Bromide detection in blood using energy dispersive X-ray fluorescence; a chemical marker supportive of drowning in seawater

Further assessments of ligase LplA-mediated modifications of proteins in vitro and in cellulo

BACKGROUND

Posttranslational modifications of proteins are catalyzed by a large family of enzymes catalyzing many chemical modifications. One can hijack the natural use of those enzymes to modify targeted proteins with synthetic chemical moieties. The lipoic acid ligase LplA mutants can be used to introduce onto the lysine sidechain lipoic acid moiety synthetic analogues. Substrate protein candidates of the ligase must obey a few a priori rules.

METHODS AND RESULTS

In the present report, we technically detailed the use of a cell line stably expressing both the ligase and a model protein (thioredoxin). Although the goal can be reach, and the protein visualized in situ, many experimental difficulties must be fixed. The sequence of events comprises (i) in cellulo labeling of the target protein with a N₃-lipoic acid derivative catalyzed by the mutant ligase, (ii) the further introduction by click chemistry onto this lysine sidechain of a fluorophore and (iii) the following of the labeled protein in living cells. One of the main difficulties was to assess the click chemistry step onto the living cells, because images from both control and experimental cells were similar. Alternatively, we describe at that stage, the preferred use of another technique: the Halo-Tag one that led to the obtention of clear images of the targeted protein in its cellular context. Although the ligase-mediated labeling of protein in situ is a rich domain for which many cellular tools must be developed, many difficulties must be considered before entering a systematic use of this approach.

CONCLUSIONS

In the present contribution, we added several steps of analytical characterization, both in vitro and in cellulo that were previously lacking. Furthermore, we show that the use of the click chemistry should be manipulated with care, as the claimed specificity might be not complete whenever living cells are used. Finally, we added another approach-the Halo Tag-to complete the previously suggested approaches for labelling proteins in cells, as we found difficult to strictly apply the previously reported methodology.

Trace elements in forensic human lung: A new approach to the diagnosis of seawater drowning. A preliminary study

The diagnosing of drowning remains one of the most challenging activities for the forensic pathologist. There is little information on the impact on the lung as a target organ in death by drowning. We aimed to investigate the concentration of trace elements in the lungs of people who had suffered different types of death to evaluate the discriminating ability of trace elements to identify seawater drowning (SWD). A total of 11 trace elements were analyzed by Inductively Coupled Plasma-Mass Spectrometry in 74 forensic cases. Sampler scanning electron microscopy and Energy Dispersive X-ray spectroscopy (EDX) were used to identify ultrastructural lung alterations. A Principal Component Analysis (PCA) of trace elements was carried out. The trace elements in SWD lungs were detected in the following order of concentration: Br˃Zn˃Sr˃Cr˃Cu˃As˃Pb˃Se˃Mn˃Ni˃Cd. Our results showed significantly higher concentrations of Br and Sr (P = 0.010 and P = 0.000) and significantly lower concentrations of Zn, Pb, Cu, Cd, and Se in SWD compared with other causes of death. After adjusting by confounder factors, Sr and Br remained as predictive independent factors for diagnosis of drowning (p = 0.042, in both cases). These results were confirmed by PCA, which revealed a wide separation between SWD and the rest of the causes of death. Our SWD cohort was characterized by high concentrations of the trace elements Br and Sr and low concentrations of Zn, Pb, Cu, Cd, and Se in lung tissue, while PCA showed its discriminatory capacity to identify death by seawater drowning. These findings, together with those obtained using other techniques, can be of great importance in the diagnosis of SWD.

Feasibility of Lead Exposure Assessment in Blood Spots using Energy-Dispersive X-ray Fluorescence

Collecting blood spots from newborns is a common procedure used to diagnose multiple health conditions. Fingerstick blood samples are routinely collected from children to diagnose elevated blood lead levels. In our study, we wanted to test the feasibility of using a high-power energy-dispersive X-ray fluorescence (EDXRF) device to accurately measure the concentration of lead in blood spots. We created spotted standards of a known concentration of lead on a filter paper at different volumes and concentrations. We determined the detection limit for lead through repeated measurements of our standards and calibration line slopes. We also tested the variability of the measured lead concentration across procedures and spotted blood volumes and found no significant additions to uncertainty in measurements. Finally, we compared blood lead concentrations measured by EDXRF and atomic absorption spectroscopy (AAS) and found EDXRF to be a significant predictor of blood lead (n = 22, R = 0.98, p value <0.001) with an average detection limit of 1.7 μg/dL of blood lead. This detection limit is similar to that of the AAS technique, which is commonly used in clinical testing laboratories for blood lead surveillance. These findings provide a proof of concept that blood spots measured by EDXRF may be used as a surveillance tool for lead exposure, even at elevated blood lead levels of 2-3 μg/dL.

Optical Detection of Bromide Ions Using Pt(II)-5,10,15,20-Tetra-(4-methoxy-phenyl)-porphyrin

Bromide ions are present in many environments, such as sedative drugs, methyl-bromide-treated vegetables and seawater. Excess bromide in humans interferes with iodide metabolism and is considered toxic. The need for fast and inexpensive methods for bromide detection is of interest. Spectrophotometric detection methods provide accurate and sensitive results. The well-known ability of metalloporphyrins to bind anionic ligands to the central metal ion has been exploited. The changes in the optical properties of Pt(II) 5,10,15,20-tetra(4-methoxy-phenyl)-porphyrin (PtTMeOPP) under the influence of bromide ions allowed us to achieve a fast, simple and reliable UV-vis spectrophotometric method of detection with a detection limit of 2.5 × 10−8 M and a good confidence coefficient: 99.05%. The potential interfering ions, such as Cl−, I−, NO2−, NO3−, SCN−, SO32−, SO42− and PO43− of 100-fold higher and Cl− and R-S− of 1000-fold higher concentrations in the mixture as compared to the determined concentration of bromide ions (c = 10−5 M), were tested and did not influence the results. The behavior of the sensitive porphyrin in various pH media was investigated in order to determine their influence upon the bromide detection capacity.

Determination of inorganic anions in the whole blood by ion chromatography

A fast, precise, and accurate method that can simultaneously determine 7 anions in whole blood was established by on line dialysis-double suppression ion chromatography. Performance parameters which could affect the determination of anions were optimized, including the selection of protein precipitant in samples, the amount of filtrate discarded, selection of eluent flow rate, influence of the Ag-Na column on experimental results, influence of ethylenediamines on ClO₂^-, and investigation of nitrogen drying. Finally, 3.6 mmol/L sodium carbonate was selected as eluent, with a flow rate of 0.8 mL/min, to separate the 7 anions. Blood and alcohol (v/v, 1:4) were used to precipitate the proteins in blood. The 7 anions reached an adequate recovery rate when the first 2 mL of filtrate from the C18 column was discarded. The recovery rate at LLOQ, low, medium, and high concentrations was 80-120%. The correlation coefficients (r²) of the calibration curves of the targeted anions ranged from 0.9975 to 0.9998. The limit of detection (LOD) was 0.309-7.71 μg/L. This method has simple pretreatment, high accuracy, and good reproducibility and selectivity, and is suitable for the separation and determination of anions in blood.

Electroanalytical Sensing of Bromides Using Radiolytically Synthesized Silver Nanoparticle Electrocatalysts

Monitoring bromides (Br^-) is of crucial importance since bromates, potential human carcinogens, are formed during ozonation of water containing bromides in concentrations >100 μg L^-1. Within this study, silver (Ag) and four carbon-supported Ag catalysts were synthesized by the γ-radiation method and their morphology and structure examined using transmission electron microscopy, X-ray diffraction, and UV-Vis analysis. The nanocatalysts were tested for Br^- sensing in aqueous media using cyclic voltammetry. All five Ag materials exhibited electroactivity for sensing of Br^- ions, with pure Ag catalyst giving the best response to Br^- ions presence in terms of the lowest limit of detection. Sensing of bromides was also explored in tap water after addition of bromides suggesting that herein prepared catalysts could be used for bromides detection in real samples. Furthermore, sensing of other halogen ions, namely, chlorides and iodides, was examined, and response due to chloride presence was recorded.

Diagnosis of drowning: Electrolytes and total protein in sphenoid sinus liquid

In this study, electrolyte (sodium (Na), chlorine (Cl), and magnesium (Mg)) and total protein (TP) concentrations and volume of liquid in the sphenoid sinus were examined to determine their usefulness to elucidate whether drowning occurred in freshwater or seawater. We examined 68 cases (seawater drowning group: 27 cases, freshwater drowning group: 21 cases, non-drowning group: 20 cases). There was a significant difference in Na, Cl, Mg, and TP concentrations of liquid in the sphenoid sinus among the three groups (seawater drowning, freshwater drowning, and non-drowning groups). To distinguish freshwater drowning from seawater drowning, Na, Cl, and Mg concentrations of liquid in the sphenoid sinus might serve as useful indicators.

Detection of chlorine and bromine in free liquid from the sphenoid sinus as an indicator of seawater drowning

We have investigated the usefulness of elemental analysis by energy-dispersive X-ray spectroscopy (EDX) in the examination of free liquid from the sphenoid sinus of drowning victims. We detected both chlorine and bromine in liquid taken from the sphenoid sinus of seawater drowning victims. Because these elements were below the quantification limit in freshwater cases, we could easily distinguish seawater from freshwater drowning cases. Detection of these elements from the liquid in the sphenoid sinuses of drowning victims may be useful as a supportive measure for seawater drowning.