The emerging field of metallomics refers to the entirety of research activities aimed at the understanding of the molecular mechanisms of metal-dependent life processes. This critical review discusses the concept of metallomics with a focus on analytical techniques and methods for the probing of interactions between metal ions and the organism's genome and the derived -omes: proteome and metabolome. Particular attention is paid to the in vivo screening for the native metal-protein and metal-metabolite complexes by hyphenated techniques that combine a high-resolution separation technique (gel electrophoresis, chromatography or capillary electrophoresis) with sensitive elemental (inductively coupled plasma, ICP) or molecular (electrospray or MALDI) mass spectrometric detection. The contribution of bioinformatics to the prediction of metal-binding sequences in proteins and the role of molecular biology approaches for the detection of metal-dependent genes, proteins and metabolites are highlighted (115 references).

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A laser ablation-ICPMS method using an infrared (1030 nm), low-energy (39 microJ/pulse), high repetition rate (10 kHz), femtosecond laser was developed to improve the sensitivity of detection of heteroatom-containing proteins in 1D polyacrylamide gels. A 2-mm-wide lane was ablated by ultrafast (10 cm s(-1)) back-and-forth movement of a 20-microm laser beam parallel to the protein bands while the gel advanced perpendicularly. This procedure resulted in a considerable increase in detection sensitivity (>40-fold) compared to the nanosecond 266-nm laser ablation-ICPMS, mainly because of the much larger amount of ablated material introduced into the plasma on the time scale of the dwell time of the mass spectrometer. The method was applied to the specific detection in the gel of formate dehydrogenase expressed in Escherichia coli and of selenoproteins in Desulfococcus multivorans with detection limits at the low-femtomolar levels.

The follow-up of the Heated Intraoperative Chemotherapy (HIPEC) of peritoneal carcinomatosis would benefit from the monitoring of the penetration, distribution and metabolism of the drug within the tumor. As tumor nodules can be resected during the therapy, mass spectrometry imaging is a suitable tool for the evaluation of treatment efficacy, and, as a result, the therapy can be re-optimized. In this work we demonstrate the complementarity of laser ablation (LA) ICP mass spectrometry and MALDI imaging to study the penetration and distribution of two Pt-based metallodrugs (cisplatin and oxaliplatin) in human tumor samples removed from patients diagnosed with colorectal or ovarian peritoneal carcinomatosis. LA ICP MS offered sensitive (LOD for (195)Pt 4.8 pg s(-1)) imaging of platinum quasi-independently of the original species and the sample matrix and thus an ultimate way of verifying the penetration of the Pt-containing drug or its moieties into the tumor. MALDI imaging was found to suffer in some cases from signal suppression by the matrix leading to false negatives. In the case of the oxaliplatin metallodrug, the results obtained from ICP and MALDI MS imaging were coherent whereas in the case of cisplatin, species detected by ICP MS imaging could not be validated by MALDI MS. The study is the first application of the dual ICP and MALDI MS imaging to the follow-up of metallodrugs in human tumors.

Concentrations and bioavailability of cadmium (Cd) and lead (Pb) were determined in cocoa powders and related products (beans, liquor, butter) of different geographical origins. Particular attention was paid to the fractionation of these metals, which was investigated by determining the metal fraction soluble in extractant solutions acting selectively with regard to the different classes of ligands. The targeted classes of Cd and Pb species included: water-soluble compounds, polypeptide and polysaccharide complexes, and compounds soluble in simulated gastrointestinal conditions. The bioavailability of Cd and Pb from cocoa powder, liquor and butter was evaluated using a sequential enzymolysis approach. The data obtained as a function of the geographical origin of the samples indicated strong differences not only in terms of the total Cd and Pb concentrations, but also with regard to the bioavailability of these metals. The Cd concentrations in the cocoa powders varied from 94 to 1833 microg kg(-1), of which 10-50% was potentially bioavailable. The bioavailability of Pb was generally below 10% and the concentrations measured in the cocoa powders were in the 11-769 microg kg(-1) range. Virtually all the Cd and most of Pb were found in the cocoa powder after the pressing of the liquor.

The occurrence and form of selenium and mercury were investigated in Indian Mustard, Brassica juncea, a selenium accumulating plant, which had been co-exposed to varying concentration levels of these two elements. Plants were grown and exposed in hydroponic solutions. Following exposure, root exudates were collected in fresh solutions and the head-space around the aerial portions of the plants was sampled. These samples and the harvested plant tissues were then processed for determination of Se and Hg-containing compounds. For the plant tissues, roots, stems and leaves were separated and extracted using a sequential procedure that removed watersoluble species, water-soluble proteins, and dodecyl sulfate-soluble proteins. Size exclusion chromatography allowed further fractionation. High molecular-weight selenium/mercurycontaining compounds were found primarily in the plant root extract. Evidence suggests that a Se and Hg complex of high molecular weight may be protein associated. For the analysis of exudate solutions, ion-pairing reversed phase chromatography coupled to ICP-MS was used. Multiple selenium and mercury species were detected, with one mercury-containing compound observed eluting near selenocystine. Plant head-space was sampled with solid phase microextraction and analyzed with GC-ICP-MS and GC-TOFMS. Apart from the primary selenium volatiles and elemental mercury, no volatile species simultaneously containing Se and Hg could be detected.

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