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The present paper deals with investigation of the interaction between selected simple structure Au(iii) ([AuCl4](-), [AuCl2(dmso)(2)](+), [AuCl2(bipy)](+)) and Pt(ii) ([PtCl2(dmso)(2)]) complexes with Na/K-ATPase as the target enzyme, using an experimental and theoretical approach. Reaction stoichiometries and binding constants for these enzyme/complex systems were determined, while kinetic measurements were used in order to reveal the type of inhibition. Based on the results obtained by quantum mechanical calculations (electrostatic surface potential (ESP), volume and surface of the complexes) the nature of the investigated complexes was characterized. By using the solvent accessible surface area (SASA) applied on specific inhibitory sites (ion channel and intracellular domains) the nature of these sites was described. Docking studies were used to determine the theoretical probability of the non-covalent metal binding site positions. Inhibition studies implied that all the investigated complexes decreased the activity of the enzyme while the kinetic analysis indicated an uncompetitive mode of inhibition for the selected complexes. Docking results suggested that the main inhibitory site of all these complexes is located in the ion translocation pathway on the extracellular side in the E2P enzyme conformation, similar to the case of cardiac glycosides, specific Na/K-ATPase inhibitors. Also, based on our knowledge, the hydrolyzed forms of [AuCl4](-) and [PtCl2(dmso)(2)] complexes were investigated for the first time by theoretical calculations in this paper. Thereby, a new inhibitory site situated between the M2 and M4 helices was revealed. Binding in this site induces conformational changes in the enzyme domains and perturbs the E1-E2P conformational equilibrium, causing enzyme inhibition.

The authors regret that the author names were not displayed correctly on the original manuscript. The corrected list of authors for this paper is as shown above. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

Due to controversial reports concerning antibacterial activity of different graphene based materials it is very important to investigate their antibacterial action on a wide range of Gram-positive and Gram-negative bacteria. In this paper we have investigated the structure induced phototoxic antibacterial activity of four types of graphene based materials: graphene oxide (GO), graphene quantum dots (GQDs), carbon quantum dots (CQDs) and nitrogen doped carbon quantum dots (N-CQDs). Antibacterial activity was tested on 19 types of bacteria. It is found that nanometer-size CQDs and N-CQDs are the most potent agents whereas micrometer-size GO has very poor antibacterial activity. Electron paramagnetic resonance measurements confirmed photodynamic production of singlet oxygen for all types of used quantum dots. Detailed analysis has shown that N-CQDs are an excellent photodynamic antibacterial agent for treatment of bacterial infections induced by Enterobacter aerogenes (E. aerogenes), Proteus mirabilis (P. mirabilis), Staphylococcus saprophyticus (S. saprophyticus), Listeria monocytogenes (L. monocytogenes), Salmonella typhimurium (S. typhimurium) and Klebsiella pneumoniae.

Usnic acid, a dibenzofuran, was originally isolated from lichens producing secondary metabolites, and is well known as an antibiotic, but is also endowed with several other interesting properties. Thus, the goal of this paper is the design of new usnic acid derivatives and evaluation of their antimicrobial activity. All newly synthesized compounds possess good antibacterial activity with MIC ranging from 1.02-50.93 x 10(-2) mmol mL(-1) and MBC from 2.05-70.57 x 10(-2) mmol mL(-1). The most sensitive bacterial species was Staphylococcus aureus, while Pseudomonas aeruginosa and Escherichia coli were the most resistant among the ATCC strains, and MRSA was the most resistant among all tested bacteria (ATCC and clinical isolates). Their antifungal activity was very strong (MIC = 0.35-7.53 x 10(-2) mmol mL(-1) and MFC = 0.70-15.05 x 10(-2) mmol mL(-1)) - better than those of reference compounds and usnic acid itself. The most sensitive fungal species was Trichoderma viride, while Penicillium versicolor var. cyclopium appeared to be the most resistant. It should be mentioned that in general most of the compounds showed weaker antibacterial activity, but better antifungal properties than usnic acid itself. The results allow us to conclude that the title compounds are good lead compounds for novel more active antibacterial drugs. On the other hand, these compounds are very promising as antifungals.

This paper presents a pedagogical experiment with parallel groups through which the effectiveness of the cognitive apprenticeship model of dealing with the teaching topic Carboxylic acids and their derivatives was compared with the traditional approach to the elaboration of this topic. This experiment featured the participation of 241 students aged 17, attending their third year of grammar school, natural sciences stream. The experimental group consisted of 118 students, whereas the control group was made up of 123 students. Within the framework of the experiment, a pre-test consisting of items that resembled regular textbook items was used as an instrument for checking how balanced the previously acquired knowledge concerning the teaching topic Carboxylic acids and their derivatives of the students in the two groups was. A post-test was used as an instrument for comparing the effectiveness of the two approaches, and it mostly consisted of items that required the application of the knowledge concerning the teaching topic Carboxylic acids and their derivatives in solving real-life problems. In the pre-test, no statistically significant difference in the overall percentage of correct answers given by the two groups of students was established. In the post-test, the students from the experimental group scored a statistically significant higher percentage of correct answers compared to the students from the control group. On the basis of this, it can be concluded that the applied cognitive apprenticeship approach has the potential to improve the level of students' understanding of the concepts from the topic Carboxylic acids and their derivatives, as well as the students' ability to apply the knowledge on the examples from real life.

Modified allergens are a safer and more efficient alternative to natural allergens for specific immunotherapy. As the modification of an allergen can diminish its immunogenicity due to the alteration of T-cell epitopes, in this paper we study the effects of a reversible chemical modification of Art v 1, the main allergen of mugwort pollen, on its allergenicity and immunogenicity. Modification of Art v 1 by cis-aconitylation into a polyanionic derivative (CAA) did not result in any significant structural alteration. However, IgE-binding epitopes on CAA were blocked, resulting in a reduced IgE-binding and basophil activation. Both proteins induced proliferation of CD3(+)CD4(+) T-cells in mugwort-allergic patients, but only unmodified allergens increased IL-4, IL-5 and IL-10 production. Rabbit and mouse anti-CAA antibodies exhibited cross-reactivity with native allergens and blocked human IgE-binding to Art v 1. Degradation of CAA by lysosomal fraction enzymes resulted in a similar set of peptides, harboring MHC class II-binding peptides, as unmodified proteins. Thus, cis-aconitylation modified Art v 1 had a significantly reduced allergenicity, whereas its immunogenicity was completely preserved. Acid-environment-responsive modification, which releases a full repertoire of native allergen epitopes within a particular site, can be considered a smart drug delivery system, which is able to deliver a therapeutically-effective dose in a controlled manner, and minimizes adverse side effects.

This paper describes the results achieved by high school seniors on an item which involves translation of the equation P = kT into a corresponding pictorial external representation. The majority of students (the classes of 2011, 2012 and 2013) did not give the correct answer to the multiple choice part of the translation item. They chose pictorial representations of the other gas laws (P = k/V, or V = kT) instead. Failure to choose the correct answer was surprising considering that the symbol for volume was absent which should have been the key clue. Through the analysis of students' explanations (the classes of 2011 and 2012) and interviews (the class of 2013) we considered the reasoning applied by students who chose the correct answer or distractors for the multiple choice part of the item. Among the students who answered correctly there were explanations which contained misconceptions. Several factors that lead to the unsuccessful translation between external representations have been discovered. Students interpreted the change in one quantity based on the notation for the change in another one because of deep rooted cognitive schemas about changing two quantities (volume and pressure, pressure and temperature, temperature and volume), without consideration that for such changes to be valid for gases all three quantities need to be considered for a certain amount of substance. Those cognitive schemas interfered with mathematical reasoning, i.e. students possessed limited understanding of the equations.

Information about the strength of donor-acceptor interactions in push-pull alkenes is valuable, as this so-called "push-pull effect'' influences their chemical reactivity and dynamic behaviour. In this paper, we discuss the applicability of NMR spectral data and barriers to rotation around the CQC double bond to quantify the push-pull effect in biologically important 2-alkylidene-4-oxothiazolidines. While olefinic proton chemical shifts and differences in C-13 NMR chemical shifts of the two carbons constituting the CQC double bond fail to give the correct trend in the electron withdrawing ability of the substituents attached to the exocyclic carbon of the double bond, barriers to rotation prove to be a reliable quantity in providing information about the extent of donor-acceptor interactions in the push-pull systems studied. In particular all relevant kinetic data, that is the Arrhenius parameters ( apparent activation energy Ea and frequency factor A) and activation parameters ( Delta S-double dagger, Delta H-double dagger and Delta G(double dagger)), were determined from the data of the experimentally studied configurational isomerization of ( E)-9a. These results were compared to previously published related data for other two compounds, ( Z)-1b and ( 2E, 5Z)-7, showing that experimentally determined Delta G(double dagger) values are a good indicator of the strength of push-pull character. Theoretical calculations of the rotational barriers of eight selected derivatives excellently correlate with the calculated CQC bond lengths and corroborate the applicability of Delta G(double dagger) for estimation of the strength of the push-pull effect in these and related systems.

The aim of this study was to investigate the survival of probiotics (Lactobacillus acidophilus NCFM, Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019) in milk chocolate masses prepared at temperatures 35 degrees C and 40 degrees C. The influence of probiotics and preparation temperature on rheology, particle size distribution and sensory properties of the chocolates, was examined during 6 months of storage at 20 +/- 2 degrees C. An inoculation temperature of 40 degrees C significantly improves the rheological and sensory properties of probiotic chocolate, as well as leading to the survival of L. acidophilus NCFM and L. rhamnosus HN001 strains. After 6 months of storage, the survival of these strains was above 90%, with a viable cell count of about 8.1 log(CFU g(-1)). An inoculation temperature of 40 degrees C provides higher scores of overall sensory quality (4.52-4.68), higher quality category (excellent), lower maximal viscosity (for 1.2 Pa s) of chocolates, than a temperature of 35 degrees C. Compared to the chocolate without probiotics, those inoculated at 40 degrees C achieved less increase in volume weighted mean diameter distribution (average 0.8%) than chocolates inoculated at 35 degrees C. Based on the results reported in this paper, seeding of the probiotics in industrial conditions can be done in the mixing tank (at 40 degrees C) before the phase of chocolate shaping. Addition of probiotics at this stage facilitates the manufacturing process, improves the overall quality of chocolate and preserves the probiotics as a key component of this type of product.

This paper reports a droplet-based microfluidic approach to fabricate a large number of monodisperse, portable microtissues, each in an individual drop. We use water-water-oil double emulsions as templates and spatially assemble hepatocytes in the core and fibroblasts in the shell, forming a 3D liver model in a drop.

This paper describes an electroanalytical method for the determination of metribuzin using a thin film mercury electrode by chronopotentiometry. Research included optimization of the most important parameters of chronopotentiometric analysis and the best responses were achieved in Britton-Robinson buffer at pH 5.0, using an initial potential of -0.21 V, ending potential of -1.1 V, and reduction current in the range from -4 mu A to -15 mA. Under these conditions, metribuzin was reduced in an irreversible electrode reaction process with one well-defined reduction wave at -0.83 V (vs. Ag/AgCl, KCl, 3.5 mol dm(-3)). A linear response was observed for three concentration ranges 1-5, 5-15 and 15-30 mg dm(-3), with an achieved limit of detection of 0.042 mg dm(-3). The precision was determined as a function of repeatability and reproducibility, which showed relative standard deviation values not higher than 3.18%. Various interfering substances did not interfere with metribuzin determination. The proposed method was successfully applied to tap and river water samples. The recovery values obtained for spiked river water samples were in good statistical agreement with those obtained by the LC-MS/MS method. Accordingly, the proposed chronopotentiometric methodology can be conveniently applied in the quality control of environmental water samples as a simple, sensitive, reliable and low cost method.

The electrochemical exfoliation of graphite to give one-atom-thick graphene with desirable properties is a green, cost-effective method for high-yield graphene production. This paper presents the results of electrochemical exfoliation of two different graphite precursors under an applied direct current voltage of +12 V. The used characterization techniques (elemental analysis, Fourier transform infrared spectroscopy, X-ray diffraction, X-photoelectron spectroscopy, Raman spectroscopy, field emission scanning electron microscopy and atomic force microscopy) showed that the exfoliated powder is highly functionalized with a low carbon/oxygen content that is similar to graphene oxide. The exfoliated graphene sheets dispersed in N,N'-dimethylformamide were deposited on ano-discs by vacuum filtration and transferred to glass ceramic substrates. The thermal annealing of the as-deposited films at 600 degrees C for 30 minutes resulted in an increase in the carbon/oxygen ratio by more than 3 fold and a decrease in the sheet resistance by 25%. The lowest values for the sheet resistance of the annealed graphene thin films were in the range of 0.32 +/- 0.04 to 0.84 +/- 0.1 kohm sq(-1) depending on the graphite source that was used.

Nano-sized particles of monoclinic-LaVO4 were prepared in a short reaction time of 30 minutes by employing a microwave assisted hydrothermal synthesis in the presence of glycerol, which was used both as a solvent and structure-directing agent. The tetragonal-LaVO4 is known to show strong luminescence properties when doped with Ln(3+), whereas the monoclinic-LaVO4 is usually considered not suitable for luminescence and therefore luminescence properties of monoclinic-LaVO4 doped with Ln(3+) ions are seldom investigated. Due to the scarce amount of research on the topic of luminescence of Ln(3+) doped monoclinic-LaVO4 in this paper a detailed study of solid state luminescence properties, including quantum yields, of nano-sized monoclinic-LaVO4 doped with different molar percentages of Eu3+ is presented. It was observed that the 12.5% Eu3+ doped sample showed the strongest luminescence properties. Additionally a study of the influence of different rare-earth ions (Y3+, Gd3+, Lu3+) co-doped into the particles was performed in order to explore the potential of increasing the luminescence of these materials. Furthermore stable colloidal suspensions of the Eu3+ doped monoclinic-LaVO4 nanoparticles showing strong red emission could be obtained.