Orbital dependent coherence temperature and optical anisotropy of V2O3 quasiparticles.

We report on an orbital and temperature dependent study of the onset of coherent quasiparticles in V2O3 single crystal. By using polarized infrared spectroscopy we demonstrate that the electronic coherence temperature is strongly orbital dependent, being about 400 K for [Formula: see text] orbitals and 500 K for the [Formula: see text]. This suggests that V2O3 low energy electrodynamics can be described in terms of two electron liquids differently renormalized by electronic correlations.

Terahertz plasmonic excitations in Bi2Se3 topological insulator.

After the discovery of Dirac electrons in condensed matter physics, more specifically in graphene and its derivatives, their potentialities in the fields of plasmonics and photonics have been readily recognized, leading to a plethora of applications in active and tunable optical devices. Massless Dirac carriers have been further found in three-dimensional topological insulators. These exotic quantum systems have an insulating gap in the bulk and intrinsic Dirac metallic states at any surface, sustaining not only single-particle excitations but also plasmonic collective modes. In this paper we will review the plasmon excitations in different microstructures patterned on Bi2Se3 topological insulator thin films as measured by terahertz spectroscopy. We discuss the dependence of the plasmon absorption versus the microstructure shape, wavevector, and magnetic field. Finally we will discuss the topological protection of both the Dirac single-particle and plasmon excitations.

Adverse drug reactions associated with off-label use of ketorolac, with particular focus on elderly patients. An analysis of the Italian pharmacovigilance database and a population based study.

OBJECTIVE: This study aims to evaluate the frequency of off-label use of ketorolac in Italy and the related suspected adverse drug reactions (ADRs) reported. METHODS: All the suspected cases associated with ketorolac recorded in the Italian Pharmacovigilance database were retrieved. Case evaluations were carried out in order to identify the off-label use of ketorolac. Moreover, an analysis of the inappropriate use of ketorolac was conducted using the 'Arianna' database of Caserta local health unit. RESULTS: Up to December 2014, 822 reports of suspected ADRs related to ketorolac were retrieved in the database. The use of ketorolac was classified as off-label for 553 reports and on-label for 269. Among the off-label cases, 58.6% were serious compared to 39.0% of on-label cases. Gastrointestinal events were more frequently reported with off-label use. The analysis of Arianna database showed that 37,729 out of 61,910 patients, were treated off-label. CONCLUSIONS: The off-label use of ketorolac is widespread in Italy. This use increases the risk of serious ADR, especially in in case of prolonged duration of treatment and in elderly patients. The Italian Medicine Agency has decided to accurately monitor the appropriate use of the drug in Italy and, if necessary, take measures in order to minimize the risks.

Medication is an additional source of phosphate intake in chronic kidney disease patients.

BACKGROUND AND AIMS: Hyperphosphatemia increases the risk of cardiovascular morbidity but the use of medicines as a source of phosphate has not been investigated yet. This study aims to explore the use of absorbable phosphate-containing drugs in CKD patients. METHODS AND RESULTS: Incident CKD patients were identified within the Arianna database (containing data from 158,510 persons in Caserta (Southern Italy) registered with 123 general practitioners) from 2005 to 2011. Drugs prescribed to these patients were classified as phosphate-containing based on the summary of product characteristics (SPC), PubChem and Micromedex. The number and duration of prescriptions for these drugs as well as the overall intake of phosphate were estimated. Out of 1989 CKD patients, 1381 (70%) were prescribed 266 medicinal products containing absorbable phosphate over a median follow-up of 6 years (interquartile range (IQR) = 5.2-6.0). Most patients were prescribed ATC A (650; 47.1%) and C (660; 47.8%) phosphate-containing drug products targeting the gastrointestinal and cardiovascular system for a median of 232 (IQR: 56-656) and 224 (IQR: 56-784) days respectively. CONCLUSIONS: Several medications, especially chronically prescribed ones, contain absorbable phosphate. This study's findings confirm the relevance of medicines as a phosphate source for the first time.

Observation of Dirac plasmons in a topological insulator.

Plasmons are quantized collective oscillations of electrons and have been observed in metals and doped semiconductors. The plasmons of ordinary, massive electrons have been the basic ingredients of research in plasmonics and in optical metamaterials for a long time. However, plasmons of massless Dirac electrons have only recently been observed in graphene, a purely two-dimensional electron system. Their properties are promising for novel tunable plasmonic metamaterials in the terahertz and mid-infrared frequency range. Dirac fermions also occur in the two-dimensional electron gas that forms at the surface of topological insulators as a result of the strong spin-orbit interaction existing in the insulating bulk phase. One may therefore look for their collective excitations using infrared spectroscopy. Here we report the first experimental evidence of plasmonic excitations in a topological insulator (Bi2Se3). The material was prepared in thin micro-ribbon arrays of different widths W and periods 2W to select suitable values of the plasmon wavevector k. The linewidth of the plasmon was found to remain nearly constant at temperatures between 6 K and 300 K, as expected when exciting topological carriers. Moreover, by changing W and measuring the plasmon frequency in the terahertz range versus k we show, without using any fitting parameter, that the dispersion curve agrees quantitatively with that predicted for Dirac plasmons.

Inactivation of aldophosphamide by human aldehyde dehydrogenase isozyme 3.

Tumors resistant to chemotherapeutic oxazaphosphorines such as cyclophosphamide often overexpress aldehyde dehydrogenase (ALDH), some isozymes of which catalyze the oxidization of aldophosphamide, an intermediate of cyclophosphamide activation, with formation of inert carboxyphosphamide. Since resistance to oxazaphosphorines can be produced in mammalian cells by transfecting them with the gene for human ALDH isozyme 3 (hALDH3), it seems possible that patients receiving therapy for solid tumors with cyclophosphamide might be protected from myelosuppression by their prior transplantation with autologous bone marrow that has been transduced with a retroviral vector causing overexpression of hALDH3. We investigated whether retroviral introduction of hALDH3 into a human leukemia cell line confers resistance to oxazaphosphorines. This was examined in the polyclonal transduced population, that is, without selecting out high expression clones. hALDH3 activity was 0.016 IU/mg protein in the transduced cells (compared with 2x10(-5) IU/mg in untransduced cells), but there was no detectable resistance to aldophosphamide-generating compounds (mafosfamide or 4-hydroperoxycyclophosphamide). The lack of protection was due, in part, to low catalytic activity of hALDH3 towards aldophosphamide, since, with NAD as cofactor, the catalytic efficiency of homogeneous, recombinant hALDH3 for aldophosphamide oxidation was shown to be about seven times lower than that of recombinant hALDH1. The two polymorphic forms of hALDH3 had identical kinetics with either benzaldehyde or aldophosphamide as substrate. Results of initial velocity measurements were consistent with an ordered sequential mechanism for ALDH1 but not for hALDH3; a kinetic mechanism for the latter is proposed, and the corresponding rate equation is presented.

Coding region-specific destabilization of mRNA transcripts attenuates expression from retroviral vectors containing class 1 aldehyde dehydrogenase cDNAs.

Class 1 aldehyde dehydrogenases (ALDH-1) function as drug resistance gene products by catalyzing the irreversible conversion of aldophosphamide, an active metabolite of cyclophosphamide, to an inert compound. Because the dose-limiting toxicity of cyclophosphamide is myelosuppression, retrovirus-mediated transfer of ALDH-1 to bone marrow cells has been proposed as a protective strategy. Here we show that expression of ALDH-1 vectors was problematic due to low levels of ALDH-1 mRNA accumulation. A number of vectors containing several different ALDH-1 cDNAs were introduced into a variety of different cell lines either by transfection or transduction. Detectable ALDH-1 protein and enzyme activity was only seen in one transfected cell clone. Cells transduced with ALDH-1 retroviral vectors had no detectable protein expression and very low levels of ALDH-1 mRNA. Analogous vectors containing other drug resistance cDNAs led to much higher levels of steady-state mRNA. The mRNA half-life from ALDH-1 vectors was less than 2 hr suggesting that vector-derived mRNAs were destabilized by ALDH-1 coding sequences. These results suggest that methods which increase the stability of ALDH-1 mRNAs will be important for increased drug resistance in retrovirally transduced hematopoietic cells.

Mapping the mechanism-based modification sites in L-aspartase from Escherichia coli.

Inactivation of the enzyme L-aspartase from Escherichia coli by the substrate analog aspartate beta-semialdehyde has previously been shown to occur by the mechanism-based conversion to the corresponding product aldehyde, followed by covalent modification of cysteine-273 (F. Giorgianni et al. (1995) Biochemistry 34, 3529). Inactivation by the product analog, fumaric acid aldehyde (FAA), has now been examined directly by adding a reduction step to the modification protocol in order to stabilize the resulting enzyme-FAA derivative(s). HPLC and mass spectrometric analyses of proteolytic digests of inactivated L-aspartase have confirmed the modification at cysteine-273, and have also identified an additional modified peptide. The inactivation at this additional site involves a crosslink between cysteine-140 and an adjacent lysine. Site-directed mutagenesis studies have shown that cysteine-140 is a very reactive and accessible nucleophile that is not, however, directly involved in enzyme activity. The adjacent lysine-139 that is modified does appear to play a role in substrate binding. A double mutant in which both of the reactive cysteines have been replaced is almost completely insensitive to modification by these substrate and product analogs.

Elimination of the sensitivity of L-aspartase to active-site-directed inactivation without alteration of catalytic activity.

The catalytic activity of the enzyme L-aspartase from Escherichia coli has previously been shown to be sensitive to sulfhydryl reagents. The use of group-specific reagents, and a sequence homology comparison study among the fumarase-aspartase family of enzymes, has not, however, lead to the identification of a specific, essential cysteinyl residue. We have recently shown that L-aspartate-beta-semialdehyde is an alternative substrate for L-aspartase, producing fumaric acid semialdehyde (FAA) which specifically inactivates the enzyme [Schindler, J. F., & Viola, R. E. (1994) Biochemistry 33, 9365]. Proteolytic digests of the resulting inactivated enzyme have now been mapped by HPLC and mass spectrometry. A specific residue (Cys-273) has been determined to be the site of FAA modification. Site-directed mutagenesis of this cysteine in the E. coli enzyme has produced altered enzymes which are considerably less sensitive to active-site-directed inactivation, while retaining full catalytic activity. Thus, cysteine-273 has been identified as an active-site nucleophile that, while not directly involved in catalysis in L-aspartase, is poised to attack an activated double bond in an enzyme-bound product analogue.

Crystallization and preliminary X-ray studies of L-aspartase from Escherichia coli.

Single crystals of L-aspartate ammonia-lyase (L-aspartase) from Escherichia coli have been obtained by microdialysis at room temperature using polyethylene glycol 3350 and sodium acetate as co-precipitants. The crystals exhibit the symmetry of space group P2(1)2(1)2 with a = 156.5 A, b = 147.6 A, c = 102.5 A and diffract at least to 2.8 A.