Antioxidant protection in cultured corneal cells and whole corneas submitted to UV-B exposure

Several corneal pathologies are characterized by the presence of reactive oxygen species (ROS); therefore, we evaluated the protection afforded by pirenoxine and melatonin to corneal cell culture and whole rabbit cornea from ultraviolet exposure and other oxidant systems. Rabbit cornea cell (SIRC) plates and whole corneas were exposed to UV-B (80 or 800 mJ/cm2) or incubated with fMLP-stimulated autologous macrophages, in the presence or absence of pirenoxine or melatonin (10(-5) M). The protective activity of compounds was assessed by measuring superoxide anion formation, inhibition of oxidation and mitochondrial viability. Moreover the ex vivo protective effect of pirenoxine and melatonin was verified in the whole cornea submitted to UV-B exposure in vitro. Our experimental data demonstrate that pirenoxine and melatonin were able to inhibit the superoxide formation and oxidative effect in cell culture and whole rabbit corneas submitted to UV-B exposure or to incubation with fMLP-stimulated autologous macrophages. Mitochondrial viability was restored in epithelial cells of rabbit cornea but not in SIRCs. Moreover, both compounds are also able to increase ex vivo epithelial corneal cell defences against the in vitro UV-B induced lipid peroxidation.     

Cyclization reactions of 1,3-dibromopropan-2-ol, 2,3-dibromopropan-1-ol and 1-bromomethyloxirane with 6-amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone

The cyclization reactions, carried out in strongly- or weakly-basic media, are described. Sometimes, 7-amino-2,3-dihydro-3-hydroxymethyl-5H-thiazolo[3,2-a]pyrimidin-5-one is separated out, together with 8-amino-3,4-dihydro-3-hydroxy-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-one, as the principal product. A mechanism of reaction, during which the cyclizating agents are changed into oxirane derivatives, is proposed. The results of single-crystal X-ray investigations on 8-amino-3,4-dihydro-3-hydroxy-7-nitroso-2H,6H-pyrimido[2,1-b][1,3]thiazin-6-one (R = 0.035 for 1013 reflections), and on 7-hydroxymethyl-6,7-dihydrothiazolo[3,2-a][1,2,3]triazolo[4,5-d]pyrimidin-9(1H)-one (R = 0.027 for 1607 reflections) are reported.     

Iridium cyclometalated complexes with axial symmetry: time-dependent density functional theory investigation of trans-bis-cyclometalated complexes containing the tridentate ligand 2,6-diphenylpyridine

A new series of iridium cyclometalated complexes with a C/N/C dppy-type ligand and a N/N/N tpy-type ligand have been synthesized and characterized by various techniques such as mass spectrometry, 1H and 13C NMR, cyclic voltammetry, both steady-state and time-resolved emission and absorption studies, and time-dependent DFT (TDDFT) calculations. The complexes exhibit strong visible absorptions and long-lived (1.6-2.0 micros) emissions (lambdamax, ca. 680 nm) in room-temperature solution. DFT calculations on the ground-state geometry match that of an X-ray crystal structure. TDDFT calculations give accurate predictions of the electronic absorption energies and intensities, while geometry optimizations on the lowest energy triplet state give accurate energies for the emission. Examination of the relevant molecular orbitals shows that the inherent asymmetry of the coordination environment offers a unique directional character to the emitting excited state, which is predominately LLCT (dppy --> tpy) in nature.     

Bioactive polymeric materials for targeted administration of active agents: synthesis and evaluation

Bioerodible polymers displaying both stealth and targeting properties for the preparation of nanosystems for targeted and controlled delivery of fibrinolytic drugs to the thrombus were prepared by straightforward synthetic routes and characterized. Poly[(maleic anhydride)-alt-(butylvinyl ether)]s were synthesized in the presence of dodecyl mercaptan as chain transfer agent allowing for the preparation of copolymers with tunable molecular weight. 2-Methoxyethanol hemiesters containing antiopsonizing molecules of poly(ethylene glycol) were prepared and further biofunctionalized with a Fab fragment by a two-step reaction. In vitro biocompatibility investigation of the prepared materials supported their suitability for biomedical applications.     

Opportunity to learn in the preparation of mathematics teachers: its structure and how it varies across six countries

Cross-national research studies such as the Program for International Student Assessment and the Third International Mathematics and Science Study (TIMSS) have contributed much to our understandings regarding country differences in student achievement in mathematics, especially at the primary (elementary) and lower secondary (middle school) levels. TIMSS, especially, has demonstrated the central role that the concept of opportunity to learn plays in understanding cross-national differences in achievement Schmidt et al., (Why schools matter: A cross-national comparison of curriculum and learning  2001). The curricular expectations of a nation and the actual content exposure that is delivered to students by teachers were found to be among the most salient features of schooling related to academic performance. The other feature that emerges in these studies is the importance of the teacher. The professional competence of the teacher which includes substantive knowledge regarding formal mathematics, mathematics pedagogy and general pedagogy is suggested as being significant—not just in understanding cross-national differences but also in other studies as well (Hill et al. in Am Educ Res J 42(2):371–406, 2005). Mathematics Teaching in the 21st Century (MT21) is a small, six-country study that collected data on future lower secondary teachers in their last year of preparation. One of the findings noted in the first report of that study was that the opportunities future teachers experienced as part of their formal education varied across the six countries (Schmidt et al. in The preparation gap: Teacher education for middle school mathematics in six countries, 2007). This variation in opportunity to learn (OTL) existed in course work related to formal mathematics, mathematics pedagogy and general pedagogy. It appears from these initial results that OTL not only is important in understanding K-12 student learning but it is also likely important in understanding the knowledge base of the teachers who teach them which then has the potential to influence student learning as well. This study using the same MT21 data examines in greater detail the configuration of the educational opportunities future teachers had during their teacher education in some 34 institutions across the six countries.     

Detection of the R553X DNA single point mutation related to cystic fibrosis by a "chiral box" D-lysine-peptide nucleic acid probe by capillary electrophoresis

In order to recognize the presence of the R553X point mutation of the cystic fibrosis (CF) gene in the human genome, a peptide nucleic acid (PNA) complementary to the mutated gene tract and bearing three adjacent chiral monomers based on D-lysine (chiral box) was synthesized and used as a probe in CE. Binding specificity was preliminarily studied with complementary and mismatched oligonucleotides by UV spectroscopy, electrospray MS, and electrophoresis, indicating a very high sequence selectivity. The chiral PNA probe was then hybridized to cyanine-5-labeled DNA samples (186 bp), obtained by PCR amplification, respectively, from: (a) normal homozygous subjects (wtDNA), (b) CF-affected homozygous subjects (mutDNA), (c) heterozygous subjects (healthy carriers) and denatured at low ionic strength. The PNA-DNA mixture was directly analyzed by CE with LIF detection: a new signal corresponding to the PNA-mutDNA duplex was observed, in the case of CF-affected homozygous subjects, whereas for the sample containing the mismatched sequence (normal homozygous wtDNA) only the signal corresponding to ssDNA (ss, single strand) was detected. In the case of heterozygous DNA, both PNA-mutDNA duplex and ssDNA were detected. With this simple assay, it was possible to discriminate in an easy way among the three cases (mutated homozygous, normal homozygous, and heterozygous subjects) with a total specificity, thus allowing a decisive advance for the diagnosis of CF.     

PHOTOOXIDATION OF HORSE AND SPERM-WHALE MYOGLOBIN SENSITIZED BY THE HEME GROUP

Abstract —The irradiation of horse and sperm-whale Fe 3 * or Fe 2* myoglobins with visible light showed that axial ligands that render the heme diamagnetic (e.g. O₂, CO or CN^-) endow the hemoproteins with a marked photosensitivity. In contrast, high-spin myoglobins are unaffected by visible light. These findings appear to be of general validity for all hemo-proteins and are in agreement with the involvment of the triplet state of the heme as the reactive intermediate. In all cases, the overall photoprocess occurs within a very narrow spatial range, leading to specific modification of these photooxidizable side chains adjacent to the chromophore. Therefore, this technique can be used to probe the environment of the prosthetic group in hemoproteins. In particular, our data suggest that, in horse myoglobin, histidines-93 and -64 represent the heme-linked and the distal imidazole groups, respectively; moreover, the thioether function of methionine-131 must be nearer the heme in horse than in sperm-whale myoglobin. The selectivity of the photoreaction can be further enhanced by a suitable choice of the sixth ligand, and/or by controlling the pH of the irradiated solution. For example, for both proteins, irradiation of the cyanide derivative results in specific photooxidation of the proximal histidine, whereas irradiation of horse CO-ferromyoglobin at pH values below 6 causes specific photooxidation of methionine-131. Consequently, this photooxidative procedure can also be utilized to monitor conformational changes upon binding of the heme with different ligands, as well as to achieve the selective modification of amino acid residues, which are usually buried inside the protein molecule.     

Combined mass quantitation and phenotyping of intact extracellular vesicles by a microarray platform

The interest towards extracellular vesicles (EVs) has grown exponentially over the last few years; being involved in intercellular communication and serving as reservoirs for biomarkers for tumors, they have a great potential for liquid biopsy development, possibly replacing many costly and invasive tissue biopsies.