Novel cotton fabric adsorbent for efficient As(V) adsorption.

A novel amine functionalized nonwoven cotton fabric (EDA-GMA-g-NCF) adsorbent material for As(V) adsorption was prepared by using plasma-initiated graft polymerization of glycidyl methacrylate (GMA) onto nonwoven cotton fabric (NCF) and then its modification with ethylenediamine (EDA). The resultant nonwoven cotton fabric adsorbent was examined by using FT-IR, SEM, and XPS techniques. As(V) adsorption experiments were performed in batch mode as a function of pH, contact time, initial concentration, coexisting ions, ionic strength, and tap water applications. Ethylenediamine carrying nonwoven cotton fabric-based functional adsorbent showed efficient, rapid As(V) removal with high adsorption capacity. The experimental data shows that adsorption mechanism fits to the Langmuir isotherm, and adsorption kinetic follows a pseudo-second-order model. Between pH 2-8 range, nonwoven cotton fabric adsorbent is effective at pH 3 for As(V) adsorption. The maximum adsorption capacity of the nonwoven cotton fabric for As(V) was 217.39 mg/g. The adsorbent could be easily regenerated at least ten cycles with 3% HNO3 solution. EDA-GMA-g-NCF was also efficient for tap water applications with high percent As(V) removal. Thermodynamic parameters show that the As(V) adsorption process was spontaneous and exothermic. Graphical abstract Preparation of cotton fabric adsorbent and As(V) treatment process.

Effects of 900 MHz radiofrequency radiation on skin hydroxyproline contents.

The present study aimed to investigate the possible effect of pulse-modulated radiofrequency radiation (RFR) on rat skin hydroxyproline content, since skin is the first target of external electromagnetic fields. Skin hydroxyproline content was measured using liquid chromatography mass spectrometer method. Two months old male wistar rats were exposed to a 900 MHz pulse-modulated RFR at an average whole body specific absorption rate (SAR) of 1.35 W/kg for 20 min/day for 3 weeks. The radiofrequency (RF) signals were pulse modulated by rectangular pulses with a repetition frequency of 217 Hz and a duty cycle of 1:8 (pulse width 0.576 ms). A skin biopsy was taken at the upper part of the abdominal costa after the exposure. The data indicated that whole body exposure to a pulse-modulated RF radiation that is similar to that emitted by the global system for mobile communications (GSM) mobile phones caused a statistically significant increase in the skin hydroxyproline level (p = 0.049, Mann-Whitney U test). Under our experimental conditions, at a SAR less than the International Commission on Non-Ionizing Radiation Protection safety limit recommendation, there was evidence that GSM signals could alter hydroxyproline concentration in the rat skin.

Autocatalytic tyrosine nitration of prostaglandin endoperoxide synthase-2 in LPS-stimulated RAW 264.7 macrophages.

In the literature, biological tyrosine nitrations have been reported to depend not only on peroxynitrite but also on nitrite/hydrogen peroxide linked to catalysis by myeloperoxidase. In endotoxin-stimulated RAW 264.7 macrophages, we have detected a major nitrotyrosine positive protein band around 72 kDa and identified it as prostaglandin endoperoxide synthase-2 (PGHS-2). Isolated PGHS-2 in absence of its substrate arachidonate was not only tyrosine-nitrated with peroxynitrite, but also with nitrite/hydrogen peroxide in complete absence of myeloperoxidase. Our data favor an autocatalytic activation of nitrite by PGHS-2 with a subsequent nitration of the essential tyrosine residue in the cyclooxygenase domain. Under inflammatory conditions, nitrite formed via NO-synthase-2 may therefore act as an endogenous regulator for PGHS-2 in stimulated macrophages. Nitration of PGHS-2 by the autocatalytic activation of nitrite further depends on the intracellular concentration of arachidonate since arachidonate reacted competitively with nitrite and could prevent PGHS-2 from nitration when excessively present.

A new pitfall in detecting biological end products of nitric oxide-nitration, nitros(yl)ation and nitrite/nitrate artefacts during freezing.

The present study shows that when freezing nitrite containing biological samples in the presence of sodium and phosphate, a process of tyrosine nitration and S-nitrosocysteine formation is observed. The underlying mechanism is obviously based on the already described pH decrease in sodium phosphate buffered solutions during the freezing process and probably involves nitrous acid as an intermediate. However, in pure potassium phosphate buffer freeze-artefacts were absent. The yield of 3-nitrotyrosine from albumin-bound or free tyrosine depends not only on the concentration of nitrite, tyrosine or protein, and sodium phosphate but also on the velocity of the freezing process. Nitrite and nitrate were quantified by the Griess/nitrate reductase assay. 3-nitrotyrosine formation was quantitatively measured by HPLC analysis with optical and electrochemical detection as well as qualitatively investigated by immunohistochemistry and slot blot analysis using 3-nitrotyrosine specific antibodies. The formation of S-nitrosocysteine was detected by S-nitrosothiol specific antibodies and quantified by a fluorometric assay. Irrespective of the mechanism and although the here presented results cannot be generalized, the data warrant caution for the analysis of nitration or nitros(yl)ation products following freezing of nitrite containing biological material.