Andrzej Plonka

Kinetics in dynamically disordered systems: Time scale dependence of reaction patterns in condensed media

The dependence of the patterns of reactions in condensed media on the time scale is rationalized in terms of the renewal theory with a fractal set of renewal moments which results from the use of Kohlrausch (1863) function to describe the structural relaxations in the systems. When the rates of relaxations exceed markedly those of reactions the classical patterns of reaction kinetics are shown to be valid for disordered systems. The dispersive nature of kinetics becomes evident when the rates of reactions approach those of structural relaxations and in the limit, corresponding to suppressed internal rearrangements, the reaction patterns are shown to be those following from reaction modeling in statically disordered systems.

Photodissociation of carbon monoxy myoglobin: Kinetics of carbon monoxide rebinding

Abstract Carbon monoxide rebinding following laser photodissociation of carbon monoxy myoglobin in frozen solutions can be adequately described using the second-order equal concentration kinetic equation with a time-dependent rate constant deducible from the Kohlrausch relaxation function.

Photodissociation of carbonmonoxy myoglobin: Kinetics of protein relaxation to the equilibrium state of deoxymyoglobin

Abstract The Kohlrausch relaxation function, exp [−( t /τ 0 ) α ], used over the years to describe non-exponential phenomena in glasses, is also capable of describing protein relaxation following laser photodissociation of carbonmonoxy myoglobin in frozen solutions.

Unexpected radical generation on γ-irradiating metastable forms of water at 77 K. Invited Lecture

The effects of γ-irradiating three metastable forms of water at 77 K have been studied by electron spin resonance spectroscopy and are compared with those of hexagonal ice. Two amorphous forms of water were made by so-called hyperquenching of liquid water droplets (hyperquenched glassy water, HGW) and by deposition of water vapours (amorphous solid water, ASW) at 77 K. Metastable cubic ice was made either by heating HGW, or by hyperquenching liquid water droplets at 170 K. Whereas γ-irradiation of hexagonal ice at 77 K produces only OH radicals as primary radiation product, on γ-irradiation of HGW and ASW comparable yields of OH and HO2 radicals were observed, and their ratio did not depend on radiation dose. Mainly OH radicals were formed on γ-irradiating cubic ice made directly from liquid water. In contrast, comparable amounts of OH and HO2 radicals were formed on irradiation of cubic ice made by heating HGW, and their relative yields depend strongly on the irradiation dose. HO2 radicals are formed as primary products of radiation, as are OH radicals, and their formation is attributed to the abundant presence of defects, with two oxygens facing each other without hydrogen in between, in HGW, in ASW and in disordered regions of cubic ice. When small amounts of thymine were added to HGW, thymine radicals were formed by addition of atomic hydrogen on γ-irradiation already at 77 K at the expense of the relative contribution of HO2 radicals. This is not due to scavenging of once-formed HO2 radicals by thymine, but it occurs concurrently with HO2 radical formation. Therefore, it is rationalized by a concerted process involving the primary intermediate H2O+. The radiation effect on thymine must be indirect because of the large water-to-thymine ratio of ≈104 in homogeneous glassy solution. Possible implications of these studies are discussed for our understanding of (i) defects in metastable forms of water and their detection via HO2 radical formation, (ii) radiation damage to biomolecules in aqueous solution, and (iii) radical generation on high-energy irradiation of ASW in outer space and the secondary formation of stable molecules on decay of the radicals.

Dispersive recombination in condensed phases

Two interpretations of the parameter α are presented for a second-order equal-concentration kinetic equation with time-dependent reaction rate coefficient k(t) ∝tα−1, 0<α⩽1. The first, valid for any system, is in terms of the activation energy distribu for recombination and follows from the time dependence of the activation energy implied by the form of k(t). The second, valid for systems in which the time dependence of k(t) results from a distribution of reaction rates, is analogous to the interpretation of stretched exponentials as a superposition of exponential decays.

Radioluminescence kinetics of frozen solutions of LiCl

Abstract Isothermal luminescence (ITL) of γ-irradiated frozen solutions of LiCl follows the first-order rate equation with a time-dependent rate constant of the form k(t) = Btα-1, where B and 0

Single-crystal electron spin resonance studies on radiation-produced species in ice Ih. Part 2.—The HO2 radicals

The X-band e.s.r. spectra were recorded at 4 K for single crystals of hexagonal D2O ice gamma-irradiated at 77 K. From the measurements at 4 K the g tensors as well as the direction cosines were determined for O– radicals formed from OD radicals upon cooling. There are two sets of O– radicals derivable directly from three sets of OD radicals trapped in ice Ih. The sp2 hybridization of valence orbitals for O– radicals is consistent with anisotropic g tensors.

Purification and partial characterization of goose ceruloplasmin

The preparation and properties of ceruloplasmin from goose blood plasma are described. Ammonium sulfate was used to precipitate the crude protein followed by adsorption and elution from DEAE-Sephadex A-50. Further treatment with an ethanol-chloroform mixture and Sephadex G-200 yielded an intensely blue protein possessing a high degree of chemical purity and biological activity. Goose ceruloplasmin, existing in two forms, appears to be a single polypeptide, apparent Mr121,300, with an A610/A280 ratio of 0.07. Copper represented 0.32%, which corresponded to six atoms of copper per protein molecule. Although the amount of EPR-detectable copper was the same as in mammalian ceruloplasmins there were some differences in EPR parameters, mainly in A parallel. Goose ceruloplasmins amino acid composition, although similar in many residues to human ceruloplasmin, was lower in tyrosine, cystine/cysteine, and acidic amino acids. Valine was found as the N-terminal amino acid. Hexose, hexosamine, sialic acid, and fucose accounted for 6.65% of the weight. Goose protein contained only half the sialic acid of human ceruloplasmin. Two values for Km using either p-phenylenediamine (0.64 and 0.053 mM) or o-dianisidine (0.76 and 0.15 mM) were evaluated from Lineweaver-Burk plots. EPR studies on reactions with water radiolysis products at cryogenic temperatures allowed us to discover that goose ceruloplasmin, like human and bovine ceruloplasmins, possesses superoxide dismutase activity.

ESR investigations of radiation grafting of methyl methacrylate in aqueous emulsion onto chrome-tanned pig skin

Abstract Upon λ-irradiation at 77 K of the aqueous emulsions of methyl methacrylate embedded into chrome-tanned pig skins there are formed only the radicals of collagen and of 2-el-2mehtylo-propionic acid methyl ester. The presence of water in the system increases markedly the radiation yield of collagen radicals. During gradual heating up the polymerization reactions start and the macro-radical of growing polymer is observed. Chromium does not participate in the processes of initiation and grafting.

Phenomenological interpretation of kinetics with time-dependent specific reaction rates

Abstract Specific reaction rates depend on time for reactions proceeding on time scales comparable to or shorter than those of internal rearrangements in the reaction system renewing the environment of reactants. For a time-dependent specific reaction rate, k ( t ), using the concept of energy profile along the reaction path, one finds the potential energy barrier separating reactants from products to evolve in time during the reaction course. This evolution is described in terms of a distribution function related directly to the distribution function of logarithms of lifetimes calculable from the kinetic equations with k ( t ). This advanced approach is compared with that in which the kinetic equations with k ( t ) are interpreted in terms of superposition of classical reaction patterns.