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    Wyświetlanie 1-14 z 14
    Tytuł:
    140 lat pisma kosmos
    Autorzy:
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1034652.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Przyrodników im. Kopernika
    Tematy:
    historia pisma Kosmos
    Polskie Towarzystwo Pzryrodników im. Kopernika
    Opis:
    The history of KOSMOS and present standing of the journal are shortly outlined on the occasion of its 140. anniversary.
    KOSMOS has been founded by The Polish Copernicus Society of Naturalists, as a monthly scientific almanac, the first volume of which has been published 140 years ago in 1886. The aim of the journal was to help the Society to fulfill its statuary objectives - advancement of knowledge in the field of natural sciences, in particular of physiographical ones, as well as cataloguing and protection of monuments of nature. Therefore, content of the journal included both original and review papers, chronical and bibliographic notes. Although the seat of the Society and the journal was then in the city of Lwow, within the Austrian Partition of Poland (called The Kingdom of Galicia and Lodomeria), KOSMOS served also polish authors and readers from the Russian and Prussian Partitions, and from abroad. The journal has been published in Lwow also after formation of the Polish Republic (1918) until the II World War. Appearance of specialized learned societies and journals, forced The Polish Copernicus Society of Naturalists in 1928 to split KOSMOS into two series with identical numeration of the volumes: Series A, Dissertations (original papers with English or French summaries), and Series B, Reviews (devoted to popularization of science). After the War, KOSMOS was reactivated in 1952, in Warsaw, as a review journal devoted solely to popularization of biological sciences and with anew volume's numeration. For a couple of years (1952-1956) the journal has been extensively used for insemination of pseudo-scientific ideas of Lysenkoism in genetics and evolutionary biology, recognized at that time as obligatory ones in the USSR. With the appearance of a younger generation of editors, in the middle of 70-thies of the former century, a stepwise modernization of the journal has begun. There were introduced: thematic issues devoted to current topics and organized mostly by invited guest-editors, English summaries of articles, modern graphical layout with an added journal's subtitle "Problems of biological sciences" (1997), and finally - a parallel, freely accessible, internet edition (since 2002). Information about the content, editor(s) names and their institutional affiliation, and year of publication of the thematic issues in the period 1983-2015 is presented in tabular form in the text. Also tabulated is statistical information about the number of researchers affiliated with particular scientific institutions who authored or co-authored papers published in the period of 2000-2015, documenting that majority of the authors were affiliated with universities and institutes of the Polish Academy of Sciences of broadly recognized high scientific standing. Statistical information indicating high popularity of the journal's internet edition is presented in the form of plots: (i) of the number of visits from individual IP's of the readers and the number of articles downloaded monthly between 2002 and 2015, and (ii) of the number of articles downloaded during the whole year 2015 from particular archival volumes 2002-2014. In spite of the high standing and popularity of the journal, the Society encounters steady financial problems with coverage of its publication cost. This is mainly due to insufficient and fluctuating support from the public funds. A helping hand has been offered recently by the authorities of the Nicolas Copernicus University in Toruń, the Scientific Publishing House of which became co-publisher of KOSMOS since 2012.
    Źródło:
    Kosmos; 2016, 65, 2; 151-161
    0023-4249
    Pojawia się w:
    Kosmos
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Intramolecular electron transfer between tryptophan radical and tyrosine in oligoproline-bridged model peptides and hen egg-white lysozyme
    Autorzy:
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1044887.pdf
    Data publikacji:
    1997
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Źródło:
    Acta Biochimica Polonica; 1997, 44, 4; 627-644
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of mixed-salt effects on thermodynamic and kinetic parameters of RNA polymerase-promoter DNA complexes in terms of equivalent salt concentrations. General applicability to DNA complexes
    Autorzy:
    Łoziński, Tomasz
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1040491.pdf
    Data publikacji:
    2009
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    protein-DNA complexes
    salt-dependence of equilibrium and kinetic constants
    mixed salts effects
    equivalent salt concentrations
    Opis:
    Facile evaluation of mixed-salt effect on the strongly salt-dependent thermodynamic and kinetic parameters of protein-DNA complexes is of importance for relevant biochemical and biophysical studies. In pursuit of this aim, binding isotherms for open transcription complex (RPo) of Escherichia coli RNA polymerase (R) at λPR promoter DNA (P) were determined as a function of salt concentration in pure NaCl and Tris/HCl solutions, and as a function of [NaCl] in the presence of fixed concentrations of MgCl2 and Tris/HCl. A concept of equivalent salt concentrations, i.e. concentrations at which the binding equilibrium constant is the same, was introduced and applied for prediction of binding isotherms in mixed salt solutions. Full coincidence between the experimental and predicted isotherms indicated that individual contributions of salts to the global salt-effect are additive in a broad range of salt concentrations. A generalized formula for calculation of salt equivalents characteristic for any of the thermodynamic or kinetic parameters of a complex (e.g., free energy, binding equilibrium and association/dissociation kinetic rate constants) is presented and its applicability to a number of protein-DNA complexes and dsDNA melting demonstrated using authors' own and literature data.
    Źródło:
    Acta Biochimica Polonica; 2009, 56, 4; 695-702
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mg2+ ions do not induce expansion of the melted DNA region in the open complex formed by Escherichia coli RNA polymerase at a cognate synthetic Pa promoter. A quantitative KMnO4 footprinting study
    Autorzy:
    Łoziński, Tomasz
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1044146.pdf
    Data publikacji:
    2001
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    permanganate footprinting
    open promoter complex
    thymine oxidation
    effect of magnesium ions
    RNA polymerase
    Opis:
    Footprinting studies of prokaryotic open transcription complexes (RPO), based on oxidation of pyrimidine residues by KMnO4 and/or OsO4 at a single oxidant dose, have suggested that the extent of DNA melting in the transcription bubble region increases in the presence of Mg2+. In this work, quantitative KMnO4 footprinting in function of the oxidant dose of RPO, using Escherichia coli RNA polymerase (Eσ70 ) at a fully functional synthetic promoter Pa having -35 and -10 consensus hexamers, has been used to determine individual rate constants of oxidation of T residues in this region at 37°C in the absence of Mg2+ and in the presence of 10 mM MgCl2, and to evaluate therefrom the effect of Mg2+ on the extent of DNA melting. Population distributions of end-labeled DNA fragments corresponding to oxidized Ts were quantified and analyzed according to the single-hit kinetic model. Pseudo-first order reactivity rate constants, ki, thus obtained demonstrated that Mg2+ ions bound to RPO merely enhanced the reactivity of all 11 oxidizable thymines between the +3 and -11 promoter sites by a position-dependent factor: 3-4 for those located close to the transcription start point +1 in either DNA strand, and about 1.6 for those located more distantly therefrom. On the basis of these observations, we conclude that Mg2+ ions bound to RPO at Pa do not influence the length of the melted DNA region and propose that the higher reactivity of thymines results mainly from lower local repulsive electrostatic barriers to MnO4- diffusion around carboxylate binding sites in the catalytic center of RPO and promoter DNA phosphates.
    Źródło:
    Acta Biochimica Polonica; 2001, 48, 2; 495-510
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Mg2+ on kinetics of oxidation of pyrimidines in duplex DNA by potassium permanganate.
    Autorzy:
    Łoziński, Tomasz
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1044147.pdf
    Data publikacji:
    2001
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    oxidation of pyrimidines
    thymine glycol
    magnesium ions
    rate constant of oxidation
    pDS3 plasmid DNA
    quantitative permanganate footprinting
    Opis:
    Potassium permanganate oxidation of pyrimidine bases is often used to probe single-stranded regions in functional DNA-protein complexes. However, so far reactivity of these bases in double-stranded DNA has not been studied quantitatively. We have investigated the kinetics of oxidation of pyrimidines in supercoiled pDS3 plasmid dsDNA by quantitative KMnO4 footprinting, in connection with parallel studies on the effect of Mg2+ on kinetics of oxidation of individual thymines in the single-stranded region of the open transcription complex of Escherichia coli RNA polymerase at a cognate Pa promoter contained in this plasmid. Rate constants of oxidation for pyrimidines, kj, in selected regions of pDS3 DNA, including Pa promoter, were determined under single-hit reaction conditions in the absence and presence of 10 mM MgCl2. Their values appeared to be sequence-dependent and were: (i) the largest for Ts in 5'TA3' and 5'TC3' steps, while 2-4 times smaller for 5'-adjacent ones in TT(A,G,C) and TTT(A) runs, (ii) for Cs in 5'TC3' steps 2-4 fold smaller than for adjacent Ts, and (iii) in the presence of Mg2+ generally larger by a sequence-dependent factor: in 5'TC3' steps of about 2 and 4 for Ts and Cs, respectively, in 5'TA3' steps of TTA and TTTA sequences for 3'-terminal Ts of about 3, while for their 5'-neighbors of a distinctly smaller value of about 2. Comparison of kj data for corresponding Ts located between +1 and -10 regions of Pa promoter in dsDNA and in ssDNA form in the open transcription complex, reported elsewhere, demonstrates that reactivity of pyrimidines in dsDNA is by 2-3 orders of magnitude smaller. The effect of Mg2+ in dsDNA is interpreted in terms of electrostatic barrier to diffusion of MnO4- on DNA surface, which is lowered by diffusive binding of these ions to backbone phosphates, involving also sequence-specific contacts with bases in the minor and major grooves of B-DNA.
    Źródło:
    Acta Biochimica Polonica; 2001, 48, 2; 511-523
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of reversed orientation and length of An·Tn DNA bending sequences in the -35 and spacer domains of a consensus-like Escherichia coli promoter on its strength in vivo and gross structure of the open complex in vitro
    Autorzy:
    Łoziński, Tomasz
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1045193.pdf
    Data publikacji:
    1996
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Źródło:
    Acta Biochimica Polonica; 1996, 43, 1; 265-279
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of distortions by A-tracts of promoter B-DNA spacer region on the kinetics of open complex formation by Escherichia coli RNA polymerase.
    Autorzy:
    Kolasa, Iwona
    Łoziński, Tomasz
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1043363.pdf
    Data publikacji:
    2003
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    RNA polymerase-promoter interaction
    A-tract
    DNA bending
    kinetics of open complex formation
    promoter spacer region
    Escherichia coli RNA polymerase
    Opis:
    A-tracts in DNA due to their structural morphology distinctly different from the canonical B-DNA form play an important role in specific recognition of bacterial upstream promoter elements by the carboxyl terminal domain of RNA polymerase α subunit and, in turn, in the process of transcription initiation. They are only rarely found in the spacer promoter regions separating the -35 and -10 recognition hexamers. At present, the nature of the protein-DNA contacts formed between RNA polymerase and promoter DNA in transcription initiation can only be inferred from low resolution structural data and mutational and crosslinking experiments. To probe these contacts further, we constructed derivatives of a model Pa promoter bearing in the spacer region one or two An (n = 5 or 6) tracts, in phase with the DNA helical repeat, and studied the effects of thereby induced perturbation of promoter DNA structure on the kinetics of open complex (RPo) formation in vitro by Escherichia coli RNA polymerase. We found that the overall second-order rate constant ka of RPo formation, relative to that at the control promoter, was strongly reduced by one to two orders of magnitude only when the A-tracts were located in the nontemplate strand. A particularly strong 30-fold down effect on ka was exerted by nontemplate A-tracts in the -10 extended promoter region, where an involvement of nontemplate TG (-14, -15) sequence in a specific interaction with region 3 of σ-subunit is postulated. A-tracts in the latter location caused also 3-fold slower isomerization of the first closed transcription complex into the intermediate one that precedes formation of RPo, and led to two-fold faster dissociation of the latter. All these findings are discussed in relation to recent structural and kinetic models of RPo formation.
    Źródło:
    Acta Biochimica Polonica; 2003, 50, 4; 909-920
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of An tracts within the UP element proximal subsite of a model promoter on kinetics of open complex formation by Escherichia coli RNA polymerase.
    Autorzy:
    Kolasa, Iwona
    Łoziński, Tomasz
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1043730.pdf
    Data publikacji:
    2002
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    UP element
    consensus-like promoters
    DNA bending An tracts
    kinetics of transcription open complex formation
    Escherichia coli RNA polymerase
    Opis:
    In the open transcription complex (RPo), Escherichia coli RNA polymerase s70 and α subunits are known to be in contact with each other and with the promoter region overlapping the -35 hexamer and the proximal part of the UP element. To probe the effect of An DNA bending tracts in this region on initiation of transcription, kinetics of the formation of RPo by Escherichia coli RNA polymerase at two groups of synthetic consensus-like promoters bearing single DNA bending tracts (i) A5 within the proximal subsite region of the UP element (promoters Pk and Pl) and (ii) A5 (Pg) or A8 (Pm) in the region including the downstream end of the proximal UP subsite and the -35 consensus hexamer was studied in vitro using the fluorescence-detected abortive initiation assay. The kinetic data obtained demonstrate that the overall second-order rate constant ka of RPo formation is: (i) by almost one order of magnitude larger at Pk and Pl, relative to that at a control unbent promoter, and mainly due to a higher value of the equilibrium constant, K1, of the initial closed complex; and (ii) several-fold smaller at Pg and Pm owing to a strongly decreased value of K1. For Pm, the latter parameter was found to be dependent exponentially on four Mg2+ ions, as compared with the seven ions remaining in equilibrium with the initial closed complex at the parent Pa promoter. This indicates that promoter region bearing a stiff A8·T8 fragment of B'-DNA forms a smaller number of ionic contacts with the α subunit. These findings provide a new insight to and support the present model of interactions between RNA polymerase α and s70 subunits with the proximal UP subsite and the -35 region of promoters.
    Źródło:
    Acta Biochimica Polonica; 2002, 49, 3; 659-669
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mg 2+ Does not induce isomerization of the open transcription complex Escherichia coli RNA polymerase at the model Pα promoter bearing consensus -10 and -35 hexamers.
    Autorzy:
    Kolasa, Iwona
    Łoziński, Tomasz
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1044041.pdf
    Data publikacji:
    2001
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Tematy:
    effect of Mg2+
    transcription open complex
    kinetics and thermodynamics of transcription initiation
    Opis:
    The kinetics and thermodynamics of the formation of the transcriptional open complex (RPo) by Escherichia coli RNA polymerase at the synthetic Pα promoter bearing consensus -10 and -35 recognition hexamers were studied in vitro. Previously, this promoter was used as a control one in studies on the effect of DNA bending by An·Tn sequences on transcription initiation and shown to be fully functional in E. coli (Łoziński et al., 1991, Nucleic Acids Res. 19, 2947; Łoziński & Wierzchowski, 1996, Acta Biochim. Polon. 43, 265). The data now obtained demonstrate that the mechanism of Pα-RPo formation and dissociation conforms to the three-step reaction model: bind-nucleate-melt, commonly accepted for natural promoters. Measurements of the dissociation rate constant of Pα -RPo as a function of MgCl2 concentration allowed us to determine the number of Mg2+ ions, nMg≈ 4, being bound to the RPo in the course of renaturation of the melted DNA region. This number was found constant in the temperature range of 25-37°C, which indicates that under these conditions the complex remaines fully open. This observation, taken together with the recent evidence from independent of the presence of Mg2+ ions (Łoziński & Wierzchowski, 2001, Acta KMnO4 footprinting studies that the length of the melted region in Pα-RPo at 37°C is Biochim. Polon. 48, 495), testifies that binding of Mg2+ to RPo does not induce its further isomerization, which has been postulated for the λPR-RPo complex (Suh et al., 1992, Biochemistry 31, 7815; 1993, Science 259, 358).
    Źródło:
    Acta Biochimica Polonica; 2001, 48, 4; 985-994
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    CD investigations on conformation of H-X-(Pro)i_n-Y-OH peptides (X = Trp, Tyr; Y = Tyr, Met); models for intramolecular long range electron transfer
    Autorzy:
    Wierzchowski, Kazimierz
    Majcher, Krystyna
    Poznański, Jarosław
    Powiązania:
    https://bibliotekanauki.pl/articles/1045260.pdf
    Data publikacji:
    1995
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Źródło:
    Acta Biochimica Polonica; 1995, 42, 2; 259-268
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Conformation of the N(CH_3)_2 group in cytosine and in simple model pyrimidines and pyridines. Steric effects of ortho-methyl substitution on infrared spectra and molecular dipole moments
    Autorzy:
    Litońska, Ewa
    Kułakowska, Zbigniew
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1046222.pdf
    Data publikacji:
    1979
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Źródło:
    Acta Biochimica Polonica; 1979, 26, 1-2; 39-54
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Thermochemistry of aqueous solutions of alkylated nucleic acid bases. VI. Enthalpies of hydration of 2-alkyl-9-methyladenines
    Autorzy:
    Zielenkiewicz, Anna
    Zielenkiewicz, Wojciech
    Sukhodub, Leonia
    Glukhova, Olga
    Wierzchowski, Kazimierz
    Powiązania:
    https://bibliotekanauki.pl/articles/1045929.pdf
    Data publikacji:
    1987
    Wydawca:
    Polskie Towarzystwo Biochemiczne
    Źródło:
    Acta Biochimica Polonica; 1987, 34, 2; 157-164
    0001-527X
    Pojawia się w:
    Acta Biochimica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-14 z 14

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