Charuvila T. Aravindakumar

Bio: Charuvila T. Aravindakumar is an academic researcher from Mahatma Gandhi University. The author has contributed to research in topics: Radiolysis & Radical. The author has an hindex of 26, co-authored 119 publications receiving 1934 citations. Previous affiliations of Charuvila T. Aravindakumar include Max Planck Society & Katholieke Universiteit Leuven.

Nitric oxide induces Zn2+ release from metallothionein by destroying zinc-sulphur clusters without concomitant formation of S-nitrosothiol.

Abstract: The reaction of nitric oxide (NO) with metallothionein (MT) has been investigated at neutral pH under strictly anaerobic conditions. It is observed that NO mediates zinc release from MT by destroying zinc-sulphur clusters, but that it does not by itself S-nitrosylate MT in contrast to common belief. Zinc release and loss of thiolate groups under anaerobic conditions is found to be much slower than under aerobic conditions. The observed percentage loss of Zn(2+) and thiolate groups after 3 h of NO treatment are 62 and 39%, respectively. The reaction of NO with cysteine is reinvestigated and it is found that cysteine is quantitatively converted to cystine after 5 min of NO treatment at pH 7.3. At lower pH, a much lower rate of conversion is observed confirming the base-catalysed nature of the reaction of NO with thiols. On the basis of these results, a reaction mechanism involving electrophilic attack of NO on thiolate groups and subsequent formation of a nitrogen-centred radical, MTSN(. )OH, as intermediate is proposed for the reaction of NO with MT that leads to zinc release.

Degradation of pharmaceuticals by ultrasound-based advanced oxidation process

Abstract: Water pollution by pharmaceutically active compounds is an emerging issue. Toxicological studies reveal that pharmaceuticals are indeed toxic for living organisms. The lack of suitable treatment technology for the complete removal of pharmaceuticals is therefore a major challenge. Advanced oxidation processes are emerging removal techniques that have many advantages versus conventional technologies. Many studies indicate that advanced oxidation processes, either in single or in combination with other degradation techniques, can enhance the degradation of pharmaceuticals in aqueous solutions. Here, we review the degradation of pharmaceuticals by sonolysis, an oxidation processes using ultrasound. In this technique, hydroxyl radicals are generated by pyrolytic cleavage of water molecules. We review the influence of operational parameters, additives and hybrid techniques on the degradation of pharmaceuticals. The maximum degradation of organic compounds was observed in the frequency range of 100–1000 kHz, which is in the high-frequency medium-power ultrasound. Even though almost all the experiments presented more than 90 % removal and good biodegradability of the target compound, good mineralization and the toxicity removal were hardly achieved. The efficiency of the degradation varies with water matrixes and varying pH. Major pathways of degradation are hydroxylation, dehalogenation, demethylation, decarboxylation, deamination, etc. More hybrid techniques have to be developed to scale up the application of ultrasound.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Electrochemical advanced oxidation processes: A review on their application to synthetic and real wastewaters

Abstract: Over the last decades, research efforts have been made at developing more effective technologies for the remediation of waters containing persistent organic pollutants. Among the various technologies, the so-called electrochemical advanced oxidation processes (EAOPs) have caused increasing interest. These technologies are based on the electrochemical generation of strong oxidants such as hydroxyl radicals ( OH). Here, we present an exhaustive review on the treatment of various synthetic and real wastewaters by five key EAOPs, i.e., anodic oxidation (AO), anodic oxidation with electrogenerated H 2 O 2 (AO-H 2 O 2 ), electro-Fenton (EF), photoelectro-Fenton (PEF) and solar photoelectro-Fenton (SPEF), alone and in combination with other methods like biological treatment, electrocoagulation, coagulation and membrane filtration processes. Fundamentals of each EAOP are also given.

Persulfate-Based Advanced Oxidation: Critical Assessment of Opportunities and Roadblocks.

Abstract: Reports that promote persulfate-based advanced oxidation process (AOP) as a viable alternative to hydrogen peroxide-based processes have been rapidly accumulating in recent water treatment literature. Various strategies to activate peroxide bonds in persulfate precursors have been proposed and the capacity to degrade a wide range of organic pollutants has been demonstrated. Compared to traditional AOPs in which hydroxyl radical serves as the main oxidant, persulfate-based AOPs have been claimed to involve different in situ generated oxidants such as sulfate radical and singlet oxygen as well as nonradical oxidation pathways. However, there exist controversial observations and interpretations around some of these claims, challenging robust scientific progress of this technology toward practical use. This Critical Review comparatively examines the activation mechanisms of peroxymonosulfate and peroxydisulfate and the formation pathways of oxidizing species. Properties of the main oxidizing species are scrutinized and the role of singlet oxygen is debated. In addition, the impacts of water parameters and constituents such as pH, background organic matter, halide, phosphate, and carbonate on persulfate-driven chemistry are discussed. The opportunity for niche applications is also presented, emphasizing the need for parallel efforts to remove currently prevalent knowledge roadblocks.

Bisphenol S and F: A Systematic Review and Comparison of the Hormonal Activity of Bisphenol A Substitutes.

Abstract: BackgroundIncreasing concern over bisphenol A (BPA) as an endocrine-disrupting chemical and its possible effects on human health have prompted the removal of BPA from consumer products, often label...