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    Wyświetlanie 1-15 z 15
    Tytuł:
    Biblioteki związków chemicznych
    Libraries of chemical compounds
    Autorzy:
    Zwoliński, K. M.
    Leśnikowski, Z. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/172580.pdf
    Data publikacji:
    2012
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    biblioteka chemiczna
    biblioteka wirtualna
    przestrzeń chemiczna
    związki naturalne
    leki
    virtual library
    chemical library
    chemical space
    drugs
    natural products
    Opis:
    Over the past decade one can observe a scientific revolution taking place resulting in an explosion of new biotechnologies. Moreover, with the end of the human genome project and following expansion of the extensive genetic research an unprecedented number of new biological targets useful in drug design have been identified. Simultaneously, new methods such as combinatorial synthesis have expanded the overall size of chemical libraries and high-throughtput technologies have enabled to screen more than one million compounds a day [43]. However, an increasing size of chemical libraries in a random fashion may not necessary increase a probability of success and the overall number of successfully identified leads. Thus, success of any drug discovery program depend heavily on the assumed selection criteria of appropriate molecules [58] which properties should maximize the chances of identifying ligands for any given target. Selection criteria used for compounds to generate diverse as well as focused chemical libraries are briefly discussed in the present overview. We describe the most important quality factors such as size, diversity and chemical tractability which should be always kept in mind during the design of chemical libraries. Chemical space is enormous and limited only by a chemist`s imagination. The number of possible drug-like molecules within chemical space has been estimated to be around 1060 [17]. In contrast the overall number of atoms in the observable Universe is approximately 1080. It is obvious that it is impossible to synthesize every possible molecule so one need to explore only those regions of chemical space which are enriched with molecules of appropriate structure and function. Recent strategies for the design of high-quality collections of structurally diverse sets of small molecules are discussed in the context of probing the chemical space in order to find new biologically active structures.
    Źródło:
    Wiadomości Chemiczne; 2012, 66, 7-8; 741-765
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Peptydoglikan : budowa, rola biologiczna oraz synteza
    Peptidoglycan : structure, biological activity and chemical synthesis
    Autorzy:
    Samaszko-Fiertek, J.
    Dmochowska, B.
    Madaj, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/171802.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    peptydoglikan
    synteza chemiczna
    biosynteza
    aktywność biologiczna
    peptidoglycan
    chemical synthesis
    biosynthesis
    biological activity
    Opis:
    The most important component of bacterial cell walls especially Gram-positive bacteria is peptidoglycan, called also murein, PGN. The first time this synonym was used in 1964 by Weidel and Pelzer [1]. Peptidoglycan is present in the outer layer of the cytoplasmic membrane and its structure. The structure of peptidoglycan depends on the bacteria strain. It is estimated that in Gram-negative bacteria, it occupies only about 10–20% of the total area of the cell wall, when in Gram-positive bacteria it is 50 and up to 90% of all space. Problems with isolation with high purity of biological material shows the need for developing techniques for chemical synthesis of peptidoglycan fragments and their analogs. In past few years there has been a growing interest within the synthesis of compounds glycoprotein (glycopeptides, peptidoglycan, etc.). As a basis for the construction of cell walls of many bacteria. Despite intensive research and gain significant knowledge of the physical and biological, chemical synthesis or biosynthesis (Fig. 5 and 6) of peptidoglycan, not so far failed to unambiguously determine its three-dimensional structure. The works of Kelman and Rogers [15] and Dimitriev [20] nearer picture of its structure. However, the time to develop in vivo visualization of cell structure it will be difficult to identify correctly peptidoglycan three-dimensional structure. Due to the important biological roles of murein, many research centers have taken to attempt their chemical synthesis. For biological research began to use chemically synthesized peptidoglycan fragments which guaranteed both uniform and a certain structure. An important roles in the development of methods of chemical synthesis of peptidoglycan had H. Chowdhury work, Fig. 8 [35], Hesek, Fig. 9 and 10 [36, 37], Dziarskiego [38] and Boneca [39] and Inamury [34, 40].
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 7-8; 513-540
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Metody chemicznej ligacji w syntezie peptydów i białek. Część 2
    Chemical ligation methods in the synthesis of peptides and proteins. Part 2
    Autorzy:
    Jędrzejewska, K.
    Kropidłowska, M.
    Wieczerzak, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/172242.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    natywna chemiczna ligacja
    synteza peptydów
    tioester
    native chemical ligation
    peptide synthesis
    thioester
    Opis:
    Proteins are synthesized only by living organisms. Today, we are able to receive them by recombinant protein expression in bacterial cells. This technique is very useful and gives satisfactory amount of desirable material but it precludes the possibility of introduction of some chemical modifications that are often obligatory. For this reason, chemical synthesis of longer peptide chains is still important and is the object of scientists attention. Over the last century, notion of peptide synthesis took a new meaning. Nowadays, we know a number of innovative methods and also automated devices which help us to make progress in this area. Nevertheless, the synthesis of longer, more complicated peptide chains and proteins still constitutes a problem. Native chemical ligation (NCL) has facilitated the synthesis of numerous complex peptide and protein targets. Expansion of ligation techniques has allowed the entry of peptides into the world of therapeutic drugs [1]. NCL reactions are carried out in aqueous solution and give good yields. Due to mild conditions, NCL overcomes racemic and solubility problems encountered in classical peptide synthesis using protected fragments. The challenge is to synthesize the C-terminal thioester-containing peptide necessary for the transesterification reaction, which is the first step of linking the peptide fragments [2]. In this review we discuss the evolution, advantages and potential applications of chemical ligation reactions. In the first part of this article we described the utility of native chemical ligation approach to non-cysteine containing peptides. This part details a number of important approaches to the synthesis of peptides bearing a C-terminal thioester. Contemporary applications of these techniques to the total chemical synthesis of proteins are also presented.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 9-10; 747-761
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Chemiczna biologia syntetyczna
    Chemical synthetic biology
    Autorzy:
    Huszcza, Ewa
    Powiązania:
    https://bibliotekanauki.pl/articles/1853725.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    biologia syntetyczna chemiczna
    ksenobiologia
    komórka minimalna
    chemical synthetic biology
    xenobiology
    minimal cell
    Opis:
    Synthetic biology, which in 2020 turned 20 years old, is a very dynamically developing field. Unlike traditional molecular and cellular biology, synthetic biology focuses on the design and construction of parts, devices and systems such as enzymes, genetic circuits, metabolic pathways, etc. that can be modeled and adapted to specific requirements, and assembly into integrated systems for solving specific problems. The basic assumption of synthetic biology is the application of engineering principles such as standardization and modularity. Synthetic biology is traditionally dominated by top-down approaches that incorporate or redesign well-characterized standard biological parts into cellular systems. In synthetic biology research there are also bottom-up approaches aiming to construct cell-like systems starting with molecular building blocks. This complementary approach is called "chemical synthetic biology." In this case the goal is to use unnatural chemicals to reproduce biological behavior. Under the bottom-up approach synthetic biology involves construction of so-called minimal cells or living cells from scratch and creating orthogonal biological systems based on biochemistry not found in nature. Bottom-up approaches complement the study of living cells, facilitate the definition of principles governing biological organization and identify new systems for biotechnological production. Examples of breakthrough achievements in chemical synthetic biology such as peptide nucleic acids and selected developments over the past few years are presented in this review article.
    Źródło:
    Wiadomości Chemiczne; 2021, 75, 9-10; 1413-1438
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Grzyby i odpady grzybowe jako nowe prekursory do otrzymywania adsorbentów węglowych
    Mushroom and mushroom residues as new precursors for carbon adsorbents
    Autorzy:
    Koźlarek, Natalia
    Bazan-Woźniak, Aleksandra
    Pietrzak, Robert
    Powiązania:
    https://bibliotekanauki.pl/articles/2086743.pdf
    Data publikacji:
    2022
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    biowęgiel
    właściwości fizykochemiczne
    fizyczna i chemiczna aktywacja
    adsorpcja
    biocarbon
    physicochemical properties
    physical and chemical activation
    adsorption
    Opis:
    Undesirable changes in the bacteriological, physical and chemical properties of water are a consequence of introduction of excessive amounts of inorganic and organic materials to it. These pollutants limit or prevent the use of water for drinking, food production and household purposes. The greatest amounts of pollutants enter the watersystem with sewage. Also the pesticides,surfactants, organic dyes, artificial fertilizers along with municipal and industrial waste can easily enter water system and threaten the organisms living there. Another, equally important problem is the pollution of atmospheric air. Emission of solid liquid or gas pollutants to the atmosphere has been proved to have significant impact on human health, climate and nature. That is why the search for new and more effective technologies for the environment purification is a continuous challenge. Recently, increasingly often carbon materials are used as effective adsorbents of pollutants from liquid and gas phases.
    Źródło:
    Wiadomości Chemiczne; 2022, 76, 3-4; 221--236
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zastosowanie spektrometrii atomowej i spektrometrii mas w badaniu specjacji chemicznej
    On the use of atomic and mass spectrometry for the investigation of chemical speciation
    Autorzy:
    Bulska, E.
    Wojciechowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172606.pdf
    Data publikacji:
    2015
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    specjacja chemiczna
    spektrometria atomowa
    spektrometria mas
    techniki łączone
    chemical speciation
    atomic spectrometry
    mass spectrometry
    coupled techniques
    Opis:
    Selected examples of studies conducted by the research group from Laboratory of the Basic Aspect of Analytical Chemistry (Faculty of Chemistry, University of Warsaw), related to the investigation of chemical speciation with the use of coupled techniques were discussed in this work. The pioneering investigation was focused on the study of the speciation of mercury in fish tissues and in clinical samples. Then, the intensive researches were conducted towards understanding of the speciation of antimony and selenium in water, plants and clinical objects. Interestingly, the evaluation of the speciation of aluminium become a challenge in respect of the establishing of the reliable analytical procedure, and the use of flow injection for sample operation were explored in this case. The last but not least, the non – routine analytical procedure was developed in the case of zinc speciation in plant exposed to the harmful environmental conditions.
    Źródło:
    Wiadomości Chemiczne; 2015, 69, 9-10; 701-718
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Chemiczna modyfikacja nanoproszków diamentowych otrzymywanych metodą detonacyjną
    Chemical modificaton of nanodiamond powders produced by detonation method
    Autorzy:
    Adach, K.
    Skolimowski, J.
    Mitura, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/172694.pdf
    Data publikacji:
    2013
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    nanomateriały
    nanoproszki diamentowe
    oczyszczanie
    chemiczna modyfikacja
    funkcjonalizacja powierzchni
    nanomaterials
    diamond nanopowders
    purification
    chemical modification
    surface functionalization
    Opis:
    Nanodiamonds are diamond particles measured in nanometers. The ideal nanodiamond molecule should have surface ability to bind with many organic groups. They are also susceptible to chemical modifications. Nanodiamonds due to their biocompatibility and low toxicity, can be used for biological materials or in medicine. They can also be used as drug carriers and as covalent and electrostatic binding to the active biomolecules. This review describes the chemical modification of nanodiamond powders. This research work aimed and gain new knowledge, understanding and interpretation of the phenomena occure during the chemical functionalization of nanodiamond powders. An observation and an analysis of the mechanisms of chemical bonds formation or physical interactions will broaden the knowledge in this field. An examination of the impact of organic groups on the nanodiamond surface and onto its physical and chemical properties contribute to the selection of the best method of modification. An implementation research allows to broaden the knowledge in the field of chemical surface modification of nanodiamonds powders.
    Źródło:
    Wiadomości Chemiczne; 2013, 67, 1-2; 111-132
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Metody chemicznej ligacji w syntezie peptydów i białek. Część 1
    Chemical ligation methods in the synthesis of peptides and proteins. Part 1
    Autorzy:
    Kropidłowska, M.
    Jędrzejewska, K.
    Wieczerzak, E.
    Powiązania:
    https://bibliotekanauki.pl/articles/171570.pdf
    Data publikacji:
    2017
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    natywna chemiczna ligacja
    NCL
    kinetycznie kontrolowana ligacja
    KCL
    synteza peptydów
    native chemical ligation
    kinetically controlled ligation
    peptide synthesis
    Opis:
    Proteins are biological macromolecules affecting very important functions in the body. They are involved in many biochemical processes. They can perform catalytic functions acting as enzymes. They also participate in the transport of many small molecules and ions – for example one molecule of hemoglobin carries four molecules of oxygen. In addition, proteins serve as antibodies and are involved in transmission of nerve impulses as receptor proteins. Because peptides and proteins perform so important functions, to study them it is essential to obtain these compounds in the greatest possible amounts. The compounds can be obtained generally by three main methods: • by isolation of the native peptides and proteins • by expression in microorganisms • by chemical synthesis. Each of the above methods has its advantages and disadvantages, but only the chemical synthesis gives the possibility to introduce modifications to the structure of the resulting protein, such as the insertion of new functional groups, to give the product in the final form and with satisfactory yield. In this review we present the application of chemical ligation methods in the synthesis of peptides and proteins. We describe in details mechanism of native chemical ligation method and the conditions necessary to carry the reaction [1]. The synthesis of long polypeptide chains by kinetically controlled ligation (KCL) is also depicted [2]. This part of the paper also details a number of approaches to noncysteine containing peptides by chemical ligation methods.
    Źródło:
    Wiadomości Chemiczne; 2017, 71, 9-10; 727-746
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Visualization of proteolytic enzymes using mass cytometry : compatible chemical probes
    Wizualizacja enzymów proteolitycznych za pomocą sond chemicznych oraz cytometrii masowej
    Autorzy:
    Groborz, Katarzyna
    Poręba, Marcin
    Powiązania:
    https://bibliotekanauki.pl/articles/2057909.pdf
    Data publikacji:
    2021
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    sonda chemiczna
    cytometria masowa
    enzymy proteolityczne
    nowotwory
    śmierć komórki
    chemical probe
    mass cytometry
    proteolytic enzymes
    cancer
    cell death
    Opis:
    Proteolytic enzymes, also known as peptidases or proteases, are protein catalysts that are primarily responsible for the hydrolysis of a peptide (amide) bond in peptide and protein substrates. By selective hydrolysis of selected substrates, these enzymes control many physiologically important processes including programmed cell death, blood coagulation cascade, protein maturation, fibrinolysis and many others. On the other hand, however, the imbalance in proteases activity leads to the development of diseases, including cancer, neurodegenerative diseases and coronary diseases etc.. In recent decades there has been great progress in studying the biological functions of many proteolytic enzymes. These observations were made possible through the use of various research techniques including genomics, epigenomics and proteomics. However, a major limitation of these techniques is the lack of information about the exact catalytic activity of the enzymes. For this reason, chemical probes are the most convenient toll for functional investigation of proteolytic enzymes. According to the generally accepted convention, chemical probes are compounds that can detect the catalytic activity of proteolytic enzymes. In general, chemical-based probes (activity-based probes, ABPs) consist of three main components: (1) a reactive binding group that binds permanently to the enzyme active site, (2) a recognition sequence (usually a peptide), which is responsible for the selective binding of a given probe to an individual enzyme or group of enzymes, and (3) a tag, mainly a fluorophore, enabling for detection of the probe-enzyme complex. However, the current limitation of ABPs is that only up to four enzymes can be detected and visualized in parallel, which significantly impedes their application for multi-parametric analysis. To date, the detection of proteases with the use of ABPs was limited to individual enzymes being investigated one by one, thus the obtained picture was far from being complete. In this review we describe the development of a new type of enzyme ABPs, so called TOF-probes that are compatible with mass cytometry format. The application of metal isotopes instead of fluorophores, makes possible to significantly increase the number of enzymes, which can be simultaneously visualized using chemical probes. Mass cytometry is a revolutionary technology that adopts atomic mass spectrometry into flow cytometry applications. The excellence of this method is that each metal isotope (mostly from lanthanides) has its own peak on mass spectrum, which eliminates the problem of signal overlap, thus allows for monitoring of more than 40 parameters at single cell level.
    Źródło:
    Wiadomości Chemiczne; 2021, 75, 11-12; 1171--1191
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Nowiczok(I) i substancje A
    Novichok agents and A substances
    Autorzy:
    Kloske, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/171616.pdf
    Data publikacji:
    2018
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    Nowiczok
    substancje grupy A
    broń chemiczna
    fosforoorganiczne bojowe środki trujące
    Novichok
    A-class chemical warfare agents
    chemical warfare
    organophosphorus chemical warfare agents
    Opis:
    When we hear the slogan ‘chemical weapons’, we are usually reminded of a photograph of marching geese, like the blind Ententa soldiers who were darkened after the Ypres chemical attack in Breugel’s painting. After the end of World War I, the unconventional arms race began and it was not certain that it had ended with the collapse of the Union of Soviet Socialist Republics (USSR) and the subsequent signing of the Chemical Weapons Convention (CWC) in 1993. Today, we know that Russia’s introduction of the CWC into its legal system has in no way disrupted the development of a new, fourth generation of chemical warfare agents (FGA or NTA - Non-Traditional Agents), culminating in the development of Group A substances, the popular media substances known as Novichok. The range of confirmed and openly available data is not large and the rest of the information is a compilation of various, sometimes contradictory, information. The article is an attempt to organize an open resource of knowledge and bring Novichok closer to a wider audience.
    Źródło:
    Wiadomości Chemiczne; 2018, 72, 9-10; 723-765
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    O siłach napędowych w przyrodzie : koncepcje, interpretacje, nieporozumienia
    About driving forces in nature : concepts, interpretations and misunderstandings
    Autorzy:
    Orlik, Marek
    Powiązania:
    https://bibliotekanauki.pl/articles/2200428.pdf
    Data publikacji:
    2023
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    termodynamika chemiczna
    entropia
    entalpia swobodna
    energia swobodna Helmholtza
    współrzędna reakcji
    reguła Le Chateliera-Brauna
    chemical thermodynamics
    entropy
    free Gibbs energy
    free Helmholtz energy
    reaction coordinate
    Le Chatelier-Braun principle
    Opis:
    Prepared for presentation within the Didactic Section of Polish Chemical Society, the study summarizes selected problems and concepts of teaching the basics of chemical reaction energetics as part of chemical undergraduate studies. The following problems are discussed: 1) indication of misunderstandings related to the definition of standard states in thermodynamics, with particular emphasis on the unfortunate assignment of the temperature of 298.15 K as "standard temperature", 2) problems with the interpretation of entropy as a "measure of disorder", with a recommendation regarding for understanding entropy as a measure of the number of ways to distribute the total energy of the system between the available degrees of freedom of motions, in terms of the quantum representation, i.e. the energy characteristics of a substance through sequences of energy levels, 3) a proposal to introduce the issue of thermodynamic driving forces of a chemical reaction based on the characteristics of the water evaporation process under different conditions, which favors the distinction of any reaction driving force from its standard driving force, as well as the distinction of such forces for isochoric and isobaric systems, both one- and multi-component, (4) the necessity to take into account the entropy of mixing of reagents to deepen the understanding of changes in the driving force of the reaction on the way to the state of chemical equilibrium, and 5) various interpretations of the influence of temperature on the equilibrium composition of the reacting system (Le Chatelier-Braun rule), with a recommendation for molecular interpretation, showing the role of differences in energies and sequences of energy levels of reactants and products for the value and direction of changes of the equilibrium constants of the reaction with temperature, taking into account also the principles of statistical thermodynamics. An additional aim of the article is to emphasize the importance of elementary mathematical education for mastering the basic laws governing the course of physicochemical processes, as well as for true understanding of chemistry, in general.
    Źródło:
    Wiadomości Chemiczne; 2023, 77, 1-2; 1--34
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zastosowanie soli chinoliniowych i pirydyniowych do oznaczania wybranych związków siarki w próbkach biologicznych
    Application of quinolinium and pyridinium salts for determination of selected sulfur compounds in biological samples
    Autorzy:
    Furmaniak, P.
    Wyszczelska-Rokiel, M.
    Kubalczyk, P.
    Głowacki, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/171524.pdf
    Data publikacji:
    2014
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    sole pirydyniowe
    sole chinoliniowe
    aminokwasy tiolowe
    derywatyzacja chemiczna
    chromatografia cieczowa
    wysokosprawna chromatografia cieczowa
    elektroforeza kapilarna
    pyridinium salts
    quinolinium salts
    thiol amino acids
    chemical derivatization
    high performance liquid chromatography
    capillary electrophoresis
    Opis:
    Quinolinium and pyridinium salts belong to the group of onium compounds and are widely used in organic, structural and analytical chemistry. Their synthesis is mainly based on quaternization of the nitrogen atom in a heterocyclic ring [4, 13, 23]. In analytical chemistry quinolinium and pyridinium salts such as 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT) or 1-benzyl-2-chloropyridinium bromide (BCPB) perform very well as thiol specific derivatization reagents in terms of derivatization reaction velocity, stability, chromatographic properties of the derivatives, and thus, amenability to automatization [18–22, 32–42]. Analytical procedures for thiol determination usually involve reduction of disulfide bonds with tris(2-carboxyethyl)phosphine, tri-n-butylphosphine or mercaptoethanol, chemical derivatization of the sulfur compound with the use of 2-halopyridinium or 2-haloquinolinium salts and then deproteinization, followed by ion-pair reversed-phase HPLC or CE separation and spectrophotometric detection. Derivatization reaction takes advantage of great susceptibility of quinolinium or pyridinium molecules at 2-position to nucleophilic displacement, and a high nucleophilicity of the thiol group. Derivatization reaction mixture is usually ready to be analyzed just after mixing of the substrates. CMQT and BCPB exhibit very high reactivity toward thiols [44, 45], sulfides [63] as well as thiosulfates [40, 54]. 2-S-quinolinium and 2-S-pyridinium derivatives possess advantageous spectrophotometric and chromatographic properties. They are stable and more hydrophobic than thiols themselves, possessing a well-defined absorption maximum in the UV region. The reaction is accompanied by an analytically advantageous bathochromic shift from reagent maximum to the maximum of the derivative. Thanks to this phenomenon it is possible to use a large excess of derivatization reagent in order to drive the reaction to completion and avoid a huge signal of unreacted compound on the chromatogram [26]. Elaborated with the use of onium salts methods have proven to be useful in quantitative HPLC and CE analysis of endogenous and exogenous low-molecular-weight biological thiols in human body fluids, plant extracts and some groceries [44, 45].
    Źródło:
    Wiadomości Chemiczne; 2014, 68, 3-4; 211-232
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Projekt Avogadro (IAC) i redefinicja jednostki liczności materii
    Avogadro project (IAC ) and redefinition of the mole
    Autorzy:
    Chyla, W. T.
    Powiązania:
    https://bibliotekanauki.pl/articles/171644.pdf
    Data publikacji:
    2012
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    metrologia chemiczna
    liczność materii
    redefinicja mola
    projekt Avogadro
    International Avogadro Coordination
    IAC
    Nowy SI
    Kwantowy SI
    AF-SI
    chemical metrology
    amount of substance
    redefinition of the mole
    Avogadro project
    New SI
    Quantum SI
    Opis:
    The paper presents the International Avogadro Coordination (IAC ) and the problem of redefinition of the unit of amount of substance (the mole) in the context of a comprehensive reform of the international system of units (SI ) that is expected to conclude in a few years. The redefinition program, known as the New SI or the Quantum SI , draws on Maxwell’s concept of replacing artifact standards with atomic standards, which are considered stable and available – at least in principle – to everybody, everywhere and at any time; the idea has been generalized and the present tendency is to define base units in terms of physical constants. Redefinition of the mole is a spin-off project associated with redefinition of the kilogram; two high-purity, 28Si-enriched silicon spheres were manufactured to make possible very accurate measurements of their parameters in order to determine (“count”) the number of silicon atoms in each of the two spheres. Initially, the project has been designed to determine the Avogadro constant, with the intent to redefine the kilogram as the mass of an exactly specified number of atoms. Once the consensus had been reached that the kilogram should be defined by fixing the numerical value of the Planck constant and the unit of mass should be realized with the use of the watt balance, the Avogadro project of silicon spheres was reinterpreted and became the basis for the redefinition and realization of the mole. In this paper, I discuss the origins of the Avogadro project (IAC ), the physical principle of a very accurate measurement of the Avogadro constant and technical details of the realization of that project. The problem of resolving the discrepancy between results of the IAC and the watt balance project is reviewed. The current status of the IAC is discussed and difficulties with the proposed wording of the New SI redefinition of the mole are indicated. It is expected that all the technical problems can be resolved before the next meeting of the CGPM, where voting on implementation of the New SI is expected.
    Źródło:
    Wiadomości Chemiczne; 2012, 66, 7-8; 767-787
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-15 z 15

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