Mechanism of complex formation between [AuCl4] – and L-methionine

The kinetics of the reaction between tetrachloroaurate(III) ion and L-methionine has been studied spectrophotometrically by using stopped-flow technique in 0.1 M HClO4 as the function of temperature. The fast reaction was ascribed to the formation of short living square-planar [AuCl2Met]+ complex ion, that was reduced in the slower reaction step. The activation parameters (∆H≠ and ∆S≠ ) for complex formation were determined. The entropy of activation was compatible with an associative reaction mechanismPhysical chemistry 2006 : 8th international conference on fundamental and applied aspects of physical chemistry; Belgrade (Serbia); 26-29 September 200

Influence of maltodextrin dextrose equivalent value on rheological and dispersion properties of sunflower oil in water emulsions

Effect of dextrose equivalent (DE) of maltodextrin present in continuous phase on flow along with dispersion properties of sunflower oil in water emulsions has been investigated. Both, rheological and disperse characteristics of the emulsions were greatly influenced by continuous phase viscosity and thus by the DE value of maltodextrin.. The smaller DE value the greater high shear viscosity and the smaller the droplet size. Irrespective of the amount and DE value of maltodextrin used was, all the emulsions showed a pseudoplastic behaviour

Biological Activity of Some Cobalt(II) and Molybdenum(VI) Complexes: in vitro Cytotoxicity

Cytotoxicity and cell growth inhibition studies were performed for five distinct cobalt(ll) [Co2(acac)tpmc](ClO4)3, [Co2(dibzac)tpmc](ClO4)3, [Co2(hfac)tpmc](CIO4)2, [Co2(tmhd)tpmc](CIO4)3 and [Co2(ox)tpmc](CIO4)2.3H20 and five molybdenum(Vl) complexes, [MoO2(pipdtc)2], [MoO2(morphdtc)], [MoO2(timdtc)2], [MoO2(pzdtc)2] and [MoO2(N-Mepzdtc)2]. The former were tested in two leukemia cell lines: chronic myelogenic leukemia (K562) and human promyelocytic cell line (U937). They showed to have relatively high toxicity in K562 cells and a relatively low cytotoxicity in U937 cells, as assessed by both MTT and Trypan Blue assays. The five molybdenum complexes were tested in human promyelotic U937 cell line and they showed to have high toxicity

Rheological properties of hydroxypropylmethyl cellulose/sodium dodecylsulfate mixtures

Rheological properties of mixtures of hydroxypropylmethyl cellulose (HPMC), a nonionic associative cellulose ether, and sodium dodecylsulfate (SDS), an anionic surfactant, were investigated by viscosity measurements performed at different shear rates (0.1-6000 s-1). HPMC/SDS mixtures containing different concentrations of SDS (CSDS=0.00-3.50 % w/w) and HPMC concentrations which corresponded to the overlap parameter c/c*=3, 6, and 12 were prepared. All HPMC/SDS mixtures were found to be shear-thinning when examined in a low-end-to mid-range of the applied shear rates. The degree of shear-thinning, n, and viscosity of the mixtures were influenced by composition of HPMC/SDS mixtures and HPMC-SDS complex formation. The changes in n ranged from values typical for highly shear thinning to almost perfectly Newtonian liquids, and were more pronounced as c/c* was increased from 3 to 6 and 12. A change in flow profile and a buildup of the first normal stress difference (N1) was observed in HPMC/SDS mixtures with c/c*=6 and 12 and CSDS 0.55-1.00 % and 0.55-2.50 %, respectively, when a critical shear rate, crit. was exceeded, suggesting that a shear-induced structure formation in the mixtures took place. [Projekat Ministartsva nauke Republike Srbije, br. Grant III 46010

Komparativno elektrohemijsko ispitivanje nekih kobalt(III)i kobalt(II) kompleksa sa azamakrocikličnim i β-diketonato ligandima

The electrochemical properties of eight mixed-ligand cobalt(III) and co balt(II) complexes of the general formulas [CoIII(Rac)cyclam (ClO4)2 (1)–(4) and [Co2II(Rac)tpmc](ClO4)3 (5)–(8) were studied. The substances were investigated in aqueous NaClO4 solution and non-aqueous LiClO4/CH3CN solution by cyclic voltam metry at a glassy carbon electrode. In aqueous solution, cyclam and Rac ligands being soluble in water undergo anodic oxidation. Coordination to Co(III) in complexes 1–4, stabilizes these ligands but reversible peaks in catohodic region indicate the redox reaction CoIII/CoII ion. In the case of the binuclear Co(II) complexes 5–8, peaks recorded on the CVs represent oxidation of the bridged Rac ligand. The complexes examined influence the cathodic reaction of hydrogen evolution in aqueous solutions by shifting its potential to more negative values and its current is increased. In non-aqueous solution the CVs of the ligands show irreversible anodic peaks for cyclam, tpmc and for the Rac ligands soluble in acetonitrile. The absence of any peaks in the case of the investigated complexes 1–4 indicates that coordination to Co(III) stabilizes both the cyclam and Rac ligands. Cyclic voltammograms of the complexes 5–8 show oxidation processes of the Rac ligand and Co(II) ions but the absence of a highly anodic peak of the coordinated macrocycle tpmc shows its stabilization. Contrary to in aqueous solution, the redox reaction Co(III)/Co(II) does not occur in acetonitrate indicating a higher stability of the complexes 1–4 in this media in comparison with the binuclear cobalt(II)-tpmc complexes 5–8.Cikličnom voltametrijom ispitano je osam kompleksa kobalta(III) i kobalta(II)sa mešovitim ligandima, opšte formule CoIII(Rac)cyclam (ClO4)2 (1)–(4) i CoII(Rac)tpmc (ClO4)3 (5)–(8), u vodenoj (NaClO4) i nevodenoj (LiClO4/CH3CN) sredini. U vodenoj sredini cyclam i Rac ligandi podležu anodnoj oksidaciji. Koordinacija sa Co(III) u komp- leksima (1)–(4) stabilizuje ove ligande ali dolazi do redoks reakcije Co(III)/Co(II).U slučaju binukelarnih Co(II) kompleksa (5)–(8) dolazi do oksidacije Rac liganada. Ispitivani kompleksi u vodenom rastvoru utiču na reakciju izdvajanja vodonika katodno pomerajući potencijal i povećavajući struju. U nevodenim rastvorima anodno se oksiduju oba makrociklična (cyclam i tpmc) i Rac ligandi rastvorni u acetonitrilu. Međutim, u ovim rastvorima Co(III) kompleksa ne dolazi do elektrohemijskih reakcija što znači ne samo da i ovde koordinacija sa kobaltom stabilizuje ligande već nema ni redoks reakcije za kobalt. Sa druge strane, u Co(II) komplesima stabilizovan je tpmc ali se oksiduju Rac ligandi i Co(II) pa su tako u nevodenim rastvorima kompleksi Co(III) stabiliniji od binukelarnih Co(II)-tpmc kompleksa

Kinetics of J-aggregation of Tc-coated au colloidal nanoparticles in aqueous solution

The kinetics of J-aggregation of thiacyanine dye (TC, 5,5’–disulfopropyl 3,3’– dichlorothiacyanine sodium salt) was studied in the presence of gold colloid. The synthesized Au colloidal dispersions were characterized by UV-Vis spectrophotometry. Kinetic measurements were carried out using a stopped-flow method to study the mechanism of J-aggregation, capturing both the slow and the fast phases of J-aggregate formation

3D finite element electrical model of larval zebrafish ECG signals

Assessment of heart function in zebrafish larvae using electrocardiography (ECG) is a potentially useful tool in developing cardiac treatments and the assessment of drug therapies. In order to better understand how a measured ECG waveform is related to the structure of the heart, its position within the larva and the position of the electrodes, a 3D model of a 3 days post fertilisation (dpf) larval zebrafish was developed to simulate cardiac electrical activity and investigate the voltage distribution throughout the body. The geometry consisted of two main components; the zebrafish body was modelled as a homogeneous volume, while the heart was split into five distinct regions (sinoatrial region, atrial wall, atrioventricular band, ventricular wall and heart chambers). Similarly, the electrical model consisted of two parts with the body described by Laplace’s equation and the heart using a bidomain ionic model based upon the Fitzhugh-Nagumo equations. Each region of the heart was differentiated by action potential (AP) parameters and activation wave conduction velocities, which were fitted and scaled based on previously published experimental results. ECG measurements in vivo at different electrode recording positions were then compared to the model results. The model was able to simulate action potentials, wave propagation and all the major features (P wave, R wave, T wave) of the ECG, as well as polarity of the peaks observed at each position. This model was based upon our current understanding of the structure of the normal zebrafish larval heart. Further development would enable us to incorporate features associated with the diseased heart and hence assist in the interpretation of larval zebrafish ECGs in these conditions