Jasmina Savić

Toxic effects of diazinon and its photodegradation products

The toxic effects of diazinon and its irradiated solutions were investigated using cultivated human blood cells (lymphocytes and erythrocytes) and skin fibroblasts. Ultra Performance Liquid Chromatography (UPLC)-UV/VIS system was used to monitor the disappearance of starting diazinon during 115-min photodegradation and formation of its by-products (diazoxon and 2-isopropyl-6-methyl-4-pyrimidinol (IMP)) as a function of time. Dose-dependent AChE and Na(+)/K(+)-ATPase inhibition by diazinon was obtained for all investigated cells. Calculated IC(50) (72 h) values, in M, were: 7.5x10(-6)/3.4x10(-5), 8.7x10(-5)/6.6x10(-5), and 3.0x10(-5)/4.6x10(-5) for fibroblast, erythrocyte and lymphocyte AChE/Na(+)/K(+)-ATPase, respectively. Results obtained for reference commercially purified target enzymes indicate similar sensitivity of AChE towards diazinon (IC(50) (20 min)-7.8x10(-5)M), while diazinon concentrations below 10mM did not noticeably affect Na(+)/K(+)-ATPase activity. Besides, diazinon and IMP induced increasing incidence of micronuclei (via clastogenic mode of action) in a dose-dependent manner up to 2x10(-6)M and significant inhibition of cell proliferation and increased level of malondialdehyde at all investigated concentrations. Although after 15-min diazinon irradiation formed products do not affect purified commercial enzymes activities, inhibitory effect of irradiated solutions on cell enzymes increased as a function of time exposure to UV light and resulted in significant reduction of AChE (up to 28-45%) and Na(+)/K(+)-ATPase (up to 35-40%) at the end of irradiation period. Moreover, photodegradation treatment strengthened prooxidative properties of diazinon as well as its potency to induce cytogenetic damage.

Influence of sodium dodecyl sulfate on the kinetics of complex formation between [PdCl(dien)]+ and sulfur containing ligands l-cysteine and glutathione

Abstract The effect of sodium dodecyl sulfate (SDS) micelles on the kinetics of the complex formation between [PdCl(dien)]+ and sulfur containing ligands l -cysteine and glutathione (GSH) was investigated by using the stopped-flow technique under pseudo-first order conditions (ligand in excess) in the acidity range from pH 1 to 6. The presence of anionic micelles induced the acceleration of the complex formation in the entire acidity range with the maxima corresponding to the first protolytic constant of the ligands. This effect was interpreted in terms of the attractive electrostatic interaction between reacting species and the micellar surface and their effective concentration in the vicinity of micelles. An increase of the ionic strength leads to a decrease of the rate of complex formation in the presence of anionic micelles due to competition of reactive species with cations originating from inert salt for the micellar surface. The calculation of activation parameters revealed that the entropy of activation is strongly negative in the presence and in the absence of micelles, which is compatible with an associative reaction mechanism.

Application of flavonoids -quercetin and rutin -as new matrices for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of Pt(II) and Pd(II) complexes

Attempts are being made to overcome the resistance of tumour cells to platinum (Pt) drugs by the synthesis of new generations of Pt complexes, and it is important to find appropriate and simple methods for the characterization of those novel complexes. The additional applicability of such a method for the analysis of the interactions of metal complexes with biomolecules would be advantageous. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) seems to possess the capability to become this method of choice, since it could be applied to low-mass complexes as well as for the analysis of large biomolecules. In this work the applicability of flavonoids - quercetin and rutin - as matrices for MALDI-TOFMS analysis of dichlorido(ethylendiamine)platinum(II) ([PtCl(2)(en)]), dichlorido(diaminocyclohexane)platinum(II) ([PtCl(2)(dach)]) and chloride (diethylenetriamine) palladium(II) chloride ([PdCl(dien)]Cl) complexes is demonstrated. Spectra of Pt(II) and Pd(II) complexes recorded in the presence of quercetin and rutin are rather simple: Pt(II) complexes generate [M+Na](+) or [M+K](+)ions, whereas the investigated Pd(II) complex gives ions generated by the loss of one Cl(-) or HCl. Flavonoids give a relatively small number of well-defined ions in the low-mass region (at m/z 303.3 for quercetin and m/z 633.5 for rutin). Quercetin and rutin can be applied in much lower concentrations than other common MALDI matrices and require rather low laser intensity. We speculate that flavonoids stabilize the structures of the metal complexes and that they may be useful for the analysis of other biologically active metal complexes, thus implying their broader applicability.

Kinetics of 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene-3,6-disulphonic acid immobilization on anion exchangers

The sorption of 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene-3,6-disulfonic acid onto the anion exchange resins Dowex 1-X8 and Dowex 2-X8 from aqueous solutions of between pH 1 and 10 was studied spectrophotometrically. Conditions for obtaining modified sorbents with a given capacity for the azo compound were investigated. The absorption and reflectance spectra of the sorbed dye were traced. The immobilized reagent retained chromic characteristics similar to those it had in solution. The mechanism of sorption was investigated under static conditions in the temperature range of 0 to 25°C by following the amount of sorbed dye as a function of contact time. The sorption was a first-order process in all cases. Pore diffusion was found to be the rate-limiting step in the sorption process. Diffusion coefficient values of from 6.0 × 10–7 to 7.4 × 10–7 cm2/s were calculated from the experimental results. The values of the activation energy of PACA sorption were found to be –8.56 and –8.05 kJ/mol for Dowex 1-X8 and Dowex 2-X8, respectively.

Interaction of the [PtCl2(DMSO)2] complex with L-cysteine.

The reaction between [PtCl2(DMSO)2] and L-cysteine (L-Cys) has been investigated in the presence of micelles of sodium dodecyl sulfate (SDS) - as a model for biological membranes. Additionally, the inhibitory effect of [PtCl2(DMSO)2] on the Na+,K+-ATPase activity and its partial prevention with 10 mM L-Cys were demonstrated. The interaction of L-Cys with [PtCl2(DMSO)2] resulted in the formation of a [Pt(DMSO)2(L-Cys)2]2+ (DMSO)2] complex, which most probably occurs through stepwise replacement of Cl- with L-Cys. It has also been demonstrated that neither the pH value nor SDS affects the composition of the new complex. On the other hand, the pH value and SDS do affect the reaction rate, most probably due to electrostatic interactions with reactants. In summary, this study can be used as a simple model approach for the investigation of reaction mechanisms between platinum complexes and various biomolecules, and for the determination of potential toxicity and/or side effects of antitumour platinum drugs.

Oxidation of Quercetin by Myeloperoxidase

Study of effect of myeloperoxidase on quercetin at pH 6.0 indicated quercetin oxidation via the formation of the oxidation product. The stability of quercetin and oxidation product was investigated as a function of time by using spectrophotometric and HPLC techniques. The apparent pseudo first-order rate constants were calculated and discussed.

Brain Injury Alters Ectonucleotidase Activities and Adenine Nucleotide Levels in Rat Serum / Povreda Mozga Menja Ektonukleotidazne Aktivnosti I Nivo Adeninskih Nukleotida U Serumu Pacova

Summary Background: Cortical stab injury (CSI) induces changes in the activity, expression and cellular distribution of specific ectonucleotidases at the injury site. Also, several experimentally induced neuropathologies are associated with changes in soluble ectonucleotidase activities in the plasma and serum, whilst various insults to the brain alter purine compounds levels in cerebrospinal fluid, but also in serum, indicating that insults to the brain may induce alterations in nucleotides release and rate of their hydrolysis in the vascular system. Since adenine nucleotides and adenosine regulate diverse cellular functions in the vascular system, including vascular tone, platelet aggregation and inflammatory responses of lymphocytes and macrophages, alterations of ectonucleotidase activities in the vascular system may be relevant for the clinical outcome of the primary insult. Methods: We explored ectonucleotidase activities using specific enzyme assays and determined adenine nucleotides concentrations by the UPLC method in the rat serum after cortical stab injury. while phosphodiesterase activity remained unchanged. Also, at 4-h postinjury a marked decrease in ATP concentration and more than 2-fold increase in AMP concentration were recorded. Conclusions: CSI induces rapid up-regulation of nucleotide catabolizing soluble ectonucleotidases in rat serum, which leads to the observed shift in serum nucleotide levels. The results obtained imply that ectonucleotidases and adenine nucleotides participate in the communication between the brain and the vascular system in physiological and pathological conditions and thereby may be involved in the development of various human neuropathologies. Kratak sadržaj Uvod: Ubodna povreda mozga dovodi do promena u aktivnosti, ekspresiji i ćelijskoj distribuciji određenih ektonuk- leotidaza na mestu povrede. Pored toga, neke eksperimen- talno izazvane neuropatologije povezane su sa promenama solubilnih ektonukleotidaznih aktivnosti u plazmi i serumu, dok različite povrede mozga menjaju nivoe purina u cere- brospinalnoj tečnosti, ali i u serumu, ukazujući da povreda mozga može da dovede do promena u oslobađanju nukleo- tida i u stepenu njihove hidrolize u vaskularnom sistemu. Kako adeninski nukleotidi i adenozin regulišu raznovrsne ćelijske funkcije u vaskularnom sistemu, uključujući vasku- larni tonus, agregaciju trombocita i zapaljenski odgovor lim- focita i makrofaga, promene ektonukleotidaznih aktivnosti u vaskularnom sistemu mogu biti značajne za klinički ishod pri- marne povrede. Metode: Primenom specifičnih enzimskih eseja pratili smo ektonukleotidazne aktivnosti, a upotrebom UPLC metode odredili smo koncentracije adeninskih nukleotida u serumu pacova nakon ubodne povrede korteksa. Rezultati: Četiri sata nakon povrede, ATP- i AMP-hidrolizu- juće aktivnosti bile su povišene za približno 60%, odnosno 40%, dok je fosfodiesterazna aktivnost ostala nepromenjena. Pored toga, 4 h nakon povrede zabeleženo je značajno povećanje koncentracije ATP i više nego dvostruko povećanje nivoa АМР Zaključak: Ubodna povreda mozga dovodi do naglog poras- ta hidrolizujućih aktivnosti solubilnih ektonukleotidaza u seru- mu pacova,| što vodi uočenoj promeni nivoa nukleotida. Dobijeni rezultati pokazuju da ektonukleotidaze i adeninski nukleotidi posreduju u komunikaciji između mozga i vasku- larnog sistema, kako u fiziološkim tako i u patološkim uslovi- ma, te stoga mogu biti uključeni u razvoj različitih neuropa- tologija kod čoveka.

Kinetic investigation of the immobilization of chromotropic acid derivatives onto anion exchange resin

The adsorption kinetics of pyrazol- (РАСА) and imidazol-azo-chromo-tropic acid (IACA) onto Dowex 1-X8 resin, as a function of the dye concentration and temperature were investigated at pH 4.5. The pseudo-first- and second-order kinetic models and intraparticle diffusion model were used to describe the obtained kinetic data. The adsorption rate constants were found to be in the order of magnitude 10-2 min-1 for all of the used kinetics models. The adsorption capacity increases with increasing initial dye concentration. The study of adsorption kinetics at different temperatures (in the range from 5 to 25 °C) reveals an increase in the rate of adsorption and adsorption capacity with increasing temperature. The activation energy (in the case of РАСА 16.6 kJ/mol, and for IACA 11.3 kJ/mol) was determined using the Arrhenius dependence. Electrostatic interactions between the dye and resin beads were shown to be the adsorption mechanism.

Erratum to “Kinetics of 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene-3,6-disulphonic acid immobilization on anion exchangers” [Colloids Surf. A: Physicochem. Eng. Aspects 215 (2003) 277]

Erratum Erratum to “Kinetics of 1,8-dihydroxy-2-(pyrazol-5-ylazo)-naphthalene-3,6-disulphonic acid immobilization on anion exchangers” [Colloids Surf. A: Physicochem. Eng. Aspects 215 (2003) 277] Vesna Vasic a,∗, Jasmina Savic a, Vesna Pavelkic a, Slobodan Milonjic b a Department of Physical Chemistry, VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro b Chemical Dynamics Laboratory, VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and Montenegro Available online 16 September 2005