Wiadomości Chemiczne, 1996, 50. Back   |  Home page

Formulation of an advanced statistical theory of biochemical processes needs simple but adequate models of phenomena underlying microscopic dynamics of biomolecules, in particular enzymatic proteins. A synthetic picture of protein dynamics emerging from the recent studies is outlined and two classes of theoretical models of slow activated dynamics of conformational transitions within the native state are described. In models of the Protein-Glass type, successive conformational transitions are treated as diffusion of structural defects in liquid-like regions surrounding solid-like fragments of protein secondary structure. Alternatively, in models of the Protein-Machine type, the dynamics of conformational transitions is approximated by a quasi-continuous diffusive motion of solid-like structural elements relative to each other. A particular Protein-Machine model is applied in constructing a microscopic theory of enzymatic reaction involving a single chemical transformation of substrate. The rule seems to be that it is the process of conformational diffusion, and not the details of chemical transformation, that affects the rate of enzymatic reactions. Under this assumption the reaction pathways in the initial and stationary stages can differ. A possibility is indicated of direct coupling of several reactions taking place at the same multienzyme complex.

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Wiadomości Chemiczne, 1996, 50, 3.
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The close-packed structure of a protein molecule stabilized by a cooperative network of interactions forms a unit in which local alterations induced by binding of ligands may be propagated to other parts. The disruption of tertiary interaction, which associates the larger alterations, introduces local melting of protein structure. Chromonic liquid crystalline meso-phase entities of rod-like or ribbon-like supra-molecular organisation recognise and anchor to molten areas in b-pleated sheets, stabilising the altered conformation. This again produces higher stability for the ligand-protein complex and hence may be followed by increased activity or inhibition, opening the prospect for practical use of this phenomenon.

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Wiadomości Chemiczne, 1996, 50, 29.
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Construction and thermalization of a hydrated phosphatidylcholine bilayer is described. In the liquid-crystalline phase of the bilayer, which corresponds to the physiological state of biomembranes, a large number of phospholipid molecules are linked by water molecules to form clusters. These water bridges decay and form continually but the lifetime of a fraction of them is in the nanosecond time scale. These suggest a possibility that water bridges can, together with other interactions, stabilize the membrane structure.

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Wiadomości Chemiczne, 1997, 50, 41.
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The design and development of new drugs for existing diseases is increasingly concerned with enzyme inhibitors. Very considerable progress has been made in this area over the last few years, especially with the advent of mechanism-based inactivators, heralded by the use of low-molecular inhibitors of proteolytic enzymes. Basing on the chemical mechanism of enzymatic catalysis these enzymes were divided into four groups: serine, cysteine, aspartic and metallo-proteinases. The knowledge of catalytic function at their active sites is a good basis for the design of potent inhibitors of these enzymes as shown in this paper using representative examples.

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Wiadomości Chemiczne, 1997, 50, 51.
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Thrombin plays an important role in thrombosis and hemostasis. On the other hand, thrombin may also be involved in pathological situations such as thromboembolic disorders. Thus, it is important to be able to control the action of this enzyme. A great number of synthetic direct thrombin inhibitors have recently been made. They block either the thrombin catalytic site and/or an anion-binding exo-site which is a recognition site for some of its substrates (fibrinogen, thrombin receptor, thrombomodulin) or act on the enzyme both sites (bivalent inhibitors). This review article describes the design based on the crystal structure and structure-activity relationships, of new potent, bivalent thrombin inhibitors.

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Wiadomości Chemiczne, 1997, 50, 77.
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Radiationless energy transfer is a widely used method in studies on structure and dynamics of conformational changes of biomolecules. Steady-state measurements of energy transfer are applied to estimate an average interchromophoric distance and also to study distance distribution using dynamic fluorescence quenching or performing measurements for series of compounds with different critical Förster distances but having the same conformation. In this review theoretical and practical aspects of fluorescence energy transfer are described.

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Wiadomości Chemiczne, 1996, 50, 99.
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Actin is probably the most abundant protein in nature, present in all eucariotic cells, always involved in determination of the shape and mobility of the cell. This review presents NMR data which concern the effect of the actin polymerization, a structure of its nucleotide complex and the effect of Ca²⁺/Mg²⁺ metal ion exchange at the high-affinity binding site.

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Wiadomości Chemiczne, 1996, 50, 125.
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This article is a short review considering the metal ions interaction, mostly Cu²⁺ ions, with sulfonamide moiety. Different coordination behaviour of ligands containing this donor system depends on metal ion and the conditions in which complexes are formed. Sulfonoamide substituent on the N-terminal amino group of amino acids and peptides is very effective binding site to Cu(II) ion due to more acidic nitrogen of sulfonamide group. The para-substituent of phenylsulfonyl moiety have very strong impact on sulfonamide nitrogen binding ability.

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Wiadomości Chemiczne, 1996, 50, 143.
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The subject of the paper is the scientific biography of Polish biologist - Stefan Kopeć, who as the first discovered endocrinology system of insects.

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Wiadomości Chemiczne, 1996, 50, 155.
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Wiadomości Chemiczne, 1996, 50, 161.
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Recognition of the importance of complexes containing macrocyclic ligands for bioinorganic chemistry, supramolecular catalysis, biomedical applications, for separation and encapsulation processes, formation of compounds with unusual properties and structures, has led to a considerable efforts in developing reliable syntheses for these compounds. The effective method for the synthesis of macrocyclic Schiff base complexes involves an in situ approach wherein the presence of a metal ion in the cyclization reaction markedly increases the yield of the cyclic product. The metal ion plays an important role in directing the steric course of the reaction and this effect has been termed the metal-template effect. This article reviews the progress made in synthesis of metal ion complexes of Schiff base macrocycles through application of the above technique. The factors which prove to be of importance in directing the synthetic pathway in the Schiff base systems and must be taken into account in the design and synthesis of the desired products, are discussed.

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Wiadomości Chemiczne, 1996, 50, 171.
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Among numerous enzymes useful for organic synthesis, lipases are the most widely used. These enzymes have several properties which make them interesting as catalysts in organic synthesis, for instance, wide substrate acceptability, ease of handling, non-requirement for co-factors and, moreover, they are catalytically active in organic solvents. This paper reviews useful reactions catalyzed by lipases. Special attention is focused on the synthesis of biologically active compounds.

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Wiadomości Chemiczne, 1996, 50, 193.
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Two approaches to synthesis of pyran derivatives by heterodiene cycloaddition are reviewed. The first is the cycloaddition with the inverse electron demand of 1-oxa-1,3-butadiene with enol ethers or enamines. The second is the cycloaddition of 1,3-butadienes to carbonyl compounds. Some examples of the application of this methodology in synthesis of natural products are presented.

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Wiadomości Chemiczne, 1996, 50, 213.
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In spite of the general opinion about the azide group, polymers containing them are sufficiently safe and stable materials. This fact has been explained on the basis of the special and general properties of the azide groups.

In this paper we present the following subjects connected with these polymers: methods of monomers and oligomers preparation, oligomers crosslinking and curing. Particular attention is paid to thermochemical properties of the azide polymers and high energetic materials composed of them.

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Wiadomości Chemiczne, 1996, 50, 241.
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The variety of synthesis methods of organic peroxides R¹OOR² (R¹ = H, alkyl, aralkyl; R² = alkyl, aralkyl) have been reviewed.

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Wiadomości Chemiczne, 1996, 50, 261.
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Methods to obtain propylene oxide, both the commercial ones and those under investigation, are reviewed.

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Wiadomości Chemiczne, 1996, 50, 295.
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The public has many misconceptions about the relationship between environmental pollution and human cancer. Underlying these misconceptions is an erroneous believe that nature is benign. Below we highlight eight of these misconceptions and describe the scientific information that undermines each one.

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Wiadomości Chemiczne, 1996, 50, 317.
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Wiadomości Chemiczne, 1996, 50, 345.
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In this paper we report the proton-acceptor properties for very strong neutral nitrogen bases as: guanidines, amidines, proton sponges, poliamines, cryptands and Schwesinger bases (phosphazenes).

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Wiadomości Chemiczne, 1996, 50, 367
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In this review are presented the physico-chemical and electrochemical properties of tetraazamacrocyclic complexes of transition metals, especially of Ni, and applications of this class of complexes in catalysis, analysis and medicine.

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Wiadomości Chemiczne, 1996, 50, 399.
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Fuel cell is a system which converts chemical energy of a fuel and an oxidant directly into the electrical energy. Methanol fuel cell seems to be promising for large-scale commercialization, in contrast to hydrogen-fed cells, especially in transportation. The limitation for methanol system is nowadays due to low catalytic activity of the electrodes, especially anodes. The best catalytic material seems to be platinum in composition with some other metals, as tin and ruthenium, which act as promotors of electrochemical processes. Promotors weaken the negative influence of catalyst poisons generated during the oxidation of methanol. Application of solid polymer electrolytes in methanol fuel cell allows to elevate the working temperature of the cell, which results in higher current densities. Methanol fuel cell presents several advantages: lack of toxic emission (CO, hydrocarbons, lead, sulphur), relatively low operating temperature.

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Wiadomości Chemiczne, 1996, 50, 437.
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Interstitial alloys are formed by the incorporation of nitrogen or carbon into the lattices of early transition metals to produce a class of compounds with metallic character. They demonstrate excellent catalytic activity, similar to those of noble metals in wide variety of reactions: hydrogenolysis, hydroprocessing, isomerization, ammonia synthesis. Methods of synthesis as well as the structure of interstitial alloys are reviewed. Results of investigation of their catalytic properties as the hydrotreatment catalysts are reviewed and discussed.

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Wiadomości Chemiczne, 1996, 50, 455.
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A critical review of worldwide investigations of environmental and occupational health effects due to exposures to 2,3,7,8-tetrachlorodibenzodioxin (TCDD) is presented. Initial Swedish results on extreme carcinogenicity of dioxine are compared with two series of German and American studies which do not confirm the early Swedish observations.

Cancer, birth defects, and other toxic effects are seen in animals only at doses close to those that cause overt toxic effects in adult animals. It is argued that humans have never been exposed to comparable exposure levels. Consequently, there is no convincing evidence for human cancer risk increase related to dioxin exposures.

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Wiadomości Chemiczne, 1996, 50, 469.
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Present state of understanding the structure and the electrochemical behaviour of metallic glasses in various environments is summarized. Emphasis is placed on the experimental evidence concerning the ability to passivate, stability of the passive state of these alloys including the susceptibility to pitting, as well as on details of the characteristic features and peculiarities of these systems. The stationary behaviour, based on recent models for homogenous alloys, is discussed. The role of amorphous alloys in electrocatalysis and perspective of their application in this area are pointed out.

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Wiadomości Chemiczne, 1996, 50, 497.
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Wiadomości Chemiczne, 1996, 50, 517.
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Wiadomości Chemiczne, 1996, 50, 521.
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The biography of Bronisław Lachowicz (1856-1903) is outlined and his role in the development of Chemistry Department of the Lvov University during the last two decades of XIX century enhanced. Lachowicz was the first Polish university teacher reading lectures on physical chemistry. The bibliography of Lachowicz`s scientific papers is given and those concerning miscellaneous physicochemical problems are critically reviewed.

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Wiadomości Chemiczne, 1996, 50, 535.
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An overview is presented of computer modelling and simulation methods that play an increasing role in drug design: quantum chemical methods, molecular mechanics, molecular dynamics and Brownian dynamics. The application of molecular dynamics for the prediction of thermodynamic properties like free energy differences and binding constants is discussed. The Brownian dynamics method is presented in connection with the calculation of effective electrostatic forces using the Poisson-Boltzmann equation, which allows one to sample ligand-binding geometries and to predict the kinetics of diffusion-limited enzyme reactions. New techniques that have recently been extensively developed, such as the global energy minimization and quantum-classical dynamics methods, are also introduced. The molecular modelling methods are illustrated with selected examples.

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Wiadomości Chemiczne, 1996, 50, 563.
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The short review supplements the previous article which is a translated version of the paper: B. Lesyng and J.A. McCammon, Molecular modeling methods. Basic techniques and challenging problems. Pharmac. Ther., 1994, 60, 149-167. The role of molecular modeling in the framework of computer simulation techniques in natural sciences is shortly discussed here. Supplementary literature on a broad class of algorithms and on new computer technologies is given.

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Wiadomości Chemiczne, 1996, 50, 587.
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Application of the title method is presented for searching the conformational space in small flexible molecules for assignment of relative configuration of stereogenic centers and for recognition of intermolecular interactions in solution.

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Wiadomości Chemiczne, 1996, 50, 591.
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Time-resolved fluorescence quenching is an important method for studying diffusion-controlled reactions and in addition Single Photon Counting (SPC) techniques give data curves with high precision. A particularly important case is a diffusion-limited reaction with a time-dependent reaction rate coefficient, which in the initial stages is described by nonstationary solutions of the diffusion equations. In this paper an explicit form of an equation for the reaction rate coefficient, k(t), is given along with functions - obtained by using these equations - describing the decay of donor fluorescence in the presence of a quencher, I(t). It is also demonstrated how the dynamics of bimolecular processes may be studied by using dynamic measurements I(t) and/or Stern-Volmer kinetic curves.

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Wiadomości Chemiczne, 1996, 50, 607.
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Possibilities of application of the Hammett equation to the study of proton transfer equilibria for polyfunctional and tautomeric systems are presented and illustrated.

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Wiadomości Chemiczne, 1996, 50, 625.
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Wiadomości Chemiczne, 1996, 50, 653.
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This article traces the life and work of seven women, i.e. H. Brooks, E. Gleditsch, M.Sybil Leslie, E. Ramstedt, J. Szmidt, I. Joliot-Curie and A. Dorabialska working in Maria Skłodowska-Curie Laboratory and shows the role of her as supervisor.

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Wiadomości Chemiczne, 1996, 50, 671.
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The Rietveld method - a tool for crystal structure refinement from powder X-ray data - is presented. An example illustrating the procedure of Rietveld refinement of magnesium hexaaqua bromate structure is also included.

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Wiadomości Chemiczne, 1996, 50, 687.
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Some theoretical and technological aspects of the chemical uranium enrichment are discussed. The CHEMEX liquid-liquid extraction, Asahi (ACEP) ion-exchange, and MLIS and AVLIS laser methods are presented. A careful analysis of the influence of the odd neutron number of isotope on its chemical behaviour (the even-odd effect) has brought us to the conclusion that there must exist an opposite effect for nuclids with extra stable nuclei. This hypothesis is to be verified for ¹⁴²₆₀Nd, ²⁰⁸₈₂Pb, and ₅₀Sn vs other isotopes of these "magic" nuclids.

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Wiadomości Chemiczne, 1996, 50, 701.
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In this publication the physicochemical parameters of anions having an influence on the selective anion complexation by receptor molecules were described in detail. The value of hydration energy, by charge distribution in molecule, Lewis acid-base character (as well as Pearson`s hardness) and the anion size were chosen as the most important properties of anions. The types of selective anion recognition by receptor molecules and possible chemical interactions between "host" and "guest" were discussed. The main part of this work contains a literature review concerning anion selective receptors, divided on four groups based on different interaction with ion (electrostatic, hydrogen bonding, coordination and covalent).

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Wiadomości Chemiczne, 1996, 50, 721.
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The paper describes results and research done on the influence of the war gases, dumped in the Southern Baltic Sea between 1945 and 1948, on people who live and work in this area.

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Wiadomości Chemiczne, 1996, 50, 745.
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Advanced methods of characterization of structural and energetic properties of microporous carbonaceous adsorbents are reviewed. The porous structure of carbonaceous adsorbents, its creation, classification, and influence on the sorption properties is discussed. A main focus was placed on molecular adsorption and its use for studying solid adsorbents. It was shown that the structural heterogeneity of carbonaceous adsorbents can be characterized in terms of the pore volume distribution, which can be obtained by Jaroniec-Choma, Horvath-Kawazoe or density functional theory methods. However, the energetic heterogeneity of these adsorbents can be characterized in terms of the adsorption energy distribution obtained by the condensation approximation method or regularization methods. These methods were illustrated by using our experimental results and theoretical calculations for carbonaceous adsorbents.

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Wiadomości Chemiczne, 1996, 50, 759.
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The possibilities of direct conversion of methane to ethylene in the catalytic process of oxidative coupling have been presented. The literature data and the autor`s own results have been taken into consideration. The paper was presented at the conference "Natural Gas for Chemical Technology", Puławy, June 1-2, 1995.

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Wiadomości Chemiczne, 1996, 50, 789.
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Wiadomości Chemiczne, 1996, 50, 807.
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The architecture of the self-organizing maps and their implementations in chemistry have been reviewed. In particular the comparisons of the protein sequences, the mapping of chemical molecules and the analysis of the pollution emission sources have been illustrated. All the procedures discussed were designed successfully to form interesting and efficient methods of chemometric analysis.

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Wiadomości Chemiczne, 1996, 50, 817.
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A matrix method of generating, balancing and determining the number of independent reactions has been described and discussed.

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Wiadomości Chemiczne, 1996, 50, 827.
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The application in detection systems of a new generation of photomultipliers - micro-channel plates - at the end of the last decade enabled considerable progress in experimental studies of fast bimolecular reactions. This paper presents results of studies of fluorescence quenching partly controlled by diffusion in solutions, with particular emphasis on the transient effect. This paper also reports on previous experimental studies in which the Smoluchowski-Collins-Kimbal kinetics model with a time dependent reaction rate coefficient was applied.

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Wiadomości Chemiczne, 1996, 50, 841.
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Adaptive biological effects of ionizing radiation occur at near natural doses. This disagrees with non-threshold relationship, which is a basis of the current radiation protection. Vast literature demonstrates that such effects, occuring at molecular, cellular and population levels, result in increased longevity and decreased cancer incidence. Exposure to lower than natural radiation causes deficiency symptoms.

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Wiadomości Chemiczne, 1996, 50, 857.
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The use of zirconium compounds in catalytic systems has been growing considerably. The major interest is connected with zirconium dioxide - which in the form both of a single oxide and combined oxides - has been proved to be a very promising catalyst for various reactions. In this paper the properties and examples of application of ZrO₂ as catalyst and catalyst support have been reviewed.

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Wiadomości Chemiczne, 1996, 50, 879.
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The paper is a review dealing with the problem of bromine-containing by-products formed by application of strong oxidants in water treatment technology. By-products resulting from reaction of organic and inorganic "precursors" in treated water containing bromides with strong oxidants: chlorine, ozone, chloramine and chlorine dioxide are described. The possible sources of bromide in natural waters, formation of bromine-containing by-products, health risk arising from their presence in drinking water, the technology of removal of these compounds from drinking water as well as analytical methods for their determination have been discussed.

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Wiadomości Chemiczne, 1996, 50, 903.
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Solid state NMR spectroscopy was used to study the structure and dynamics of phosphoroorganic dichalcogenes with general formula RR`P(S)XX(S)PRR` where X = S, Se. X-ray diffraction has revealed that the conformation of (S)PXXP(S) backbone depends on R, R` substituents and can adopt anti-anti, anti-syn, and syn-syn geometry. The interaction between p-electrons of X atoms and empty d_xz and d_yz orbials of phosphorus has influence on geometry of S = P-X unit. For anti-anti conformation the P-X distances are shorter and S = P-X angles smaller compared to syn-syn conformation. The changes of local environment of phosphorus were recognized by ³¹P CP/MAS experiment. The investigation of series of bis(organothiophosphoryl) disulfides has allowed to establish the relationship between ³¹P chemical shift parameters; anisotropy D, asymmetry h , principal elements of chemical shift tensor d and molecular structure of S=P-S-S-P=S fragment.

The question of correlation between the number of resonances in the isotropic part of spectrum and molecular symmetry established by single-crystal X-ray diffraction was discussed. Moreover, the ³¹P CP/MAS nad ⁷⁷Se CP/MAS experiments for phosphoroorganic dichalcogenides were used to study different polymorphic forms, inclusion complexes, solvates as well as phase transitions below melting point. The deuterated solvents occluded in the crystal lattice of inclusion complexes were investigated by means of ¹H-²H CP/MAS NMR technique.

The line-sharpe analysis of the "Pake doublet" for static ²H experiment and ¹³C CP/MAS technique were employed to investigation of the intermolecular dynamics of aliphatic and/or aromatic groups directly bonded to phosphorus.

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Wiadomości Chemiczne, 1996, 50, 925.
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Wiadomości Chemiczne, 1996, 50, 951.
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