Cross-oxidation of angiotensin II by glycerophosphatidylcholine oxidation products

Peptide and protein lipoxidation is a deleterious process which has been related to several degenerative conditions. In the present study, the interaction of lipid secondary oxidation products with peptides was investigated by evaluating the modifications occurring to angiotensin II (Ang-II) in the presence of an oxidizing polyunsaturated glycerophospholipid (1-palmitoyl-2-arachidonoyl-glycerophosphatidylcholine, PAPC). PAPC oxidation was promoted by Fenton chemistry and the oxidation products were incubated with Ang-II. The reaction products were finally analysed by off-line nanospray high-performance liquid chromatography/matrix-assisted laser desorption/ionization tandem mass spectrometry (nano-HPLC/MALDI-TOF-MS/MS). Ang-II was found to form adducts with 26 different aldehydes, leading to 37 distinct reaction products. Modification of Ang-II occurred through reaction with reactive carbonyl species (RCS) originating from fatty acyl chain cleavage, while interactions with the oxidized phospholipid could not be detected. Adduction was observed to occur both by Michael and Schiff base mechanisms, most prevalently taking place at the peptide N-terminus or the arginine residue. Histidine modification could only be demonstrated to occur via Michael addition with two aldehydes: 4-hydroxy-2-nonenal (HNE) and 2-octenal. The highly reactive 4-oxo-2-nonenal (ONE) was shown to react preferentially with the arginine side chain, while malondialdehyde addition could only be confirmed at the N-terminus. Aspartic acid oxidative decarboxylation, amino acid side chain oxidation, multiple adduction or peptide cross-links could not be perceived. The inability to detect these reaction products is indicative of their low abundance or non-existence in competitive reaction conditions. The multiplicity of peptide modifications described emphasizes the complexity of lipoxidation, the effects of which are not possible to fully understand by the evaluation of independent reaction products.     

Thermal stability of P3HT and P3HT:PCBM blends in the molten state

The thermal stability of poly(3-hexylthiophene) (P3HT) in its molten state was investigated in air and nitrogen atmospheres under no illumination conditions, with the aim of testing the feasibility of processing it using polymer melt techniques. A large set of different experimental characterization techniques was used including thermogravimetric analysis (TGA), rotational rheometry, infrared spectroscopy (FTIR-ATR), proton nuclear magnetic resonance spectroscopy (¹H-NMR), gel permeation chromatography (GPC), UV-Vis and fluorescence spectroscopy. The results obtained strongly suggest that the processing of P3HT in its molten state is possible, without noticeable degradation, if carried out under nitrogen atmosphere and if the processing (residence) times are relatively short. Conversely, as expected, in a normal air atmosphere P3HT degrades rapidly at temperatures above its melting point. The effect of PCBM on the thermal stability of P3HT:PCBM blends in the molten state was also studied using TGA, and in air atmosphere PCBM is shown to delay oxidation.     

Endopolysaccharides from Ganoderma resinaceum, Phlebia rufa, and Trametes versicolor Affect Differently the Proliferation Rate of HepG2 Cells

Fungi have been used for medicinal purposes for long time by Asian countries, being a putative source of powerful new phytopharmaceuticals such as polysaccharides. The aim of this study was to extract endopolysaccharides (IPS) from Ganoderma resinaceum, Phlebia rufa, and Trametes versicolor, grown under submerged culture, to compare crude IPS production, total carbohydrate, and protein yield, and to study the effect of these IPS on HepG2 cells proliferation rate. Total biomass produced by G. resinaceum, P. rufa, and T. versicolor was (in gram per liter) 3.32?±?0.80, 5.42?±?0.58, and 4.2?±?1.29 and the IPS yield (as the biomass percent) was 9.9?±?0.05, 29.0?±?6.3, and 9.1?±?3.1 %, respectively. Characterization of IPS has shown different proportion between total sugar and protein being, on average 6.04, 10.74, and 22.62, for G. resinaceum, T. versicolor, and P. rufa, respectively. The IPS effect, at 50, 100, and 200 μg?mL^?1 on HepG2 cell growth and viability was negligible for G. resinaceum and P. rufa but, in the case of T. versicolor, 200 μg?mL^?1 of IPS evoked 40 % reduction on cell growth. The results suggest that the intracellular polysaccharides from T. versicolor are a potential source for bioactive molecules with anti-proliferative properties.     

Rare earths/main group metal alkyls catalytic systems for the 1,4‐trans stereoselective coordinative chain transfer polymerization of isoprene

A series of lanthanum and neodymium complexes comprising the half‐lanthanidocenes Cp*La(BH₄)₂(THF)₂ (Cp* = C₅Me₅) ( 1 ) and Cp*Nd(BH₄)₂(THF)₂ ( 2 ), the trisborohydrides La(BH₄)₃(THF)₃ ( 3 ) and Nd(BH₄)₃(THF)₃ ( 4 ), the trichlorides LaCl₃(THF)₃ ( 5 ) and NdCl₃(THF)₃ ( 6 ), the triisopropoxides La(OⁱPr)₃ ( 7 ) and Nd(OⁱPr)₃ ( 8 ), and the triaryloxide Nd(OC₆H₃‐^tBu₂‐2,6)₃ ( 9 ) has been assessed for the chain transfer polymerization of isoprene. A transmetalation process is occurring efficiently with the borohydride complexes in the presence of magnesium dialkyl. A gradual decrease of the 1,4‐trans stereoselectivity of the reaction is observed at the benefit of 3,4‐selectivity with increasing quantities of magnesium dialkyl. This can be at least partially attributed to the growth of 3,4 polyisoprene units onto the magnesium atom. By combining dialkylmagnesium and trialkylaluminum, a 1,4‐trans stereospecific reversible coordinative chain transfer polymerization of isoprene is reached using the half‐lanthanocene Cp*La(BH₄)₂(THF)₂. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of Ortho-alkoxy-aryl Carboxamides via Palladium-Catalyzed Aminocarbonylation

Various aryl carboxamides with alkoxy substituents at the ortho-position, applicable as direct intermediates toward novel ligands, were synthesised via aminocarbonylation of aryl-iodides (2-iodoanisole, 5-chloro-7-iodo-8-methoxy-quinoline, and 5-chloro-7-iodo-8-benzyloxy-quinoline) in the presence of in situ generated palladium(0) catalysts. Simple primary and secondary amines as well as aminoacid esters were used as N-nucleophiles. The optimization of the reaction conditions allowed the preferential formation of carboxamides or ketocarboxamides by simple or double carbon monoxide insertion, respectively. A strong dependence of the chemoselectivity on carbon monoxide pressure was observed.     

Utility function estimation: The entropy approach

The maximum entropy principle can be used to assign utility values when only partial information is available about the decision maker’s preferences. In order to obtain such utility values it is necessary to establish an analogy between probability and utility through the notion of a utility density function. In this paper we explore the maximum entropy principle to estimate the utility function of a risk averse decision maker.     

Phase diagram of the random Heisenberg antiferromagnetic spin-1 chain

We present a new perturbative real space renormalization group (RG) to study random quantum spin chains and other one-dimensional disordered quantum systems. The method overcomes problems of the original approach which fails for quantum random chains with spins larger than S=1/2. Since it works even for weak disorder, we are able to obtain the zero temperature phase diagram of the random antiferromagnetic Heisenberg spin-1 chain as a function of disorder. We find a random singlet phase for strong disorder. As the disorder decreases, the system shows a crossover from a Griffiths to a disordered Haldane phase.     

Solvent and salting effects on sample preparation for the determination of fenofibric acid in human plasma by HPLC-DAD

The solvent and salting effects induced on the sample preparation procedure applied to plasma samples containing fenofibric acid and 4-chlorophenyl-4′-hydroxyphenyl methanone (internal standard) are evaluated. Sodium chloride addition during a deproteinization step using both methanol and phosphoric acid influences the recovery of the analytes as well as the selectivity of the process. The chromatographic method allows high sample volume injection (500 μl) with the focusing of both analytes in the stationary phase. The synthesized high porosity octadecylsilica material allows a fast elution gradient at 4 ml/min flow-rate and a complete analysis within 7 min. UV-detection is made at 295 nm and quantitation limit in the 20 ng/ml concentration level can be achieved. The method can be successfully applied for bioequivalence studies on fenofibrate, administrated as prodrug (fenofibric acid represents its main active metabolite) in pharmaceutical formulations. The main parameters used in studying the retention behavior of the internal standard and FEFA were also estimated.