naphthoquinones and imidazole

The electrochemical detection methods have emerged as a potential alternative to the bench-top optical systems in monitoring nucleic acid amplification. DNA intercalating redox reporters play a crucial role in such monitoring schemes. Here, a series of bisintercalating redox probes have been tailor-made to meet specific requirements of electrochemical quantitative loop-mediated isothermal amplification (qLAMP). The probes composed of two naphthoquinone-imidazole (NQIM) derivatives as signal motifs that are covalently bridged by different linkers (R). They are bis-NQIM-R; R = Alkane (Ak), ethylene glycol (EG) and phenyl (Ph). The linkers allow the probes to be fine-tuned for securing ideal redox reporter. DNA binding studies via electrochemical and fluorescence techniques demonstrate that the bis-NQIM-R probes possess better ds-DNA bisintercalating ability compared to their mono-analogs. The bis-NQIM-Ph was implemented in a real-time electrochemical qLAMP, for which a prototype custom-made device that can perform fully automated multiplexed analyses is devised. A single copy of Salmonella DNA was quantified in just 10 min and the performance is comparable to the benchtop fluorescence method. Thus, the bisintercalating redox reporters incorporated electrochemical detection schemes hold great promise in qLAMP.

Topics: Biosensing Techniques; DNA; DNA, Bacterial; Electrochemical Techniques; Equipment Design; Humans; Imidazoles; Intercalating Agents; Lab-On-A-Chip Devices; Naphthoquinones; Nucleic Acid Amplification Techniques; Oxidation-Reduction; Salmonella; Salmonella Infections; Time Factors

Ambient particulate matter (PM) can cause adverse health effects via their ability to produce reactive oxygen species (ROS). Humic-like substances (HULIS), a complex mixture of amphiphilic organic compounds, have been demonstrated to contain the majority of redox activity in the water-extractable organic fraction of PM. Reduced organic nitrogen compounds, such as alkaloids resulting from biomass burning emissions, are among HULIS constituents. In this study, we examined the redox activities of pyridine, imidazole and their alkyl derivatives using a cell-free dithiothreitol (DTT) assay under simulated physiological conditions (37 °C, pH = 7.40). These compounds were found to have little redox activity on their own as measured by the DTT assay, but they enhanced ROS generation catalyzed by 1,4-naphthoquinone (as a model quinone compound) and HULIS isolated from multiple aerosol samples. The enhancement effect by the individual nitrogen-containing bases was determined to be proportional to their amount in the assay solutions. It is postulated that the underlying mechanism involves the unprotonated N atom acting as a H-bonding acceptor to facilitate hydrogen-atom transfer in the ROS generation cycle. The enhancement capability was found to increase with their basicity (i.e., pKa of their conjugated acids, BH(+)), consistent with the proposed mechanism for enhancement. Among the imidazole homologues, a linear relationship was observed between the enhancement factors (in log scale) of the unprotonated form of the imidazole compounds (B) and the pKa of their conjugated acids (BH(+)). This relationship predicts that the range of alkylimidazole homologues (C6-C13) observed in atmospheric HULIS would be 1.5-4.4 times more effective than imidazole in facilitating HULIS-mediated ROS generation. Our work reveals that the ability of atmospheric PM organics to catalyze generation of ROS in cells could be affected by coexisting redox inactive organic constituents and suggests further work deploying multiple assays be conducted to quantify redox capabilities and enhancement effects of the HULIS components.

Topics: Aerosols; Dithiothreitol; Humic Substances; Hydrogen Bonding; Imidazoles; Models, Theoretical; Naphthoquinones; Nitrogen; Oxidation-Reduction; Particulate Matter; Pyridines; Reactive Oxygen Species; Water

We developed a new spectrofluorometric method for qualitative and quantitative determination of cyanide in water using the incorporation of naphthoquinone imidazole boronic-based sensors (m-NQB and p-NQB) and a cationic surfactant, certyltrimethyl ammonium bromide (CTAB). This micellar system exhibited great selectivity for cyanide detection with an assistance of the cationic surface of micelle. The interaction of boronic acid of the sensor toward cyanide in CTAB micellar media gave a quantitative measure of cyanide concentration in the micromolar level. Under the optimal condition, fluorescence intensity at 460 nm of m-NQB and p-NQB provided two sets of linear ranges, 0.5-15 μM and 20-40 μM and the limit of cyanide detection of 1.4 μM. Hence, both sensors in CTAB aqueous micellar system offered a considerably promising cyanide detection with 1000-fold enhancement of the detection limit compared to those studied in DMSO: H(2)O. The proposed sensors could also be used to determine cyanide in water with good analytical characteristics.

Topics: Boronic Acids; Cetrimonium; Cetrimonium Compounds; Cyanides; Imidazoles; Micelles; Naphthoquinones; Spectrometry, Fluorescence; Surface-Active Agents; Water Pollutants, Chemical

This work describes the application of counter-current chromatography (CCC) as a useful, fast and economic alternative for the isolation and purification of heterocyclic derivatives from lapachol and beta-lapachone, two naturally occurring compounds from Tabebuia species, and nor-beta-lapachone, a synthetic congener of lapachol. The discussed data comprise four examples of purification of synthetic reactions with different solvent systems - the mixture of the oxazole and the imidazole from beta-lapachone; the quinoxaline from nor-beta-lapachone; and the purification of the N-oxides from the quinoxaline and the phenazine from nor-beta-lapachone from their respective not fully reacted substrates by means of aqueous reversed- and normal-phase elution modes and non-aqueous solvent systems. Traditional purification of these reaction products by silica gel column chromatography demanded a large amount of solvent and time and, in some cases, serious degradation of the products occurred, leading to low yield of the reaction. High-speed counter-current chromatography (HSCCC) was used as an alternative to optimize the process and raise the yield of the reactions.

Topics: Activating Transcription Factor 6; Chromatography, Thin Layer; Countercurrent Distribution; Cyclization; Imidazoles; Molecular Structure; Naphthoquinones; Oxazoles; Quinoxalines

Topics: Anthelmintics; Anti-Infective Agents; Chemistry, Pharmaceutical; Imidazoles; Naphthalenes; Naphthoquinones; Pharmacology; Research; Salts