Hydrazyl,Nitronyl-, and imino-nitroxides: Synthesis,properties and reaction with nitric oxide and nitrogen dioxide

Ten novel and stable free radicals of nitronyl-, imino-nitroxide and hydrazyl type compounds were synthesized and their physico-chemical properties investigated. UV-Vis and ESR spectroscopic data, as well as the lipophilicities and specific hydrophobic areas of the compounds are compiled. The reaction of these radical compounds with nitric oxide and nitrogen dioxide was also investigated. The radicals synthesized, show selectivity in their reaction with these nitric oxides, depending on their structure (nitronyl-nitroxide radicals react with NO, while hydrazyl radicals react with NO₂). The processes are easily monitored by UV-Vis or ESR spectroscopy.     

When is Mass Spectrometry Combined with Affinity Approaches Essential? A Case Study of Tyrosine Nitration in Proteins

Tyrosine nitration in proteins occurs under physiologic conditions and is increased at disease conditions associated with oxidative stress, such as inflammation and Alzheimer??s disease. Identification and quantification of tyrosine-nitrations are crucial for understanding nitration mechanism(s) and their functional consequences. Mass spectrometry (MS) is best suited to identify nitration sites, but is hampered by low stabilities and modification levels and possible structural changes induced by nitration. In this insight, we discuss methods for identifying and quantifying nitration sites by proteolytic affinity extraction using nitrotyrosine (NT)-specific antibodies, in combination with electrospray-MS. The efficiency of this approach is illustrated by identification of specific nitration sites in two proteins in eosinophil granules from several biological samples, eosinophil-cationic protein (ECP) and eosinophil-derived neurotoxin (EDN). Affinity extraction combined with Edman sequencing enabled the quantification of nitration levels, which were found to be 8?% and 15?% for ECP and EDN, respectively. Structure modeling utilizing available crystal structures and affinity studies using synthetic NT-peptides suggest a tyrosine nitration sequence motif comprising positively charged residues in the vicinity of the NT- residue, located at specific surface- accessible sites of the protein structure. Affinities of Tyr-nitrated peptides from ECP and EDN to NT-antibodies, determined by online bioaffinity- MS, provided nanomolar K_D values. In contrast, false-positive identifications of nitrations were obtained in proteins from cystic fibrosis patients upon using NT-specific antibodies, and were shown to be hydroxy-tyrosine modifications. These results demonstrate affinity- mass spectrometry approaches to be essential for unequivocal identification of biological tyrosine nitrations.     

Azorubine: physical,thermal and bioactive properties of the widely employed food,pharmaceutical and cosmetic red azo dye material

Journal of Thermal Analysis and Calorimetry - Azorubine (E122), an azoic dye with the chemical formula C20H12N2Na2O7S2, has a wide range of applications in the food and cosmetic industries....     

A covariance fitting approach for correlated acoustic source mapping

Microphone arrays are commonly used for noise source localization and power estimation in aeroacoustic measurements. The delay-and-sum (DAS) beamformer, which is the most widely used beamforming algorithm in practice, suffers from low resolution and high sidelobe level problems. Therefore, deconvolution approaches, such as the deconvolution approach for the mapping of acoustic sources (DAMAS), are often used for extracting the actual source powers from the contaminated DAS results. However, most deconvolution approaches assume that the sources are uncorrelated. Although deconvolution algorithms that can deal with correlated sources, such as DAMAS for correlated sources, do exist, these algorithms are computationally impractical even for small scanning grid sizes. This paper presents a covariance fitting approach for the mapping of acoustic correlated sources (MACS), which can work with uncorrelated, partially correlated or even coherent sources with a reasonably low computational complexity. MACS minimizes a quadratic cost function in a cyclic manner by making use of convex optimization and sparsity, and is guaranteed to converge at least locally. Simulations and experimental data acquired at the University of Florida Aeroacoustic Flow Facility with a 63-element logarithmic spiral microphone array in the absence of flow are used to demonstrate the performance of MACS.     

Area-selective signal parameter estimation for two-dimensional MR spectroscopy data

We consider the problem of parametric spectral analysis of two-dimensional (2D) magnetic resonance spectroscopy (MRS) data. Estimating the signal components from 2D MRS data is becoming common practice in many clinical MR applications. The most frequently used signal processing tool for this estimation problem is the non-parametric 2D-FFT. There are several alternative parametric methods available to perform this analysis, yet their computational complexity is generally rather high and it becomes prohibitive when the number of points in the measured data matrix is large. In this paper, we propose a novel signal parameter estimation technique which operates on a pre-specified sub-area of the 2D spectrum. This area-selective approach can be used either to estimate only the signal components of main interest in the data, or to compute signal parameter estimates of all present signal components as the computational burden for each sub-area is low. In the numerical example section we consider both simulated data and in vitro 1H data acquired from a 1.5 T MR scanner.     

Thermal behaviour and adsorption properties of some benzothiazole derivatives

The thermal stability and the adsorption properties have been investigated for three benzothiazole compounds: 2-mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole sulfenamide (NCBSA), and 2,2′-dibenzothiazole disulphide (BTD), reported in our early studies as corrosion inhibitors for carbon steel in different media. The electrochemical results were used to calculate the degree of surface coverage (θ). The adsorption mechanism of the three inhibitors was discussed according to the free energy of adsorption ( \( \Delta G_{{\text{ads}}}^{\circ } \) ) value obtained from Temkin adsorption isotherm, this being the best way to quantitatively express the adsorption process of their molecules on carbon steel surface. Thus, a mixed type mechanism involving the synergism between physisorption and chemisorption was proposed. The thermal analysis curves showed that, for the occurred events up to 470 °C, mass losses take place with endothermic effects followed by the total oxidation of the residue with an exothermic effect around 520 °C. Consequently, their effectiveness follows the order: BTD > NCBSA ≥ MBT, while the thermal stability ranges as follows: NCBSA < BTD ≤ MBT.     

Rotationally resolved electronic spectroscopy of a nonlinear carbon chain radical C6H4

Rotationally resolved electronic spectrum of the origin band in the 2A″-X2A″ transition of a nonlinear carbon chain radical C₆H₄⁺ has been recorded in the 604 nm region using cw cavity ring down spectroscopy. The radical was produced by a discharge through an acetylene-helium mixture in a supersonic planar expansion. The rotational structure has been analysed and precisely determined. A band having a-type prolate rotational structure has also been observed near 581 nm. By considering the results of ab initio calculations this band is assigned to a transition involving the excitation of the ν₁₂ fundamental in the upper 2A″ electronic state of the same C₆H₄⁺ isomer.