Marius Zaharia

Quenching of Tryptophan Fluorescence in the Presence of 2,4-DNP, 2,6-DNP, 2,4-DNA and DNOC and Their Mechanism of Toxicity

Although they are widely used as insecticides, acaricides and fungicides in the agriculture or as raw materials in the dye industry, dinitrophenols (DNPs) are extremely noxious, death cases having been registered. These compounds produce cataracts, lower leucocyte levels, disturb the general metabolism and can cause cancer. It is also assumed that DNPs hinder the proton translocation through the mitochondrial inner membrane and therefore inhibit oxidative phosphorylation. Their fluorescence quenching properties can help understand and explain their toxicity. Fluorescence quenching of tryptophan was tested using different dinitrophenols such as 2,4-dinitrophenol (2,4-DNP), 4,6-dinitro-orthocresol (DNOC), 2-[(2,4-dinitrophenyl)amino]acetic acid (GlyDNP), 2-(1-methyl-heptyl)-4.6-dinitrophenyl crotonate (Karathan), 2-amino-5-[(1-((carboxymethyl)amino)-3-((2,4-dinitrophenyl)thio)-1-oxopropan-2-yl)amino]-5-oxopentanoic acid (SDN GSH), 2,4-dinitroanisole (2,4-DNA) and 2,4-dinitrobenzoic acid (2,4-DNB). 2,4-DNP and DNOC showed the highest tryptophan fluorescence quenching constant values, these being also the most toxic compounds. The electronic chemical potential value of the most stable complex of 2,4-DNP-with tryptophan is higher than the values of the electronic chemical potentials of complexes corresponding to the derivatives.

Letter: Study on the mechanism of ferrite-induced dinitrophenol photodegradation

We report here the effectiveness of gas chromatography mass spectrometry techniques in establishing the ferrite-associated photocatalytic degradation mechanism of pesticide 2,4-dinitrophenol (2,4-DNP). Unlike the previously discussed DNP-degradation mechanisms that involve either oxidation or reduction reactions, ferrite-based ultraviolet (UV) photodegradation of DNP affords the nontoxic 6-hydroxy-3,5-dinitrohexa-2,4-dienal by an unusual water addition to the benzene core. We searched for and demonstrated the presence of an epoxide of DNP within the photodegradation process, which may unambiguously explain the novel photochemical mechanism. During the 15 min UV photoinduced process, DNP degradation efficiency on the zinc ferrite catalyst was calculated to be 82%, whereas the first-order kinetic rate constant k was as high as 3.4 × 10−2 min−1.

Ninhydrin-based spectrophotometric assays of trace cyanide

Abstract The extreme toxicity of cyanide, its wide industrial application as well as its continued illegal use generate research interest in different fields of science, imposing multidisciplinary approach to study cyanide poisoning. We show here that the reaction between cyanide and ninhydrin can be performed at ambient conditions; however, the ninhydrin reagent has to be freshly prepared in oxygen free solvent. Besides, we show that the reading of the absorbance at 485 nm might be more suitable and reliable than that at 590 nm, where the pH-dependent blue colored cyanide-ninhydrin adduct is less stable. Ninhydrin-based color reagent can be used to quantify the cyanide released from plant seeds. In sodium carbonate medium, the proposed assay is fast, cheap and environmentally friendly

Banned dinitrophenols still trigger both legal and forensic issues

ABSTRACT Numerous hazardous chemicals from various industrial sources enter the environment daily; some of them can be used both as drugs and as toxins. Many of these compounds, including dinitrophenols, such as 2,4-dinitrophenol (2,4-DNP), 4,6-dinitrocresol (DNOC), and 2-sec-butyl-4,6-dinitrophenol (dinoseb), are widely used pesticides that persist in some contaminated soils. They have been found in groundwater, causing health and environmental hazards, and are subjects of forensic toxicology. Dinitrophenols have multiple biological and noxious effects based on a mechanism of action characteristic to metabolic inhibitors. Although banned, they have pharmaceutical activity and can be purchased on the Internet as ingredients of weight-loss pills. Many death cases have been reported as accidents in agriculture or as overdoses in weight-loss diets. In this article, we discuss legal aspects of dinitrophenol usage, as well as their biological effect and possible mechanisms of toxicity.

Improved ninhydrin-based reagent for spectrophotometric determination of ppb levels of cyanide

ABSTRACT Cyanide is an extremely severe poison that has been raising concerns and controversies regarding its toxic effects on humans and the environment. A short-term human exposure to elevated levels can induce coma or death. Toxic effects occur at blood cyanide concentrations of 0.05 mg/dL, while death can occur at levels of 0.3 mg/dL. Numerous law and systems regulate cyanide levels in various environments. To exemplify, the maximum contamination limit imposed by United States Environmental Protection Agency in drinking water is 200 µg/L, while the European Union presents a lower limit of 50 µg/L. Ninhydrin has proved to be an effective color reagent for the spectrophotometric determination of trace levels of cyanide. This article reports a ninhydrin-based color reagent that was employed in cyanide determination involving real samples of water, cigarette smoke, urine, and cyanogenic plants, achieving an appropriate sample pretreatment procedure for cyanide liberation and separation. The reaction between cyanide and ninhydrin is fast enough to be performed at ambient conditions, but the ninhydrin reagent must be freshly prepared in oxygen-free solvent. Beers law is obeyed in the range between 20 and 400 ppb CN− (r = 0.992; N = 7) with molar absorptivity of 1.4 × 105 L mol−1 cm−1 and limit of detection of 8 ppb cyanide. Recovery at 100 ppb CN− was (100.5 ± 0.1) %, whereas precision was 1.7%. Also, absorbance at 485 nm proved to be temperature-dependent, with a maximum at ambient conditions. Throughout all measurements, the ninhydrin-based assay proved to be reliable, economical and environmentally friendly. Significance of the assay for the determination of cyanide in the field of environmental forensics, as well as its potential aid in elucidating incidents with legal consequences are highlighted.

Aβ1–16 conformational changes induced by heavy metals, antioxidants, and corn zeins: CD, AFM, SEM, and FT-IR studies

Amyloid-beta (known also as Aβ or A-beta or beta-amyloid) is a peptide of 36–43 amino acids that appears to be the main constituent of amyloid plaques in the brains of Alzheimer’s disease (AD) patients. The transformation process from α-helix to β-sheet structures appears to be one of the major factors in the genesis and evolution of a variety of neurodegenerative diseases such as AD, Parkinson’s disease (PD), and several prion diseases [1,2]. Metal-based reactions of some polypeptides and proteins are considered as a common denominator for neurodegenerative diseases (Figure 1) [3,4]. Amyloid-β (Aβ) aggregates are associated with Alzheimer’s disease (AD), and may be promoted by the trace amounts of metal ions like aluminium, iron, zinc or copper [5–11]. For example, copper ions cause the peptide aggregation to a great extent and highly increase the neurotoxicity exhibited by Aβ1–40 in cell culture [11].