Snežana Miljanić

Bio: Snežana Miljanić is an academic researcher from University of Zagreb. The author has contributed to research in topics: Silver nanoparticle & Raman spectroscopy. The author has an hindex of 13, co-authored 44 publications receiving 576 citations.

Schiff Bases Derived from Aminopyridines as Spectrofluorimetric Analytical Reagents

Abstract: Fluorescence characteristics of Schiff bases derived from aminopyridines and salicylaldehyde were studied and possibilities of their analytical application were discussed. It is shown that these compounds can be used for spectrofluorimetric monitoring of small pH changes as well as for sensitive metal ion determinations. As an illustration of metal ion determination, a spectrofluorimetric procedure for analysis of Cu2+ is presented. Determination of Cu2+ was based on the quenching effect of Cu2+ on the fluorescence of N, N'-bis(salicylidene)-2, 3-pyridinediamine in dioxan/water 1/1 (volume fraction of dioxan, phi = 50%). Under optimal conditions (pH = 8.9, lambda(ex) = 340 nm, lambda(em) = 385 nm, c(ligand) = 1.0 x 10(-5) M), the linearity range of the calibration curve was 30-350 mu g L-1 Cu2+. The procedure is fast, simple and reproducible. It is characterized by high sensitivity and satisfactory selectivity. An additional advantage of Schiff bases derived from aminopyridines as analytical reagents lies in the simplicity of preparation procedures, enabling improvement of the determination methods not only by optimization of experimental conditions, but also by designing suitable structural characteristics of the reagent.

Alteration of cholinesterase activity as possible mechanism of silver nanoparticle toxicity

Abstract: Due to their broad-spectrum antimicrobial activity, silver nanoparticles (AgNPs) have been used in a large number of commercial and medical products. Such proliferated AgNP production poses toxicological and environmental issues which need to be addressed. The present study aimed to investigate the effects of AgNPs on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), important enzymes in areas of neurobiology, toxicology and pharmacology. Three different AgNPs, prepared by the chemical reduction using trisodium citrate, hydroxylamine hydrochloride (Cl-AgNPs), and borohydride following stabilization with poly(vinyl alcohol), were purified and characterised with respect to their sizes, shapes and optical properties. Their inhibition potential on AChE and BChE was evaluated in vitro using an enzyme assay with o-nitrophenyl acetate or o-nitrophenyl butyrate as substrates, respectively. All three studied AgNPs were reversible inhibitors of ChEs. Among tested nanoparticles, Cl-AgNP was found to be the most potent inhibitor of both AChE and BChE. Although the detailed mechanism by which the AgNPs inhibit esterase activities remains unknown, structural perturbation of the enzyme may be the common mode of ChE inhibition by AgNPs.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Gels with sense: supramolecular materials that respond to heat, light and sound

Abstract: Advances in the field of supramolecular chemistry have made it possible, in many situations, to reliably engineer soft materials to address a specific technological problem. Particularly exciting are “smart” gels that undergo reversible physical changes on exposure to remote, non-invasive environmental stimuli. This review explores the development of gels which are transformed by heat, light and ultrasound, as well as other mechanical inputs, applied voltages and magnetic fields. Focusing on small-molecule gelators, but with reference to organic polymers and metal–organic systems, we examine how the structures of gelator assemblies influence the physical and chemical mechanisms leading to thermo-, photo- and mechano-switchable behaviour. In addition, we evaluate how the unique and versatile properties of smart materials may be exploited in a wide range of applications, including catalysis, crystal growth, ion sensing, drug delivery, data storage and biomaterial replacement.