José Luis López-Paz

Dual-Polarization Interferometry: A Novel Technique To Light up the Nanomolecular World

Nanomolecular World Jorge Escorihuela,† Miguel Ángel Gonzaĺez-Martínez,† Jose ́ Luis Loṕez-Paz,† Rosa Puchades,† Ángel Maquieira,† and David Gimenez-Romero*,‡ †Department of Chemistry, Institute of Molecular Recognition and Technological Development, Universitat Politec̀nica de Valeǹcia, Camino de Vera s/n, 46022 Valeǹcia, Spain ‡Physical Chemistry Department, Faculty of Chemistry, Universitat de Valeǹcia, Avenida Dr. Moliner 50, 46100 Burjassot, Valeǹcia, Spain

Analysis of Pesticides by Flow Injection Coupled with Chemiluminescent Detection: A Review

The analyses of pesticides carried out by coupling flow injection analysis with chemiluminescence (CL) detection during the last ten years are reported in this review. The review is divided into three sections devoted to the different families of pesticides, namely, organophosphorus, carbamates (together with dithiocarbamates), and other pesticides from the remaining groups. Relevant analytical data such as limits of detection, dynamic ranges, recoveries, and sample pretreatments are recorded in three tables. Descriptions about the fundamentals of the CL systems used, and new promising approaches such as photoinduced chemiluminescence (PICL), multicommutation, and molecular connectivity are also included.

Native vs photoinduced chemiluminescence in dimethoate determination.

The determination of dimethoate using either its native chemiluminescent (CL) properties or its photoinduced chemiluminescence obtained by irradiation with a 15 W low-pressure mercury lamp was studied. Thereby, two flow injection systems (FIA) with and without irradiation were exhaustively optimized and their analytical characteristics studied. Better sensitivity and selectivity was found in absence of irradiation, due to the enhancing effect of hexadecylpyridinium chloride (HPC), which acted as a sensitizer. In the developed FIA-CL system, the alkaline hydrolysis of dimethoate with NaOH was performed on-line in presence of HPC. The oxidation of the product of hydrolysis with Ce(IV) in hydrochloric medium induced chemiluminescence. The method provided a limit of detection of only 0.05 ng mL(-1) without any pre-treatment. However, the combination with solid phase extraction allowed the removal of some potential interferents as well as the preconcentration of the pesticide. Finally, the developed method was successfully applied to natural waters with recoveries between 95 and 108%.

Determination of N-methylcarbamate pesticides using flow injection with photoinduced chemiluminescence detection

A sensitive, economic, rapid and simple method for the determination of four N-methylcarbamate pesticides: methomyl (2.0–80 μg L−1), aldicarb (5.0–50 μg L−1), butocarboxim (2.0–60 μg L−1) and oxamyl (2.0–60 μg L−1); is reported. It relies on the coupling of photoinduced chemiluminescence (PICL) detection with flow injection (FI) methodology. The automation of FI together with the use of light as a reagent decreased the environmental impact of the analysis. The proposed method was based on the oxidation of these pesticides, previously irradiated on-line with UV light, with cerium(IV), using quinine as a sensitiser. Limits of detection below the legal limits (100 ng L−1) established by the European Union for drinking waters were obtained without the need of preconcentration steps. A good inter-day reproducibility (1.6–6.4%, n = 5), repeatability (rsd = 2.7 %, n = 25) and high throughput (123 h−1) were achieved. The method was successfully applied to the determination of methomyl in natural waters with mean recoveries ranging from 90% to 98%.

Development of a Flow Injection Manifold for Napropamide Determination by Photo-Induced Chemiluminescence

A new, rapid, and simple method is proposed for the determination of the pesticide napropamide by photo-induced chemiluminescence detection coupled with a flow injection analysis (FIA) system. The emission was obtained by oxidation with periodate in basic medium, of the photoproducts generated on-line by UV irradiation (254 nm) of napropamide in acidic SDS (sodium dodecyl sulfate) medium. The flow method, in combination with the solid phase extraction (SPE) performed off-line with C18 cartridges, allowed the determination of this pesticide over the 0.8–14.0 µ gL−1 range, with a limit of detection of 0.3 µ gL−1. The relative standard deviation (n = 9) at 2.5 µ gL−1 level was 4.3% for the combined FIA-SPE system. After testing the influence of several potential interfering compounds, including ions and other pesticides, the method was successfully applied to the determination of napropamide in spiked water samples with recoveries between 96–103%.

Fast Determination of Thiacloprid by Photoinduced Chemiluminescence

A new and sensitive application of chemiluminescence detection has been developed for the determination of the pesticide thiacloprid in water. It was based on the on-line photoreaction of thiacloprid in a basic medium, with quinine acting as the sensitizer of the chemiluminescent response; cerium (IV) in sulfuric acid medium was used as the oxidant. High degrees of automation and reproducibility were achieved using a flow-injection analysis (FIA) manifold. The validation of the method was performed in terms of selectivity, linearity, limit of detection (LOD), precision, and accuracy. Liquid chromatography with ultraviolet (UV) detection was used as reference for mineral, tap, ground, and spring water samples. The proposed method is fast (with a throughput of 130 h−1), sensitive (LOD of 0.8 ng mL−1 without preconcentration steps and of 0.08 ng mL−1 with solid-phase extraction [SPE]), low cost, and possible to couple with separation methods for the simultaneous determination of other pesticides. The enhanced chemiluminescence intensity was linear with the thiacloprid concentration above the 2–80 and 80–800 ng mL−1 ranges. A possible reaction mechanism is also discussed.

Mapping molecular binding by means of conformational dynamics measurements

Protein–protein interactions are key in virtually all biological processes. The study of these interactions and the interfaces that mediate them play a key role in the understanding of biological function. In particular, the observation of protein–protein interactions in their dynamic environment is technically difficult. Here two surface analysis techniques, dual polarization interferometry and quartz crystal microbalance with dissipation monitoring, were paired for real-time mapping of the conformational dynamics of protein–protein interactions. Our approach monitors this dynamics in real time and in situ, which is a great advancement within technological platforms for drug discovery. Results agree with the experimental observations of the interaction between the TRIM21α protein and circulating autoantibodies via a bridging bipolar mechanism. This work provides a new chip-based method to monitor conformational dynamics of protein–protein interactions, which is amenable to miniaturized high-throughput determination.

Development of a Photoinduced Chemiluminescent Method for the Determination of the Herbicide Quinmerac in Water

A new, simple, and sensitive method, based on photoinduced chemiluminescence, was developed for the determination of quinmerac. The photoproduct, obtained after ultraviolet irradiation in basic medium, was mixed with sodium sulfite (sensitizer), and Ce(IV) (oxidant) in acid medium. A wide linear dynamic range (2–600 ng mL−1) and a limit of detection of 0.6 ng mL−1 were obtained without any pretreatment (0.08 ng mL−1 after solid-phase extraction). The determination was performed using a flow-injection manifold, which allowed a high throughput (144 h−1). The interday reproducibility was 5.6% (n = 5), and the intraday repeatability was 3.9 and 2.9% for 20 and 200 ng mL−1 of quinmerac, respectively (n = 21). Finally, the method was applied to surface water and groundwater, with recoveries ranging from 78.1 to 94.5%.

New structural insights into the role of TROVE2 complexes in the on-set and pathogenesis of systemic lupus erythematosus determined by a combination of QCM-D and DPI

AbstractThe mechanism of self-recognition of the autoantigen TROVE2, a common biomarker in autoimmune diseases, has been studied with a quartz crystal microbalance with dissipation monitoring (QCM-D) and dual polarization interferometry (DPI). The complementarity and remarkable analytical features of both techniques has allowed new insights into the onset of systemic lupus erythematosus (SLE) to be achieved at the molecular level. The in vitro study for SLE patients and healthy subjects suggests that anti-TROVE2 autoantibodies may undergo an antibody bipolar bridging. An epitope-paratope-specific binding initially occurs to activate a hidden Fc receptor in the TROVE2 tertiary structure. This bipolar mechanism may contribute to the pathogenic accumulation of anti-TROVE2 autoantibody immune complex in autoimmune disease. Furthermore, the specific calcium-dependent protein-protein bridges point out at how the TRIM21/TROVE2 association might occur, suggesting that the TROVE2 protein could stimulate the intracellular immune signaling via the TRIM21 PRY-SPRY domain. These findings may help to better understand the origins of the specificity and affinity of TROVE2 interactions, which might play a key role in the SLE pathogenesis. This manuscript gives one of the first practical applications of two novel functions (−df/dD and Δh/molec) for the analysis of the data provided by QCM-D and DPI. In addition, it is the first time that QCM-D has been used for mapping hidden Fc receptors as well as linear epitopes in a protein tertiary structure. Graphical abstractᅟ