Rada M. Baošić

Identification of protein binders in artworks by MALDI-TOF/TOF tandem mass spectrometry

Aim of this work is to propose an analytical protocol for proteinaceous binder identification in paintings using tryptic peptide analysis and MALDI-TOF mass spectrometry strengthened with MALDI-TOF/TOF tandem mass spectrometry (LIFT method). Proteinaceous binders are enzymatically digested with trypsin. From each individual protein frequently occurring in binders, a specific set of peptides is releasing during enzymatic digestion giving a peptide mass fingerprint (PMF) of that particular protein. The most intensive peptide peaks in PMF were determined and annotated with their corresponding amino acid sequence by MALDI-TOF/TOF analysis and subsequent database search. Before analyzing historical painting samples, procedure was tested and optimized on several painting model samples for a reliable and efficient identification of proteinaceous materials. The method is avoiding sample manipulation as much as possible in order to reduce sample loss. Since the applied procedures led to protein identification of binding media in model samples, MALDI-TOF/TOF was for the first time applied for analysis of proteinaceous binders in old painting samples.

Physicochemical, Antioxidant and Sensory Properties of Peach Wine Made from Redhaven Cultivar

Physicochemical, sensory, and health-related characteristics of peach wine produced from Redhaven variety and selected white wines produced from various grape varieties were determined and compared. The alcohol content, titratable acidity, and total extract of peach wine was significantly lower compared with that of white wines, while its pH value was higher. The content of total phenolics (TPC) and flavonoids (TFC) of peach wine (402.53 mg/L GAE and 332.67 mg CAE/L, respectively) have been found significantly higher in comparison with that of white wines (TPC range 243.67-319.00 mg/L GAE, TFC range 129.67-175.17 mg CAE/L). The main phenolic compounds found in peach wine were chlorogenic acid, caffeic acid, and catechin (3.59, 0.87, and 0.60 mg/L, respectively). Antioxidant capacities were strongly correlated with total phenolics with correlation coefficients over 0.99. The highest antioxidant capacity was ascribed to peach wine. The results of sensory analysis indicated that the peach wine was very well accepted by the regular consumers of wine and can be a very interesting product in the market.

Thin-layer chromatography of mixed tris-β-diketonato metal complexes on polyacrylonitrile sorbent

Abstract The effect of the composition of mixed tris-β-diketonato metal complexes on their h R F values obtained by a thin layer of polyacrylonitrile sorbent was examined with two series of complexes of the type [M(acac) 3− n (phacphac) n ] and [M(acac) 3− n (phacphSac) n ], where M is Co(III), Cr(III) or Ru(III), acac=2,4-pentanedionato ion, phacphac=1,3-diphenyl-1,3-propanedionato ion and phacphSac=3-mercapto-1,3-diphenyl-prop-2-en-1-on ion ( n =0–3). Ten mobile phases were used for their chromatographic separation. In all instances h R F values of the examined complexes decrease when the oxygen atom in β-diketonato ligand is substituted by a less electronegative sulphur atom. It has also been established that the substitution of acac ligand results in a h R F value decrease. In all the examined cases a linear dependence between the R M values of the complexes and the number of acac ligands substituted by phacphSac ligands was established. The separation mechanisms and the separation factors are discussed.

Electrospray ionization linear trap quadrupole Orbitrap in analysis of old tempera paintings: application to nineteenth-century Orthodox icons

Proteomic approach in combination with mass spectrometry demonstrates a great potential for identification of proteinaceous materials in works of art. In this study we used a linear trap quadrupole Orbitrap (LTQ-Orbitrap), a state-of-the-art mass spectrometer for parts per million accuracy analyses of peptides behind tryptic hydrolysis. After the efficiency of the proteomic method was confirmed for reference and model samples, micro-samples from historical paintings were for the first time analysed using this technique. Superior performances of the liquid chromatography–mass spectrometry approach using a LTQ-Orbitrap mass spectrometer allowed identification of egg yolk peptides in two samples from nineteenth-century Orthodox icons, indicating egg tempera as the painting technique. Accurate precursor ion masses, in the range of ±2 ppm, and retention times of tryptic peptides strengthen protein identification. Additionally, in all historical samples the presence of animal glues suggested that the ground layer was likely bound using bovine collagen. Comparing to results acquired using matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry in our previous study, here we achieved higher ion scores and protein scores, better sequence coverage and more identified proteins. In fact, a combination of the two mass spectrometric techniques provided overlapping and complementary data, related to the detection of peptides with different physicochemical properties.

Estimation of the hydrophobicity of tris-β-diketonato complexes from reversed-phase thin-layer chromatographic data

Experimental RM values for two series of ß-diketonato complexes, M(acac)3-n(phacphac)n and M(acac)3-n(phSacphSac)n, where M represents cobalt(III) or chromium(III), have been determined by reversed-phase thin-layer chromatography on RP-18 silica with binary tetrahydrofuran-water, acetonitrile-water, and acetone- water mobile phases. RM0 0 values were determined for the different mobile phase mixtures by linear extrapolation to 0% (v/v) organic modifier. Lipophilicity C0 was calculated as the ratio of the intercept and slope values. Chromatographically obtained lipophilicity was correlated with calculated Clog P values.

Influence of organic modifiers on RP-TLC determination of lipophilicity of some polydentate Schiff bases

The lipophilic character of polydentate Schiff bases was investigated by reversed-phase thin-layer chromatography. In order to determine retention parameter as a measure of the lipophilicity of the tested compounds, three different binary solvent systems, composed of water and organic modifier (methanol, acetonitrile, and tetrahydrofuran), were used. Lipophilicity parameters together with 2D molecular descriptors were subjected to the multivariate statistical analysis. Principal component analysis was employed to reveal the most influential factors governing the lipophilicity of the investigated compounds. Finally, the influence of organic modifier on determination of lipophilicity parameters was discussed.Graphical abstract

The effect of the electronegativity of donor atoms in coordinated β -diketonato ligands on the chromatographic behavior of metal complexes

The effect on chromatographic behavior, on thin layers of silica gel, of the electronegativity of ligator atoms has been studied for three series of β-diketonato complexes of the type [M(acac)3-(phac-phac)n], [M(acac)3-n(phacphSac)n], and [M(acac)3-n(phSacphSac)n] (where M represents cobalt(IH), chromium(HI) or ruthenium(IH), acac is the 2,4-pentanedionato ion, phacphac is the 1,3-diphenyl-1,3-propanedionato ion, phacphSac is 3-mercapto-l,3-diphenyl-prop-2-en-1-one, phSacphSac is the 3-mercapto-1,3-diphenyl-prop-2-en-1-tion ion, and n - 0-3). For chromatographic separations, ten typical normal-phase mobile phases were used, five mono-component and five two-component. For all the complexes examined it was found that substitution of the donor oxygen atom by a less electronegative sulfur atom resulted in increased mobility of the complex. It was also established that substitution of the acac ligand resulted in increased hRF values. For all the complexes examined a linear dependence was observed between the RM values of the complexes and the number of acac ligands substituted by phSacphSac ligands. On the basis of these results, possible separation mechanisms are discussed.

Electrochemical, theoretical, and morphological studies of antioxidant fullerosteroids

Four fullerosteroidal conjugates, previously confirmed to express two- to threefold better antioxidant activity in vitro than C60, were subjected to additional studies, including electrochemical, theoretical, and morphological examination. All tested compounds underwent reversible, diffusion-controlled reductions. A notable influence of the solvent properties on the reduction potential, the level of aggregation, and the lowest unoccupied molecular orbital (LUMO) energy was observed. Theoretical calculations indicated that the energy gain obtained by an intermediate formation, together with compounds’ polarizability, polarity, and lipophilicity contributed to the radical quenching capacity. Very large supramolecular aggregates of all fullerosteroidal esters with no hierarchical arrangement were observed in precipitated samples, while solvent induced self-assembling led to round nanoplates, which further arranged to flower-shaped hierarchically ordered architectures or uniformly distributed discoid particles. As in electrochemical studies, fine tuning of the aggregation level was achieved by the solvent.Graphical abstract

Development of a Flow Injection System for Differential Pulse Amperometry and Its Application for Diazepam Determination

This work presents the development of a flow injection system for differential pulse amperometry (DPA) for diazepam determination in the presence of oxygen. The thin flow cell consisted of the bare glassy carbon electrode, reference silver/silver chloride, and stainless steel as the auxiliary electrode. Electrochemical reduction of diazepam (DZP) was characterised by cyclic voltammetry. Azomethine reduction peak was used for DZP quantification. The detector response was linear in the range 20–250 µmol/dm3 of diazepam, with a calculated detection limit of 3.83 µg/cm3. Intraday and interday precision were 1.53 and 10.8%, respectively. The method was applied on three beverage samples, energetic drink, and two different beer samples, and obtained recoveries were from 93.65 up to 104.96%. The throughoutput of the method was up to 90 analyses per hour.

Effect of substituents on prediction of TLC retention of tetra-dentate Schiff bases and their Copper(II) and Nickel(II) complexes.

The objectives of this study were to gain insights into structure-retention relationships and to propose the model to estimating their retention. Chromatographic investigation of series of 36 Schiff bases and their copper(II) and nickel(II) complexes was performed under both normal- and reverse-phase conditions. Chemical structures of the compounds were characterized by molecular descriptors which are calculated from the structure and related to the chromatographic retention parameters by multiple linear regression analysis. Effects of chelation on retention parameters of investigated compounds, under normal- and reverse-phase chromatographic conditions, were analyzed by principal component analysis, quantitative structure-retention relationship and quantitative structure-activity relationship models were developed on the basis of theoretical molecular descriptors, calculated exclusively from molecular structure, and parameters of retention and lipophilicity.