STUDIA CHEMIA - Issue no.2 / 2016 - Table of contents

In the present study, the gene of phenylalanine 2,3-aminomutase from Pantoea agglomerans (PaPAM) was cloned into pET-19b vector and used for its expression in competent Escherichia coli cells. The recombinant plasmid, PaPAM-pET-19b, was transformed into competent E. coli strain BL21(DE3)pLysS cells. Overnight culture of the transformed bacteria was induced by the addition of isopropylthio-β-D-galactoside (IPTG) to the final concentrations of 0.1, 0.5 and 1 mM. Also, the effects of different temperatures (18, 25 and 30°C) and the incubation time of PaPAM were examined. The fermentation process was scaled up to 10 L fermentor. Affinity purification conditions were analyzed by SDS-PAGE. The Tm and the activity of the purified enzyme was also investigated.

Keywords: phenylalanine 2,3-aminomutase, Pantoea agglomerans, optimization, protein expression

In the present study the molecular cloning, expression and purification of recombinant PcPAL, with a cleavable N-terminal His-tag is described. The PcPAL gene was cloned into pET-19b vector and transformed to different E.coli host cells. The optimization of expression and purification processes provided recombinant protein with high purity in its native, tetrameric fold with a yield of 7-8 mg protein / 1 L culture. The activity of the recombinant protein was tested towards its natural substrate L-Phe, the KM, and kcat values suggesting excellent catalytic properties of the recombinant enzyme.

Keywords: phenylalanine ammonia-lyase, Petroselinum crispum, molecular cloning, expression and expression optimization

The main aim of this study was to create mutant strains with lambda Red recombination system from an Escherichia coli strain which was isolated from animal faeces. E. coli Ter8/1 strain was genetically modified using lambda Red recombination system and two mutant strains were obtained, TerP01, in which the gene of pyruvate formate lyase was inactivated, and TerPL02, in which the genes of pyruvate formate lyase and lactate dehydrogenase were inactivated. The analysis of product formation in dualphase fermentation and in minimal salts medium with three carbon sources was performed. The first mutant, TerP01, produced a large amount of lactic acid with small amount of byproduct formation. In the case of the second mutant, TerPL02, lactic acid production has been finished and succinic acid production increased significantly.

Keywords: Escherichia coli, lambda Red recombination system, fermentation, glycerin, glucose, xylose

3,5-Disubstituted isoxazoles have been designed and synthesized to be used as central units for bent-core mesogens. The substituents at position 3 of the isoxazole ring are either hydroxymethyl or carboxyl, while alkenylterminated substituents have been inserted at position 5. A multi-step reaction sequence comprising the O-alkylation of 4-hydroxyacetophenone with the suitable alkenyl halide, the Claisen-type condensation with diethyl oxalate and the cyclization to isoxazole led to the isoxazole esters as key intermediates, which were subsequently reduced and hydrolyzed to the corresponding isoxazol-3-ylmethanols and isoxazole-3-carboxilic acids, respectively.

Keywords: liquid crystals, bent-core, ring closure, isoxazole

Pitofenone hydrochloride (PF.HCl) is a pharmaceutical substance used as an antispasmodic drug. The inclusion compounds of β-cyclodexdrin (β-CD) with pitofenone hydrochloride (PF.HCl) have been prepared by co precipitation and freeze-drying methods in order to increase the capacity user acceptance to wafer interest in terms of their taste. For physical chemical characterization the inclusion compounds were analyzed by powder X-ray diffraction, FTIR and ss-NMR spectroscopy, DSC, SEM and the structural architecture of the inclusion compound was proposed by molecular modeling techniques. The new product obtained can be used in the pharmaceutical industry because it provides improved smell and taste as compared to the starting substance.

Keywords: pitofenone hydrochloride, β-cyclodextrin, SEM, DSC, magnetic and FTIR spectroscopy, molecular modeling

The site at Suceag, Cluj county, Romania, is composed of three different overlapping settlements, each having its own chronology: the first one is dated during the time of the Roman province of Dacia, the second one dated between the second half of the 4th century and the beginning of the 5th century AD and the last one broadly dated during the 7th-8th century AD. Because of this particular situation, our first attempt was to determine whether some direct connections between them truly existed. The petrographic analysis performed on a series of 56 samples coming from different types of pottery established after analysing all the ceramic material coming from the settlement at Suceag (cca. 4500 pottery fragments) showed that in this case we are only dealing with local products. The colour of the analysed potsherds vary from grey to black indicating reducing atmosphere (25 samples), from reddish-brown to yellowish-brown (24 samples) suggesting an oxidizing atmosphere during firing and 7 samples have a “sandwich”-type structure probably an incomplete thermal treatment. The matrix is relatively uniform, with clasts of various sizes (up to 3-4 mm). Macroscopically, quartz grains, micas, and ceramoclast could be observed. According to the microscopic grain size, two types of ceramics can be separated: semifine (lutitic-siltic-arenitic), and coarse (lutitic-arenitic-siltic). Based on the ratio between crystalline vs. amorphous phases, microcrystalline, and microcrystallineamorphous fabrics were identified. As temper, crystalloclasts (quartz, micas, iron oxi-hydroxides, feldspars, amphibole, garnets, epidote, zircon), lithoclasts (quartzite, micaschist, gneiss, limestones), and ceramoclasts were identified. The observed bioclasts are represented by algae, and foraminifera remnants. The porosity consists of both primary, and secondary pores. The pore size vary from 0.5 x 1.5 mm to1.5 x 2.0 mm. Open porosity determined by water absorption capacity vary between 9.09 % - 23.10 %. The X-Ray diffraction analyses confirm the microscopic observations. According to the macroscopic aspects, microscopic features, and physical characteristics the firing temperature of the studied ceramic fragments is estimated to be between 800-900°C.

Keywords: ancient pottery, mineralogical and physical analysis, Suceag archaeological site, Romania.

In order to assess the potential human health risk associated with the transfer of heavy metals from contaminated soil to the trophic chain, several studies were conducted regarding the contaminants known to be associated to the non-ferrous ores processing industry in Eastern Baia Mare: Cu, Mn, Zn, Pb, Cd, Cr and Ni. The transfer of heavy metals into the trophic chain has the following order: from soil to vegetation: Zn>Cd>Cu>Mn>Pb>Cr>Ni and from vegetation to milk: Zn>Cu>Cd>Pb>Ni>Cr>Mn, respectively. Based on the human risk index (HRI) calculated for each element, it was demonstrated that the ingestion of milk from the cows grassed on the contaminated area does not pose a significant risk for human health.

Keywords: milk, heavy metals, food chain, human health risk

Wheat germs are valuable bread making ingredients, but their addition in bread loaf negatively influences the bread quality by increasing the hardness and decreasing the volume. In the context of modern baking industry, with high demands for bread with superior nutritional and sensorial quality, it clearly appears to be necessary to modulate the rheological properties of dough by using additives. In this study the influence of amylase, xylanase, glucose-oxidase and ascorbic acid on the wheat/ wheat germ flours dough and bread properties was studied. Initially, the assessment of wheat germ flour substitution (0-4%) on rheological properties and bread quality of three commercial wheat flours was determined. A substitution of 4% wheat germ flour was found to be acceptable. Secondly, the effect of improvers on dough rheology and on bread quality obtained by wheat flour/wheat germ flour blends was studied. Xylanase markedly improved the elasticity and porosity. Amylase significantly increased the crust color, the porosity and the bread specific volume. Glucose-oxidase effect is related to a higher bread specific volume, an improvement of the bread shape and crumb porosity. Ascorbic acid caused a significant increment of specific volume. Enzymes and ascorbic acid can be used to improve wheat germ bread quality.

Keywords: breadmaking improvers, farinographic and alveographic parameters

The adsorption behavior of natural and acid activated Montmorillonite clays from Maroua (Far North region of Cameroon) were studied by batch adsorption method. Carotene adsorption was monitored by measuring the absorbance of the mixture before and after adsorption experiments. The effect of contact time, temperature and initial carotene concentration were analyzed. It was found that the amount of carotene adsorbed increases with contact time and the adsorption equilibrium was attained after 30 min irrespective of the adsorbent used. Temperature has little effect on the adsorption process. The amount of β-carotene adsorbed at equilibrium increased with the initial carotene concentration. Kinetic modeling shows that experimental data follows pseudo-first order, pseudo-second order and intraparticle diffusion models. The line best fit was obtained with the pseudo second order diffusion model. Langmuir, Freundlich, and Temkin isotherms models were used to adjust the equilibrium data. The line best fit was obtained with the Freundlich model. The small values of the Freundlich constants and that of the energy constant of Temkin model revealed that the adsorption of carotene on clays is a physical process.

Keywords: Montmorillonite, carotene, palm oil, adsorption modelling.

The purpose of this study was to determine and analyse the chemical composition of essential oils of dry lavender flowers from the area of Budva and Rovinj and to compare to the results obtained in the commercially available sample in Montenegro. Based on gas chromatography (GC and GC/MS) analysis approximately 100 components were identified in the analysed samples, which makes 96.95% to 99.74% of the components present in essential oils. The analysis has shown that oxygenated monoterpenes were the dominant group of compounds. The significant difference in oxygenated monoterpene content between the samples from the area of Budva (71.74%) and Rovinj (91.79%) and the commercially available sample (87.63%) was noted. The most abundant oxygenated monoterpenes in the lavender oil sample from Budva region were linalool and borneol (27.32% and 20.24% respectively); the sample from Rovinj contained linalool and camphor (47.67% and 11.82% respectively) and commercial sample camphor and linalool (21.23% and 19.92% respectively). Monoterpene hydrocarbons were present in a significantly lower percentage in the commercial sample (2.64%) and in a sample from Rovinj (3.57%), while the high content occurred in the sample from the climate of Montenegrin seaside (Budva) (23.74%) with the dominant constituent β- phellandrene (19.1%). The oxygenated sesquiterpenes were slightly less present in the sample from Rovinj (1.14%) and Budva (1.88%), and almost twice as much present in the commercial sample (4.37%) represented with caryophyllene oxide as the dominant ingredient in all three samples; the samples from Rovinj, Budva and commercial ones contained 0.36%, 0.43% and 2.78% respectively. Hydrocarbon sesquiterpenes were insignificantly present in the analysed samples. Hydrocarbon sesquiterpenes were insignificantly presented in the commercial sample (0.83%); the sample from Budva (1.38%) and in a sample from Rovinj (1.66%). As the dominant constituent was sesquisabinen (1.0%) in the sample from Budva and trans-(E)-caryophyllene in a sample from Rovinj (0.58%) and commercial sample (0.22%).

Keywords: lavender, essential oil, isolation, identification, chemical composition

Abstract: The catalytic behavior of Ni/γ-Al2O3 catalyst modified with Cu, Ag, and Au was investigated in the process of ethanol steam reforming. The catalysts were prepared by co-impregnation and were characterized by specific surface area determination (SBET), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD) The data obtained from the experiments revealed that even at temperature as low as 350°C the ethanol is converted entirely, showing high selectivity for H2 and CH4.The activity of the Ni/γ-Al2O3 is only slightly increased by the addition of the supplementary metals. Nevertheless, the addition of metals to Ni/γ-Al2O3 has a positive effect in diminishing the quantity of CO2 produced in the reaction. The promoted alumina Ni catalysts present a higher stability in some experimental conditions.

Keywords: Ethanol steam reforming, Ni-catalysts, hydrogen production

Abstract: In this paper, a kinetic study about the oxidation of methanol to formaldehyde on Fe2O3-MoO3 oxide catalyst was investigated. Results about the changes of the conversion at different contact times and the way the composition of the mixture respectively temperature influence the oxidation process, is submitted. The parameters were elected so that they match with those of the existing industrial reactors. We analyzed the influence of the above mentioned parameters on the rate of the process. Processing the experimental results in ln k -T ^-1 coordinates allowed the determination of the activation energy and the establishment of the corresponding mechanisms. The results, Ea=57.23 kJ/mol, indicate that under 520K the mass transformation processes (chemical reaction, adsorption – desorption) are the limiting ones the oxidation process. At temperatures higher than 535K the value of the activation energy, Ea=9.39 kJ/mol, emphasizes that limiting are the inner/outer diffusion phenomena. In the temperature range 520K – 535K, when Ea=25 – 42 kJ/mol, the process is carried out after a combined macrokinetic model (mass transfer –transformation).

Keywords: methanol oxidation process, kinetic study, macrokinetic model

A rapid, accurate and economic procedure has been applied to extract and analyze trace level of ochratoxin A (OTA) in instant coffee. The OTA was extracted and cleaned-up by methanol extraction followed by retention on IRA-400 anion exchanger and quantified by Ultra Performance Liquid Chromatography (UPLC) with MS/MS detection. Under optimum conditions, the detection limit (S/N = 3) was 0.05 ng/g and recoveries of OTA at spiking levels of 5, 10, and 20 ng/mL, were 82.67 ± 8.05%, 96.87 ± 4.63%, and 98.25 ± 4.46% respectively.

Keywords: ochratoxin A; mycotoxin; instant coffee; contamination; UPLC-MS

Curcumin [1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6- heptadiene - 3,5-dione] is a phenolic substance derived from the root of the Curcuma longa L plant. It is used as antiproliferative, anti-invasive and antiangiogenic agent with anti-inflammatory functions, cancer chemopreventive activity and antioxidant properties. The aim of the study was to assess curcumin in rat plasma by HPLC with 425 nm UV detection at specified time intervals (15, 30, 60, 90, 120, 150, 180 minutes) in a treatment plan containing Curcumin in order to diminish acute muscular inflammation and oxidative stress. The concentration of curcumin in rat plasma was evaluated comparatively in a preventive plan (curcumin administration first, then induced inflammation) versus a therapeutic plan (induced inflammation followed by curcumin administration) on 6 adult female Wistar-Bratislava albino rats assigned to three groups. The HPLC results showed a decrease of curcumin concentration, with time, in all study groups. The statistical analysis (MANOVA) of the obtained data certified that the treatment plan applied to each group influenced the evolution of curcumin concentration in a significant way. A decrease in the amount of curcumin was noticed when inflammation occurred in the body, most probably determined by the accelerated metabolism in the presence of inflammation. The study of oxidative stress levels measured by the variables MDA and PC was performed in different rat tissues: muscle, liver and kidneys, for each study group and the highest results were registered in the muscle. The results obtained in both our research directions validated the antiinflammatory and antioxidant effect of curcumin.

Keywords: Curcumin, inflammation, HPLC, oxidative stress

The purpose of this electrone microscopy study was to identify and specify structural and ultrastructural changes occurring in the vulvar epithelium of ovariectomised female rats, as well as their reactivity to the administration of injectable oestrogens. We used 30 female Wistar white rats, distributed in four groups with 1 control group, to which oestrogenic treatment was administered. The hormone replacement therapy with injectable oestrogens (Estradiol, Estradurin, Sintofolin), at a dose of 0.2 mg/rat/day was administered for 14 days. Afterwards, all animals were sacrificed and vulvar biopsies were taken, which were then processed using optical microscopy (the semithin section technique) and transmission electron microscopy (TEM) techniques. This study showed that injectable oestrogen treatment over a period of 14 consecutive days enables the recovery of each tissue layer, with regard to the structural and ultrastructural modifications arising in ovariectomised female rats.

Keywords: oestrogens, optical microscopy, transmission electron microscopy, structure, atrophy, vulvar hyperplasia

The clinical success of aesthetic ceramic fused to metal or composite resin bonded to metal restorations depends on the quality and strength of composite/ceramic bonding. To investigate the ceramic and composite surface adhesion to the surface of the alloys, samples were prepared by metallographic techniques and then were analyzed by Scanning Electron Microscopy (SEM). We studied a total of four samples of superalloys, denoted S1, S2, S3, and S4. Each of these was treated with: Vita ceramic powders, Noritake ceramic powders, Premise Indirect composite and an indigenous composite C1. At a magnification level of x1500, the adherence between the layers and the surface irregularities of the layers that improve the adherence could be properly observed. It is worth noting that after the sample preparation procedure, samples S1, S2 and S4 were damaged, the only sample remaining in a good condition was sample S3.

Keywords: Superalloys, Composite, Ceramic Materials, Microstructural Analysis, Scanning Electron Microscopy

The aim of this study was to assess the ability of chromophore to improve laser whitening procedures on bovine teeth. The teeth were previously stained with black tea. We evaluated the color change with the help of the Vita Easy Shade Spectrophotometer. Two batches of four teeth were prepared and immersed for 14 days in a solution of black tea. For the bleaching, an experimental gel was used. Batch I was kept in the gel without chromophore and batch II in the gel with chromophore. The teeth from both batches were kept for 30 sec in the gel and were afterwards irradiated with a diode laser (980nm). The statistical analysis showed significant differences between T1 (the measurement of the color after the staining process) and T2 (the measurement of color after the whitening process) for the first batch and T0 (the initial measurement of the color of the teeth) and T2 (the measurement of color after the whitening process) for the second batch.

Keywords: dental bleaching, laser, bovine teeth, experimental gel

This study presents the evolution of specific parameters of raw water quality from the Strâmtori-Firiza Lake, which is the raw water source of the water plant in Baia Mare town, Romania. Parameters such as temperature, turbidity, oxidability were recorded over a four years interval. A comprehensive database on the evolution of these water parameters was thus created showing the tendency of these parameters across time. The possible correlations among the parameters were investigated. Positive correlations were found for oxidability and Al content and also for turbidity and oxidability. Temperature and turbidity were found to be highly variable (2-17°C, 3-53 NTU) across seasons. In order to improve the turbidity of treated water, two coagulants were tested: basic polyaluminum chloride (PAC) and aluminum sulphate (SA) evaluating the efficiency of the two treatment methods. While the traditionally used aluminum sulphate was found to be effective only when the temperature and turbidity were high: temperature >10ºC, turbidity >10 NTU (nephelometric turbidity unit), PAC emerged as an efficient clarifying agent even at low temperature and turbidity.

Keywords: treatment, drinking water, polyaluminum chloride, coagulation

Improved dental materials are a requirement in these modern times, because of the highly percent of dental decay found at children. Four commercial pit and fissure sealants have been studied in respect of water sorption and solubility (1, 3, 7 and 14 days).These measurements prove the stability of a material, as well as the adhesion to enamel and the resistance to wear. The materials taking into account are two resin- based sealants - Fotoseal® (Babeş- Bolyai University, Raluca Ripan Chemistry Research Institute), Fissurit FX® (VoCo), one gass-ionomer - Fuji Triage® (GC Fuji) and one compomer - Dyract Seal® (Dentsply). The statistical analysis used a Mixt ANOVA design, with the significance level set at p ≤0.01. Firstly, there were analised the differences between the days of measurement, without taking into account the material type. Secondly, there were examined the differences between materials and finally, the interaction between material type and day of measurement. We also calculated the magnitude of the clinical effect of material type, on each of the days of measurement. Differences in chemical composition determine a modified behavior of these materials. The results showed that Fissurit FX had the lowest values of water sorption and solubility, closely followed by Fotoseal. Dyract Seal had higher values. In the same time, Fuji Triage showed the highest rates for water sorption and a fluctuant behavior concerning solubility, with increased level in the first day of measurement, decreased values in the next days (3, 7) and another small enhancement in the last day of measurement (14).

Keywords: dental materials, composite resin, glass-ionomers, compomer, water sorption, solubility

New E-glass fiber reinforced composites developed to serve cranio-facial bone reconstruction were investigated using scanning electron microscopy, atomic force microscopy and X ray diffraction to evaluate their morphology and structure. The morphological analysis of the external surface of experimental composite materials has shown that the reinforcing material was well incorporated in the polymer matrix and no monofilaments of fiber glass could be observed on the material surface. Structure analysis of the experimental composites revealed the optimal interfacial adhesion obtained using A 174 silane. Woven E glass fibers were more favourable than unidirectional fibers for manufacturing cranio-facial implants. The flexural strength of the experimental composite materials was directly influenced by the degree of reinforcement. Taking into account the obtained results, the perspective of continuing the studies appears for improving the mechanical properties so as to be as close as possible to the ones of the human bone.

Keywords: biocomposites, reconstructive surgery, surface, interface, bending test, scanning electron microscopy, atomic force microscopy, elemental distribution

This study was conducted to review the current scientific literature regarding the fixing systems for CAD-CAM prosthetic restoration. An electronic search was conducted for relevant articles using PubMed database followed by manual search, with the following association of terms: (CAD CAM, cements) then (CAD CAM, cements, bonding) and finally (CAD CAM, cements, bonding agents). The study included articles published between 01.01.1995 and 01.09.2015. A table was designed for this review with the following information: authors, CAD-CAM system used, fixing agent/agents used, restoration type and abutment type. The most studied dental CAD-CAM system was Cerec and the most used fixing agent was RelyX. In summary, the objective of any surface treatment method is to enhance the adhesive bond strength and durability.

Keywords: CAD CAM, crowns, dental cements, bonding agents