bluuebunny/crossref_metadata_2025 huggingface dataset:
A standardless ZAF correction for semi‐quantitative electron probe microanalysis of microscopical particles
Authors: Van Borm W. A. , Adams F. C.
Published: May 2005

A procedure for automaied microanalysis is adapted from a correction procedure for bulk samples. A particle size correction, based on the projected diameter of the particle, assumed to be spherical, is implemented when the diameter is less than or equal to the electron interaction diameter. A bulk correction is applied in the opposite case. The method is applicable to K‐ and L‐lines for the elements Na to Bi. The method is implemented in a FORTRAN computer program QUANTA written for personal computers. The procedure offers interactive control of several parameters of a single ZAF correction as it is capable of processing the massive amount of data produced by automated analysis of large particle collections. The method uses literature data on a number of fundamental parameters and performs the ZAF corrections by making a compromise between calculation speed and accuracy using first‐order corrections for backscattering, absorption and secondary fluorescence effects. It was tested on a set of alloy standards, mineral standards and mineral particle standards.
IUPAC—nomenclature system for x‐ray spectroscopy
Authors: Jenkins R. , Manne R. , Robin R. , Senemaud C.
Published: May 2005

This report is one of a series on the nomenclature for spectrochemical analysis issued by the International Union of Pure and Applied Chemistry. It concerns a new notation for X‐ray emission lines and absorption edges, to be called IUPAC Notation, which replaces the existing Siegbahn notation. It is based upon the energy level designation and has the advantage of being simple and easy to apply to any kind of transition. Moreover, it is consistent with the notations used in electron spectroscopy.

The document first discusses the terms currently used in X‐ray spectroscopy and then describes the principles of the IUPAC notation with reference to the X‐ray levels and the X‐ray transitions. The correspondence between Siegbahn and IUPAC notations for all X‐ray lines is given in a table. Finally, the document gives the units and conversion factors used in the X‐ray range.
X‐ray fluorescence analysis of tree rings
Authors: Gilfrich J. V. , Gilfrich N. L. , Skelton E. F. , Kirkland J. P. , Qadri S. B. , Nagel D. J.
Published: May 2005

X‐ray fluorescence analysis was applied to the determination of the concentration of trace elements in the growth rings of trees. Some of these mineral elements can affect the growth and development of the plant. The results of the analytical measurements can provide information concerning the geochemical and atmospheric environment to which the tree has been exposed. It has been demonstrated that conventional x‐ray fluorescence equipment is adequate to perform such measurements but, more important, the high intensity available from synchrotron radiation is an ideal source to probe the spatial variation in the low‐level concentrations which can be transposed to an absolute temporal scale knowing the history of the tree. The ability to aperture or focus the synchrotron radiation to submillimeter size allows several points within individual rings to be analyzed, permitting a study of differences within a single growing season.

Concentrations of mineral elements were determined in two types of tree samples, a cross‐section of the trunk of a small sassafras tree and an incremental core from a red oak. Two experimental arrangements were employed, a special energy‐dispersive x‐ray analyzer with a primary beam size of 0.5 mm and a beam line at the National Synchrotron Light Source where the radiation was focused and apertured to 50 μm × 1 mm. Concentrations as low as 1 ppm were determined for nine elements. Major year‐to‐year variations were observed, implying that cross‐ring elemental migration is slow (possibly negligible). The x‐ray technique is fast and non‐destructive, permitting the sample to be retained for additional studies.
Comparison of highly oriented pyrolytic and ordinary graphite as polarizers of Mo Kα radiation in EDXRF
Authors: Kanngiesser Birgit , Beckhoff Burkhard , Swoboda Walter
Published: May 2005

Highly oriented pyrolytic graphite (HOPG) and ordinary graphite were compared with respect to detection limits as excitation targets in a triaxial EDXRF set‐up. HOPG as a Bragg polarizer of Mo Kα x‐rays did not show appreciable advantages over ordinary graphite as a Barkla scatterer. Under relatively wide collimation conditions necessary to obtain a sufficient count rate in analytical practice, HOPG acts mainly as a Barkla scatterer.
A peak‐to‐background method for electron‐probe x‐ray microanalysis applied to individual small particles
Authors: Lábár János L. , Török Szabina
Published: May 2005

A peak‐to‐background (P/B) method was implemented for standardless analysis of bulk samples. Components of the model were selected from the literature on the basis of comparison with the present experimental results. Pouchou and Pichoir's characteristic x‐ray intensity calculations combined with Small et al. bremsstrahlung model proved to be the most successful in this respect. An empirical modification seems to be necessary to improve the agreement between calculated and measured P/Bs for the Lα lines of single‐element samples. For modelling the dependence of the measured P/B on the particle size, small particles are approximated as thin layers. Preliminary experimental results illustrate that even such a rough approximation works.
Determination of impurities in nuclear‐grade uranium compounds by x‐ray fluorescence spectrometry
Authors: Al‐ammar Assa d. S. , Ali F. H.
Published: May 2005

A method in described for the simultaneous determination of trace concentrations of Ca, Cr, Cu, Fe, Mn, Ni, Mo, As, Zn, Co, Th, V and Ti in nuclear‐grade uranium oxides or other uranium compounds by x‐ray fluorescence spectrometry without the use of chemical treatment. The limits of detection are Mo 25, As 40, Cu 5, Ni 29, Co 17, Fe 5, Mn 30, Cr 8, Th 7, Zn 5, V 52, Ti 10 and Ca 80 ppm. Samples are prepared in the form of double‐layer pellets with starch as a binding agent. Standards are prepared in a U3O8 matrix, which is more chemically stable than other uranium oxides. The dynamic ranges of the calibration graphs are very large because, for all impurity elements, they are linear over three orders of magnitude of concentration. The method is fast, since it requires no chemical treatment and only limited manipulations. The method has good precision for the impurity elements.
Energy‐dispersive W Kα1 spectrometer for trace element analysis of rare‐earth elements
Authors: Manninen S. , Karhumaa R.
Published: May 2005

A spectrometer based on the use of monochromatic W Kα1 radiation for trace element studies of rare earth elements up to Z = 68 is described. Examples including both liquid and solid samples are included. Special attention is given to the contributions arising from Compton scattering and multiple scattering in the sample matrix. The results are compared with those obtained using a 241 Am γ‐source.
Measurements of L1, Lα, Lβ and Lγ x‐ray fluorescence cross‐sections in heavy elements excited by 36.62, 43.69, 48.30, 50.20 and 53.50 keV photons
Authors: Rao D. V. , Cesareo R. , Gigante G. E.
Published: May 2005

L1, Lα, Lβ and Lγ x‐ray fluorescence cross‐sections were measured in Au and Pb at excitation energies of 36.62, 43.69, 48.30, 50.20 and 53.50 keV. Measurements were made using an x‐ray tube with a secondary exciter system as the excitation source. The x‐ray tube with a secondary target arrangement was used to obtain high intensity with a high degree of monochromatization. By using an x‐ray tube it is possible to measure L x‐ray fluorescence cross‐sections even for low‐intensity x‐rays (L1). The experimental results were compared with the theoretically calculated values of L x‐ray fluorescence cross‐sections and a fairly good correspondence was observed.
Chemical characterization of environmental particulate matter using synchrotron radiation
Authors: Török Sz. , Faigel Gy. , Jones K. W. , Rivers M. L. , Sutton S. R. , Bajt S.
Published: May 2005

First results from a new program for chemical characterization of environmental particulates using synchrotron radiation are described. Trace element concentrations and chemical state determinations were made on fly ash samples from lignite‐fired power stations. The experiments were based on the use of x‐rays produced by an electron beam passing a bending magnet at the Brookhaven National Synchrotron Light Source. The high brilliance, energy tunability and almost complete polarization of the x‐rays were used as the basis of a versatile X‐ray microscope (XRM) at the X26 beam line. Mössbauer spectroscopy was employed as a complementary method for determination of the compounds in the iron‐containing fly ash particles. The results demonstrate the practicality and strengths of using the synchrotron XRM for measurements of trace elements in fly ash particles and for the determination of oxidation states using x‐ray absorption near‐edge structure.
Analytical electron microscopy of thin segregated layers
Authors: Faulkner R. G. , Morgan T. S. , Little E. A.
Published: May 2005

Analytical convolution methods used to explain the interaction of a fine electron beam with a thin segregated layer in a typical electron microscope specimen are described. Expressions are derived which quantify the shape of the measured concentration profile determined in the microscope by scanning the beam across the segregated layer. The expression contains parameters concerned with the beam profile and the thickness of the segregated layer. The method is applied to grain boundary segregation studies of neutron‐irradiated ferritic‐martensitic steels.
Measuring system for obtaining concentration profiles in supported catalysts using electron‐probe microanalysis. Influence of standards
Authors: Viturro H. , Bonetto R. D. , Pizzio L. R. , Vázquez P. G. , Sanchez M. , Alvarez A. G.
Published: May 2005

A system based on the EDAX 9100 analyser was developed to obtain concentration profiles. Even though the system can be used on any type of flat specimens, in this study it was used for measuring the tungsten (W) concentration on rough spherical specimens of the W–γ‐Al2O3 supported catalyst. The concentration gradient of the active component from the periphery to the centre of the particle is often an important factor in determining catalyst performance. The purpose was to determine the concentration profile of W along the radius of a sphere with a large enough number of experimental points to draw accurate information in a short time. In this way, a considerable number of impregnated spheres can be analysed, and average results can be calculated and taken as representative values of the population under study. The method developed provides highly satisfactory results, making it very useful for the systematic study of this type of specimen. Obviously, the use of this system can be extended to metallurgical and mineralogical specimens.
Coherent and incoherent scattering of 42.75 and 47.24 keV x‐ray photons scattered from Al, Cu, Y, Mo, Au and Pb
Authors: Rao D. V. , Gigante G. E. , Cesareo R.
Published: May 2005

Using nearly monoenergetic unpolarized Kα x‐ray photons, measurements were made of the coherent and Compton scattered intensity in the atomic region 13 ⩽ Z ⩽ 82 at an angle of 90° with a high‐resolution Si(Li) detection system. In order to improve the efficiency of the detection system, the excitation source, detector and the sample assembly were placed in a vacuum chamber and a pressure of 10−2 mbar was maintained throughout the measurements. Experimental scattering cross‐sections are compared with the normalized integrated cross‐sections based on form factor and incoherent scattering functions. Experimental coherent scattering cross‐sections are higher than the theoretical values, indicating the resonance behaviour, fine structure effects and oscillation of coherent intensity around the absorption edges. Experimental incoherent scattering cross‐sections are lower than the theoretical estimates for heavy elements, indicating the effect of electron binding at low photon energies.
Analysis of DNA double strand breakage and repair using orthogonal field alternation gel electrophoresis
Authors: Contopoulou C. Rebecca , Cook Vincent E. , Mortimer Robert K.
Published: May 2005

Orthogonal field alternation gel electrophoresis (OFAGE) allows separation of DNA molecules in the size range of 200 kb to 3000 kb. These sizes encompass the chromosome sizes of the genome ofSaccharomyces cerevisiae. Using this technique, we have found that yeast cells exposed to X‐rays generate a smear of DNA fragments corresponding to the products of random, independent double strand breaks, and that the bands corresponding to unbroken chromosomes decrease in intensity in direct proportion to chromosome size. If exposed wild type cells are permitted time to repair (5 h at 30°C on YEPD), the fragments partially disappear and the chromosome bands reappear, although at less than normal intensity. In certain radiation‐sensitive mutants (rad51,rad52andrad54), the fragment smear appears following X‐ray exposure but no repair of broken chromosomes occurs. In fact, loss of the fragments occurs; this could appear as partial repair using other procedures.
Nucleotide phosphotransferase, nucleotide kinase and inorganic pyrophosphatase activities of killer virions of yeast
Authors: Georgopoulos Denise E. , Leibowitz Michael J.
Published: May 2005

The intracellular killer virions of yeast co‐purify with an RNA polymerase activity which catalyzes the synthesis of fulllength transcripts of the two viral genomic double‐stranded RNA segments. This polymerase utilizes ribonucleoside diphosphates or triphosphates as substrates. The virions have other associated nucleotide‐metabolizing enzyme activities, including nucleoside diphosphate kinase, adenosine monophosphate kinase, and nucleoside triphosphate phosphotransferase, an activity which catalyzes the exchange of gamma‐phosphate from any ribonucleoside triphosphate with any ribonucleoside or deoxyribonucleoside triphosphate. The purified virions also contain an inorganic pyrophosphatase activity. These enzymes may allow the virus to utilize nucleotide pools distinct from those utilized in host cell transcription.
Ethanol and the fluidity of the yeast plasma membrane
Authors: Jones Rodney P. , Greenfield Paul F.
Published: May 2005

Evidence is presented for an exponential increase in yeast plasma membrane fluidity (as meaured by pasive permeability to acetic acid) with ethanol concentration. The role of adaptation of yeast cells to ethanol can be seen in the existence of a threshold concnetration before the onset of an observed fluidizing effect. The physiological state of the yeast cells is also demonstrated to influence the sensitivity of the membrane to fluidizatio by ethanol. On the basis of these results, the concept that increased fluidity is an adaptive response conferring ethanol tolerance is disputed. An alternative hypothesis, namely that the observed increase in fluidity is the net result of a number of more fundamental changes, is presented to explain the observed effects.
Genetic analysis of the gene ICL1 of the yeast Yarrowia lipolytica
Authors: Barth Gerold , Weber Herbert
Published: May 2005

The gene ICL1 codes for the tetrameric enzyme isocitrate lyase of Y. lipolytica. Twenty icl1− alleles have been analysed for their reversion frequency, their interallelic complementation pattern, and the position of the corresponding mutation site on the fine structure map of the gene ICL1. One intragenic temperature‐sensitive revertant of the allele icl1D‐39 was isolated, which expressed a thermolabile enzyme. In spite of the fact that no nonsense mutations have been detected, the direction of transcription of the gene ICL1 was inferred from the localization of a linked cis‐dominant regulatory mutation site. The size of the mitotic map of this gene suggests that recombination frequency in Y. lipolytica is lower than in Saccharomyces cerevisiae.
Pleiotropic mutations in Saccharomyces cerevisiae affecting sterol uptake and metabolism
Authors: Lewis T. L. , Keesler G. A. , Fenner G. P. , Parks L. W.
Published: May 2005

Sterol uptake control mutants (upc−) have been isolated via ethylmethanesulfonate mutagenesis from wild‐type Saccharomyces cerevisiae. These mutants are heme and sterol competent but possess the ability to accumulate exogenous sterol(s) under aerobic conditions. Previous demonstrate sterol uptake only in a hem−, erg− background; however, the Upc− strains described here are Hem+ and do not require exogenous sterol for growth. We were unable to obtain viable hem+, erg−, upc+ recombinants; such combinations appear to be lethal. Isolates of Upc mutants demonstrated different levels of sterol uptake, and sterol analysis revealed a broad phenotypic range with regard to amounts and accumulation of ergosterol and non‐ergosterol sterols. Assays of acyl CoA: ergosterol acyltransferase and sterol ester hydrolase showed no apparent difference in activity between Upc mutants and the wild type.
Purification and properties of dihydroxyacetone reductase and 2,3‐butanediol dehydrogenase from Candida utilis CBS 621
Authors: Verduyn Cornelis , Breedveld Guido J. , Scheffers W. Alexander , Van Dijken Johannes P.
Published: May 2005

Candida utilis CBS 621 contained four different enzymes capable of reducing carbonyl compounds such as dihydroxyacetone, acetoin, diacetyl, acetol, methylglyoxal and acetone, namely alcohol dehydrogenase, acetone reductase, dihydroxyacetone reductase and 2,3‐butanediol dehydrogenase. The dihydroxyacetone reductase of C. utilis did not oxidize glycerol, thus providing evidence that this enzyme cannot function as a glycerol‐2‐dehydrogenase during growth of the yeast on glycerol. This enzyme may, however, play a role in the assimilation of 2,3‐butanediol by C. utilis. The organism also contained a separate 2,3‐butanediol dehydrogenase which was unable to reduce dihydroxyacetone. Both dihydroxyacetone reductase and 2,3‐butanediol dehydrogenase were present at very high activities during growth of C. utilis on a variety of substrates, including 2,3‐butanediol.
Analysis of chromosomal DNA patterns of the genus Kluyveromyces
Authors: Sor Frédéric , Fukuhara Hiroshi
Published: May 2005

Using an improved procedure of pulsed field gel electrophoresis, yeast chromosomes were separated over a wide range of molecular size (250–4000 kbp) on single gels. The chromosomal DNA patterns of all the species belonging to the genus Kluyveromyces were examined. Within the species K. marxianus, the varieties lactis, drosophilarum and vanudenii showed closely related patterns; very different from them, the varieties bulgaricus and marxianus were related to each other, forming a distinct group; the strains commonly called ‘K. lactis’ and ‘K. fragilis’ were unambiguously different from each other in chromosome patterns. These differences were correlated with the presence of characteristic repetitive sequence elements in the mitochondrial DNA of the former group and not in the latter. Analysis of Candida macedoniensis, which had been considered to be an anamorph of K. marxianus var. marxianus, showed that these two yeast species were indeed similar in chromosome patterns and in mitochondrial DNA restriction patterns.
Cloning and analysis of the Kluyveromyces lactis TRP1 gene: A chromosomal locus flanked by genes encoding inorganic pyrophosphatase and histone H3
Authors: Stark Michael J. R. , Milner Jonathan S.
Published: May 2005

The TRP1 gene of the yeast Kluyveromyces lactis has been cloned from a genomic library by complementation of the Saccharomyces cerevisiae trpl‐289 mutation. The gene was located within the clone by transposon mutagenesis and the coding region identified by DNA sequencing. This has indicated that K. lactis TRP1 encodes a 210‐amino acid polypeptide which shows 53% identity to the homologous S. cerevisiae protein. The K. lactis TRP1 gene has been disrupted by substituting the S. cerevisiae URA3 gene for a large part of the TRP1 coding sequence. Replacement of the chromosomal TRP1 locus with this construction has enabled the production of non‐reverting trp1− strains of K. lactis, while a genetic analysis of the disrupted allele confirmed that the TRP1 gene had been cloned. DNA sequencing has also shown that the K. lactis TRP1 sequences is flanked by genes encoding inorganic pyrophosphatase and histone H3, which we have designated IPP and HHT1 respectively. Hybridization studies have shown that in common with S. cerevisiae, K. lactis has two copies of the histone H3 gene. Each H3 gene is closely linked to a gene encoding histone H4 and in both yeast species the IPP gene is tightly linked to one of the histone gene pairs.
RAG1 and RAG2: Nuclear genes involved in the dependence/independence on mitochondrial respiratory function for growth on sugars
Authors: Goffrini P. , Algeri A. A. , Donnini C. , Wesolowski‐Louvel M. , Ferrero I.
Published: May 2005

The analysis of five independent isolates of Kluyveromyces lactis shows that CBS 2359, CBS 683 and CBS 4574 could grow in the presence of mitochondrial inhibitors (antimycin A, oligomycin or erythromycin) and that CBS 2360 and CBS 141 were unable to grow in the presence of drugs. The resistant growth was observed only on glucose and not on other fermentable carbon sources (galactose, lactose).

The phenotype ‘growth on glucose in the presence of mitochondrial inhibitors’ was called Rag+. This phenotype was found to be controlled by two unlinked nuclear genes: RAG1 and RAG2. Either of their recessive alleles, rag1 and rag2, led to the Rag− phenotype (i.e. the failure of growth on glucose in the presence of antimitochondrial drugs).

Rag− strains represent the case in which fermentative growth becomes absolutely dependent on the functioning of the normal respiratory chain.
Structural comparison of the Pichia pastoris alcohol oxidase genes
Authors: Koutz Patricia , Davis Geneva R. , Stillman Cathy , Barringer Kevin , Cregg James , Thill Gregory
Published: May 2005

In methylotrophic yeasts, alcohol oxidase is the first enzyme in the methanol‐utilization pathway. The genome of one such yeast, Pichia pastoris, contains two alcohol oxidase genes, AOX1 and AOX2. Sequence analysis indicated that each gene encodes a similar protein of 663 amino acids. The protein‐coding regions of the genes were 92% and 97% homologous at the nucleotide and predicted amino acid sequence levels, respectively. In contrast to homology observed within the protein‐coding portions of the AOX genes, no homology was found in either the 5′ or 3′ non‐coding regions. Although alcohol oxidase is found in peroxisomes of P. pastoris, the AOX amino acid sequences did not contain a peptide sequence similar to the peroxisomal transport sequence found at the C‐terminus of some peroxisomally located proteins in higher eukaryotes.
Transport of L‐leucine in the fission yeast Schizosaccharomyces pombe
Authors: Sychrová Hana , Horák Jaroslav , Kotyk Arnošt
Published: May 2005

Transport of L‐leucine into Schizosaccharomyces pombe cells from the stationary phase of growth (after preincubation for 60 min with 1% glucose) proceeds uphill, practically unidirectionally, and is mediated by at least two systems: a high‐affinity system with a KT of 0·045 mmol 1−1 and Jmax of 3·3 nmol min−1 (mg dry weight)−1 and a low‐affinity system with a KT of 1·25 mmol 1−1 and Jmax of 16·0 nmol min−1 (mg dry weight)−1. The high‐affinity system has a pH optimum at 3.2, the accumulation ratio is highest at a cell density of 2–4 mg dry weight per ml and decreases with increasing leucine concentration. Transport of leucine by the high‐affinity system is strongly inhibited by proton conductors, ammonium ions and by most amino acids, but only L‐phenylalanine, L‐isoleucine, L‐valine and L‐cysteine behave as fully competitive inhibitors. Systems of L‐leucine transport in S. pombe are not constitutive. Transport activity appears only after preincubation of cells with a suitable source of energy. If cycloheximide is added during preincubation with glucose, no transport systems for leucine are synthesized. After removal of glucose, the activity of transport systems decays with a half‐time of about 20 min. The presence of cyclic AMP increases the initial rate of leucine uptake only in cells preincubated with glucose and in the absence of cycloheximide.
Overproduction of glycolytic enzymes in yeast
Authors: Schaaff Ine , Heinisch Jürgen , Zimmermann Friedrich K.
Published: May 2005

Eight different enzyymes for glycolysis and alcoholic fermentation were overproduced in a common Saccharomyces cerevisiae strain by placing their genes on multicopy vectors. The specific enzyme activities were increased between 3·7‐and 13·9‐fold above the wild‐type level. The overproduction of the different glycolytic enzymes had no effect on the rate of ethanol formation, even with those enzymes that catalyse irreversible steps: hexokinase, phosphofructokinase and pyruvate kinase. Also the simultaneous increase in the activities of pairs of enzymes such as pyruvate kinase and phosphofructokinase or pyruvate decarboxylase and alcohol dehyrogenase, did not increase the rate of ethanol production. The levels of key glycolytic metabolites were also normal, compared to the reference strain.
Intracellular and extracellular levels of cyclic AMP during the cell cycle of Saccharomyces cerevisiae
Authors: Smith Maxine E. , Dickinson J. Richard , Wheals Alan E.
Published: May 2005

Using the techniques of centrifugal elutriation it was demonstrated that during the cell division cycle of the budding yeast Saccharomyces cerevisiae there are stage‐specific fluctuations in the intracellular concentration of adenosine 3′,5′‐cyclic monophosphate (cAMP). Results shown here indicate that the intracellular concentration of cAMP is at its highest during the division cycle, and its lowest immediately prior to and just after cell sepraration. Results also show the extrusion of extracellular cAMP into the medium by Saccharomyces cerevisiae, extracellular cAMP levels being ten to one hundred times higher than intracellular levels. During the cell of Saccharomyces cerevisiae the extracellular level of cAMP does not fluctuate.
A novel aspartyl protease allowing KEX2‐independent MFα propheromone processing in yeast
Authors: Egel‐Mitani Michi , Flygenring Hanne Pia , Hansen Mogens Trier
Published: May 2005

Mutants of Saccharomyces cerevisiae which lack the KEX2‐encoded endopeptidase are unable to process proteolytically the mating factor alpha (MFα) propheromone produced from the chromosomal MFα1 and MFα2 genes (Julius et al., 1983). Overproduction of pheromone precursor from multiple, plasmid‐borne MFα genes did, however, lead to the production of active MFα peptides in the absence of the KEX2 gene product. S. cerevisiae therefore must possess an alternative processing enzyme. The cleavage site of this enzyme appeared identical to that of the KEX2‐encoded endopeptidase. To identify the gene responsible for the alternative processing, we have isolated clones which allowed production of mature MFα in a kex2‐disrupted strain even from the chromosomal MFα genes. The gene isolated in this way was shown also to be essential for the KEX2‐independent processing of propheromone overproduced from plasmid‐borne MFα1. The amino acid sequence deduced from the gene shows extensive homology to a number of aspartyl proteases including the PEP4 and BARI gene products from S. cerevisiae. In contrast to the BARI gene product, the novel aspartyl protease (YAP3 for Yeast Aspartyl Protease 3) contains a C‐terminal serine/threonine‐rich sequence and potential transmembrane domain similar to those found in the KEX2 gene product. The corresponding gene YAP3 was located to chromosome XII. The normal physiological role of the YAP3 gene product is not known. Strains disrupted in YAP3 are both viable and able to process the mating factor a precursor.
Substrate‐accelerated death of Saccharomyces cerevisiae CBS 8066 under maltose stress
Authors: Postma Erik , Verduyn Cornelis , Kuiper Arthur , Scheffers W. Alexander , Van Dijken Johannes P.
Published: May 2005

When Saccharomyces cerevisiae CBS 8066 was grown under maltose limitation, two enzymes specific for maltose utilization were present: a maltose carrier, and the maltose‐hydrolysing α‐glucosidase. The role of these two enzymes in the physiology of S. cerevisiae was investigated in a comparative study in which Candida utilis CBS 621 was used as a reference organism.

Maltose pulses to a maltose‐limited chemostat culture of S. cerevisiae resulted in ‘substrate‐accelerated death’. This was evident from: (1) enhanced protein release from cells: (2) excretion of glucose into the medium; (3) decreased viability. These effects were specific with respect to both substrate and organism: pulses of glucose to maltose‐limited cultures of S. cerevisiae did not result in cell death, neither did maltose pulses to maltose‐limited cultures of C. utilis. The maltose‐accelerated death of S. cerevisiae is most likely explained in terms of an uncontrolled uptake of maltose into the cell, resulting in an osmotic burst. Our results also provide evidence that the aerobic alcoholic fermentation that occurs after pulsing sugars to sugar‐limited cultures of S. cerevisiae (short‐term Crabtree effect) cannot solely be explained in terms of the mechanism of sugar transport. Both glucose and maltose pulses to maltose‐limited cultures triggered aerobic alcohol formation. However, glucose transport by S. cerevisiae occurs via facilitated diffusion, whereas maltose entry into this yeast is mediated by a maltose/proton symport system.
Osmoregulatory active sodium‐glycerol co‐transport in the halotolerant yeast Debaryomyces hansenii
Authors: Lucas Candida , Da Costa M. , Van Uden N.
Published: May 2005

Several authors have shown that the halotolerant yeast Debaryomyces hansenii, when growing exponentially in glucose medium in the presence of sodium chloride, maintains osmotic balance by establishing sodium and glycerol gradients of opposite signs across the plasma membrane. Evidence is presented here that the two gradients are linked through a sodium‐glycerol symport that uses the sodium gradient as a driving force for maintaining the glycerol gradient. The symporter also accepts potassium ions as co‐substrate. The kinetic parameters at 25°C, pH 5·0 were the following: Vmax, decreasing from over 500 to less than 40 μmol g−1 per h over a concentration range of 0–3 M extracellular sodium chloride; Km (glycerol) 0·40–0·6 mM over the same range; Km (sodium ions) 16·0 ± 3·21μM; Km, (potassium ions) 10·4 ± 3·6μM. Furthermore, it was observed that glycerol uptake was accompanied by proton uptake when extracellular sodium chloride was present and that the protonophore carbonylcyanide‐M‐chlorophenylhydrazone induced collapse of the glycerol gradient, supporting earlier proposals by others that the sodium gradient is maintained by an active sodium‐proton exchange mechanism.
The alcohol dehydrogenase system in the yeast, Kluyveromyces lactis
Authors: Saliola Michele , Shuster Jeffrey R. , Falcone Claudio
Published: May 2005

We have studied the alcohol dehydrogenase (ADH) system in the yeast Kluyvefromyces lactis. Southern hybridization to the Saccharomyces cerevisiae ADH2 gene indicates four probable structural ADH genes in K. lactis. Two of these genes have been isolated from a genomic bank by hybridization to ADH2. The nucleotide sequence of one of these genes shows 80% and 50% sequence identity to the ADH genes of S. cerevisiae and Schizosaccharomyces pombe respectively. One K. lactis ADH gene is preferentially expressed in glucose‐grown cells and, in analogy to S. cerevisiae, was named K1ADH1. The other gene, homologous to K1ADH1 in sequence, shows an amino‐terminal extension which displays all of the characteristics of a mitochondrial targeting presequence. We named this gene K1ADH3. The two genes have been localized on different chromosomes by Southern hybridization to an orthogonal‐field‐alternation gel electrophoresis‐resolved K. lactis genome. ADH activities resolved by gel electrophoresis revealed several ADH isozymes which are differently expressed in K. lactis cells depending on the carbon source.
Cell fusion of Saccharomyces cerevisiae fragile mutants
Authors: Philipova D. H. , Venkov P. V.
Published: May 2005

Fragile mutants of Saccharomyces cerevisiae are defective in the structure of the cell wall and plasma membrane. The mutant cells lyse in hypotonic solutions but grow exponentially when osmotic stabilizer is induced in the medium. These mutants display a general increase in the permeability of the plasma membrane. We show here that fragile yeast cells of the same mating type can fuse without protoplast formation. The frequency of cell × cell fusion is lower than that observed for protoplast × protoplast fusion and can be significantly increased if the cells of one partner are converted to protoplasts. Microscopic observations and genetic analysis demonstrate that the hybrids obtained are fusion products. The fusion between fragile cells is explained in terms of the existence of local defects on their surface where the cell wall is thinner (or even missing), thus allowing a direct contact of cells by means of their plasma membranes.
The chromosomal constitution of wine strains of Saccharomyces cerevisiae
Authors: Bakalinsky Alan T. , Snow Richard
Published: May 2005

A general procedure is described for determining the chromosomal constitution of industrial strains of Saccharomyces cerevisiae based on analysis of segregation frequencies for input markers among random spore progeny of industrial‐laboratory strain hybrids. The multiple auxotrophic haploid testers used carried a dominant erythromycin‐resistance marker, allowing hybrids to be selected in mass matings with produced by the wild‐type industrial strains. Analysis a number of independent crosses between the haploid testers and an unselected population of spores of each wine strain distinguished between disomic, trisomic and tetrasomic chromosomal complements in the parents. Possible explanations for a significant class of aberrant segregation frequencies are discussed.

Results of the analysis indicate that UCD Enology 522 (Montrachet) is diployed and possibly trisomic for chromosome VII; 522X is diploid; UCD Enology 505 (California Champagne) is disomic for chromosome XVI, trisomic for chromosomes I, II, III, VI, VIII, IX, X, XII, XV, tetrasomic for chromosomes IV, XI, XIII, XIV and either trisomic or tetrasomic for chromosomes V and VII; and that UCD Enology 595 (Pasteur Champagne) is disomic for chromosomes I, II, III, IX, XVI, trisomic for chromosomes IV, VI, X, XII, XIV, XV, tetrasomic for chromosomes V, VIII, XI, XIII, and either disomic or tetrasomic for chromosome VII.
III. Yeast sequencing reports. Determination of the sequence of the yeast YCL313 gene localized on chromosome III. Homology with the protein disulfide isomerase (PDI gene product) of other organisms
Authors: Scherens B. , Dubois E. , Messenguy F.
Published: May 2005

We have determined the nucleotide sequence of the YCL313 gene as part of the YIp5 A1G clone localized on the left arm of chromosome III. This YCL313 gene encodes a protein of 522 amino acids (MW 58·3 kDa) which has large homologies with the human, mouse, chicken, bovine and rat PDI gene products. In these organisms the PDI gene encodes the protein disulfide isomerase (EC 5.3.4.1) also called S–S rearrangase, an enzyme that catalyses the rearrangements of S–S bonds in proteins. This enzyme is probably involved in protein folding within the lumen of the endoplasmic reticulum.

These sequence homologies suggest that YCL313 is the yeast equivalent of the PDI gene. Gene disruption of YCL313 leads to a lethal phenotype indicating that this gene is essential for cell survival.
A new glucose‐repressible gene identified from the analysis of chromatin structure in deletion mutants of yeast SUC2 locus
Authors: Igual J. Carlos , Matallana Emilia , Gonzalez‐Bosch Carmen , Franco Luis , Pérez‐Ortin José E.
Published: May 2005

We have previously shown that some changes occur in the chromatin structure of the 3′ flank of the yeast SUC2 gene in going from a repressed to an active state. In an attempt to find out the causes of these changes, we have carried out experiments in which mutant copies of SUC2 locus lacking either 5′ or 3′ flanks have been analysed for their transcriptional activity and chromatin structure. These experiments allowed us to discard any relationship between SUC2 transcription and chromatin changes within its 3′ flank. Sequencing of this flank and mRNA analysis, however, resulted in the location of a putative peroxisomal 3‐oxoacyl‐CoA thiolase gene (POT1), which is repressible by glucose. The disruption of the gene produced a yeast strain unable to use oleic acid as a carbon source. This is the first time that chromatin structure analysis has permitted the identification of new gene.
Two genes encoding putative mitochondrial alcohol dehydrogenases are present in the yeast Kluyveromyces lactis
Authors: Saliola Michele , Gonnella Roberta , Mazzoni Cristina , Falcone Claudio
Published: May 2005

Four structural genes encoding isozymes of the alcohol dehydrogenase (ADH) system in the yeast Kluyveromyces lactis have been identified by hybridization to ADH2 DNA probes from Saccharomyces cerevisiae. In this paper we report on the isolation of KlADH4 and the complete sequencing of KlADH3 and KlADH4, two genes which show high homology to KlADH1, the ADH gene previously isolated in K. lactis, and to the ADH genes of S. cerevisiae. When compared with KlADH1, both KlADH3 and KlADH4 encode amino‐terminal extensions which show the characteristics of the mitochondrial targeting sequences. These extensions are poorly conserved both at the nucleotide and the amino acid level. Suprisingly, the KlADH4 extension shows a higher identity at the amino acid level to the one encoded by ADH3 of S. cerevisiae than to the KlADH3 presequence. KlADH3 and KlADH4, in contrast to the ADH3 gene of S. cerevisiae, show a strong bias in the choice of codons.
Analysis of the expression and secretion of the Candida tsukubaensis α‐glucosidase gene in the yeast Saccharomyces cerevisiae
Authors: Kinsella B. T. , Cantwell B. A.
Published: May 2005

The α‐glucosidase gene of Candida tsukubaensis is contained within a 3·47 kb BamH1‐Mlu1 fragment which, when introduced into Saccharomyces cerevisiae AH22 on a yeast–Escherichia coli shuttle vector, allows the transformants to utilize maltose as sole carbon source. Thus, the cloned gene confers a dominant selectable phenotype on transformed strains of S. cerevisiae which are otherwise unable to grow in nutrient media containing maltose, dextrin or other α‐1,4‐linked α‐D‐glucopyranosides, specifically hydrolysed by the α‐glucosidase. The cloned enzyme expressed in yeast is secreted into the extracellular medium in a glycosylated form which accounts for up to 60% of the secreted protein and has a molecular size of 70–80 kilodalton (kDa). Deglycosylation of the α‐glucosidase showed that the enzyme is composed of two distinct polypeptides with subunit molecular weights of 63–65 kDa (peptide 1) and 50–52 kDa (peptide 2). An increase in the level of expression of the α‐glucosidase by yeast transformants in selective minimal medium was obtained by using a vector with increased copy number containing the leu2‐d gene as selectable marker. The α‐glucosidase gene promoter functions more effectively than the Gal1–10 promoter in directing α‐glucosidase expression in S. cerevisiae. It also directs the expression of high levels of β‐galactosidase activity in yeast when fused to a promoterless E. coli lacZ gene. Expression of the α‐glucosidase gene under the control of its own promoter is constitutive, orientation dependent and not subject to catabolite repression.
Glucan structure in a fragile mutant of Saccharomyces cerevisiae
Authors: Blagoeva J. , Stoev G. , Venkov P.
Published: May 2005

The phenotype of VY1160 fragile Saccharomyces cerevisiae mutant is characterized by cell lysis upon transfer to hypotonic solutions and increased permeability of cells growing in osmotically stabilized media. Two mutations, srb1 and ts1, have been identified in VY1160 cells and previous studies have shown that the increased permeability is due to the ts1 mutation which causes a shortening of mannan side‐chains. Here we report that the srb1 mutation, which is the genetic determinant of cell lysis, is responsible for quantitative and structural changes of glucans. Experiments with isogenic determinant of cell lysis, is responsible for quantitative and structural changes of glucans. Experiments with isogenic single mutation strains, genetic studies coupled with quantitative measurements of glucan content per cell, and methylation analysis of glucans provide evidence that srb1 mutation leads to (i) formation of mechanically unstable cell wall network made of insoluble glucan fibrils which are shorter and contain β(1–6) inter‐residue linkages and (ii) insufficient filling of the space between the fibrils due to a shortage of the alkali‐soluble glucan. Although growing exponentially in osmotically stabilized media, the srb1 cells cannot resist an osmotic shock and, hence, burst immediately.
Cloning and sequencing of the yeast Saccharomyces cerevisiae SEC1 gene localized on chromosome IV
Authors: Aalto M. K. , Ruohonen L. , Hosono K. , Keränen S.
Published: May 2005

The SEC1 gene of yeast Saccharomyces cerevisiae was cloned by complementing the temperature‐sensitive mutantion of sec1‐1 at 37°C, and its nucleotide sequence was determined. SEC1 is a single copy gene and encodes a protein of 724 amino acids and 83,490 daltons with a predicted pI value of 6·11. Hydrophobicity plotting showed no clearly hydrophobic regions suggesting a soluble nature for the protein. Amino acid sequence comparisons revealed no obvious homologies with the proteins in the SWISSPROT databank. Two consensus sequences for the cdc2 encoded protein kinase recognition site were revealed within Sec1p. The codon usage suggests a low expression level for SEC1. The 5′ non‐translated region contains two TATA‐like sequences at ‐52 and ‐215 nucleotides from the translation start site. Two potential regulatory sequences for DNA binding proteins were found in the non‐coding 5′ region: a HAP2/HAP3 consensus recognition sequence at nucleotide ‐154 and a BAF1 consensus recognition sequence at nucleotide ‐136. The SEC1 specific probe detected a 2400 nucleotides long transcript, which was in reasonable agreement with the 2172 nucleotides long open reading frame.
Repression of a mating type cassette in the fission yeast by four DNA elements
Authors: Ekwall Karl , Nielsen Olaf , Ruusala Tarmo
Published: May 2005

The fission yeast, Schizosaccharomyces pombe, expresses one of two alternative mating types. They are specified by one of two determinants (M or P) present at the mat1 locus. In addition, silent copies of M and P are present on the same chromosome. In the present work we demonstrate that the difference between the active and the silent stage of the P determinant is controlled by four repressive elements that are located at the silent locus. There are two elements to the left and two to the right of the mating type cassette. Both elements to the left and either one of the two elements to the right are required for an effective blockage of transcription. When they are combined, the four elements define a highly efficient silencer functionally similar to the HMRE and HMLE and HMLI silencers in Saccharomyces cerevisiae. In addition, the DNA surrounding the silent P locus confers symmetric partitioning in mitosis to Schizosaccharomyces pombe ars plasmids.
Transport of lactic acid in Kluyveromyces marxianus: Evidence for a monocarboxylate uniport
Authors: Fonseca A. , Spencer‐Martins I. , Van Uden N.
Published: May 2005

Lactic acid‐grown cells of a strain of Kluyveromyces marxianus transported D‐and L‐lactic acid by a saturable mechanism that was partially inducible and subject to glucose repression, with the following kinetic parameters at pH 5·4: Vmax = 1·00 (±0·13) mmol h−1 per g dry weight and Ks = 0·42 (±0·08) mM. Lactic acid transport was competitively inhibited by pyruvic, glycolic, acetic and bromoacetic acids. The latter, a non‐metabolizable analogue, was transiently accumulated, the extent depending on the extracellular pH. The pH dependence of the Ks values for undissociated lactic acid and for the lactate anion indicated that the latter was the transported species. Lactate uptake was not accompanied by the simulatate uptake of protons, potassium ions or sodium ions excluding symport mechanisms. Initial lactic acid uptake led to transient membrane hyperpolarization as measured with a fluorescent dye excluding also an electroneutral anion antiport mechanism. It was concluded that lactate anions use a monocarboxylate uniport and that the counter anion, possibly bicarbonate, uses a separate channel, the coupling being electrical and loose.
The product of the YCR105 gene located on the chromosome III from Saccharomyces cerevisiae presents homologies to ATP‐dependent permeases
Authors: Purnelle Bénédicte , Skala Jacek , Goffeau André
Published: May 2005

During the systematic sequencing of chromosome III from Saccharomyces cerevisiae, carried out by a network of laboratories sponsored by the Commission of the European Community, we have identified the open reading frame YCR105 located on fragment J11D from the circular derivative of chromosome III in strain XJ24–24a (Palzkill et al., 1986). YCR105 is immediately centromere proximal to the PGK gene (opposite strand) on the right arm of chromosome III about 20 kb from the centromere.
Molecular cloning of the γ‐glutamylcysteine synthetase gene of Saccharomyces cerevisiae
Authors: Ohtake Yasuyuki , Yabuuchi Seizou
Published: May 2005

The 4·4 kb SphI DNA fragment (GSH1) that complements the γ‐glutamylcysteine synthetase‐deficient mutation (gsh1) of Saccharomyces cerevisiae YH1 was cloned into vector plasmid YEp24. Gene disruption of the cloned fragment confirmed that this segment was the same gene as gsh1. Mutant strain YH1 with this plasmid not only restored γ‐glutamylcysteine synthetase (GSH‐1) activity but the glutathione content and the growth rate. DNA sequence analysis of the SphI fragment showed that the GSH1 structural gene contained 2034 bp and predicted a polypeptide of 678 amino acids. The deduced amino acid sequence had about a 45% homology to that of rat kidney GSH‐I, but a very low homology (about 26%) to that of Escherichia coli GSH‐I. Northern analysis showed that GSH1 had been transcribed into an approximately 2·7 kb mRNA fragment. Southern analysis showed that GSH1 mapped at chromosome X.
Dosage‐dependent translational suppression in yeast Saccharomyces cerevisiae
Authors: Chernoff Yury O. , Inge‐Vechtomov Sergey G. , Derkach Irina L. , Ptyushkina Marina V. , Tarunina Olga V. , Dagkesamanskaya Adilya R. , Ter‐Avanesyan Michael D.
Published: May 2005

The overexpression of SUP35 (SUP2) wild‐type gene, caused by increase of its copy number, induces an omnipotent suppression similar to the phenotype of mutants for this gene. The effectt of extra‐SUP35 was detected for moderate or even low copy number. Moreover, overdosage of the fragment including only the 5′‐flanking region and N‐terminal 100 bp of protein‐coding sequence of SUP35 leads to allosuppression. Multi‐SUP35 gene was also icompatible with extrachromosomal suppressor factor ψ, presumbaly because of high level of mistranslation. The suppressor effect caused by overdosage of another gene, SUP45 (SUP1), is much lower and can be detected only for one construction which is derived from high copy number plasmid. Suppression induced by extra‐SUP35 and especially by extra‐SUP45 is affected by the cell environment. A model predicting that the balance of gene products is a key for regulation of translational fidelity is discussed.