little effect on the reversal mechanism. These observations along with magnetization data was used to estimate the role of top and bottom Pt in the origin of perpendicular magnetic anisotropy as well as magnetization switching mechanism in Pt/Co/Pt thin films. Also, with an increase in the bottom Cu dusting from 0.2 to 0.4nm there was an increase in the number of nucleation sites resulting in the transformation of domain wall patterns from a smooth interface type to a finger like one and finally to maze type.

  4. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  5. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  6. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  7. 21 CFR 866.5785 - Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test systems.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... techniques, antibodies to S. cerevisiae (baker's or brewer's yeast) in human serum or plasma. Detection of S... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Anti-Saccharomyces cerevisiae (S. cerevisiae... Immunological Test Systems § 866.5785 Anti-Saccharomyces cerevisiae (S. cerevisiae) antibody (ASCA) test...

  8. Expression of acylphosphatase in Saccharomyces cerevisiae enhances ethanol fermentation rate

    SciTech Connect

    Raugei, G.; Modesti, A.; Magherini, F.

    1996-06-01

    Previous experiments in vitro have demonstrated the ability of acylphosphatase to increase the rate of glucose fermentation in yeast. To evaluate the possibility of increasing fermentation in vivo also, a chemically synthesized DNA sequence coding for human muscle acylphosphatase was expressed at high level in Saccharomyces cerevisiae. Ethanol production was measured in these engineered strains in comparison with a control. Acylphosphatase expression strongly increased the rate of ethanol production both in aerobic and anaerobic culture. This finding may be potentially important for the development of more efficient industrial fermentation processes. 20 refs., 5 figs.

  9. Immobilized cell cross-flow reactor. [Saccharomyces cerevisiae

    SciTech Connect

    Chotani, G.K.; Constantinides, A.

    1984-01-01

    A cross-current flow reactor was operated using sodium alginate gel entrapped yeast cells (Saccharomyces cerevisiae) under growth conditions. Micron-sized silica, incorporated into the biocatalyst particles (1 mm mean diameter) improved mechanical strength and internal surface adhesion. The process showed decreased productivity and stability at 35/sup 0/C compared to the normal study done at 30/sup 0/C. The increased number of cross flows diminish the product inhibition effect. The residence time distribution shows that the cross-flow bioreactor system can be approximated to either a train of backmixed fermentors in series or a plug flow fermentor with moderate axial dispersion.

  10. Transfer RNA splicing in Saccharomyces cerevisiae: defining the substrates.

    PubMed Central

    Ogden, R C; Lee, M C; Knapp, G

    1984-01-01

    The primary sequences of all the tRNA precursors which contain intervening sequences and which accumulate in the Saccharomyces cerevisiae rnal mutant are presented. A combination of DNA and RNA sequence analysis has led to elucidation of the primary sequence of four hitherto uncharacterized precursors. The location of the intervening sequence has in all cases been unambiguously determined by analysis of the intermediates in the splicing reaction. Secondary structures based upon the tRNA cloverleaf are shown for all the tRNA precursors and discussed with respect to common recognition by the yeast splicing endonuclease. Images PMID:6096826

  11. SACCHAROMYCES CEREVISIAE Recessive Suppressor That Circumvents Phosphatidylserine Deficiency

    PubMed Central

    Atkinson, Katharine D.

    1984-01-01

    Phenotypic reversion of six independent Saccharomyces cerevisiae cho1 mutants was shown to be due predominantly to mutation of an unlinked gene, eam1. The eam1 gene was located very close to ino1 on chromosome X by meiotic tetrad analysis. Recessive eam1 mutations did not correct the primary cho1 defect in phosphatidylserine synthesis but made endogenous ethanolamine available for sustained nitrogenous phospholipid synthesis. A novel biochemical contribution to nitrogenous lipid synthesis is indicated by the eam1 mutants. PMID:17246236

  12. Serotypes in Saccharomyces telluris: Their relation to source of isolation

    USGS Publications Warehouse

    Hasenclever, H.F.; Kocan, R.M.

    1973-01-01

    Three serotypes have been characterized with three reference strains of Saccharomyces telluris and designated as A, B, and C. One reference strain of Torpulopsis bovina, the imperfect form of S. telluris, belonged to serotype B. Strains of S. telluris isolated from four columbid species were serotyped. All 98 strains of this yeast isolated from Columba livia belonged to serotype B. Three other columbid species, C. leucocephala, C. fasciata, and Zenaidura macroura harbored strains of serotype C only. Serotype A was not isolated from any of the avian species.

  13. Mutants of the Formyltetrahydrofolate Interconversion Pathway of SACCHAROMYCES CEREVISIAE

    PubMed Central

    McKenzie, K. Q.; Jones, Elizabeth W.

    1977-01-01

    Thirteen mutants of Saccharomyces cerevisiae that lack one or more of the three enzyme activities of the pathway for interconversion of tetrahydrofolate coenzymes at the formate level of oxidation have been isolated. They do not require adenine. All fail to complement mutations in the ade3 locus. Mutations that greatly reduce activity for one enzyme also reduce activity for the other two interconversion enzymes. The three enzyme activities cochromatograph on TEAE-cellulose columns. A mutation that eliminates synthetase activity also alters the chromatographic behavior of the remaining cyclohydrolase and dehydrogenase activities. It is suggested that the three activities reside in an enzyme complex encoded by the ade3 locus. PMID:328341

  14. Use of bimolecular fluorescence complementation in yeast Saccharomyces cerevisiae.

    PubMed

    Skarp, Kari-Pekka; Zhao, Xueqiang; Weber, Marion; Jantti, Jussi

    2008-01-01

    Visualization of protein-protein interactions in vivo offers a powerful tool to resolve spatial and temporal aspects of cellular functions. Bimolecular fluorescence complementation (BiFC) makes use of nonfluorescent fragments of green fluorescent protein or its variants that are added as "tags" to target proteins under study. Only upon target protein interaction is a fluorescent protein complex assembled and the site of interaction can be monitored by microscopy. In this chapter, we describe the method and tools for use of BiFC in the yeast Saccharomyces cerevisiae. PMID:19066026

  15. Mutagenesis protocols in Saccharomyces cerevisiae by in vivo overlap extension.

    PubMed

    Alcalde, Miguel

    2010-01-01

    A high recombination frequency and its ease of manipulation has made Saccharomyces cerevisiae a unique model eukaryotic organism to study homologous recombination. Indeed, the well-developed recombination machinery in S. cerevisiae facilitates the construction of mutant libraries for directed evolution experiments. In this context, in vivo overlap extension (IVOE) is a particularly attractive protocol that takes advantage of the eukaryotic apparatus to carry out combinatorial saturation mutagenesis, site-directed recombination or site-directed mutagenesis, avoiding ligation steps and additional PCR reactions that are common to standard in vitro protocols. PMID:20676972

  16. RNAi-Assisted Genome Evolution (RAGE) in Saccharomyces cerevisiae.

    PubMed

    Si, Tong; Zhao, Huimin

    2016-01-01

    RNA interference (RNAi)-assisted genome evolution (RAGE) applies directed evolution principles to engineer Saccharomyces cerevisiae genomes. Here, we use acetic acid tolerance as a target trait to describe the key steps of RAGE. Briefly, iterative cycles of RNAi screening are performed to accumulate multiplex knockdown modifications, enabling directed evolution of the yeast genome and continuous improvement of a target phenotype. Detailed protocols are provided on the reconstitution of RNAi machinery, creation of genome-wide RNAi libraries, identification and integration of beneficial knockdown cassettes, and repeated RAGE cycles. PMID:27581294

  17. Isobutanol production from D-xylose by recombinant Saccharomyces cerevisiae.

    PubMed

    Brat, Dawid; Boles, Eckhard

    2013-03-01

    Simultaneous overexpression of an optimized, cytosolically localized valine biosynthesis pathway together with overexpression of xylose isomerase XylA from Clostridium phytofermentans, transaldolase Tal1 and xylulokinase Xks1 enabled recombinant Saccharomyces cerevisiae cells to complement the valine auxotrophy of ilv2,3,5 triple deletion mutants for growth on D-xylose as the sole carbon source. Moreover, after additional overexpression of ketoacid decarboxylase Aro10 and alcohol dehydrogenase Adh2, the cells were able to ferment D-xylose directly to isobutanol. PMID:23279585

  18. Differential repair of UV damage in Saccharomyces cerevisiae.

    PubMed Central

    Terleth, C; van Sluis, C A; van de Putte, P

    1989-01-01

    Preferential repair of UV-induced damage is a phenomenon by which mammalian cells might enhance their survival. This paper presents the first evidence that preferential repair occurs in the lower eukaryote Saccharomyces cerevisiae. Moreover an unique approach is reported to compare identical sequences present on the same chromosome and only differing in expression. We determined the removal of pyrimidine dimers from two identical alpha-mating type loci and we were able to show that the active MAT alpha locus is repaired preferentially to the inactive HML alpha locus. In a sir-3 mutant, in which both loci are active this preference is not observed. Images PMID:2664708

  19. Resistive random access memory utilizing ferritin protein with Pt nanoparticles

    NASA Astrophysics Data System (ADS)

    Uenuma, Mutsunori; Kawano, Kentaro; Zheng, Bin; Okamoto, Naofumi; Horita, Masahiro; Yoshii, Shigeo; Yamashita, Ichiro; Uraoka, Yukiharu

    2011-05-01

    This study reports controlled single conductive paths found in resistive random access memory (ReRAM) formed by embedding Pt nanoparticles (Pt NPs) in NiO film. Homogeneous Pt NPs produced and placed by ferritin protein produce electric field convergence which leads to controlled conductive path formation. The ReRAM with Pt NPs shows stable switching behavior. A Pt NP density decrease results in an increase of OFF state resistance and decrease of forming voltage, whereas ON resistance was independent of the Pt NP density, which indicates that a single metal NP in a memory cell will achieve low power and stable operation.

  20. Dehydrogenation of benzene on Pt(111) surface

    NASA Astrophysics Data System (ADS)

    Gao, W.; Zheng, W. T.; Jiang, Q.

    2008-10-01

    The dehydrogenation of benzene on Pt(111) surface is studied by ab initio density functional theory. The minimum energy pathways for benzene dehydrogenation are found with the nudge elastic band method including several factors of the associated barriers, reactive energies, intermediates, and transient states. The results show that there are two possible parallel minimum energy pathways on the Pt(111) surface. Moreover, the tilting angle of the H atom in benzene can be taken as an index for the actual barrier of dehydrogenation. In addition, the properties of dehydrogenation radicals on the Pt(111) surface are explored through their adsorption energy, adsorption geometry, and electronic structure on the surface. The vibrational frequencies of the dehydrogenation radicals derived from the calculations are in agreement with literature data.

  1. Preparation of onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts for oxygen reduction reaction in fuel cells

    NASA Astrophysics Data System (ADS)

    Lim, Taeho; Kim, Ok-Hee; Sung, Yung-Eun; Kim, Hyun-Jong; Lee, Ho-Nyun; Cho, Yong-Hun; Kwon, Oh Joong

    2016-06-01

    Onion-like Pt-terminated Pt-Cu bimetallic nano-sized electrocatalysts (Pt/Cu/Pt/C) were synthesized by using an electroless deposition method. The synthesized Pt/Cu/Pt/C consisted of a Pt-enriched shell, a sandwiched Pt-Cu alloy layer, and a Pt core. The Pt/Cu/Pt/C showed higher electrocatalytic activity toward oxygen reduction reaction in half-cell test than that of commercial Pt/C due to an electronic structure change in the Pt-enriched shell, resulting from the sandwiched Pt-Cu alloy layer underneath. The stability of the Pt/Cu/Pt/C was examined by using both half-cell and single-cell degradation tests. In both tests, the Pt/Cu/Pt/C exhibited stronger resistance to catalyst degradation than that of the commercial Pt/C. It is notable that cell performance with the Pt/Cu/Pt/C was fully recovered by N2 purging after single-cell degradation testing, indicating there was no permanent damage to the electrocatalyst during the test. It is suggested that thermodynamically-stable structure of the Pt/Cu/Pt/C contributed to the improved stability.

  2. Synthesis and magnetic properties of Fe-Pt-B nanocomposite permanent magnets with low Pt concentrations

    SciTech Connect

    Zhang Wei; Louzguine, Dmitri V.; Inoue, Akihisa

    2004-11-22

    Microstructure and magnetic properties of melt-spun Fe{sub 80-x}Pt{sub x}B{sub 20} (x=20,22,24) alloy ribbons have been investigated. A homogeneous nanoscale mixed structure with amorphous and fcc {gamma}-FePt phases was formed in the melt-spun ribbons. The average sizes of the amorphous and fcc {gamma}-FePt phases are about 5 nm, and the enrichment phenomenon of B is recognized in the coexistent amorphous phase. The melt-spun ribbons exhibit soft magnetic properties. The nanocomposite structure consisting of fct {gamma}{sub 1}-FePt, fcc {gamma}-FePt, and Fe{sub 2}B phases was obtained in the melt-spun ribbons annealed at 798 K for 900 s, and their average grain sizes are about 20 nm. The remanence (B{sub r}), reduced remanence (M{sub r}/M{sub s}), coercivity ({sub i}H{sub c}), and maximum energy product (BH){sub max} of the nanocomposite alloys are in the range of 0.93-1.05 T, 0.79-0.82, 375-487 kA/m, and 118-127 kJ/m{sup 3}, respectively. The good hard magnetic properties are interpreted as resulting from exchange magnetic coupling between nanoscale hard fct {gamma}{sub 1}-FePt and soft magnetic fcc {gamma}-FePt or Fe{sub 2}B phases.

  3. Synthesis and Characterization of Pt(IV) Fluorescein Conjugates to Investigate Pt(IV) Intracellular Transformations

    PubMed Central

    Song, Ying; Suntharalingam, Kogularamanan; Yeung, Jessica S.; Royzen, Maksim; Lippard, Stephen J.

    2013-01-01

    Pt(IV) anticancer compounds typically operate as prodrugs that are reduced in the hypoxic environment of cancer cells, losing two axial ligands in the process to generate active Pt(II) species. Here we report the synthesis of two fluorescent Pt(IV) prodrugs of cisplatin in order to image and evaluate the Pt(IV) reduction process in simulated and real biological environments. Treatment of the complexes dissolved in PBS buffer with reducing agents typically encountered in cells, glutathione or ascorbate, afforded a 3- to 5-fold fluorescence turn-on owing to reduction and loss of their fluorescein-based axial ligands, which are quenched when bound to platinum. Both Pt(IV) conjugates displayed moderate cytotoxicity against human cancer cell lines, with IC50 values higher than that of cisplatin. Immunoblotting and DNA flow cytometry analyses of one of the complexes, Pt(IV)FL2, revealed that it damages DNA, causing cell cycle arrest in S or G2/M depending on exposure time, with ultimately triggering of apoptotic cell death. Fluorescence microscopic studies prove that Pt(IV)FL2 enters cells intact and undergoes reduction intracellularly. The results are best interpreted in terms of a model in which the axial fluorescein ligands are expelled through lysosomes, with the platinum(II) moiety generated in the process binding to genomic DNA, which results in cell death. PMID:23957697

  4. Discovery of the Pt-Based Superconductor LaPt5As.

    PubMed

    Fujioka, Masaya; Ishimaru, Manabu; Shibuya, Taizo; Kamihara, Yoichi; Tabata, Chihiro; Amitsuka, Hiroshi; Miura, Akira; Tanaka, Masashi; Takano, Yoshihiko; Kaiju, Hideo; Nishii, Junji

    2016-08-10

    A novel superconductor, LaPt5As, which exhibits a new crystal structure was discovered by high-pressure synthesis using a Kawai-type apparatus. A superconducting transition temperature was observed at 2.6 K. Depending on the sintering pressure, LaPt5As has superconducting and non-superconducting phases with different crystal structures. A sintering pressure of around 10 GPa is effective to form single-phase superconducting LaPt5As. This material has a very unique crystal structure with an extremely long c lattice parameter of over 60 Å and corner-sharing tetrahedrons composed of network-like Pt layers. Density functional theory calculations have suggested that the superconducting current flows through these Pt layers. Also, this unique layered structure characteristic of LaPt5As is thought to play a key role in the emergence of superconductivity. Furthermore, due to a stacking structure which makes up layers, various structural modifications for the LaPt5As family are conceivable. Since such a high-pressure synthesis using a Kawai-type apparatus is not common in the field of materials science, there is large room for further exploration of unknown phases which are induced by high pressure in various materials. PMID:27461965

  5. Tailoring Curie temperature and magnetic anisotropy in ultrathin Pt/Co/Pt films

    NASA Astrophysics Data System (ADS)

    Parakkat, Vineeth Mohanan; Ganesh, K. R.; Anil Kumar, P. S.

    2016-05-01

    The dependence of perpendicular magnetization and Curie temperature (Tc) of Pt/Co/Pt thin films on the thicknesses of Pt seed (Pts) and presence of Ta buffer layer has been investigated in this work. Pt and Co thicknesses were varied between 2 to 8 nm and 0.35 to 1.31 nm (across the spin reorientation transition thickness) respectively and the Tc was measured using SQUID magnetometer. We have observed a systematic dependence of Tc on the thickness of Pts. For 8nm thickness of Pts the Co layer of 0.35nm showed ferromagnetism with perpendicular anisotropy at room temperature. As the thickness of the Pts was decreased to 2nm, the Tc went down below 250K. XRD data indicated polycrystalline growth of Pts on SiO2. On the contrary Ta buffer layer promoted the growth of Pt(111). As a consequence Ta(5nm)/Pt(3nm)/Co(0.35nm)/Pt(2nm) had much higher Tc (above 300K) with perpendicular anisotropy when compared to the same stack without the Ta layer. Thus we could tune the ferromagnetic Tc and anisotropy by varying the Pts thickness and also by introducing Ta buffer layer. We attribute these observations to the micro-structural evolution of Pts layer which hosts the Co layer.

  6. Nuclear Data Sheets for {sup 170}Pt

    SciTech Connect

    Baglin, Coral M.

    1999-02-22

    Nuclear structure data pertaining to 170Pt have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation of170Pt supersedes the previous publication (Coral M. Baglin,Nuclear Data Sheets 77,125 (1996) (literature cutoff date October 1995)), and includes literature available by 17 February 1999. The newly incorporated references are: 98Se20, 98Ki20, 97Ju04, 96Bi07 and 95Au04. Three new data sets have been added, as follows:174Hg ? decay,171Au p decay (1.02 ms), (HI,xn?).

  7. Pt-Ni and Pt-Co Catalyst Synthesis Route for Fuel Cell Applications

    NASA Technical Reports Server (NTRS)

    Firdosy, Samad A.; Ravi, Vilupanur A.; Valdez, Thomas I.; Kisor, Adam; Narayan, Sri R.

    2013-01-01

    Oxygen reduction reactions (ORRs) at the cathode are the rate-limiting step in fuel cell performance. The ORR is 100 times slower than the corresponding hydrogen oxidation at the anode. Speeding up the reaction at the cathode will improve fuel cell efficiency. The cathode material is generally Pt powder painted onto a substrate (e.g., graphite paper). Recent efforts in the fuel cell area have focused on replacing Pt with Pt-X alloys (where X = Co, Ni, Zr, etc.) in order to (a) reduce cost, and (b) increase ORR rates. One of these strategies is to increase ORR rates by reducing the powder size, which would result in an increase in the surface area, thereby facilitating faster reaction rates. In this work, a process has been developed that creates Pt-Ni or Pt-Co alloys that are finely divided (on the nano scale) and provide equivalent performance at lower Pt loadings. Lower Pt loadings will translate to lower cost. Precursor salts of the metals are dissolved in water and mixed. Next, the salt mixtures are dried on a hot plate. Finally, the dried salt mixture is heattreated in a furnace under flowing reducing gas. The catalyst powder is then used to fabricate a membrane electrode assembly (MEA) for electrochemical performance testing. The Pt- Co catalyst-based MEA showed comparable performance to an MEA fabri cated using a standard Pt black fuel cell catalyst. The main objective of this program has been to increase the overall efficiencies of fuel cell systems to support power for manned lunar bases. This work may also have an impact on terrestrial programs, possibly to support the effort to develop a carbon-free energy source. This catalyst can be used to fabricate high-efficiency fuel cell units that can be used in space as regenerative fuel cell systems, and terrestrially as primary fuel cells. Terrestrially, this technology will become increasingly important when transition to a hydrogen economy occurs.

  8. Sintering Behavior of Spin-coated FePt and FePtAu Nanoparticles

    SciTech Connect

    Kang, Shishou; Jia, Zhiyong; Zoto, Ilir; Reed, R. C.; Nikles, David E.; Harrell, J. W.; Vemuru, Krishnamurthy V; Porcar, L.

    2006-01-01

    FePt and [FePt]{sub 95}Au{sub 5} nanoparticles with an average size of about 4 nm were chemically synthesized and spin coated onto silicon substrates. Samples were subsequently thermally annealed at temperatures ranging from 250 to 500 C for 30 min. Three-dimensional structural characterization was carried out with small-angle neutron scattering (SANS) and small-angle x-ray diffraction (SAXRD) measurements. For both FePt and [FePt]{sub 95}Au{sub 5} particles before annealing, SANS measurements gave an in-plane coherence length parameter a = 7.3 nm, while SAXRD measurements gave a perpendicular coherence length parameter c = 12.0 nm. The ratio of c/a is about 1.64, indicating the as-made particle array has a hexagonal close-packed superstructure. For both FePt and FePtAu nanoparticles, the diffraction peaks shifted to higher angles and broadened with increasing annealing temperature. This effect corresponds to a shrinking of the nanoparticle array, followed by agglomeration and sintering of the nanoparticles, resulting in the eventual loss of positional order with increasing annealing temperature. The effect is more pronounced for FePtAu than for FePt. Dynamic coercivity measurements show that the FePtAu nanoparticles have both higher intrinsic coercivity and higher switching volume at the same annealing temperature. These results are consistent with previous studies that show that additive Au both lowers the chemical ordering temperature and promotes sintering.

  9. Efficient Pt catalysts for polymer electrolyte fuel cells

    SciTech Connect

    Fournier, J.; Gaubert, G.; Tilquin, J.Y.

    1996-12-31

    Commercialization of polymer electrolyte fuel cells (PEFCs) requires an important decrease in their production cost. Cost reduction for the electrodes principally concerns the decrease in the amount of Pt catalyst necessary for the functioning of the PEFC without affecting cell performance. The first PEFCs used in the Gemini Space Program had a loading of 4-10 mg pt/cm{sup 2}. The cost of the electrodes was drastically reduced when pure colloidal Pt was replaced by Pt supported on carbon (Pt/C) with a Pt content of 0.4 Mg/cm{sup 2}. Since the occurrence of that breakthrough, many studies have been aimed at further lowering the Pt loading. Today, the lowest loadings reported for oxygen reduction are of the order of 0.05 mg pt/cm{sup 2}. The carbon support of commercial catalysts is Vulcan XC-72 from Cabot, a carbon black with a specific area of 254 m{sup 2}/g. Graphites with specific areas ranging from 20 to 305 m{sup 2}/g are now available from Lonza. The first aim of the present study was to determine the catalytic properties for 02 reduction of Pt supported on these high specific area graphites. The second aim was to use Pt inclusion synthesis on these high area graphites, and to measure the catalytic performances of these materials. Lastly, this same Pt-inclusion synthesis was extended even for use with Vulcan and Black Pearls as substrates (two carbon blacks from Cabot). All these catalysts have been labelled Pt-included materials to distinguish them from the Pt-supported ones. It will be shown that the reduced Pt content Pt-included materials obtained with high specific area substrates a are excellent catalysts for oxygen reduction, especially at high currents. Therefore, Pt inclusion synthesis appears to be a new method to decrease the cathodic Pt loading.

  10. A multiplex set of species-specific primers for rapid identification of members of the genus Saccharomyces.

    PubMed

    Muir, Alastair; Harrison, Elizabeth; Wheals, Alan

    2011-11-01

    The Saccharomyces genus (previously Saccharomyces sensu stricto) formally comprises Saccharomyces arboricola, Saccharomyces bayanus, Saccharomyces cariocanus, Saccharomyces cerevisiae, Saccharomyces kudriavzevii, Saccharomyces mikatae, Saccharomyces paradoxus and Saccharomyces pastorianus. Species-specific primer pairs that produce a single band of known and different product size have been developed for each member of the clade with the exception of S. pastorianus, which is a polyphyletic allopolyploid hybrid only found in lager breweries, and for which signature sequences could not be reliably created. Saccharomyces cariocanus is now regarded as an American variant of S. paradoxus, and accordingly a single primer pair that recognizes both species was developed. A different orthologous and essential housekeeping gene was used to detect each species, potentially avoiding competition between PCR primers and overlap between amplicons. In multiplex format, two or more different species could be identified in a single reaction; double and triple hybrids could not always be correctly identified. Forty-two unidentified yeasts from sugar cane juice fermentations were correctly identified as S. cerevisiae. A colony PCR method was developed that is rapid, robust, inexpensive and capable of automation, requires no mycological expertise on the part of the user and is thus useful for large-scale preliminary screens. PMID:22093682

  11. Asymmetry in effective fields of spin-orbit torques in Pt/Co/Pt stacks

    SciTech Connect

    Hin Sim, Cheow Cheng Huang, Jian; Tran, Michael; Eason, Kwaku

    2014-01-06

    Measurements of switching via spin-orbit coupling mechanisms are discussed for a pair of inverted Pt/Co/Pt stacks with asymmetrical Pt thicknesses. Taking into account the planar Hall effect contribution, effective fields of spin-orbit torques (SOT) are evaluated using lock-in measurements of the first and second harmonics of the Hall voltage. Reversing the stack structure leads to significant asymmetries in the switching behavior, including clear evidence of a nonlinear current dependence of the transverse effective field. Our results demonstrate potentially complex interplay in devices with all-metallic interfaces utilizing SOT.

  12. 'Yeast mail': a novel Saccharomyces application (NSA) to encrypt messages.

    PubMed

    Rosemeyer, Helmut; Paululat, Achim; Heinisch, Jürgen J

    2014-09-01

    The universal genetic code is used by all life forms to encode biological information. It can also be used to encrypt semantic messages and convey them within organisms without anyone but the sender and recipient knowing, i.e., as a means of steganography. Several theoretical, but comparatively few experimental, approaches have been dedicated to this subject, so far. Here, we describe an experimental system to stably integrate encrypted messages within the yeast genome using a polymerase chain reaction (PCR)-based, one-step homologous recombination system. Thus, DNA sequences encoding alphabetical and/or numerical information will be inherited by yeast propagation and can be sent in the form of dried yeast. Moreover, due to the availability of triple shuttle vectors, Saccharomyces cerevisiae can also be used as an intermediate construction device for transfer of information to either Drosophila or mammalian cells as steganographic containers. Besides its classical use in alcoholic fermentation and its modern use for heterologous gene expression, we here show that baker's yeast can thus be employed in a novel Saccharomyces application (NSA) as a simple steganographic container to hide and convey messages. PMID:25238077

  13. The Saccharomyces Genome Database: Exploring Biochemical Pathways and Mutant Phenotypes.

    PubMed

    Cherry, J Michael

    2015-12-01

    Many biochemical processes, and the proteins and cofactors involved, have been defined for the eukaryote Saccharomyces cerevisiae. This understanding has been largely derived through the awesome power of yeast genetics. The proteins responsible for the reactions that build complex molecules and generate energy for the cell have been integrated into web-based tools that provide classical views of pathways. The Yeast Pathways in the Saccharomyces Genome Database (SGD) is, however, the only database created from manually curated literature annotations. In this protocol, gene function is explored using phenotype annotations to enable hypotheses to be formulated about a gene's action. A common use of the SGD is to understand more about a gene that was identified via a phenotypic screen or found to interact with a gene/protein of interest. There are still many genes that do not yet have an experimentally defined function and so the information currently available can be used to speculate about their potential function. Typically, computational annotations based on sequence similarity are used to predict gene function. In addition, annotations are sometimes available for phenotypes of mutations in the gene of interest. Integrated results for a few example genes will be explored in this protocol. This will be instructive for the exploration of details that aid the analysis of experimental results and the establishment of connections within the yeast literature. PMID:26631123

  14. Evolutionary engineering of Saccharomyces cerevisiae for efficient aerobic xylose consumption.

    PubMed

    Scalcinati, Gionata; Otero, José Manuel; Van Vleet, Jennifer R H; Jeffries, Thomas W; Olsson, Lisbeth; Nielsen, Jens

    2012-08-01

    Industrial biotechnology aims to develop robust microbial cell factories, such as Saccharomyces cerevisiae, to produce an array of added value chemicals presently dominated by petrochemical processes. Xylose is the second most abundant monosaccharide after glucose and the most prevalent pentose sugar found in lignocelluloses. Significant research efforts have focused on the metabolic engineering of S. cerevisiae for fast and efficient xylose utilization. This study aims to metabolically engineer S. cerevisiae, such that it can consume xylose as the exclusive substrate while maximizing carbon flux to biomass production. Such a platform may then be enhanced with complementary metabolic engineering strategies that couple biomass production with high value-added chemical. Saccharomyces cerevisiae, expressing xylose reductase, xylitol dehydrogenase and xylulose kinase, from the native xylose-metabolizing yeast Pichia stipitis, was constructed, followed by a directed evolution strategy to improve xylose utilization rates. The resulting S. cerevisiae strain was capable of rapid growth and fast xylose consumption producing only biomass and negligible amount of byproducts. Transcriptional profiling of this strain was employed to further elucidate the observed physiology confirms a strongly up-regulated glyoxylate pathway enabling respiratory metabolism. The resulting strain is a desirable platform for the industrial production of biomass-related products using xylose as a sole carbon source. PMID:22487265

  15. Sequence Diversity, Reproductive Isolation and Species Concepts in Saccharomyces

    PubMed Central

    Liti, Gianni; Barton, David B. H.; Louis, Edward J.

    2006-01-01

    Using the biological species definition, yeasts of the genus Saccharomyces sensu stricto comprise six species and one natural hybrid. Previous work has shown that reproductive isolation between the species is due primarily to sequence divergence acted upon by the mismatch repair system and not due to major gene differences or chromosomal rearrangements. Sequence divergence through mismatch repair has also been shown to cause partial reproductive isolation among populations within a species. We have surveyed sequence variation in populations of Saccharomyces sensu stricto yeasts and measured meiotic sterility in hybrids. This allows us to determine the divergence necessary to produce the reproductive isolation seen among species. Rather than a sharp transition from fertility to sterility, which may have been expected, we find a smooth monotonic relationship between diversity and reproductive isolation, even as far as the well-accepted designations of S. paradoxus and S. cerevisiae as distinct species. Furthermore, we show that one species of Saccharomyces—S. cariocanus—differs from a population of S. paradoxus by four translocations, but not by sequence. There is molecular evidence of recent introgression from S. cerevisiae into the European population of S. paradoxus, supporting the idea that in nature the boundary between these species is fuzzy. PMID:16951060

  16. Functional Genomics Using the Saccharomyces cerevisiae Yeast Deletion Collections.

    PubMed

    Nislow, Corey; Wong, Lai Hong; Lee, Amy Huei-Yi; Giaever, Guri

    2016-01-01

    Constructed by a consortium of 16 laboratories, the Saccharomyces genome-wide deletion collections have, for the past decade, provided a powerful, rapid, and inexpensive approach for functional profiling of the yeast genome. Loss-of-function deletion mutants were systematically created using a polymerase chain reaction (PCR)-based gene deletion strategy to generate a start-to-stop codon replacement of each open reading frame by homologous recombination. Each strain carries two molecular barcodes that serve as unique strain identifiers, enabling their growth to be analyzed in parallel and the fitness contribution of each gene to be quantitatively assessed by hybridization to high-density oligonucleotide arrays or through the use of next-generation sequencing technologies. Functional profiling of the deletion collections, using either strain-by-strain or parallel assays, provides an unbiased approach to systematically survey the yeast genome. The Saccharomyces yeast deletion collections have proved immensely powerful in contributing to the understanding of gene function, including functional relationships between genes and genetic pathways in response to diverse genetic and environmental perturbations. PMID:27587784

  17. The mannoprotein of Saccharomyces cerevisiae is an effective bioemulsifier.

    PubMed Central

    Cameron, D R; Cooper, D G; Neufeld, R J

    1988-01-01

    The mannoprotein which is a major component of the cell wall of Saccharomyces cerevisiae is an effective bioemulsifier. Mannoprotein emulsifier was extracted in a high yield from whole cells of fresh bakers' yeast by two methods, by autoclaving in neutral citrate buffer and by digestion with Zymolase (Miles Laboratories; Toronto, Ontario, Canada), a beta-1,3-glucanase. Heat-extracted emulsifier was purified by ultrafiltration and contained approximately 44% carbohydrate (mannose) and 17% protein. Treatment of the emulsifier with protease eliminated emulsification. Kerosene-in-water emulsions were stabilized over a broad range of conditions, from pH 2 to 11, with up to 5% sodium chloride or up to 50% ethanol in the aqueous phase. In the presence of a low concentration of various solutes, emulsions were stable to three cycles of freezing and thawing. An emulsifying agent was extracted from each species or strain of yeast tested, including 13 species of genera other than Saccharomyces. Spent yeast from the manufacture of beer and wine was demonstrated to be a possible source for the large-scale production of this bioemulsifier. PMID:3046488

  18. Temperature dependence of oxygen reduction activity at Nafion-coated bulk Pt and Pt/carbon black catalysts.

    PubMed

    Yano, Hiroshi; Higuchi, Eiji; Uchida, Hiroyuki; Watanabe, Masahiro

    2006-08-24

    Oxygen reduction reaction (ORR) activity and H(2)O(2) formation at Nafion-coated film electrodes of bulk-Pt and Pt nanoparticles dispersed on carbon black (Pt/CB) were investigated in 0.1 M HClO(4) solution at 30 to 110 degrees C by using a channel flow double electrode method. We have found that the apparent rate constants k(app) (per real Pt active surface area) for the ORR at bulk-Pt (with and without Nafion-coating) and Nafion-coated Pt/CB (19.3 and 46.7 wt % Pt, d(Pt) = 2.6 to 2.7 nm) thin-film electrodes were in beautiful agreement with each other in the operation conditions of polymer electrolyte fuel cells (PEFCs), i.e., 30-110 degrees C and ca. 0.7 to 0.8 V vs RHE. The H(2)O(2) yield was 0.6-1.0% at 0.7-0.8 V on all Nafion-coated Pt/CB and bulk-Pt and irrespective of Pt-loading level and temperature. Nafion coating was pointed out to be a major factor for the H(2)O(2) formation on Pt catalysts modifying the surface property, because H(2)O(2) production was not detected at the bulk-Pt electrode without Nafion coating. PMID:16913788

  19. Surface structure and chemistry of Pt/Cu/Pt(1 1 1) near surface alloy model catalyst in CO

    NASA Astrophysics Data System (ADS)

    Zeng, Shibi; Nguyen, Luan; Cheng, Fang; Liu, Lacheng; Yu, Ying; Tao, Franklin (Feng)

    2014-11-01

    Near surface alloy (NSA) model catalyst Pt/Cu/Pt(1 1 1) was prepared on Pt(1 1 1) through a controlled vapor deposition of Cu atoms. Different coordination environments of Pt atoms of the topmost Pt layer with the underneath Cu atoms in the subsurface result in different local electronic structures of surface Pt atoms. Surface structure and chemistry of the NAS model catalyst in Torr pressure of CO were studied with high pressure scanning tunneling microscopy (HP-STM) and ambient pressure X-ray photoelectron spectroscopy (AP-XPS). In Torr pressure of CO, the topmost Pt layer of Pt/Cu/Pt(1 1 1) is restructured to thin nanoclusters with size of about 1 nm. Photoemission feature of O 1s of CO on Pt/Cu/Pt(1 1 1) suggests CO adsorbed on both edge and surface of these formed nanoclusters. This surface is active for CO oxidation. Atomic layers of carbon are formed on Pt/Cu/Pt(1 1 1) at 573 K in 2 Torr of CO.

  20. PT3 Papers. [SITE 2001 Section].

    ERIC Educational Resources Information Center

    Pierson, Melissa, Ed.; Thompson, Mary, Ed.; Adams, Angelle, Ed.; Beyer, Evelyn, Ed.; Cheriyan, Saru, Ed.; Starke, Leslie, Ed.

    This document contains the papers on the PT3 (Preparing Tomorrow's Teachers to use Technology) program from the SITE (Society for Information Technology & Teacher Education) 2001 conference. Topics covered include: modeling instruction with modern information and communications technology; transforming computer coursework for preservice teachers;…

  1. Structural and magnetic properties of the ordered FePt{sub 3}, FePt and Fe{sub 3}Pt nanoparticles

    SciTech Connect

    Liu, Yang; Jiang, Yuhong; Zhang, Xiaolong; Wang, Yaxin; Zhang, Yongjun; Liu, Huilian; Zhai, Hongju; Liu, Yanqing; Yang, Jinghai; Yan, Yongsheng

    2014-01-15

    The Fe{sub x}Pt{sub 100−x} nanoparticles (NPs) with different nominal atomic rations (30≤x≤80) were synthesized at 700 °C by the sol–gel method. The structure, morphology and magnetic properties of the samples were investigated. When the Fe content in the Fe–Pt alloy NPs was 30 at%, FePt{sub 3} NPs were successfully synthesized. With the increase in Fe content up to 50 at%, it was found that the superlattice reflections (0 0 1) and (1 1 0) appeared, which indicated the formation of the L1{sub 0}-FePt phase. Meanwhile, the FePt{sub 3} fraction was reduced. When the Fe content increased to 60 at%, single-phase L1{sub 0}-FePt NPs were synthesized. The coercivity (Hc), saturation magnetization (Ms) and chemical order parameter S for Fe{sub 60}Pt{sub 40} NPs were as high as 10,200 Oe, 17.567 emu/g and 0.928, respectively. With the further increase of the Fe content to 80 at%, only Fe{sub 3}Pt phase existed and the Hc of the Fe{sub 3}Pt NPs decreased drastically to 360 Oe. - Graphical abstract: Fe{sub 3}Pt, FePt and FePt{sub 3} nanoparticles was obtained by sol–gel method. The effect of iron and platinum content on structural and magnetic properties of the FePt nanoparticles was investigated. Display Omitted - Highlights: • L1{sub 2}-FePt{sub 3}, L1{sub 0}-FePt and L1{sub 2}-Fe{sub 3}Pt NPs were synthesized by sol–gel method. • The chemical order parameter S affects the magnetic properties of the Fe–Pt alloy. • Structural and magnetic properties of the Fe–Pt alloy NPs were studied. • The synthetic route in this study will open up the possibilities of practical use.

  2. Irreversible modification of magnetic properties of Pt/Co/Pt ultrathin films by femtosecond laser pulses

    SciTech Connect

    Kisielewski, J.; Dobrogowski, W.; Kurant, Z.; Stupakiewicz, A.; Tekielak, M.; Maziewski, A.; Kirilyuk, A.; Kimel, A.; Rasing, Th.; Baczewski, L. T.; Wawro, A.

    2014-02-07

    Annealing ultrathin Pt/Co/Pt films with single femtosecond laser pulses leads to irreversible spin-reorientation transitions and an amplification of the magneto-optical Kerr rotation. The effect was studied as a function of the Co thickness and the pulse fluence, revealing two-dimensional diagrams of magnetic properties. While increasing the fluence, the creation of two branches of the out-of-plane magnetization state was found.

  3. Simulation of electroforming of the Pt/NiO/Pt switching memory structure

    NASA Astrophysics Data System (ADS)

    Sysun, V. I.; Sysun, I. V.; Boriskov, P. P.

    2016-05-01

    We analyze experimental data on a transient thermal electroforming of a Pt/NiO/Pt unipolar memory switching structure. Numerical simulation of this process shows that the channel can be identified with the melting region of nickel oxide, in which its cross section is determined by the maximal breakdown current, a considerable contribution to which can come from a parasitic capacitance. Rough analytic approximations are given for estimating the channel formation parameters.

  4. Unusual cluster shapes and directional bonding of an fcc metal: Pt/Pt(111).

    PubMed

    Schmid, Michael; Garhofer, Andreas; Redinger, Josef; Wimmer, Florian; Scheiber, Philipp; Varga, Peter

    2011-07-01

    Small clusters of Pt adatoms grown on Pt(111) exhibit a preference for the formation of linear chains, which cannot be explained by simple diffusion-limited aggregation. Density functional theory calculations show that short chains are energetically favorable to more compact configurations due to strong directional bonding by d(z)(2)-like orbitals, explaining the stability of the chains. The formation of the chains is governed by substrate distortions, leading to funneling towards the chain ends. PMID:21797553

  5. Microstructure and magnetization reversal of L10-FePt/[Co/Pt]N exchange coupled composite films

    NASA Astrophysics Data System (ADS)

    Guo, H. H.; Liao, J. L.; Ma, B.; Zhang, Z. Z.; Jin, Q. Y.; Wang, H.; Wang, J. P.

    2012-04-01

    Two series of perpendicular exchange coupled composites (ECC) films are prepared by dc magnetron sputtering, FePt(5)/[Co(0.2)/Pt(0.3)]N (ECC-I-N) and FePt(5)/[Co(0.2)/Pt(0.6)]N (ECC-II-N), respectively. Structure analyses reveal the epitaxial growth on (001) oriented L10 FePt island-like grains of [Co/Pt]N with (200) orientation. Coercivity HC and remanent coercivity HCR of both series samples decrease sharply compared to FePt, with the increase of the thickness of [Co/Pt]N. The angular dependence of HCR shows excellent angular tolerance.

  6. Reactivity of atomically dispersed Pt(2+) species towards H2: model Pt-CeO2 fuel cell catalyst.

    PubMed

    Lykhach, Yaroslava; Figueroba, Alberto; Camellone, Matteo Farnesi; Neitzel, Armin; Skála, Tomáš; Negreiros, Fabio R; Vorokhta, Mykhailo; Tsud, Nataliya; Prince, Kevin C; Fabris, Stefano; Neyman, Konstantin M; Matolín, Vladimír; Libuda, Jörg

    2016-03-01

    The reactivity of atomically dispersed Pt(2+) species on the surface of nanostructured CeO2 films and the mechanism of H2 activation on these sites have been investigated by means of synchrotron radiation photoelectron spectroscopy and resonant photoemission spectroscopy in combination with density functional calculations. Isolated Pt(2+) sites are found to be inactive towards H2 dissociation due to high activation energy required for H-H bond scission. Trace amounts of metallic Pt are necessary to initiate H2 dissociation on Pt-CeO2 films. H2 dissociation triggers the reduction of Ce(4+) cations which, in turn, is coupled with the reduction of Pt(2+) species. The mechanism of Pt(2+) reduction involves reverse oxygen spillover and formation of oxygen vacancies on Pt-CeO2 films. Our calculations suggest the existence of a threshold concentration of oxygen vacancies associated with the onset of Pt(2+) reduction. PMID:26908194

  7. Alloy Cu3Pt nanoframes through the structure evolution in Cu-Pt nanoparticles with a core-shell construction

    PubMed Central

    Han, Lin; Liu, Hui; Cui, Penglei; Peng, Zhijian; Zhang, Suojiang; Yang, Jun

    2014-01-01

    Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for catalysis. Herein, we present an unique structure transformation phenomenon for the fabrication of alloy Cu3Pt nanoframes with polyhedral morphology. This strategy starts with the preparation of polyhedral Cu-Pt nanoparticles with a core-shell construction upon the anisotropic growth of Pt on multiply twinned Cu seed particles, which are subsequently transformed into alloy Cu3Pt nanoframes due to the Kirkendall effect between the Cu core and Pt shell. The as-prepared alloy Cu3Pt nanoframes possess the rhombic dodecahedral morphology of their core-shell parents after the structural evolution. In particular, the resulting alloy Cu3Pt nanoframes are more effective for oxygen reduction reaction but ineffective for methanol oxidation reaction in comparison with their original Cu-Pt core-shell precursors. PMID:25231376

  8. Preparation of Pt Nanocatalyst on Carbon Materials via a Reduction Reaction of a Pt Precursor in a Drying Process.

    PubMed

    Lee, Jae-Young; Lee, Woo-Kum; Rim, Hyung-Ryul; Joung, Gyu-Bum; Weidner, John W; Lee, Hong-Ki

    2016-06-01

    Platinum (Pt) nanocatalyst for a proton-exchange membrane fuel cell (PEMFC) was prepared on a carbon black particle or a graphite particle coated with a nafion polymer via a reduction of platinum(II) bis(acetylacetonate) denoted as Pt(acac)2 as a Pt precursor in a drying process. Sublimed Pt(acac)2 adsorbed on the nafion-coated carbon materials was reduced to Pt nanoparticles in a glass reactor at 180 degrees C of N2 atmosphere. The morphology of Pt nanoparticles on carbon materials was observed by scanning electron microscopy (SEM) and the distribution of Pt nanoparticles was done by transmission electron microscopy (TEM). The particle size was estimated by analyzing the TEM image using an image analyzer. It was found that nano-sized Pt particles were deposited on the surface of carbon materials, and the number density and the average particle size increased with increasing reduction time. PMID:27427723

  9. Alloy Cu3Pt nanoframes through the structure evolution in Cu-Pt nanoparticles with a core-shell construction

    NASA Astrophysics Data System (ADS)

    Han, Lin; Liu, Hui; Cui, Penglei; Peng, Zhijian; Zhang, Suojiang; Yang, Jun

    2014-09-01

    Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for catalysis. Herein, we present an unique structure transformation phenomenon for the fabrication of alloy Cu3Pt nanoframes with polyhedral morphology. This strategy starts with the preparation of polyhedral Cu-Pt nanoparticles with a core-shell construction upon the anisotropic growth of Pt on multiply twinned Cu seed particles, which are subsequently transformed into alloy Cu3Pt nanoframes due to the Kirkendall effect between the Cu core and Pt shell. The as-prepared alloy Cu3Pt nanoframes possess the rhombic dodecahedral morphology of their core-shell parents after the structural evolution. In particular, the resulting alloy Cu3Pt nanoframes are more effective for oxygen reduction reaction but ineffective for methanol oxidation reaction in comparison with their original Cu-Pt core-shell precursors.

  10. Adsorption of ethene on Pt(1 1 1) and ordered Pt xSn/Pt(1 1 1) surface alloys: A comparative HREELS and DFT investigation

    NASA Astrophysics Data System (ADS)

    Essen, J. M.; Haubrich, J.; Becker, C.; Wandelt, K.

    2007-08-01

    The adsorption of ethene (C 2H 4) on Pt(1 1 1) and the Pt 3Sn/Pt(1 1 1) and Pt 2Sn/Pt(1 1 1) surface alloys has been investigated experimentally by high-resolution electron energy loss spectroscopy and temperature programmed desorption. The experimental results have been compared with density functional theory (DFT) calculations allowing us to perform a complete assignment of all vibration modes and loss features to the species present on the surfaces. On Pt(1 1 1) as well as on the Pt-Sn surface alloys an η2 di-σ-bonded conformation of ethene has been found to be the most stable adsorbed form. In addition to this majority species a minor amount of π-bonded ethene has been identified, which is more abundant on the Pt 2Sn surface alloy than on the other surfaces. Additionally the HREELS spectra of ethene on Pt(1 1 1) and the Pt-Sn surface alloys differ only slightly in terms of the energetic positions of the loss peaks.

  11. Synthesis And Characterization of Gamma-Al2O3-Supported Pt Catalysts From Pt(4) And Pt(6) Clusters Formed in Aqueous Solutions

    SciTech Connect

    Siani, A.; Wigal, K.R.; Alexeev, A.S.; Amiridis, M.D.

    2009-05-26

    Highly dispersed Pt catalysts were prepared by deposition of Pt{sub 4} and Pt{sub 6} clusters, initially formed in unprotected and poly(vinyl alcohol) (PVA)-protected colloidal Pt suspensions, onto a {gamma}-Al{sub 2}O{sub 3} surface. These catalysts were characterized by extended X-ray absorption fine structure (EXAFS) and Fourier transform infrared (FTIR) spectroscopies. The EXAFS results indicate that the supported Pt species formed were very similar in structure to those of the original clusters in the corresponding colloidal suspensions. The FTIR results further indicate that the {gamma}-Al{sub 2}O{sub 3}-supported Pt{sub 4} clusters have significantly lower chemisorptive properties compared with larger supported Pt nanoparticles; nevertheless, the Pt{sub 4}/{gamma}-Al{sub 2}O{sub 3} sample was active for the oxidation of CO with no need for additional activation treatment. In fact, treatment of this sample with H{sub 2} at 150--200 {sup o}C led to the formation of Pt aggregates with sizes of 1.0--1.6 nm, demonstrating that the surface Pt4 species readily sintered in this temperature range under reducing conditions.

  12. Probing the solvent shell with 195Pt chemical shifts: density functional theory molecular dynamics study of Pt(II) and Pt(IV) anionic complexes in aqueous solution.

    PubMed

    Truflandier, Lionel A; Autschbach, Jochen

    2010-03-17

    Ab initio molecular dynamics (aiMD) simulations based on density functional theory (DFT) were performed on a set of five anionic platinum complexes in aqueous solution. (195)Pt nuclear magnetic shielding constants were computed with DFT as averages over the aiMD trajectories, using the two-component relativistic zeroth-order regular approximation (ZORA) in order to treat relativistic effects on the Pt shielding tensors. The chemical shifts obtained from the aiMD averages are in good agreement with experimental data. For Pt(II) and Pt(IV) halide complexes we found an intermediate solvent shell interacting with the complexes that causes pronounced solvent effects on the Pt chemical shifts. For these complexes, the magnitude of solvent effects on the Pt shielding constant can be correlated with the surface charge density. For square-planar Pt complexes the aiMD simulations also clearly demonstrate the influence of closely coordinated non-equatorial water molecules on the Pt chemical shift, relating the structure of the solution around the complex to the solvent effects on the metal NMR chemical shift. For the complex [Pt(CN)(4)](2-), the solvent effects on the Pt shielding constant are surprisingly small. PMID:20166712

  13. Structural investigation of ultrathin Pt/Co/Pt trilayer films under EUV irradiation

    NASA Astrophysics Data System (ADS)

    Dynowska, E.; Pelka, J. B.; Klinger, D.; Minikayev, R.; Bartnik, A.; Dluzewski, P.; Jakubowski, M.; Klepka, M.; Petruczik, A.; Seeck, O. H.; Sobierajski, R.; Sveklo, I.; Wawro, A. A.; Maziewski, A.

    2015-12-01

    Trilayer systems containing ultrathin (3 nm) cobalt layer grown on 5 nm thick Pt buffer layer and covered with 3 nm thick Pt cap layer grown at room temperature by molecular beam epitaxy on the Al2O3(00.1) substrate have been irradiated by nanosecond extreme ultraviolet light pulses. It was previously evidenced that light irradiation induced irreversible change of direction of magnetization in such nanostructures. In order to understand the reasons of such behavior the structural studies with the use of X-ray diffraction and transmission electron microscopy of the as-grown and irradiated samples have been done. It was found that irradiation leads to intermixing of cobalt with platinum giving rise to creation of Pt1-xCox disordered alloy. The methodology of determination of the strain state of the layers, relaxed lattice parameter of the unit cell and the composition of Pt1-xCox alloys has been developed and described in details. The results of structural studies of the as grown Pt/Co/Pt nanostructures as well as those modified by irradiation are presented in this paper.

  14. Compositional superlattices based on PtCl/PtBr MX materials

    SciTech Connect

    Saxena, A.; Huang, X.Z.; Bishop, A.R.

    1992-01-01

    We consider theoretically a novel class of compositional superlattices consisting of alternating layers of quasi-one-dimensional (QlD) MX (halogen-bridged, transition metal) chain materials. In particular, we have studied a superlattice based on the PtCl/PtBr unit where the Peierls band gap for PtCl is [approximately]2.4 eV and [approximately]1.5 eV for PtBr. We have calculated electronic properties, optical absorption and vibrational properties (e.g. Raman spectrum) of an MX superlattice using a discrete, two-band, tight-binding Peierls-Hubbard model. The electronic band structure reveals a typical subband structure and varies with the relative lengths of the constituent PtCl and PtBr units. The MX superlattice can be thought of as an analog of a GaAs/GaAl[sub x]As[sub 1-x] compositional superlattice but with the added feature that the optical, transport and various other physical properties are modified due to presence of nonlinear excitations (e.g. polarons) in the doped samples.

  15. The Mechanism of Direct Formic Acid Fuel Cell Using Pd, Pt and Pt-Ru

    NASA Astrophysics Data System (ADS)

    Kamiya, Nobuyuki; Liu, Yan; Mitsushima, Shigenori; Ota, Ken-Ichiro; Tsutsumi, Yasuyuki; Ogawa, Naoya; Kon, Norihiro; Eguchi, Mika

    The electro-oxidation of formic acid, 2-propanol and methanol on Pd black, Pd/C, Pt-Ru/C and Pt/C has been investigated to clear the reaction mechanism. It was suggested that the formic acid is dehydrogenated on Pd surface and the hydrogen is occluded in the Pd lattice. Thus obtained hydrogen acts like pure hydrogen supplied from the outside and the cell performance of the direct formic acid fuel cell showed as high as that of a hydrogen-oxygen fuel cell. 2-propanol did not show such dehydrogenation reaction on Pd catalyst. Platinum and Pt-Ru accelerated the oxidation of C-OH of 2-propanol and methanol. Slow scan voltammogram (SSV) and chronoamperometry measurements showed that the activity of formic acid oxidation increased in the following order: Pd black > Pd 30wt.%/C > Pt50wt.%/C > 27wt.%Pt-13wt.%Ru/C. A large oxidation current for formic acid was found at a low overpotential on the palladium electrocatalysts. These results indicate that formic acid is mainly oxidized through a dehydrogenation reaction. For the oxidation of 2-propanol and methanol, palladium was not effective, and 27wt.%Pt-13wt.%Ru/C showed the best oxidation activity.

  16. Modification of Pt/Co/Pt film properties by ion irradiation

    NASA Astrophysics Data System (ADS)

    Avchaciov, K. A.; Ren, W.; Djurabekova, F.; Nordlund, K.; Sveklo, I.; Maziewski, A.

    2015-09-01

    We studied the structural modifications of a Pt/Co/Pt trilayer epitaxial film under Ga+ 30-keV ion irradiation by means of classical molecular dynamics and Monte Carlo simulations. The semiclassical tight-binding second-moment approximation potential was adjusted to reproduce the enthalpies of formation, the lattice constants, and the order-disorder transition temperatures for Co-Pt alloys. We found that during irradiation, the sandwich-type Pt(fcc)/Co(hcp)/Pt(fcc) film structure underwent a transition to the new solid solution α -Co /Pt (fcc ) phase. Our analysis of the short-range order indicates the formation, within a nanosecond time scale, of a homogeneous chemically disordered solution. The longer time-scale simulations employing a Monte Carlo algorithm demonstrated that the transition from the disordered phase to the ordered L 10 and L 12 phases was also possible but not significant for the changes in perpendicular magnetic anisotropy (PMA) observed experimentally. The strain analysis showed that the Co layer was under tensile strain in the lateral direction at the fluences of 1.5 ×1014-3.5 ×1014ionscm -2 ; this range of fluences corresponds to the appearance of PMA. This strain was induced in the initially relaxed hcp Co layer due to its partial transformation to the fcc phase and to the influence of atomic layers with larger lattice constants at upper/lower interfaces.

  17. An evaluation of Pt sulfite acid (PSA) as precursor for supported Pt catalysts

    SciTech Connect

    Regalbuto, J.R.; Ansel, O.; Miller, J.T.

    2010-11-12

    As a catalyst precursor, platinum sulfite acid (PSA) is easy to use and not relatively expensive, and is a potentially attractive precursor for many types of supported catalysts. The ultimate usefulness for many catalyst applications will depend on the extent that Pt can be dispersed and sulfur eliminated. To our knowledge, there exists no detailed characterization in the catalysis literature of PSA and the nanoparticulate Pt phases derived from it during catalyst pretreatment. To this end a series of supports including alumina, silica, magnesia, niobia, titania, magnesia and carbon were contacted with PSA solutions and subsequently analyzed with extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) analysis, and x-ray photoelectron spectroscopy (XPS) to characterize the Pt species formed upon impregnation, calcination, and reduction. While all catalysts show retention of some S, reasonably small particle sizes with relatively little Pt-S can in some instances be produced using PSA. The amount of retained sulfur appears to decrease with decreasing surface acidity, although even the most acidic supports (niobia and silica) display some storage of S even while only Pt-O bands are observed after calcination or reoxidation. More sulfur was eliminated by high temperature calcinations followed by reduction in hydrogen, at the expense of increasing Pt particle size.

  18. Non-Saccharomyces and Saccharomyces strains co-fermentation increases acetaldehyde accumulation: effect on anthocyanin-derived pigments in Tannat red wines.

    PubMed

    Medina, Karina; Boido, Eduardo; Fariña, Laura; Dellacassa, Eduardo; Carrau, Francisco

    2016-07-01

    During fermentation, Saccharomyces cerevisiae releases into the medium secondary metabolic products, such as acetaldehyde, able to react with anthocyanins, producing more stable derived pigments. However, very limited reports are found about non-Saccharomyces effects on grape fermentation. In this study, six non-Saccharomyces yeast strains, belonging to the genera Metschnikowia and Hanseniaspora, were screened for their effect on red wine colour and wine-making capacity under pure culture conditions and mixed with Saccharomyces. An artificial red grape must was prepared, containing a phenolic extract of Tannat grapes that allows monitoring changes of key phenol parameters during fermentation, but without skin solids in the medium. When fermented in pure cultures, S. cerevisiae produced higher concentrations of acetaldehyde and vitisin B (acetaldehyde reaction-dependent) compared to M. pulcherrima M00/09G, Hanseniaspora guillermondii T06/09G, H. opuntiae T06/01G, H. vineae T02/05F and H. clermontiae (A10/82Fand C10/54F). However, co-fermentation of H. vineae and H. clermontiae with S. cerevisiae resulted in a significantly higher concentration of acetaldehyde compared with the pure S. cerevisiae control. HPLC-DAD-MS analysis confirmed an increased formation of vitisin B in co-fermentation treatments when compared to pure Saccharomyces fermentation, suggesting the key role of acetaldehyde. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26888345

  19. One-Step Synthesis of Pt/Graphene Composites from Pt Acid Dissolved Ethanol via Microwave Plasma Spray Pyrolysis.

    PubMed

    Jo, Eun Hee; Chang, Hankwon; Kim, Sun Kyung; Choi, Ji-Hyuk; Park, Su-Ryeon; Lee, Chong Min; Jang, Hee Dong

    2016-01-01

    Pt nanoparticles-laden graphene (Pt/GR) composites were synthesized in the gas phase from a mixture of ethanol and Pt precursor by microwave plasma spray pyrolysis. The morphology of Pt/GR composites has the shape of wrinkled sheets of paper, while Pt nanoparticles (Pt NPs) that are less than 2.6 nm in the mean diameter are uniformly well deposited on the surface of GR sheets stacked in only three layers. The Pt/GR composite prepared with 20 wt% of Pt had the highest specific surface area and electrochemical surface area of up to 402 m(2) g(-1) and 77 m(2) g(-1) (Pt), respectively. In addition, the composite showed superior electrocatalytic activity compared with commercial Pt-carbon black. The excellent electrocatalytic activity was attributed to the high specific surface area and electrochemical surface area of the Pt/GR composite directly produced by microwave plasma spray pyrolysis. Thus, it is clearly expected that the Pt/GR composite is a promising material for DMFC catalysts. PMID:27622908

  20. Investigation of the electrocatalysis for oxygen reduction reaction by Pt and binary Pt alloys: an XRD, XAS and electrochemical study

    SciTech Connect

    Mukerjee, S.; McBreen, J.; Srinivasan, S.

    1995-12-31

    Electrocatalysis for the oxygen reduction reaction (ORR) on five binary Pt alloy electrocatalysts (PtCr/C, PtMn/C, PtFe/C, PtCo/C and PtNi/C) supported on carbon have been investigated. The electrochemical characteristics for ORR in a proton conducting fuel cell environment has been correlated with the electronic and structural parameters determined under in situ conditions using XANES and EXAFS technique respectively. Results indicate that all the alloys possess higher Pt 5d band vacancies as compared to Pt/C. There is also evidence of lattice contraction in the alloys (supported by XRD results). Further, the Pt/C shows increase in Pt 5 d band vacancies during potential transitions from 0.54 to 0.84 V vs. RHE, which has been ration@ on the basis of OH type adsorption. In contrast to this, the alloys do not exhibit such an enhancement. Detailed EXAFS analysis supports the presence of OH species on Pt/C and its relative absence in the alloys. Correlation of the electrochemical results with bond distances and d-band vacancies show a volcano type behavior with the PtCr/C on top of the curve.

  1. Surface enrichment of Pt in Ga2O3 films grown on liquid Pt/Ga alloys

    NASA Astrophysics Data System (ADS)

    Grabau, Mathias; Krick Calderón, Sandra; Rietzler, Florian; Niedermaier, Inga; Taccardi, Nicola; Wasserscheid, Peter; Maier, Florian; Steinrück, Hans-Peter; Papp, Christian

    2016-09-01

    The formation of surface Ga2O3 films on liquid samples of Ga, and Pt-Ga alloys with 0.7 and 1.8 at.% Pt was examined using near-ambient pressure (NAP) X-ray photoelectron spectroscopy (XPS). Thickness, composition and growth of the oxide films were deduced as a function of temperature and Pt content of the alloys, in ultra-high vacuum and at oxygen pressures of 3 × 10- 7, 3 × 10- 3 and 1 mbar. We examined oxide layers up to a thickness of 37 Å. Different growth modes were found for oxidation at low and high pressures. The formed Ga2O3 oxide films showed an increased Pt content, while the pristine GaPt alloy showed a surface depletion of Pt at the examined temperatures. Upon growth of Ga2O3 on Pt/Ga alloys a linear increase of Pt content was observed, due to the incorporation of 3.6 at.% Pt in the Ga2O3. The Pt content in Ga2O3, at the examined temperatures and bulk Pt concentrations is found to be independent of pressure, temperature and the nominal Pt content of the metallic alloy.

  2. Granular nanostructures and magnetic characteristics of FePt-TiO{sub 2}/FePt-C stacked granular films

    SciTech Connect

    Ono, Takuya Moriya, Tomohiro; Hatayama, Masatoshi; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2014-05-07

    To realize a granular film composed of L1{sub 0}-FePt grains with high uniaxial magnetic anisotropy energy, K{sub u}, and segregants for heat-assisted magnetic recording, the FePt-TiO{sub 2}/FePt-C stacked film was investigated. The FePt-TiO{sub 2}/FePt-C stacked film has well-isolated granular structure with average grain size of 6.7 nm because the FePt-TiO{sub 2} film follows the FePt-C template film in microstructural growth. However, the K{sub u} value is quite low for total thickness of 9 nm: 5 × 10{sup 6} erg/cm{sup 3}. Exploration of the thickness dependence of L1{sub 0}-FePt(001) peaks in XRD spectra and cross-sectional TEM images suggest that degradation of the L1{sub 0} ordering appears near the middle of the FePt-TiO{sub 2} layer. The EDX-STEM mapping reveals that Ti atoms exist within the FePt grains in addition to the grain boundary. This indicates the possibility that TiO{sub 2} tends to be incorporated into the FePt grains and that it prevents L1{sub 0}-ordering of the FePt grains along the normal-to-plane direction.

  3. New Crystal Structures Identified for PtO and PtO2 using Density Functional Theory Calculations

    NASA Astrophysics Data System (ADS)

    da Silva, Juarez L. F.; Nomiyama, Ricardo K.; Piotrowski, Mauricio J.

    2012-02-01

    Platinum plays an important role in catalysis and electrochemistry, and it has been known that the direct interaction of oxygen with Pt surfaces can lead to the formation of platinum oxides (PtOx), which can affects the reactivity. To contribute to the atomistic understanding of the atomic structure of PtOx, we report a density functional theory study of the atomic structure of bulk PtOx (1 <=x <=2). From our calculations, we identified a lowest energy structure (GeS-type, space group Pnma) for PtO, which is 0.181 eV lower in energy than the structure suggested by Moore and Pauling (PtS-type). Furthermore, two atomic structures were identified for PtO2, which are almost degenerate in energy with the lowest energy structure reported so far for PtO2 (CaCl2-type). Based on our results and analysis, we suggest that Pt and O atoms tends to form octahedron motifs in PtOx even at lower O composition by the formation of Pt-Pt bonds.

  4. High-Temperature Regeneration of Perpendicular Exchange Bias in a Pt/Co/Pt/α-Cr2O3/Pt Thin Film System

    NASA Astrophysics Data System (ADS)

    Shiratsuchi, Yu; Takechi, Yuichiro; Toyoki, Kentaro; Nakano, Yuuta; Onoue, Satoshi; Mitsumata, Chiharu; Nakatani, Ryoichi

    2013-12-01

    We found the regeneration of perpendicular exchange bias at high temperature in the Pt-capping/Co/Pt-spacer/α-Cr2O3/Pt-buffer thin film with an ultrathin (0.2 nm) Pt-spacer layer after the disappearance at low temperature. Abrupt changes in the coercivity accompany the abrupt disappearance and regeneration of exchange bias. The direction of the regenerated exchange bias could be reversed by altering the ferromagnetic spin orientation during temperature rise. The exchange bias did not regenerate when the Pt spacer layer was grown at a slow growth rate, suggesting that the growth mode of Pt on the α-Cr2O3 layer affects the regeneration feature.

  5. Magnetic properties of ultrathin Ni/Co/Pt(111) films

    NASA Astrophysics Data System (ADS)

    Su, C. W.; Shern, C. S.; Yao, Y. D.

    2004-06-01

    Magnetic properties of one monolayer (ML) Ni/1 ML Co/Pt(111) film upon thermal annealing were investigated. Increases in polar Kerr rotation correspond to the topmost Ni layer incorporated with the second Co layer on Pt, and the further alloying of Co-Pt during the annealing. Interestingly, Curie temperature shifted dramatically to 325 K when the film was annealed at 830 K. The alloy formation of Ni-Pt and top-layer enrichment of Pt may be the main reason causing the great shift of Curie temperature.

  6. Exactly solvable PT -symmetric models in two dimensions

    NASA Astrophysics Data System (ADS)

    Agarwal, Kaustubh S.; Pathak, Rajeev K.; Joglekar, Yogesh N.

    2015-11-01

    Non-Hermitian, PT -symmetric Hamiltonians, experimentally realized in optical systems, accurately model the properties of open, bosonic systems with balanced, spatially separated gain and loss. We present a family of exactly solvable, two-dimensional, PT potentials for a non-relativistic particle confined in a circular geometry. We show that the PT -symmetry threshold can be tuned by introducing a second gain-loss potential or its Hermitian counterpart. Our results explicitly demonstrate that PT breaking in two dimensions has a rich phase diagram, with multiple re-entrant PT -symmetric phases.

  7. Adsorbed water and CO on Pt electrode modified with Ru

    NASA Astrophysics Data System (ADS)

    Futamata, Masayuki; Luo, Liqiang

    Highly sensitive ATR-SEIRA spectroscopy was exploited to elucidate water, CO and electrolyte anions adsorbed on the Ru modified Pt film electrode. CO on Ru domains was oxidized below ca. +0.3 V, followed by pronounced water adsorption. Since the oxidation potential of CO on Pt domain was significantly reduced compared to bare Pt, these water molecules on Ru obviously prompt CO oxidation on adjacent Pt surface as consistent with the bifunctional mechanism. Diffusion of adsorbate from Ru to Pt surfaces was indicated in dilute CH 3OH solution by spectral changes with potential.

  8. Purification of fluorescently labeled Saccharomyces cerevisiae Spindle Pole Bodies

    PubMed Central

    Davis, Trisha N.

    2016-01-01

    Centrosomes are components of the mitotic spindle responsible for organizing microtubules and establishing a bipolar spindle for accurate chromosome segregation. In budding yeast, Saccharomyces cerevisiae, the centrosome is called the spindle pole body, a highly organized tri-laminar structure embedded in the nuclear envelope. Here we describe a detailed protocol for the purification of fluorescently labeled spindle pole bodes from S. cerevisiae. Spindle pole bodies are purified from yeast using a TAP-tag purification followed by velocity sedimentation. This highly reproducible TAP-tag purification method improves upon previous techniques and expands the scope of in vitro characterization of yeast spindle pole bodies. The genetic flexibility of this technique allows for the study of spindle pole body mutants as well as the study of spindle pole bodies during different stages of the cell cycle. The ease and reproducibility of the technique makes it possible to study spindle pole bodies using a variety of biochemical, biophysical, and microscopic techniques. PMID:27193850

  9. Production of natural products through metabolic engineering of Saccharomyces cerevisiae.

    PubMed

    Krivoruchko, Anastasia; Nielsen, Jens

    2015-12-01

    Many high-value metabolites are produced in nature by organisms that are not ideal for large-scale production. Therefore, interest exists in expressing the biosynthetic pathways of these compounds in organisms that are more suitable for industrial production. Recent years have seen developments in both the discovery of various biosynthetic pathways, as well as development of metabolic engineering tools that allow reconstruction of complex pathways in microorganisms. In the present review we discuss recent advances in reconstruction of the biosynthetic pathways of various high-value products in the yeast Saccharomyces cerevisiae, a commonly used industrial microorganism. Key achievements in the production of different isoprenoids, aromatics and polyketides are presented and the metabolic engineering strategies underlying these accomplishments are discussed. PMID:25544013

  10. Mutations in Ran system affected telomere silencing in Saccharomyces cerevisiae

    SciTech Connect

    Hayashi, Naoyuki Kobayashi, Masahiko; Shimizu, Hiroko; Yamamoto, Ken-ichi; Murakami, Seishi; Nishimoto, Takeharu

    2007-11-23

    The Ran GTPase system regulates the direction and timing of several cellular events, such as nuclear-cytosolic transport, centrosome formation, and nuclear envelope assembly in telophase. To gain insight into the Ran system's involvement in chromatin formation, we investigated gene silencing at the telomere in several mutants of the budding yeast Saccharomyces cerevisiae, which had defects in genes involved in the Ran system. A mutation of the RanGAP gene, rna1-1, caused reduced silencing at the telomere, and partial disruption of the nuclear Ran binding factor, yrb2-{delta}2, increased this silencing. The reduced telomere silencing in rna1-1 cells was suppressed by a high dosage of the SIR3 gene or the SIT4 gene. Furthermore, hyperphosphorylated Sir3 protein accumulated in the rna1-1 mutant. These results suggest that RanGAP is required for the heterochromatin structure at the telomere in budding yeast.