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A unique technique for studying the process of nitric oxide release of NO donors under oxidative and reductive condition is proposed based on the fragmentation of N-nitrosoamines. The technique is likely to be applicable to the generation and study of nitrenium cations and amide anions [R.sub.2][N.sup.[+/-]] under matrix and ambient conditions.

Pulse radiolysis, steady-state methods and laser flash photolysis techniques have been used to characterize two different tautomeric types of radical cations produced from 1,8-acridinediones.

Pulse radiolysis can be used to analyze sequential electron-proton addition to various NAD+ model compounds. A stepwise electron-proton-electron transfer in NADH-NAD+ type transformations involves two tautometic types of the NADH radical cation.

The radical cations from three NADH model compounds were studied with a focus on the potential formation of tautomeric enol radical cations.

Research was conducted to examine the electronic absorption spectrum of the hexamethyl(Dewar benzene) radical cation. Samples were prepared by immersing room-temperature solutions in liquid nitrogen. Photochemical reactions were performed with a 450 W xenon arc lamp as a light source. Results based on the distribution of reaction rates clearly suggest that the activation barrier for the process is strongly influenced by environmental factors.

The temperature-dependent photochemistry of a second nitrene precursor of phenylnitrene, sulfoximine, was examined in the presence of amine. The temperature dependence of the distribution of stable products is not caused by an excited state of the nitrene precursor. Energy transfer has been used to establish the singlet and triplet energies of phenyl azide.

The article discusses a new approach, where in several zinc-catalyzed cycloisomerization reactions are conducted for the synthesis of different furans and furopyrimidine nucleosides. The methodology is shown to be extremely effective and advantageous, as it is inexpensive with small reaction time.

The primary products of redox reactions involving the radical ions of the antipsoriatic drug anthralin are presented. It is found that the addition an electron to anthralin significantly increases its ability to act as a hydrogen atom donor and that it acts better than CH2Cl2 in scavenging the electrons that are liberated in the process and forming the radical ion.

The inversion of the keto-enol stability order of dialuric acid on ionization is calculated and the radical cations in both forms are characterized. The results have shown that both neutral keto and enol forms are energetically close, while under favorable conditions, the auto-oxidation of dialuric acid involves participation of the enol form.

Two mechanisms of the interconversion of NADH and NAD(super +1) in the coenzyme itself and in its analogues are discussed. Direct characterization of the transient species in the stepwise process and inversion of the stability order of the keno and enol tautomers is presented.

The formation of NADH radical cation in reactions with one-electron oxidants was observed for the first time. Transient products involving two tautomeric (keto and enol) forms of radical cation and neutral radical were spectroscopically characterized by means of pulse radiolysis.

A study of phosphoric acid-solvent-methacrylate-based polymer gel electrolytes is reported that have ionic conductivities above 5 x 10(super -4) S.cm(super -1) at ambient temperature. The objective is to understand better the interaction of orthophosphoric acid with the solvent and the polymer gel to gain information on possible proton-conduction mechanisms.

The sequential electron-proton-electron transfer processes in the oxidation of 3,6-diamino-10-methylacridan, an uncharged precursor of acriflavine, are studied. The conformational relaxation of the radical cations in rigid matrices, induced by thermal softening of the matrix, led to flattening of the intermediate radical cations.

The effect of filler surface group on the conductivity, ion-ion, ion-polymer interactions and microstructure of PEG-LiClO(sub 4)-Al(sub 2)O(sub 3) composite polymer electrolytes is examined. The addition of the filler results in the changes in ionic association as studied by FT-IR and by applying the Fuoss-Kraus formalism to the slat concentration dependence of the molar conductivity of the composite electrolytes studied.

The radiolytic ionization of radical cations generated upon one-electron oxidation of the model synthetic NADH analogues was examined to determine whether hydrogen atom transfer affects the thermodynamic stabilization of these cations. Pulse radiolysis was performed to determine activation barriers in the hydrogen atom shift. The results of the study are presented and discussed.

The tunneling rate control of enolization in electron-transfer-iduced tautomerization inmethylindanones is examined.

Fluorescence correlation spectroscopy(FCS) is frequently usedto study the processes of restricted diffusion. The most importantquantity to determine is the size of the structures that hinder theBrownian motion of the molecules. We study three qualitatively differentmodels of restricted diffusion, widely applied in biophysics and materialscience: Diffusion constrained by elastic force (i), walking confineddiffusion (ii), and hop diffusion (iii). They cover the diversityof statistical behaviors, from purely Gaussian (i) to sharply non-Gaussianon intermediate time scales (ii) and, additionally, discrete (iii).We test whether one can use the Gaussian approximation of the FCSautocorrelation function to interpret the non-Gaussian data. We showthat (i–iii) have approximately the same mean square displacements.Using simulations, we show that the FCS data suspected of restricteddiffusion can be reliably interpreted using one archetypal model (i).Even if the underlying mechanism of the restriction is different orunknown, the accuracy of fitting the confinement size is excellent,and diffusion coefficients are also estimated with a good accuracy.This study gives a physical insight into the statistical behaviorof different types of restricted diffusion and into the ability offluorescence correlation spectroscopy to distinguish between them. [ABSTRACT FROM AUTHOR]

Myeloperoxidase (MPO) is an important component of the human innate immune system and the main source of a strong oxidizing and chlorinating species, hypochlorous acid (HOCl). Inadvertent, misplaced, or excessive generation of HOCl by MPO is associated with multiple human inflammatory diseases. Therefore, there is a considerable interest in the development of MPO inhibitors. Here, we report the synthesis and characterization of a boronobenzyl derivative of acetaminophen (AMBB), which can function as a proinhibitor of MPO and release acetaminophen, the inhibitor of chlorination cycle of MPO, in the presence of inflammatory oxidants, i.e., hydrogen peroxide, hypochlorous acid, or peroxynitrite. We demonstrate that the AMBB proinhibitor undergoes conversion to acetaminophen by all three oxidants, with the involvement of the primary phenolic product intermediate, with relatively long half-life at pH 7.4. The determined rate constants of the reaction of the AMBB proinhibitor with hydrogen peroxide, hypochlorous acid, or peroxynitrite are equal to 1.67, 1.6 × 10 4 , and 1.0 × 10 6 M -1 s -1 , respectively. AMBB showed lower MPO inhibitory activity (IC 50 > 0.3 mM) than acetaminophen (IC 50 = 0.14 mM) toward MPO-dependent HOCl generation. Finally, based on the determined reaction kinetics and the observed inhibitory effects of two plasma components, uric acid and albumin, on the extent of AMBB oxidation by ONOO - and HOCl, we conclude that ONOO - is the most likely potential activator of AMBB in human plasma.

The primary products, i.e., the radical cations and radicals obtained on oxidation of the glucobrassicin metabolites (and dietary supplements), indole-3-carbinol (I3C) and diindolylmethane (DIM), and those from parent indole (I) are characterized in an ionic liquid and in Ar matrices. The radical cations of I and I3C are stable toward (photo)deprotonation under these conditions, but the resulting radicals can be generated by UV-photolysis of the neutral precursors. Two types of radicals, obtained by loss of hydrogen from N- and C-atoms, respectively, are found for I3C and DIM.

The primary products of one-electron oxidation of clozapine and olanzapine, very effective atypical antipsychotic drugs, have been spectroscopically characterized. The oxidation process has been studied under glassy matrix conditions and by a pulse radiolysis technique in aqueous solution. The rate constants for the oxidation of clozapine with dibromide radical anion ( k = 2 x 10 (9) M (-1) s (-1)) and azide radical ( k = 2.3 x 10 (9) M (-1) s (-1)) in aqueous solution were measured. The computational DFT results support the identification of the transient species. The mechanistic aspects of reactivity of radical cations, radicals, and nitrenium cations have been investigated. A disproportionation reaction ( k > or = 1 x 10 (8) M (-1) s (-1)) was proposed as a link between the products of one-electron oxidation and formation of the nitrenium cations of clozapine and olanzapine, products likely responsible for the pathogenesis of adverse drug reactions. The rate constants for the reactions of nitrenium cation of clozapine with glutathione ( k = 3.4 x 10 (4) M (-1) s (-1)) and cysteine ( k = 9.8 x 10 (4) M (-1) s (-1)) were determined.

Paraquat and diquat undergo redox cycling mediated by xanthine oxidase in the NADH-dependent manner. In these processes, the rates of NADH oxidation and superoxide formation are increased almost 10-fold. The addition of heparin can substantially inhibit these processes. A protective role of heparin against oxygen radicals formation can be rationalized in terms of its ability to bind paraquat or diquat. The binding process has been investigated by means of the pulse radiolysis technique. Biological consequences of the binding processes are discussed.