FREE RADICALS AND EXCITED SPECIES IN THE METABOLISM OF INDOLE-3-ACETIC ACID AND ITS ETHYL ESTER BY HORSERADISH PEROXIDASE AND BY NEUTROPHILS

The peroxidative metabolization of indole-3-acetic acid, a biologically important process, has been followed by EPR spectroscopy with the aim of obtaining information on the mechanism of generation of electronically excited species. The skatole-3-methylene radical detected during oxidation by horseradish peroxidase, does not appear to be involved in a major oxygen consuming process or in the generation of singlet oxygen. The chemiluminescence spectrum exhibits several maxima, which are also observed when the ethyl ester of indole-3-acetic acid is metabolized by horseradish peroxidase or by myeloperoxidase in neutrophils. When the ester is metabolically activated in either of these systems, the EPR spectrum indicates a tertiary carbon-centered radical. This radical centered on the carbon in the 3-position participates in a chemiexcitation/emissive route. Within the cell, this emissive process is responsible for a large part of the oxygen consumed. Some of the emitters originate in the cleavage of the 2,3 double bond. The ester, which is capable of penetrating into the cells, also emits with other myeloperoxidase-containing cells. This compound may have useful applications as an intracellular chemiluminescent probe for the presence of myeloperoxidase.     

Reduction of the benzoyl group in substituted 5-benzoyl-4,5-dihydro-1,2,4-oxadiazoles

The carbonyl group of substituted 5-benzoyl-4,5-dihydro-1,2,4-oxadiazoles can be reduced by lithium aluminium hydride at low temperature without ring opening. Mixtures of the two related diastereoisomeric benzylalcohols are obtained. Configurations were assigned by ¹H-nmr.     

OXIDATION OF INDOLE-3-ACETIC ACID BY SONICATED NEUTROPHILS. PITFALLS IN CORRELATING EPR SIGNALS AND CHEMILUMINESCENCE

Abstract –The oxidation-peroxidation of indole-3-acetic acid by sonicated neutrophils, unlike the horseradish peroxidase-catalyzed process, features not only the skatole radical, but also a tertiary carbon-centered radical in the electron paramagnetic resonance (EPR) spectrum. Moreover, emission occurs only in the red.
From the present and earlier data it is concluded that the observation of the skatole radical does not necessarily indicate its involvement in the ¹Δ_gO₂ generating process. Also unlikely is a correlation between the tertiary carbon-centered radical and red emission.
Our results indicate that in general great care must be taken in attempting to correlate EPR signals with chemi-luminescence and with oxygen consumption.     

Guest Exchange Mechanisms in Mono‐Metallic PdII/PtII‐Cages Based on a Tetra‐Pyridyl Calix[4]pyrrole Ligand

Planar pyridyl N‐oxides are encapsulated in mono‐metallic Pd^II/Pt^II‐cages based on a tetra‐pyridyl calix[4]pyrrole ligand. The exchange dynamics of the cage complexes are slow on both the NMR chemical shift and EXSY timescales, but encapsulation of the guests by the cages is fast on the human timescale. A “French doors” mechanism, involving the rotation of the meso‐phenyl walls of the cages, allows the passage of the planar guests. The encapsulation of quinuclidine N‐oxide, a sterically more demanding guest, is slower than pyridyl N‐oxides in the Pd^II‐cage, and does not take place in the Pt^II counterpart. A modification of the encapsulation mechanism for the quinuclidine N‐oxide is postulated that requires the partial dissociation of the Pd^II‐cage. The substrate binding selectivity featured by the cages is related to their different guest uptake/release mechanisms.     

Search for lepton-flavor-violating decays of the neutral kaon

The Fermilab KTeV experiment has searched for lepton-flavor-violating decays of the K(L) meson in three decay modes. We observe no events in the signal region for any of the modes studied, and we set the following upper limits for their branching ratios at the 90% C.L.: BR(K(L) --> pi(0) micro(+/-) e(-/+)) <7.6 x 10(-11); BR(K(L) --> pi(0)pi(0) micro(+/-) e(-/+)) <1.7 x 10(-10); BR(pi(0) --> micro(+/-) e(-/+)) <3.6 x 10(-10). This result represents a factor of 82 improvement in the branching ratio limit for K(L) --> pi(0) micro(+/-) e(-/+) and is the first reported limit for K(L) --> pi(0)pi(0) micro(+/-) e(-/+).     

Testing Lorentz invariance and CPT conservation with NuMI neutrinos in the MINOS near detector

A search for a sidereal modulation in the MINOS near detector neutrino data was performed. If present, this signature could be a consequence of Lorentz and CPT violation as predicted by the effective field theory called the standard-model extension. No evidence for a sidereal signal in the data set was found, implying that there is no significant change in neutrino propagation that depends on the direction of the neutrino beam in a sun-centered inertial frame. Upper limits on the magnitudes of the Lorentz and CPT violating terms in the standard-model extension lie between 10(-4) and 10(-2) of the maximum expected, assuming a suppression of these signatures by a factor of 10(-17).     

Evolution of a polysulfone nanofiltration membrane following ion beam irradiation

Ion beam irradiation was used to modify the surface of a sulfonated polysulfone water treatment membrane. A beam of 25 keV H (+) ions with four irradiation fluences (1 x 10 (13), 5 x 10 (13), 1 x 10 (14), and 5 x 10 (14) ions/cm (2)) was used to study the effects of ion beam irradiation on chemical structure, surface morphology, microstructure, and performance. XPS and ATR-FTIR analyses were performed on the virgin and irradiated membranes in order to determine the changes to chemical structure incurred by ion beam irradiation. The results showed that some sulfonic and C-H bonds were broken and new C-S bonds were formed after irradiation. AFM analysis showed that the roughness of the membranes decreased after irradiation, and the decrease in surface roughness was proportional to the increase in irradiation fluence. An increase in flux after ion beam irradiation was also observed along with a smaller flux decline during operation. Flux was not a function of irradiation fluence. Hydrophobicity, pore size distribution, and membrane rejection efficiencies were not affected by ion beam irradiation. Overall, irradiation led to an improvement in membrane performance.     

Protein-bound tyrosine oxidation,nitration and chlorination by-products assessed by ultraperformance liquid chromatography coupled to tandem mass spectrometry

Background

Free radicals cause alterations in cellular protein structure and function. Oxidized, nitrated, and chlorinated modifications of aromatic amino acids including phenylalanine and tyrosine are reliable biomarkers of oxidative stress and inflammation in clinical conditions.

Objective

To develop, validate and apply a rapid method for the quantification of known hallmarks of tyrosine oxidation, nitration and chlorination in plasma and tissue proteins providing a snapshot of the oxidative stress and inflammatory status of the organism and of target organs respectively.

Material and Methods

The extraction and clean up procedure entailed protein precipitation, followed by protein re-suspension and enzymatic digestion with pronase. An Ultra Performance Liquid Chromatography–tandem Mass Spectrometry (UPLC-MS/MS) method was developed to quantify protein released ortho-tyrosine (o-Tyr), meta-tyrosine (m-Tyr), 3-nitrotyrosine (3NO₂-Tyr) and 3-chlorotyrosine (3Cl-Tyr) as well as native phenylalanine (Phe) and tyrosine (p-Tyr) in plasma and tissue from a validated hypoxic newborn piglet experimental model.

Results

In plasma there was a significant increase in the 3NO₂-Tyr/p-Tyr ratio. On the other hand m-Tyr/Phe and 3Cl-Tyr/p-Tyr ratios were significantly increased in liver of hypoxic compared with normoxic animals. Although no significant differences were found in brain tissue, a clear tendency to increased ratios was observed under hypoxic conditions.

Conclusions

UPLC-MS/MS has proven suitable for the analysis of plasma and tissue samples from newborn piglets. The analysis of biomarkers of protein oxidation, nitration and chlorination will be applied in future studies aiming to provide a deeper insight into the mechanisms of oxidation-derived protein modification caused during neonatal asphyxia and resuscitation.     

Synthesis and Evaluation of Trypanocidal Activity of Chromane-Type Compounds and Acetophenones

American trypanosomiasis (Chagas disease) caused by the Trypanosoma cruzi parasite, is a severe health problem in different regions of Latin America and is currently reported to be spreading to Europe, North America, Japan, and Australia, due to the migration of populations from South and Central America. At present, there is no vaccine available and chemotherapeutic options are reduced to nifurtimox and benznidazole. Therefore, the discovery of new molecules is urgently needed to initiate the drug development process. Some acetophenones and chalcones, as well as chromane-type substances, such as chromones and flavones, are natural products that have been studied as trypanocides, but the relationships between structure and activity are not yet fully understood. In this work, 26 compounds were synthesized to determine the effect of hydroxyl and isoprenyl substituents on trypanocide activity. One of the compounds showed interesting activity against a resistant strain of T. cruzi, with a half effective concentration of 18.3 µM ± 1.1 and an index of selectivity > 10.9.