bluuebunny/crossref_metadata_2025_split huggingface dataset:
L x‐ray fluorescence cross‐sections in the atomic region 62 ⩽ Z ⩽ 70 excited by 15.20, 17.80, 23.62 and 24.68 keV photons
Authors: Rao D. V. , Cesareo R. , Gigante G. E. 
Published: May 2005

AbstractL x‐ray fluorescence cross‐sections were measured for the elements Sm, Ho and Yb using photon energies of 15.20, 17.80, 23.62 and 24.68 keV. Measurements were performed using an x‐ray tube with a modified exciter system as the excitation source. In order to improve the efficiency of the detection system, the excitation source, the sample and the detector assembly were placed in a vacuum chamber and a pressure of 10−2 mbar was maintained through‐out the measurements. The present system considerably reduced the scattering and background effects and improved the monochromaticity. The x‐ray transitions were chosen on the basis of experimentally observed spectra and a particular goup of x‐rays are included in the calculation of fractional x‐ray emission rates. The experimental results were in excellent agreement with theoretical values.
Description of x‐ray beams using the fluorescence yields of a set of thick targets
Authors: Martínez C. , Delgado V. 
Published: May 2005

AbstractQuantitative methods in x‐ray fluorescence analysis require a knowledge of the spectral distribution of the fluorescence‐exciting beam. The use of XRF yield measurements of a set of thick pure element targets is proposed for the description of a fluorescence‐exciting x‐ray beam, without the need to obtain its spectral distribution. This new approach is derived theoretically and verified by comparing thin‐target yields calculated from XRF yield measurements of thick pure element specimens with those obtained from a calculated spectral distribution. The difference between the two methods of obtaining the thin‐target yields is within 9% relative error.
Preparation of quartz fibre filter standards for x‐ray fluorescence analysis of aerosol samples
Authors: Haupt O. , Klaue B. , Schaefer C. , Dannecker W. 
Published: May 2005

AbstractResults are presented for an intercomparison of two different techniques to produce standard filter materials for the energy‐dispersive x‐ray analysis of aerosol filter samples. In one, multi‐element standard solutions were dropped on to Munktell quartz‐fibre filters and air dried. The other technique utilized an aerosol generator. The dried aerosol was deposited on the filter surface. Extensive calibration procedures were performed with both types of standards. The data were applied to the analysis of urban aerosol filter samples. The results indicated that the aerosol technique provides good accuracy even for elements of atomic numbers below 30. The dropping technique is not applicable for fibre filters and the calibration of light elements (atomic number < 30) and achieves lower accuracy. Therefore, the aerosol technique should be applied generally to the preparation of standard filters. This method provides small particles and homogeneous coatings of the multi‐element standards.
Studies of uranium—cerium admixture solutions by EDXRF spectroscopy
Authors: Hanif Imtiaz , Hanif J. , Hasany S. M. , Iqbal M. Zafar 
Published: May 2005

AbstractUranium and cerium were studied in nitric acid solutions after presentation to an energy‐dispersive x‐ray fluorescence (EDXRF) spectrometer on filter‐paper fixed on Scotch tape. Ce Lα and U Lα peaks were used as analyte lines after excitation with a tungsten tube target at low potential (20 kV). These non‐conventional excitation conditions were considered to be suitable for low contents of cerium strongly but high contents of uranium weakly in a nuclear fuel. Lower net integrated line intensities observed in an actinide as compared with a lanthanide are discussed along with the scattered, Auger and Coster–Kronig intensities responsible for the production of back‐ground before calibrations with known concentrations. Difficulties in establishing an explicit relationship between these with change in matrix composition are discussed. The known concentrations of the mixed solutions when compared with the results from various computer programs using regression analysis showed that the algorithm developed by Plesch and Thiele for Siemens is better than the others. An accuracy of <2% was achieved. The importance of certified, standard or simulated reference materials is realized for quality analysis of occasional samples.
Overexpression of the RAD2 gene of S. cerevisiae: Identification and preliminary characterization of Rad2 protein
Authors: Nicolet Charles M. , Friedberg Errol C. 
Published: May 2005

AbstractThe cloned RAD2 gene of S. cerevisiae was tailored into regulatable expression vectors for overexpression of Rad2 protein in E. coli and in yeast. In E. coli both Rad2/β‐galactosidase fusion protein and native Rad2 protein are insoluble, but are extractable with 1% Sarkosyl. In yeast some of the overexpressed native Rad2 protein is also insoluble; however, soluble protein is readily detected by immunoblotting with Rad2‐specific antibodies. All forms of the protein detected in transformed or untransformed yeast cells and the insoluble species in E. coli migrate in denaturing polyacrylamide gels with an apparent molecular weight considerably larger than the size predicted from the sequence of the RAD2 coding region. This property is not the result of post‐translational glycosylation detectable by binding of concanavalin A, or of phosphorylation of the protein. Overexpression of the RAD2 gene is toxic to yeast. Transformed yeast cells grow much more slowly than untransformed controls and when yeast transformants are serially propagated cultures show considerable colony heterogeneity and concomitant selection for rapidly growing variants which express less Rad2 protein. Antisera raised against Rad2/β‐galactosidase fusion protein expressed in E. coli do not cross‐react with Rad1, Rad3 or Rad10 protein in crude extracts of yeast, nor with purified E. coli UvrA, UvrB or UvrC proteins.
Expression of env sequences of the bovine leukemia virus (BLV) in the yeast Saccharomyces cerevisiae
Authors: Brantl S. , Eldarov M. A. , Rößler H. , Drescher B. , Lang H. , Rosenthal S. , Skryabin K. G. 
Published: May 2005

AbstractDNA sequences of the envelop (env) gene of the bovine leukemia virus (BLV) were expressed in the yeast saccharomyces cerevisiae. Two yeast promoters, the responsible PH05 promoter and the constitutive PGK promoter, were used to construct four expression plasmids either a sequence of the surface antigen gp51 or a (gp51 + gp30) sequence.The expressed hetrologous gene products were characterized by Western blot analysis and competitive radio‐immunoassay. By means of Northern blot analysis the steady‐state level of env‐specific mRNA was analysed.The highest expression rate was obtained from recombinant plasmid YEpSG 94 comprising a gp51 sequence—a 630 base pair fragment containing 70% of the gp51 but lacking the N terminus—as well as the PH05 promoter including PH05 signal sequence and the PH05 terminator. The recombinant gp51 was partially lycosylated but the PH05 signal peptide did not seem to be cleaved off. No immunoreactive material could be found in the periplasm or in the culture medium.By means of monoclonal antibodies directed against eight different epitopes of viral gp51, all for sequential antigenic determinants were detected in the AH 216(YEpSG 94) expression product.
Properties of enzymes which reduce dihydroxyacetone and related compounds in hansenula polymorpha CBS 4732
Authors: Verduyn Cornelis , Breedveld Guido J. , Schreuder Henk , Scheffers W. Alexander , Van Dijken Johannes P. 
Published: May 2005

AbstractHansenula polymorpha CBS 4732 grown on a variety of substrates contained very high activities of enzymes catalyzing the NADH‐linked reduction of dihydroxyacetone, acetoin, diacetyl, acetol, methylglyoxal and acetone. The enzymes catalyzing these reductions have been purified and their kinetic properties are described. Three different enzymes were found responsible for the above‐mentioned activities, namely: (1) dihydroxyacetone reductase; (2) acetone reductase; and (3) alcohol dehydrogenase.So far, the physiological function of dihydroxyacetone reductase and acetone reductase is obscure. The kinetic properties of dihydroxyacetone reductase and the regulation of the synthesis of this enzyme suggest that it does not function as a glycerol dehydrogenase.
The influence of oxygen and organic hydrogen acceotors on glycolytic dioxide production in Brettanomyces anomalus
Authors: Gaunt Davis M. , Degn Hans , Lloyd David 
Published: May 2005

AbstractThe yeast Brettanomyces anomalus showed the Custers effect in that under strictly anaerobic conditions, in the presence of glucose, CO2 production was negligble. CO2 production was stimulated by mixing anaerobic cell suspensions with an aerated glucose solution in astopped‐flow cell. Glycolytic CO2 production continued even after oxygen exhaustion. Studies using an open reaction vessel showed that the rate of glycolytic CO2 production could be increased to a maximum level by exposing the anaerobic cell suspension to brief pulses of O2. A cell suspension CO2 at a maximal rate demonstrated the Pasteur effect on switching the mobile gas to a mixture conatining oxygen (5.05 KPa). In contrast to glycolytic CO2 production in vivo nicotinamide pool responded rapidly to changes in oxygen concentration. The addition of acetaldehyde, acetone, or 3‐hydroxy‐butan‐2‐one led to a temprorary production of CO2 at an initial rate depending on the concentration of substance added according to the Michaelis–Menten equation. The maximal rates were equal with all three substances, whereas tha apparent Km values were different. The total amount of CO2 produced was 22‐fold greater than the amount of acetaldehyde added. Added organic hydrogen acceptors modulated the intracellular reedox balance of B. anomalus under conditions. These results are discussed in relation to the current hypothesis of the Custers effect.
High level of expression of a protective antigen of schistosomes in Saccharomyces cerevisiae
Authors: Loison G. , Vidal A. , Findeli A. , Roitsch C. , Balloul J. M. , Lemoine Y. 
Published: May 2005

AbstractStrains of Saccharomyces cerevisiae expressing P28‐I, an antigen inducing protection against schistosomiasis, have been constructed. Transformants containing a very high copy number of a P28‐I expression vector were selected by genetic complementation involving deficient LEU2 or URA3 alleles carried by plasmids. Using the ura3 fur1 auto‐selection system, constitutive and stable expression of P28‐I could be obtained in cultures grown in rich medium.The accumulation of the foreign protein exceeds 25% of total yeast proteins when estimated by Coomassie Brilliant Blue staining of SDS‐PAGE. Moreover, P28‐I which was located intracellularly was soluble and biologically active.
Classical transketolase functions as the formaldehyde‐assimilating enzyme during growth of a dihydroxyacetone synthase‐negative mutant of the methylotrophic yeast Hansenula polymorpha on mixtures of xylose and methanol in continuous cultures
Authors: De Koning W. , Bonting K. , Harder W. , Dijkhuizen L. 
Published: May 2005

AbstractContrary to expectation, a mutant of Hansenula polymorpha blocked in dihydroxyacetone (DHA) synthase was able to assimilate methanol‐carbon when grown in chemostat culture on mixtures of xylose and methanol. Incubation of a DHA synthase‐ and DHA kinase‐negative double mutant resulted in DHA accumulation, indicating that a DHA synthase‐type of reaction was involved. Low residual DHA synthase activity subsequently was shown to be present when using an assay with improved sensitivity. This activity was not associated with the (mutated) DHA synthase protein, which was still present in the peroxisomes, but with the enzyme transketolase. Transketolase from methanol grown cells was purified (525‐fold) to homogeneity in 9% yield. The native enzyme was dimeric, as has been reported fro other transketolases, with a subunit molecular weight of 74000. The affinity of the purified enzyme for formaldehyde was low (Km = 5 mM), but high for xylulose‐5‐phosphate (ca. 10 μM). The in vivo functioning of transketolase in formaldehyde assimilation, and the influence of the hydration state of formaldehyde is discussed.
DNA relatedness among species of the genus Zygosaccharomyces
Authors: Kurtzman C. P. 
Published: May 2005

AbstractThe extent of nuclear DNA complementarity was determined for members of the genus Zygosaccharomyces. From these comparisons, nine species have been identified: Z. baillii, Z. bisporus, Z. cidri, Z. fermentati, Z. florentinus, Z. mellis, Z. microellipsoides, Z. mrakii, and Z. riuxii. Candida mogii, the proposed anamorph of Z. rouxii, showed low relatedness to all nine species. The recently described Saccharomyces astigiensis and S. albasitensis were conspecific with Z. fermentati, and S. placentae showed high relatedness with Z. rouxii. Growth tests were defined that allow recognition of all Zygosaccharomyces species.
The start gene CDC28 and the genetic stability of yeast
Authors: Devin A. B. , Prosvirova T. Yu. , Peshekhonov V. T. , Chepurnaya O. V. , Smirnova M. E. , Koltovaya N. A. , Troitskaya E. N. , Arman I. P. 
Published: May 2005

AbstractThe cdc28‐srm mutation in Saccheromyces cerevisiae decreases spontaneous and induced mitochondrial rhomutability and the mitotic stability of native chromosomes and recombinant circular minichromosomes. The effects of cdc28‐srm on the genetic stability of cells support the hypothesis that links cell cycle regulation in yeast to changes in chromatin organization dependent on the start gene CDC28 (Hayles and Nurse, 1986).
Dekkera, Brettanomyces and Eeniella: Electrophoretic comparison of enzymes and DNA–DNA homology
Authors: Smith Maudy Th. , Yamazaki M. , Poot G. A. 
Published: May 2005

AbstractThe taxonomic status of various species of Dekkera, Brettanomyces and Eeniella was examined by electrophoretic comparison of enzymes, by deoxyribonucleic acid homology and by physiological characterization. These studies demonstrated that two teleomorphic Dekkera species, D. anomala and D. bruxellensis (Synonym. D. intermedia), and four anamorphic Brettanomyces species, B. anomalus (synonym B. claussenii), B. bruxellensis (synonym B. abstinens, B. custersii, B. Intermedius, B. lambicus), B. custersianus and B. naardenesis, can be recognized. The anamorphic genus Eeniella remained as a separate, monotypic taxon.
Increase of anion and proton permeability of Saccharomyces carlsbergensis plasmalemma by n‐alcohols as a possible cause of its de‐energization
Authors: Petrov Valery V , Okorokov Lev A. 
Published: May 2005

AbstractThe effect on n‐alcohols on ATP‐dependent generation of ΔpH and Em across the plasma membrane vesicles of the yeast Saccharomyces carlsbergenesis was investigated. The alcohols were shown to collapse ΔpH and Em in the order C2<C3<C4<C5≤C6≥C7>C8>C11, the dissipation of Em being more pronounced. Inhibition of the plasmalemma H+‐ATPase was insignificannt: at low alcohol concentrations its activity even increased. The basic reason for the toxic effect of the alcohols on the yeast cells was suggested to be due to the increase in the anion and proton permeability of the plasma membrane. Mg2+ partially prevented the increase in the plasmalemma ion permeability by the alcohols investigated.
Purification of δ‐aminolevulinate dehydratase from genetically engineered yeast
Authors: Borralho Leda M. , Ortiz Claudio H. D. , Panek Anita D. , Mattoon James R. 
Published: May 2005

AbstractSaccharomyces cerevisiae transformed with a multicopy plasmid carrying the yeast structural gene HEM2, which codes for δ‐aminolevulinate dehydratase, was enriched 20‐fold in the enzyme. Beginning with cell‐free extracts of transformed cells, the dehydratase was purified 193‐fold to near‐homogeneity. This represents a 3900‐fold purification relative to the enzyme activity in normal, untransformed yeast cells. The specific activity of the purified enzyme was 16·2 μmol h−1 per mg protein at pH 9·4 and 37·5°C. In most respects the yeast enzyme resembles mammalian enzymes. It is a homo‐octamer with an apparent Mr, of 275 000, as determined by centrifugation in glycerol density gradients, and under denaturing conditions behaved as a single subunit of Mr ≃ 37 000. The enzyme requires reduced thiol compounds to maintain full activity, and maximum activity was obtained in the presence of 1·0 mM‐Zn2+. It is sensitive to inhibition by the heavy metal ions Pb2+ and Cu2+. The enzyme exhibits Michaelis‐Menten kinetics and has an apparent Km of 0·359 mM. Like dehydratases from animal tissues, the yeast enzyme is rather thermostable. During the purification process an enhancement in total δ‐aminolevulinate dehydratase activity suggested the possibility that removal of an inhibitor of the enzyme could be occurring.
Chromosome III of Saccharomyces cerevisiae: An ordered clone bank, a detailed restriction map and analysis of transcripts suggest the presence of 160 genes
Authors: Yoshikawa Akikazu , Isono Katsumi 
Published: May 2005

AbstractUsing λ phage vector EMBL4, we isolated 344 clones containing segments of chromosome III of Saccharomyces cerevisiae, analysed their physical structure with eight restriction enzymes and sorted the data in contiguous groups with computer programmes. Furthermore, we performed Southern hybridizations between the sorted contiguous clone groups and interrelated them into larger groups. In this way, we constructed an ordered clone bank that covers almost the whole of chromosome III with a single gap of several kilobases in length. The consensus physical map thus obtained totals 334·6 kb, which is in good agreement with the size of this chromosome estimated by pulsed‐field gel electrophoresis. Southern hybridization analysis with the DNA probes containing telomere‐specific sequences showed that the bank contained a telomere at a position corresponding to the right arm terminus of chromosome III. Also, five Ty elements were found to be present. To estimate the number of genes on this chromosome and to analyse their levels of expression, we performed a series of Northern hybridization experiments using total poly(A)+ RNA from vegetatively growing cells and appropriate restriction enzyme fragments from the bank. Thus, we identified a total of 156 transcripts on chromosome III, indicating, on an average, one gene in every 2 kb on this chromosome. The transcripts were visually categorized into five groups according to their apparent levels of expression. It was found that the genes located near both termini are expressed only at low levels and that highly expressed genes are rather scattered over the chromosome.
Nucleotide sequence of the cytochrome oxidase subunit 2 and val‐tRNA genes and surrounding sequences from Kluyveromyces lactis K8 mitochondrial DNA
Authors: Hardy Chris M. , Clark‐Walker G. D. 
Published: May 2005

AbstractThe nucleotide sequence of the cytochrome oxidase subunit 2 (cox2) and val‐tRNA genes and surrounding regions from Kluyveromyces lactis mitochondrial DNA is reported. Analysis of the coding regions shows that the codons CUN (Thr), CGN (Arg) and AUA (Met) are absent in this gene. A single sequence, ATATAAGTAA, identical to the baker's yeast mtRNA polymerase recognition site, was detected upstream of val‐tRNA. This sequence is absent from regions between val‐tRNA‐cox2 and cox2‐cox1. In addition a sequence AATAATATTCTT, identical to the mRNA processing site in other yeast mitochondrial genomes is present 32–43 bp downstream to the TAA stop codon for the cox‐2 gene. Another short conserved sequence of 5 bp, TCTAA, is present upstream of the coding regions of cox2 genes in several yeasts, including K. lactis, but is not present upstream of other genes. Comparison of cox2 sequences from other organisms indicates that the mitochondrial DNA of K. lactis. is closely related to that of Saccharomyces cerevisiae.
An assay of relative cell wall porosity in Saccharomyces cerevisiae, Kluyveromyces lactis and Schizosaccharomyces pombe
Authors: De Nobel Johannes G. , Klis Frans M. , Munnik Teun , Priem Jan , Van Den Ende Herman 
Published: May 2005

AbstractWe have developed a new assay to determine relative cell wall porosity in yeasts, which is based on polycation‐induced leakage of UV‐absorbing compounds. Polycations with a small hydrodynamic radius as measured by gel filtration (poly‐L‐lysine) caused cell leakage independent of cell wall porosity whereas polycations with a large hydrodynamic radius (DEAE‐dextrans) caused only limited cell leakage due to limited passage through the cell wall. This allowed the ratio between DEAE‐dextran‐ and poly‐L‐lysine‐induced cell leakage to be used as a measure of cell wall porosity in Saccharomyces cerevisiae, Kluyveromyces lactis and Schizosaccharomyces pombe. Using this assay, we found that the composition of the growth medium affected cell wall porosity in S. cerevisiae. In addition, we could show that cell wall porosity is limited by the number of disulphide bridges in the wall and is dependent on cell turgor. It is argued that earlier methods to estimate cell wall porosity in S. cerevisiae resulted in large underestimations.
The glucanase‐soluble mannoproteins limit cell wall porosity in Saccharomyces cerevisiae
Authors: De Nobel Johannes G. , Klis Frans M. , Priem Jan , Munnik Teun , Van Den Ende Herman 
Published: May 2005

AbstractThe cell porosity of batch‐grown Saccharomyces cerevisiae was maximal in the early exponential phase and fell off rapidly to lower levels in later growth phases.Treatment of stationary‐phase cells with alpha‐mannosidase restored wall porosity to the level of cells in early exponential phase. When cells in the early exponential phase were treated with alpha‐mannosidase, or tunicamycin, an inhibitor of N‐glycosylation, even higher porosities were obtained. Mutants with truncated mannan side‐chains in their wall proteins also had very porous walls. The importance of the mannan side‐chains for wall porosity was also seen during sexual induction. Treatment with alpha pheromone, which leads to the formation of wall proteins with shorter mannan side‐chains, enhanced wall porosity.Disulphide bridges also affect cell wall porosity. They were predominantly found in the glucanase‐soluble wall proteins. Because the main part of the mannan side‐chains is also found in this family of wall proteins, our results demonstrate that the glucanase‐soluble mannoproteins limit cell wall porosity in yeast.
The complete sequence of the 8·2 kb segment left of MAT on chromosome III reveals five ORFs, including a gene for a yeast ribokinase
Authors: Thierry Agnès , Fairhead Cécile , Dujon Bernard 
Published: May 2005

AbstractWe report here the DNA sequence of a segment of chromosome III extending over 8·2 kb. The sequence was determined using the random clone strategy followed by oligonucleotide‐directed sequencing. The segments contains five long open reading frames, YCR521, 522, 523, 524 and 526, with only short distances between them. YCR523 (333 codons) endodes a ribokinase, a new function for yeast. YCR526 originates inside the MAT cassette, which is in continuity with the present segment, and extends over 358 codons outside of MAT. YCR524 (923 codons) codes for a putative membrane protein. YCR521, 522 and 524, have each been disrupted by insertion of a URA3 cassette and are non‐essential genes. An active ARS element is located within YCR523 or its vicinity.