Stresses caused by deficiency/excess of mineral nutrients or of pollution of toxic metals have already become a primary factor in limiting crop production worldwide. Genes involved in minerals and toxic metals accumulation/tolerance could be potential candidates for improving crop plants with enhanced nutritional efficiency and environmental adaptability. In this study, we first generated a high-quality yeast expression cDNA library of Brassica napus (Westar), and 46 genes mediating excess micronutrients and toxic metals detoxification were screened using the yeast genetic complementation system, including 11, 5, 6, 14, 6, and 5 genes involved in cadmium (Cd), zinc (Zn), iron (Fe), manganese (Mn), boron (B), and copper (Cu) tolerance, respectively. Characterization of genes mediating excess ions stress resistance in this study is beneficial for us to further understand ions homeostasis in B. napus.

Selenomethionine (SeMet) as a methionine analog can be incorporated into protein. In turkeys, we recently found that selenium (Se) as selenite is not metabolized to SeMet but rather to selenosugars (seleno-N-acetyl galactosamine) bound to protein as well as to selenocysteine (Sec) in selenoproteins. To characterize the metabolism of SeMet, we fed rats graded levels of SeMet from 0 to 5µg Se/g in a Se-deficient diet for 4 wk, and investigated the fate and accumulation of liver Se using high pressure liquid chromatography (HPLC) coupled with Se-specific inductively coupled plasma mass spectrometry (ICP-MS) and molecule specific (Orbitrap MS/MS) detection. Up to 0.24µg Se/g (Se requirement for maximal glutathione peroxidase activity), Sec accounted for ∼40% of total liver Se whereas SeMet only accounted for 3-11%. Analysis of water-soluble extracts found negligible low molecular weight (LMW) Se species in rats fed 0 and 0.08µg Se/g, including no SeMet. At 0.24µg Se/g and above, SeMet accounted for only 10% of LMW Se species, whereas methyl- and glutathionyl-selenosugars accounted for 70% of LMW Se species. Above the Se requirement, SeMet was ∼30% of the proteinaceous amino acids, whereas Sec levels fell to 5% in rats fed 5µg Se/g as SeMet. Last, considerably less inorganic Se was bound to liver protein with high SeMet as compared to selenite in a parallel study. SeMet is efficiently metabolized and mixes with the common Se metabolite pool, where Se is preferentially incorporated into Sec and Sec-selenoproteins until selenoproteins plateau; with high SeMet intake, Se is increasingly accumulated as LMW selenosugars and as selenosugar-decorated proteins.

Intracellular accumulation studies are a key step in metallodrug development but often variable results are obtained. Therefore, we aimed here to investigate different protocols for efficient and reproducible lysis of cancer cells in terms of protein content in lysates and in cell uptake studies of the Ru anticancer complex [chlorido(8-oxyquinolinato)(η6-p-cymene)ruthenium(II)] ([Ru(cym)(HQ)Cl]). The physical lysis methods osmosis and sonication were chosen for comparison with chemical lysis with the radioimmunoprecipitation assay (RIPA) buffer. Based on the protein content and the total Ru accumulated in the lysates, the latter determined using inductively coupled plasma-mass spectrometry, RIPA buffer was the most efficient lysis method. Measurements of plastic adsorption blanks revealed that the higher Ru content determined in the RIPA buffer lysis samples may be due a higher amount of Ru extracted from the plastic incubation plates compared with osmosis and sonication. Overall, we found that the choice of lysis method needs to be matched to the information sought and we suggest the least disruptive osmosis method might be the best choice for labile drug-biomolecule adducts. Minimal differences were found for experiments aimed at measuring the overall cell uptake of the Ru complex.

The movement of metals through the environment links together a wide range of scientific fields: from earth sciences and geology as weathering releases minerals; to environmental sciences as metals are mobilized and transformed, cycling through soil and water; to biology as living things take up metals from their surroundings. Studies of these fundamental processes all require quantitative analysis of metal concentrations, locations, and chemical states. Synchrotron X-ray tools can address these requirements with high sensitivity, high spatial resolution, and minimal sample preparation. This perspective describes the state of fundamental scientific questions in the lifecycle of metals, from rocks to ecosystems, from soils to plants, and from environment to animals. Key X-ray capabilities and facility infrastructure for future synchrotron-based analytical resources serving these areas are summarized, and potential opportunities for future experiments are explored.

The purpose of this essay is to propose that metallomic studies in the area of extracellular copper transport are incomplete without the explicit consideration of kinetics of Cu2+ion binding and exchange reactions. The kinetic data should be interpreted in the context of time constraints imposed by specific physiological processes. Examples from experimental studies of Cu2+ ion interactions with amino-terminal copper and nickel binding site/N-terminal site motifs are used to demonstrate that duration and periodicity of such processes as bloodstream transport or neurotransmission promote the reaction intermediates to the role of physiological effectors. The unexpectedly long lifetimes of intermediate complexes lead to their accumulation and novel reactivities. The emerging ideas are discussed in the context of other research areas in metallomics.

The influence of the fermentation process on selenite metabolism by a probiotic Bifidobacterium longum DD98 (B. longum DD98), and its consequent enrichment in selenium (Se) were studied. The effects of sodium selenite (Na2SeO3) concentration (18-400 μg/mL), feeding time (12, 16, and 24 h), and fermentation stage (secondary and tertiary fermentation) were evaluated by measuring i) the total Se content and its distribution between the water-soluble metabolome fraction and the water-insoluble fraction; ii) the total concentrations of the two principal Se-compounds produced: selenomethionine (SeMet) and γ-glutamyl-selenomethionine (γ-Glu-SeMet), and iii) the speciation of Se in the metabolite fraction. The results revealed that the fermentation process notably changed the Se incorporation into metabolites (γ-Glu-SeMet and free SeMet) and proteins (bound-SeMet) in B. longum DD98. In particular, the production of SeMet was negatively correlated to that of γ-Glu-SeMet when no red precipitate was seen in the bacteria. The study offers a tool for the control of the optimization of the fermentation process towards the desired molecular speciation of the incorporated Se and hence contributes to the production of Se-enriched probiotics with good qualities and bioactivities.

Metal cations have been exploited for their precipitation properties in a wide variety of studies, ranging from differentiating proteins from serum and blood to identifying the protein targets of drugs. Despite widespread recognition of this phenomenon, the mechanisms of metal-induced protein aggregation have not been fully elucidated. Recent studies have suggested that copper's (Cu) ability to induce protein aggregation may be a main contributor to Cu-induced cell death. Here, we provide the first proteome-wide analysis of the relative sensitivities of proteins across the Escherichia coli proteome to Cu-induced aggregation. We utilize a metal-induced protein precipitation (MiPP) methodology that relies on quantitative bottom-up proteomics to define the metal concentration-dependent precipitation properties of proteins on a proteomic scale. Our results establish that Cu far surpasses other metals in promoting protein aggregation and that the protein aggregation is reversible upon metal chelation. The bulk of the Cu bound in the protein aggregates is Cu1+, regardless of the Cu2+ source. Analysis of our MiPP data allows us to investigate underlying biophysical characteristics that determine a protein's sensitivity to Cu-induced aggregation, which is independent of the relative concentration of protein in the lysate. Overall, this analysis provides new insights into the mechanism behind Cu cytotoxicity, as well as metal cation-induced protein aggregation.

Stable calcium (Ca) isotope ratios are sensitive and radiation-free biomarkers in monitoring biological processes in human bodies. Recently, the Ca isotope ratios of bone, blood, and urine have been widely reported to study bone mineral balance. However, as a pure Ca crystallization product, there is no report on the Ca isotope ratios of kidney stones, even though the prevalence of kidney stones is currently on the rise. Here, we measured Ca isotope data of 21 kidney stone samples collected in Beijing, China. The δ44/42CaNIST 915a values ranged from 0.25‰ to 2.85‰ for calcium oxalate, and from 0.38‰ to 3.00‰ and 0.61‰ to 0.69‰ for carbonate apatite and uric acid, respectively. Kidney stones have heavier Ca isotope ratios than bone or blood, which is probably because complexed Ca contains more heavy Ca isotopes than free Ca2+. Ca isotope evidence suggests that magnesium (Mg) affects kidney stone formation, as the δ44/42CaNIST 915a value is inversely correlated with the Ca/Mg ratio. This study provides important preliminary reference values on the Ca isotopic composition of kidney stones and proposes a factor influencing Ca isotope fractionation in biological processes for future research.

The function of Corynebacterium glutamicum open reading frame (ORF) NCgl2684 (named nceA in this study), which was annotated to encode a metalloregulator, was assessed using physiological, genetic, and biochemical approaches. Cells with deleted-nceA (ΔnceA) showed a resistant phenotype to NiSO4 and CoSO4 and showed faster growth in minimal medium containing 20μM NiSO4 or 10μM CoSO4 than both the wild-type and nceA-overexpressing (P180-nceA) cells. In the ΔnceA strain, the transcription of the downstream-located ORF NCgl2685 (nceB), annotated to encode efflux protein, was increased approximately 4-fold, whereas gene transcription decreased down to 30% level in the P180-nceA strain. The transcriptions of the nceA and nceB genes were stimulated, even when as little as 5nM NiSO4 was added to the growth medium. Protein NceA was able to bind DNA comprising the promoter region (from -14 to+18) of the nceA--nceB operon. The protein-DNA interaction was abolished in the presence of 20μM NiSO4, 50μM CoSO4, or 50μM CdSO4. Although manganese induced the transcription of the nceA and nceB genes, it failed to interrupt protein-DNA interaction. Simultaneously, the P180-nceA cells showed increased sensitivity to oxidants such as menadione, hydrogen peroxide, and cumene hydroperoxide, but not diamide. Collectively, our data show that NceA is a nickel- and cobalt-sensing transcriptional regulator that controls the transcription of the probable efflux protein-encoding nceB. The genes are able to suppress intracellular levels of nickel to prevent reactions, which can cause oxidative damage to cellular components.

The global prevalence of autism spectrum disorder (ASD) is on the rise, and high levels of exposure to toxic heavy metals may be associated with this increase. Urine analysis is a noninvasive method for investigating the accumulation and excretion of heavy metals. The aim of this study was to identify ASD-associated urinary metal markers. Overall, 70 children with ASD and 71 children with typical development (TD) were enrolled in this retrospective case-control study. In this metallomics investigation, inductively coupled plasma mass spectrometry was performed to obtain the urine profile of 27 metals. Children with ASD could be distinguished from children with TD based on the urine metal profile, with ASD children showing an increased urine metal Shannon diversity. A metallome-wide association analysis was used to identify seven ASD-related metals in urine, with cobalt, aluminum, selenium, and lithium significantly higher, and manganese, mercury, and titanium significantly lower in the urine of children with ASD than in children with TD. The least absolute shrinkage and selection operator (LASSO) machine learning method was used to rank the seven urine metals in terms of their effect on ASD. On the basis of these seven urine metals, we constructed a LASSO regression model for ASD classification and found an area under the receiver operating characteristic curve of 0.913. We also constructed a clinical prediction model for ASD based on the seven metals that were different in the urine of children with ASD and found that the model would be useful for the clinical prediction of ASD risk. The study findings suggest that altered urine metal concentrations may be an important risk factor for ASD, and we recommend further exploration of the mechanisms and clinical treatment measures for such alterations.