STUDIA CHEMIA - Issue no. 4 / 2021 - Table of contents

The interactions between human serum albumin (HSA) and haloperidol (HPD) in the presence or absence of caffeine (CAF) with HSA were studied by fluorescence-absorption spectroscopy and molecular modeling. The results showed that the presence of CAF decreased binding constants of HPDHSA with increasing temperature from 1.07× 104 mol/dm3 to 3.13 x 102 mol/dm3. The results indicate that the HSA-HPD and HSA-CAF-HPD system is very thermally sensitive. The number of binding sites obtained at three different temperatures were close to 1 indicating the presence of one binding site of HPD, CAF on HSA. Fluorescence quenching was initiated by dynamic quenching procedure irrespective of the absence or presence of CAF. The negative value of the free energy change (ΔG) indicates a spontaneous binding process of both, HPD to HSA protein and HPD to the HSA-CAF protein complex. The values of ΔH0 < 0 and ΔS0 < 0 for binding interaction HSA-HPD and HSA-CAFHPD, indicate that interaction is enthalpy driven. Docking simulation results are confirmed that the most preferable place for binding HPD and CAF is the active site I, in domain II subdomain IIA. The present study suggested that the combined actions of HPD and CAF, may lead to further changes in HSA conformation.

Keywords: Caffeine; Interaction; Human serum albumin; Haloperidol; Fluorescence

Lead isotopic ratio determination is significantly affected by the isobaric interference of mercury (204Hg), thus many studies lack 204Pb/206Pb values. Removal of 204Hg from sample is resource consuming, while mathematical correction can be employed if the Hg isotope ratio in the sample is known. Triple quadrupole inductively coupled plasma mass spectrometry (TQ-ICP-MS) offers a mechanism for removing the 204Hg, by pressurizing the reaction cell with ammonia, that reacts with 204Hg positively charged ions rendering them neutral, thus filtering them out and removing them from the ion beam. The Pb isotope ratio determination can be used as “fingerprint” to identify the sources of contamination and environmental pollution. The method developed based on this mechanism was used for Pb isotopic ratio determination in cave sediment samples. Relative standard deviation of this method was between 0.36% - 0.59%.

Keywords: ICP-MS, Pb isotopic ratio, lead, cave sediments, triple-quadrupole

The Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy was applied for the evaluation of specific patterns for six different essential oils obtained from aromatic plants (thyme, oregano, tea tree) or common spices (clove, cinnamon, juniper). The spectral fingerprints were recorded using a Shimadzu IR Prestige-21 spectrometer in the middle infrared region (3500-650 cm-1) before and after thermal oxidation in hot air. In parallel, the peroxide index, cis-trans isomerization and lipoperoxidation were evaluated to determine their oxidative stability. Each oil showed specific FTIR spectra, especially in the fingerprint region (1650-650 cm-1), in good agreement with our previous GC-MS analysis of the same samples. The spectral patterns in this region were also correlated with their oxidative stability, chemically determined. The spectral data were processed by multivariate analysis (Metaboanalyst 5.0 software) and the discriminatory analysis helped to identify each oil pattern. This study combined the capability of ATR-FTIR-MIR spectroscopy to realize a pattern recognition of essential oils as a rapid and non-destructive method, as well the oxidative modifications, easier than chemical routine tests. This study contributes to the control of quality, authenticity, and safety of essential oils and can be extended to other extracts, used as additives or ingredients in food or cosmetic products.

Keywords: essential oils fingerprinting, Attenuated Total Reflectance Mid Infrared Spectroscopy, thermal oxidation

The global warming and aridization process in Romania presents zonal risk situations that can strongly affect the production potential and quality of carrot crops. An experiment was designed which follows the effect of technological factors on the quantity and quality of production for three varieties of carrots (Royal Chantenay, Atomic Red and Purple Haze F1), under organic cultivation conditions. 18 carrot samples were analyzed to evaluate the antioxidant capacity and total of mineral elements. For the antioxidant capacity a photochemiluminescence methods was used and the Photochem instrument from AnalytikJena togheter the ACL kit and for the total content of mineral elements was used the ICP-MS Elan Drc II Perkin- Elmer. By irrigating the carrot culture, the antioxidant capacity increases by 17.6% compared to the control sample (non-irrigated). Through chemical fertilization and zeolite fertilization of carrot culture, the antioxidant capacity increases by 3.2% and 18.8%, respectively, compared to the control sample (basic fertilization). By irrigating the carrot culture, the total content of mineral elements increases by 14.1% compared to the control sample (nonirrigated). Through chemical fertilization and fertilization with zeolite of carrot culture, the total content of minerals elements increases by 5.5% and 18.9% respectively with the control sample (basic fertilization).

Keywords: carrots, zeolites, functional foods, fertilization, irrigation, organic farming

Human exposure to phthalates (artificial phthalic acid esters) is ubiquitous because of the widespread use of these chemicals in consumer and industrial products. The aim of this study was to determine the presence and amount of the phthalates in milk and dairy products collected in Romania. Samples were gathered at several stages during the production, primary production (farm), milk collection center and retail level. Six types of phthalates were assessed by gas chromatography with mass spectrum detection (GC-MS, of which only 4 were detected in the samples - di-n-butyl phthalate (DBP), di-2-ethylhexyl phthalate (DEHP), di-n-octyl phthalate (DOP) and dibutylbenzyl phthalate (BBP). The obtained concentrations ranged between 0.060 – 0.298 mg/kg for DEHP, in raw milk samples and 0.038 - 0.173 mg/kg respectively, in commercial milk. DMP and DEP were not detected in any sample. The lowest quantity of phthalates was detected in yogurt with 0.1% fat – 0.042 mg/kg, and the largest amount was recorded in butter with 75% fat – 0.683 mg/kg. The level of total phthalates in all samples analysed did not exceed the maximum permitted limit of 60 mg/kg.

Keywords: phthalates, milk, dairy products, GC-MS

Climatic factors have a great influence on the quality of grapes and wines, thus the identification and quantification of aroma compounds from Feteasca regala wine manufactured in 2019 in three established winemaking centers from Romania (Samburesti, Corcova and Dragasani) was performed. After liquid/liquid extraction, the aromatic composition was identified and quantified by gas chromatography coupled with mass spectrometry (GC-MS). 42 aroma compounds were analyzed depending on the region of origin of the vineyards and climatic factors. Results showed significant differences between the wines regions of origin. The quantities of long-chain alcohols varied between 28644.54 μg/L and 33969.27 μg/L and esters between 4221.10 μg/L and 7901.25 μg/L. Significant quantities were determined for fatty acids and ranged between 5310.99 μg/L and 6045.15 μg/L and lactones between 727.39 μg/L and 988.01 μg/L. The most significant results regarding the aroma profile were determined for the wine from Avincis Dragasani vinery, where the climatic indicators ratio was optimum, thus conferring specific and quantifiable elements to the wine.

Keywords: GC-MS, oenological climate index, wine aroma compounds

In this study, seven jam formulations were prepared, starting with the basic formulation, containing sucrose. This sweetener was replaced by fructose, erythritol, brown sugar, coconut sugar, stevia and saccharine, making these formulations a good alternative, some of them being also suitable for diabetic patients. Titratable acidity (TA) and total soluble solids (TSS) of lingonberry jams were evaluated for changes in jam quality during storage at 4°C, 25°C (under light conditions) and 25°C (under dark conditions) for 60 days. Moreover, a sensory evaluation was performed after 180 days of storage at 4°C to assess its consumer acceptance as compared to jam made with sucrose. During storage, TA and TSS increased in the case of all samples regardless of temperature conditions. ANOVA analysis of results revealed that the changes in TA and TSS were significantly affected by the type of sweetener used in jam formulation (p < 0.05). Jams formulated with coconut sugar and stevia were assessed by the sensory panel as the most acceptable.

Keywords: titratable acidity, total soluble solids, sucrose, sweeteners, sensory properties

The important molecule tryptophan and its derivatives serotonin and melatonin have vital functions in human and plant biosystem. Recent reports claimed these molecules and parthenolide may also have a role in COVID-19 treatments. Herewith the study, contents of chlorogenic acid, cynarin, quinic acid, parthenolide, and tryptophan derivatives in leaf and flowers of seven species of Tanacetum from Turkey were examined using HPLC. The methanolic extracts of the species were also screened for their total phenolic content and DPPH scavenging activity. Regarding to HPLC data, the highest amount of chlorogenic acid and cynarin were detected in T. cilicicum, quinic acid in T. densum subsp. amani and parthenolide in T. argenteum subsp. argenteum leaves. Also, the highest amount of tryptophan and serotonin were estimated in T. argenteum subsp. argenteum. Melatonin content was highest in T. densum subsp. amani. All Tanacetum species exhibited potent antioxidant activities. T. densum subsp. amani (Afşin) flowers had higher DPPH activity than control group BHT and T. cilicicum leaves and flowers had the highest total phenolic content. Herewith, phenolic profiles of T. argenteum subsp. argenteum, T. armenum and T. densum subsp. amani and tryptophan derivates of the species were reported for the first time.

Keywords: Tanacetum, parthenolide, antioxidant activity, tryptophan, serotonin, melatonin

Motherwort (Leonurus cardiaca) and Hawthorn (Crataegus monogyna) are known from traditional phytotherapy as being effective in alleviating many cardiovascular system disorders. This paper presents the studies made to assess the phytochemical compozition of the herbal extracts prepared from Motherwort (aerial parts), Hawthorn (fruits) and Hawthorn (flowers and leaves) by maceration, percolation and reflux using a mixture of ethanol and water as solvent. Optimum extraction conditions were evaluated for enhancing the content of the active substances (certain flavones and polyphenols: anthocyanins, etc.) present in the two studied plants, that are useful in the prevention of many cardiovascular disorders. Their chemical composition was investigated using UV-VIS spectroscopy methods: total polyphenolic content, total flavones content and the antioxidant activity were determined. The study showed that reflux extraction technique is more effective for extracting polyphenolic compounds from the two studied medicinal plants. Varying the extraction parameters led to the attainment of new phytotherapeutic extracts that are optimally beneficial in the phytotherapy of cardiovascular diseases.

Keywords: Hawthorn, Motherwort, reflux, percolation, maceration, polyphenols

Mushrooms are popular food for a long time because of their high nutritional value and many pharmaceutical properties. In that context, analyzing the contents and some antioxidant properties of three wild edible mushrooms, Paxina queletii, Chlorophyllum agaricoides, and Mycenastrum corium, is important in terms of emphasizing the values of these species in nutrition. For this propose, firstly total phenolic and flavonoid contents and radical scavenging activities were assayed. Then, quantitative analysis of phenolic and volatile compounds was performed by HPLC and GC-MS. The findings of the study revealed that Mycenastrum corium has the highest total phenolic and flavonoid content with the amount of 4.17 mg GAE/g and 1.58 mg QE/g respectively. However, DPPH˙ and ABTS˙+ radical scavenging activities of C. agaricoides were found higher with the IC50 values of 20.0 μg/mL and 6.4 μg/mL. Chromatographic analysis revealed that 5 alcohols, 14 aldehydes and ketones, 2 esters, 17 alkanes-heterocyclic compounds, and 4 acids were the major contributors of the antioxidant activities of the extracts. Regarding HPLC analysis, gallic acid, naringin and trans-cinnamic were found to be major phenolic compounds available for three species.

Keywords: Chlorophyllum agaricoides, volatile compounds, Mycenastrum corium, Paxina queletii, phenolic content, radical scavenging

This study reveals the behavior of resorcinol, phloroglucinol and pyrogallol in several non-aqueous solvents (acetonitrile, acetone, dimethyl sulphoxide, dimethyl formamide, nitrobenzene, nitromethane, dichloromethane, methanol). The voltammetric curves showed that the results obtained with the outlined compounds depend strongly on the solvent used. Resorcinol and phloroglucinol undergo some fouling during their electrooxidation while pyrogallol gave reproducible voltammograms in many solvents. The optimal solvent was chosen then for the determination of pyrogallol in cooking oil taking into consideration the antifouling, miscibility, permittivity and viscosity effects with steady-state voltammetry by using microelectrode.

Keywords: Resorcinol; Phloroglucinol; Pyrogallol; Co-solvent; Microelectrode

The purpose of the study was to investigate the effects of temperature and β-carotene addition on the quality parameters of corn and palm oils subjected to heating. Vegetable oils and 0.005% β-caroten additivated oils were heated at varying temperatures (100, 130, 160, 190 and 220°C for 30 minutes) to follow quality alterations. Peroxide value, total polar compounds, refractive index value, iodine value and fatty acids composition were determined to measure the degree of oxidative rancidity. Peroxide value was significantly (p < 0.001) influenced by the type of oil, additivation and heating temperature. Palm oil with added antioxidant showed the smallest increase in polar compounds during the heat treatment. Corn oil fatty acids profile was rich in oleic (C18:1), arachidonic (C20:4), eicosenoic (C20:1), and linoleic (C18:2) fatty acids, followed by alphalinolenic (C18:3) and palmitoleic (C16:1) acids. Polyunsaturated fatty acids and monounsaturated fatty acids content decreased during heat treatment. Statistical analysis of the data revealed that the development of rancidity in vegetable oils subjected to heating was significantly (p < 0.01) reduced by the addition of β-carotene in concentration of 0.005%.

Keywords: corn oil, palm oil, heating, fatty acids profile, peroxide index, total polar compounds

The banana peel powder (BPP) was used as a low-cost adsorbent for the adsorption of Basic Red 29 (BR29) dye from aqueous solution. The FTIR, AFM and SEM analysis were conducted for the characterization of BPP. The effects of initial dye concentrations, contact time, pH, adsorbent dosage and agitation rate on the adsorption of BR29 were studied. The uptake was very rapid during the first 30 minutes and slowed down as the contact time increased. The adsorption decreased as the initial dye concentration increased while it increased as the adsorbent dosage increased. The uptake of BR29 was highest at pH 8 and the percentage uptake increased as the agitation rate increased. The adsorption kinetics of BR29 onto BPP fitted well to the pseudo-second order kinetic model. Three different isotherm models, which include Langmuir, Freundlich and Brunauer-Emmett-Teller (BET) were used to analyze the equilibrium adsorption data of BR29. The adsorption isotherm of BR29 onto BPP was better described by the Freundlich isotherm model with the coefficient of determination (R2) of 0.9956.

Keywords: Basic Red 29, Dye, Adsorption, Banana peel, Kinetic study

In this study, the reforming of kerosene was performed in a fixed-bed reactor in order to investigate the synthesis of hydrocarbon fuels. For this purpose, five Ni-based catalysts supported on Y, Mordenite, ZSM- 5, Beta, and Ferririte zeolites were prepared by deposition-precipitation method. Four main composition groups of hydrocarbons including normal paraffins, isoparaffins, cycloparaffins, and aromatics were analyzed in feed and liquid products and the effects of key parameters of the catalysts namely acidity, diameter of pores in channels, and surface area on the progress of the reforming process were surveyed. According to the analysis results, Y zeolite with higher acidity, larger pore diameter, and more surface area led to produce the most aromatic contents (57.60%) in the products. Beta increased both cycloparaffins (34.91%) and isoparaffins (34.07%) in the product. Mordenite and Ferririte effectively increased the formation of isoparaffins by 38.22% and 38.85% respectively. Meanwhile, ZSM-5 with moderate acidity, surface area, and pore size increased the cycloparaffin contents of the product (46.28%). These results highlighted the potential of each zeolite to produce a valuable product via reforming process, which meets the requirement of standard hydrocarbon fuels. Ultimately, the pathway to reforming process over each prepared catalyst was proposed.

Keywords: Reforming process, Bi-functional catalysts, Zeolite, Kerosene, Jet fuel, Reaction pathway

Versatile classical and modern methods for a new synthesis of (8E,10Z)-tetradeca-8,10-dienal based on Sonogashira cross-coupling, Cahiez-Fürstner reaction as well as other reactions using palladium, iron or copper as catalysts were described. We designed two ways employing two different strategies one of that involves an E-reduction and the other a Zreduction with crucial importance in terms of diastereoselective synthesis. From the variously formulated pheromone baits, the one containing only the active isomer showed superior activity compared to the mixture of all isomers of 8,10-tetradecandienal. The synthesis of the pure E,Z diastereoisomer allowed to clarify their structure-bioactivity relationships to reveal the diversity in the stereochemical aspects of pheromone communications.

Keywords: Cameraria ohridella, (8E,10Z)-tetradeca-8,10-dienal, Pheromone, Lure, Field Tests

This study compared marginal microleakage in case of two dental composite resins: a consecrated commercial Bis- GMA resin- IPS Empress Direct (Ivoclar Vivadent, Lichtenstein)- group A, and a recently introduced Bis- MEPP resin - Gaenial A’Chord (GC R&D Japan)- group B and to observe, by means of scanning electron microscopy (SEM), the differences between these two restorative materials when using the same adhesive system and restorative layering technique. Microleakage testing scores were higher in IPS Empress group, but the results were not statistically validated. SEM images on group A presented a highly developed hybrid layer, while for group B resin extension intersecting the hybrid layer were observed, having a similar electronic density with the adhesive layer, which demonstrates a continuity of the nanoparticles in depth. On dentincomposite interface increased number of gaps and fissures were observed, comparing to enamel-composite interface. The result from the research showed that the two compared composite resin present similar properties in terms of adhesion and microleakage.

Keywords: composite resin, Bis-GMA, Bis-MEPP, silane coating

The objective of this study was to compare the structure, morphology and enamel-composite and dentin-composite interface in the teeth of patients with chronic renal failure, predialysis and healthy patients, using two methods: atomic force microscopy (AFM) and scanning electron microscopy (SEM). Most of the tested enamel specimens showed a mixed type of failure. The AFM examination indicated a deep engraving for enamel and dentin in sick people compared to healthy people. The average value of the roughness (Ra) in enamel and dentin from healthy patients were significantly different (p < 0.001) than from enamel and dentin in patients with renal failure. Regarding the SEM images, the dentin-composite material interface in teeth extracted from healthy patients, has uniformity, compared to the dentin-composite interface in teeth extracted from predialysis patients where a discontinuous hybrid layer with some gaps was identified.

Keywords: atomic force microscopy, scanning electron microscopy, enamelcomposite interface, dentin-composite interface, predialysis

This research relates to cement-based matrix materials with self-repairing properties, based on reactive grains (Portland clinker) having the dimensions 90…160 μm and using a protective coating layer with a thickness of 4-7 μm. The material involves the use in mortars or concretes of a smart additive of a clinker reactive material covered with an impermeable polymeric coating that breaks when a crack appears in the material and allows the reaction between water and cement stone components and, consequently, the formation of a crack plugging product consisting in calcium silicate hydrates gels (CSH), superior to that of calcium carbonate precipitation. The intelligent addition is obtained by mixing the reactive material with the solution of a polymer, or with its melt (C8H8)n. The efficiency of coverage exceeds 80% in most of cases, some of them approaching even 90%. No significant effect of the ratio reactive material/polymer seems to be observed. The degree of healing of the crack is defined in the paper. The method of highlighting the self-repairing effect is based on the amount of electricity passed through the sample. The new material has practically unchanged mechanical properties, a higher hydration capacity and a longer service life-cycle.

Keywords: reactive grains, protective coating, self-repairing, new material

This paper presents some of the results of research on the introduction of the operation of drying sludge from wastewater treatment in treatment plants. Graphical representations of the experimentally determined values demonstrate the possibility of continuing the process of decreasing the humidity of dehydrated sludge, by mechanical means. Sludge drying is presented as a simple operation that can be easily introduced into the sludge treatment process. The second part of the paper presents a machine that could be executed with relatively small amounts in each treatment plant in order to achieve the drying of dehydrated sludge. The paper presents characteristics of dehydrated sludges in Cluj and Sălaj counties as well as chemical analyzes performed on dehydrated sludges. In conclusion, the paper argues that dry sludge can be removed from the waste and turned into a material resource.

Keywords: wastewater, wastewater treatment plants, sludge, waste, drying tunnel, dry mud, resource

The need for solutions in the sector of municipal waste management brings different problems which can be properly managed by using modern technologies, new ways to capitalize substrates and materials which in normal conditions are not potentially usable. The present study involves chemical and thermal analysis in order to determine the energetic potential and overall properties of one type of municipal waste sludge collected during summer in Caras-Severin County. For confidential reasons, the origin of the waste sludge will not be mentioned.

Keywords: municipal waste sludge, chemical analysis, thermogravimetry

The paper presents the rheological behavior study of cosmetic emulsions as well as their oxidation stability. The influence of temperature and of the cooling rate was determined, as well as that of the active principles content on the rheological behavior, by setting the dependence between the shear stress τ and the shear rate . The analysis of this dependence demonstrates that these emulsions present non-Newtonian behavior. The oxidation stability was monitored for 210 days by determining the peroxide value and the presence of initial and final oxidation products (by monitoring K232 and K270 values, respectively).

Keywords: cosmetic emulsions, emulsifier, mathematical models, oxidation, rheological behavior, stability, viscosity, peroxide value

The spinning disc technology (SD), with its enhanced fluid flow features, has been applied to an increasing number of fields lately. Experimental characterization of the flow on a smooth or radially/concentrically indented rotating disc, for different feeding liquid flow rates (30, 50, 70 L/h) and disc rotational speeds (200, 500, 800, 1100 rpm), using two types of feed distribution systems (one nozzle or four symmetrically distributed nozzles) has been performed, based on the pulse response technique. Based on the radial dispersion model, the Péclet number was determined for different experimental conditions and used to identify flow characteristics and to compare different spinning disc setups efficiencies. Based on the obtained experimental data, the large flowrate values and disc rotational speeds induce a flow regime closer to plug flow, however intense micromixing is achieved within an intermediate range of the studied parameters, when the turbulent wavy liquid film surface occurs, the micromixing is increased and thus, the SD technology is efficiently used. Certain flow characteristics can be achieved if the spinning disc is operated at specific parameter values.

Keywords: spinning disc, feeding system, flowrate, rotational speed, identations

Bor, Krivelj, and Bela Rivers in Eastern Serbia belong to the watershed of Timok River, which is a tributary of Danube River. These Rivers flow near to the largest mining complex in Republic of Serbia. Rivers Bosneag, Radimna and Nera from the Romanian side in Caras Severin County near to Moldova Noua are also tributary of Danube and flow in area which is affected by spreading of dust from the abandoned flotation tailing of copper mine. This study includes environmental monitoring of the surface waters in considered Romania-Serbia cross border area during 2019-2020. Chemical analyses confirmed pollution mostly with heavy metals (Fe, Mn, Cu, Zn, As, Ni, Pb, Cd) closer to mines while with larger distance pollution decrease. The measured values were compared with Serbian and Romanian legislation which confirmed moderate and high pollution depending on category of surface waters. Measured Cd concentrations were of 9.51 - 5375 μg L-1 for the IV category of River water close to Bor mine. The main anthropogenic source in Eastern Serbia was Bor mine and smelter.

Keywords: mining, surface waters, tailings, monitoring, pollution

The model combing the method UNIFAC with various model methods was applied for calculation of activity coefficients in an VLE model for hexaflourobenzene(1) benzene(2) at 333.15K, butanol(1) tetrachloroethene(2) at 101.08 kPa, carbondioxide(1) 3-pentanol(2) at 313.2K and other system compounds. The simulated results represent the overall average relative deviation below 0.5% which is comparable to the results presented by other authors in the literature. The data and results obtained for the systems are compared with the compositions predicted by the model and the sensitivity of the model parameters towards the composition data was analyzed through simulation techniques. The results predicted that overall error convergence was found to be less than 0.5 %.

Keywords: Activity coefficient, VLE, Models, convergence

A total of 45 isomers of dihydroxyfumaric acid (DHF), including 23 keto and 22 enediol forms, were identified and their geometrical isomerization and tautomerization was studied at the B3LYP level of theory using the 6–311++G(2df,2p) basis set in the gas phase and aqueous solution, and three most stable enediol structures were identified. Interconversions between the enediol forms and the keto forms proceed through two paths: (1) proton transfer (𝐸􀯔 ≈ 135–160 kJ mol-1) and (2) internal rotation (𝐸􀯔 ≈ 0.15– 75 kJ mol-1). Keto–enol tautomeric reactions of dihydroxyfumaric acid were investigated for the three most stable enediol structures. It was found that the activation energy and the free activation energy is in the range of 230–310 kJ mol-1 for the gas phase and by 50-80 kJ mol-1 lower in water, and TSs structures reveal that the carboxylic oxygen that forms the hydrogen bond in the enediol structure is involved in the mechanism of proton transfer. Furthermore, equilibrium constants have been calculated, along with the forward and reverse reaction rates for the isomerization and tautomerization reactions of the three most stable enediol structures, in gas and water.

Keywords: dihydroxifumaric acid, keto-enol tautomerism, dft study

Human proteins expressed in prokaryotic systems tend to form inclusion bodies. Proteins in inclusion bodies are inactive and the refolding of these densely packed protein molecules is affected by several factors depending on the applied refolding technique. To obtain the active form of protein the most common technique is denaturation of the protein aggregates followed by refolding of inclusion proteins. Conventional denaturants for solubilization are urea, guanidine hydrochloride and sodium dodecyl sulphate (SDS), while refolding can be achieved by several techniques found in the literature. In our study, the recombinant GST-tagged XIAP (X-linked Inhibitor of Apoptosis protein) construct was expressed as inclusion bodies. The protein was solubilized with high efficiency using N-Lauroylsarcosine (ionic detergent). A chromatography-based method using different ratios of detergents was investigated for the refolding process. Batch mode affinity purification was successfully executed using Glutathione Sepharose 4B resin and TritonX- 100, n-octyl β-D-thio-glucopyranoside (OTG) and 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate hydrate (CHAPS) detergents in the appropriate ratio. Finally, the refolded protein was purified by size-exclusion chromatography and investigated by western blot analysis.

Keywords: XIAP, inclusion body, solubilization, refolding, detergents, affinity chromatography

The aim of this work was to evaluate the antimicrobial effectiveness of a bioceramic experimental endodontic sealer (EES), alongside with its components. As a novelty, magnesium silicate was incorporated into the experimental material, in order to improve the mechanical performance of the product. The main oxide components, tricalcium silicate (Ca3SiO5) and magnesium silicate (Mg2SiO4) were synthesized in nanoparticles from specific precursors by a sol-gel method. To compare the efficiency of the new developed product, commercially available materials, with similar chemical composition, used in everyday practice, were also tested: BC Sealer, MTA Bioceramic Root Canal Sealer, and MTA Fillapex. The method employed for the present study was the agar well diffusion test (ADT). The selected microbial strains were Enterococcus faecalis and Candida albicans, frequently associated with persistent infection and recurrent infections of the endodontic space, as well as periapical pathologies refractory to endodontic treatment. Measurements of the inhibition areas were performed at 24-hour intervals for 7 consecutive days. Tricalcium silicate and all tested endodontic sealers revealed antimicrobial effectiveness against Candida albicans at 24 hours after placement, with a prolonged activity, for up to 7 days. The study revealed no antibacterial effect against Enterococcus faecalis at 24 hours nor in the following 7 days, for any of the tested samples.

Keywords: antimicrobial activity, bioceramic, endodontic sealer, tricalcium silicate

Production of health-promoting substances in plants’ metabolism may be modulated by treatment with chemical stress factors and natural bioactive compounds, which enhance stress tolerance through stimulation of biosynthesis of several protective metabolites. The aim of this work is to reveal metabolic interactions between high salinity stress (exerted by the presence of 100 mM NaCl in the mineral nutrient solution) and treatment of plants with 0.1 mM S-methylmethionine (also known as vitamin U). This plantderived bioactive compound enhances the production of antioxidants such as carotenoids, ascorbate and other phenoloids in leaves of rocket plantlets exposed to salt stress, while reducing the concentration of toxic malondialdehyde and related catabolic products of membrane lipid peroxidation. Thus, a suitable combination of high salinity and plant hardening with S-methylmethionine may improve the quality of fresh rocket leaves upon human and animal consumption.

Keywords: ascorbate, carotenoids, phenoloids, lipid peroxidation, salt stress

The non-heme diiron protein hemerythrin (Hr) has been considered as a possible alternative for semi-artificial oxygen carriers (“blood substitutes”). Studies on the stability of its octameric structure have been attempted by attaching spin labels to analyze its electron paramagnetic spectroscopy (ESR) signals. Reported here are molecular dynamics results of Hr bound with 1-oxyl-2,2,5,5-tetramethylpyrroline-3methyl (MTSSL) at the Cys51 position. Our results show that the Hr-MTSSL complex is less stable than its native form. These findings help to explain ESR signals obtained experimentally. Also, these results are crucial to understand the limitations of PEGylated spin labels for protein structural analysis and suggest the need or further exploration of other alternatives.

Keywords: hemerythrin, molecular dynamics, spin label, blood substitute, diiron