Volume 80, Issue 12

The International Symposium on Metallomics 2007 (ISM 2007), was held in Nagoya, Japan 28 November-1 December 2007. This event was organized by the Chemical Society of Japan, with sponsorship of IUPAC, in order to highlight a newly emerging scientific concept. The term "metallomics" was proposed in 2004 to describe integrated biometal science, and has been receiving growing attention because it embraces all research fields related to metals in biological systems. A better understanding of the distribution, biological roles and functions, and physiological regulation and metabolism of metals in biological systems demands interdisciplinary cooperation between scientists in a variety of fields, such as chemistry, physics, biology, medicine, pharmacy, and agriculture. Metallomics can thus be expected to play a more widely recognized role in health, the environment, nutrition, food, toxicology, public hygiene, and bioremediation, to name just a few societally important application areas. Furthermore, the development of metallomics as a scientific field complements genomics and proteomics, and contributes toward more comprehensive insights into life processes. This first International Symposium on Metallomics was attended by about 340 delegates from 30 counties. The scientific program comprised 98 oral presentations including 6 plenary, 15 keynote, and 35 invited lectures, and 124 poster presentations. The proceedings covered a broad range of topics, which were delineated as - metallomics research on (a) environment and metals, (b) metallotoxicology, (c) health and food/nutrition, and (d) plants and metals; - metallomics research combined with genomics and proteomics; - advanced technologies for trace analysis; - chemical speciation of bio-trace elements; - bioimaging and biosensing technologies; - bioinorganic chemistry of metalloproteins and metalloenzymes; - biological regulation of metals and their mechanisms of metabolism; - drug design and chemotherapy of bioinorganic medicine; - medical diagnosis of health and disease; and - development of standard reference materials for biological, clinical, and environmental analysis. The program thus provided a comprehensive overview of all aspects of current interest and activity in metallomics, and it is hoped that this collection of works from the scientific proceedings will serve as a valued record and a source of future inspiration. It is a pleasure to report that the Royal Society of Chemistry, UK, will launch a new journal entitled Metallomics - Integrated Biometal Science from January 2009 (http://www.rsc.org/Publishing/Journals/mt/index.asp), which will help to stimulate ongoing development and facilitate the exchange of information in the metallomics community. Professor Joe Caruso (Cincinnati University) will serve as editor-in-chief. An important outcome of this inaugural event is that the International Advisory Board has decided to launch a biennial series of symposia on Metallomics, and that ISM 2009 will take place in Cincinnati, USA during June 2009 under the chairmanship of Prof. Caruso. In conclusion, it is with sorrow that we report the sudden death of Prof. Kazuo T. Suzuki (Chiba University, Japan) on 15 July 2008, whilst the editorial work for this special issue was in progress. He was Co-chair of the Organizing Committee for ISM 2007 and, as one of the world leaders in this field, presented a plenary lecture on that occasion. We mourn his passing and remember his outstanding contributions to science. This will be the subject of a memorial lecture, which I expect to deliver during ISM 2009. Hiroki Haraguchi Conference Editor and Chairman

Metal ions play a fundamental role in the chemistry of life. The understanding of the molecular bases of the living process requires the knowledge of the correlations existing between metal ions and the genome and the derived -omes : transcriptome, proteome, and metabolome. An indispensable step on this way is the characterization of the coordination environment of metal ions present and the identification and quantification of metal-containing chemical species. The ensemble of research activities related to metal ions in biological systems has been recently referred to as "metallomics" [1]. The progress in this field is largely dependent on the high-throughput acquisition of multielement and -species analytical data in biological samples. The paper gives a brief overview of the state of the art of analytical techniques and methods for the multielement quantitative analysis of biological microsamples, and for the detection, identification, and quantitation of metal-containing proteins and low-molecular-weight metabolites. The potential contribution of molecular biology techniques in terms of linking information on metals and metal-species to the genome of an organism is highlighted.

Metallomics is an emerging and promising research field which has attracted more and more attention. However, the term itself might be restrictive. Therefore, the term "elementomics" is suggested to encompass the study of nonmetals as well. In this paper, the application of state-of-the-art analytical techniques with the capabilities of high-throughput quantification, distribution, speciation, identification, and structural characterization for metallomics and elementomics is critically reviewed. High-throughput quantification of multielements can be achieved by inductively coupled plasma-mass spectrometry (ICP-MS) and neutron activation analysis (NAA). High-throughput multielement distribution mapping can be performed by fluorescence-detecting techniques such as synchrotron radiation X-ray fluorescence (SR-XRF), XRF tomography, energy-dispersive X-ray (EDX), proton-induced X-ray emission (PIXE), laser ablation (LA)-ICP-MS, and ion-detecting-based, secondary-ion mass spectrometry (SIMS), while Fourier transform-infrared (FT-IR) and Raman microspectroscopy are excellent tools for molecular mapping. All the techniques for metallome and elementome structural characterization are generally low-throughput, such as X-ray absorption spectroscopy (XAS), NMR, and small-angle X-ray spectroscopy (SAXS). If automation of arraying small samples, rapid data collection of multiple low-volume and -concentration samples together with data reduction and analysis are developed, high-throughput techniques will be available and in fact have partially been achieved.

Salmon egg cells were the subject of investigation for all-elements analysis in a single biological cell, where the elements in egg cells were simultaneously determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) after microwave-assisted acid digestion. As a result, 74 elements among 78 stable isotope elements were determined or detected, although H, C, N, and O were determined separately by conventional CHN elemental analysis. In addition, the survey of protein-binding metallic elements as well as metalloid elements in salmon egg cell cytoplasm was performed by the fractionation analysis with a hyphenated system of high-performance liquid chromatography (HPLC)/ICP-MS using a 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate (CHAPS)-coated octadecylsilyl silica (ODS) column and a size exclusion chromatography (SEC) column.

Here we report a preliminary working scheme for the integrative application of transcriptomic, proteomic, and metallomic methodologies in environmental monitoring, by using as sentinel the wildlife species Mus spretus and as reference the gene/protein sequence databases from the key model species Mus musculus . We have demonstrated that the absolute transcript expression signatures quantified by reverse transcription (RT) and real-time polymerase chain reaction (PCR) of selected key genes (e.g., those coding for biotransformation enzymes) in M. spretus is a useful and reliable novel biomonitoring end-point. The suitability of commercial M. musculus oligonucleotide arrays for genome-wide transcriptional profiling in M. spretus has been also shown. Transcriptomic studies indicate considerable gene sequence similarities between both mouse species. Based on these similarities, we have demonstrated the applicability in free-living M. spretus of high-throughput proteomic methods, based on matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry (MALDI-TOFMS) analysis of tryptic 2D electrophoresis (2-DE) spot digest and peptide matching with M. musculus database. A metallomic approach based on size exclusion chromatography inductively coupled plasma-mass spectrometry (SEC-ICP-MS) was applied to trace metal-biomolecule profiles. A preliminary integration of these three -omics has been addressed to M. musculus / M. spretus couple, two rodent species that separated 3 million years ago. The integrated application of transcriptomic and proteomic data and the bidirectional use of metallomics and proteomics for selective isolation of metal-biomolecules are covered in the working scheme MEPROTRANS-triple-OMIC reported in this study.

This paper describes the development and application of new metal-tagging reagents and a novel mass spectrometer (MS) detector for a flow cytometer that enables highly multiplexed measurement of many biomarkers in individual cells. A new class of tagging reagents, based on an acrylic polymer backbone that incorporates a reproducible number of lanthanide elements, has been developed. When linked to antibodies that specifically recognize target proteins of interest, determination of the tag elements is diagnostic for the presence and quantification of the antigen. The use of enriched stable isotope tags provides the opportunity for multiparametric assay. The new instrument uses inductively coupled plasma (ICP) to vaporize, atomize, and ionize individual cells that have been probed using the metal-labeled antibodies. The elemental composition, specifically of the metal tags, is recorded simultaneously using a time-of-flight (TOF)-MS that has been specifically designed for high-speed analysis during the short transient corresponding to the individual cell event. The detector provides for well-resolved atomic fingerprints of many elemental and isotopic tags, with little overlap of neighboring signals (high abundance sensitivity) and wide dynamic range both for a single antigen and between antigens.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has become established as a very efficient and sensitive trace, ultratrace, and surface analytical technique in the life sciences. We have developed a new analytical imaging technique using LA-ICP-MS to study element distribution in biological tissues. Nowadays, LA imaging ICP-MS using double-focusing sector field (LA-ICP-SFMS) or quadrupole-based mass spectrometers (LA-ICP-QMS) can be applied as an exciting tool providing new information on the pathophysiology, pharmacology, and toxicology of elements of interest in biological systems. The quantitative determination of elements (e.g., Cu, Fe, Zn, Se, and others) in biological tissues is of growing interest especially in brain research (e.g., for studying neurodegenerative diseases such as Alzheimer's or Parkinson's disease). LA-ICP-SFMS was employed to produce images of detailed regionally specific element distributions in thin tissue sections of different sizes (such as control human or rat brain tissues or tumor regions). In addition, imaging MS using LA-ICP-QMS was applied to study the uptake and transport of nutrient and toxic elements in plant tissues. Besides the quantitative imaging of essential and toxic elements in tissues, powerful analytical techniques are also required for the determination and characterization of phosphoproteins and metal-containing proteins within a large pool of proteins, after electrophoretic separation (e.g., blue native, BN and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, SDS-PAGE) into 1D and 2D gels. LA-ICP-MS was used to detect metalloproteins in protein bands of 1D gels or protein spots separated after 2D gel electrophoresis (2D-GE). In addition to elemental determination by LA-ICP-MS, matrix-assisted laser desorption/ionization (MALDI)-MS was employed to identify metal-containing proteins. Recent progress will be discussed in applying LA-ICP-MS in the life sciences, including the imaging of thin slices of tissue and applications in proteome analysis in combination with MALDI-MS to investigate phosphoproteins and metal-containing proteins.

The feasibility of using a Compton camera for multitracer imaging has been demonstrated with the results of two biological sample imaging experiments. The distribution of the multitracer administered to a soybean sample and a tumor-bearing mouse has been visualized for each nuclide simultaneously. 3D images of the multitracer have been obtained even though the samples were measured from a fixed direction.

A variety of heme-containing gas sensor proteins have been discovered by gene analysis from bacteria to mammals. In general, these proteins are composed of an N-terminal heme-containing sensor domain and a C-terminal catalytic domain. Binding of O 2 , CO, or NO to the heme causes a change in the structure of heme, which alters the protein conformation in the vicinity of the heme, and the conformational change is propagated to the catalytic domain, leading to regulation of the protein activity. This mini-review summarizes the recent resonance Raman studies obtained with both visible and UV excitation sources for two O 2 sensor proteins, Ec DOS and HemAT- Bs . These investigations have shown the role of heme propionate hydrogen-bonding interactions in communicating the heme structural changes, which occur upon ligand binding, from heme to the protein moiety. Furthermore, it is deduced that the contact interactions between the heme 2-vinyl group and the surrounding residues are also important for signal transmission from heme to protein in Ec DOS.

Sequence databases can be searched for homologies of zinc coordination motifs with characteristic ligand signatures. Ensuing predictions that 3-10 % of the human genes encodes zinc proteins are most remarkable. But they seem conservative when considering that database mining cannot discover new signatures or coordination environments that employ nonsequential binding of ligands and sulfur-ligand bridges. Predictions also fall short for zinc/protein interactions at protein interfaces and for inhibitory zinc sites. Zinc ions transiently target proteins that are not known to be zinc proteins, adding a hitherto unrecognized dimension to the human zinc proteome. Predicted zinc sites need to be verified experimentally. The metal can be absent or sites may bind metal ions other than zinc because protein coordination environments do not have absolute specificity for zinc. The metaphor of the "galvanization of biology" continues to gain prominence in terms of the sheer number of approximately 3000 human zinc proteins and their annotation with new functions. Clearly, description of zinc proteomes cannot be pursued solely in silico and requires zinc proteomics, an integrated scientific approach. Progress hinges on a combination of bioinformatics, biology, and significantly, analytical and structural chemistry.

Iron (Fe) is an essential element for plant growth. Gramineous plants have generally developed a distinct strategy to efficiently acquire insoluble Fe, which is characterized by the synthesis and secretion of an Fe-chelating substance, phytosiderophore (PS) such as mugineic acid (MA), and by a specific uptake system for Fe(III)-PS complexes. In a previous study, we identified a gene specifically encoding an Fe(III)-PS transporter (HvYS1) in barley. This gene as well as the encoded protein is specifically expressed in the epidermal cells of the roots, and gene expression is greatly enhanced under Fe-deficient conditions. The localization and substrate specificity of HvYS1 indicate that it is a specific transporter in barley roots. In contrast, ZmYS1, which has been reported as an Fe-PS transporter from maize, possesses broad substrate specificity despite a high homology with HvYS1. By assessing the transport activity of a series of HvYS1-ZmYS1 chimeras, we revealed that the outer membrane loop between the 6 th and 7 th transmembrane regions is essential for the substrate specificity. We also achieved an efficient short-step synthesis of MA and 2'-deoxymugineic acid (DMA). Our new synthetic method enabled us to use them in a large quantity for biological studies.

The availability, distribution, and metabolism of four typical selenium sources [inorganic selenite and selenate, and organic selenomethionine (SeMet) and methylselenocysteine (MeSeCys)] were compared by administering them simultaneously through a parenteral route. The four selenium sources were each labeled with a different enriched selenium isotope ( 82 Se, 78 Se, 77 Se, and 76 Se, respectively), and administered intravenously at the dose of 25 μg Se/kg body weight each to rats that had been depleted of natural abundance selenium with a single isotope, 80 Se, by feeding 80 Se-selenite in drinking water and a selenium-deficient diet. At 1 h post-injection, the amounts of the four tracers recovered from major organs and blood comprised around 70, 55, and 50 % of the doses for selenite, MeSeCys and SeMet, and selenate, respectively, being most abundant in the liver. The intact precursors, except for selenite, were recovered from all organs. 77 Se and 76 Se of SeMet and MeSeCys origin, respectively, were much more efficiently recovered from the pancreas than selenite and selenate, in forms mostly bound to proteins together with intact forms, suggesting that SeMet and MeSeCys are preferentially distributed directly to the pancreas. The incorporations of selenium into selenoprotein P (Sel P) and selenosugars were most efficient from selenite and less efficient from SeMet, suggesting that selenite was most efficiently utilized for the syntheses of selenoproteins and selenosugars. Although selenate was partly excreted into the urine in its intact form, it was retained longer in the plasma in its intact form than the other selenium sources. The advantage of simultaneous administration of multiple precursors each labeled with a different enriched isotope to depleted hosts followed by simultaneous tracing of the labeled isotopes over the conventional method with a single tracer is emphasized together with cautions that may occur with the new multiple tracer method.

When the antitumor activity of cisplatin was discovered, no one would have thought of the existence of specific proteins able to transport Pt across the cell membrane or to specifically recognize DNA modified by this drug. However, such proteins do exist and, furthermore, are specific for the Pt substrate considered. It follows that proteins are deeply involved in managing the biological activity of cisplatin. It is expected that, after the first 20 years in which most of the efforts were devoted to understanding its mode of interaction with DNA and consequent structural and functional alterations, the role of proteins will be more deeply scavenged. How cisplatin can survive the attack of the many platinophiles present in the extracellular and intracellular media is the issue addressed in this article. Significantly, differences are observed between cisplatin, carboplatin, and oxaliplatin.

The metabolic syndrome is a group of factors associated with an increased risk of atherosclerosis and diabetes. Diabetes mellitus (DM) is classified into 2 major types - type 1 DM and type 2 DM - characterized by chronic hyperglycemia resulting from defects in insulin secretion and insulin action, respectively. Several synthetic pharmaceuticals have been developed and clinically used for treating DM; however, these pharmaceuticals continue to cause side effects. Recently, we proposed that oxovanadium(IV) (vanadyl) and zinc(II) (zinc) complexes are potent antidiabetic agents for both type 1 and type 2 DM therapy. This article reviews the vanadyl- and zinc-allixin and their related complexes that are being currently developed as novel types of antidiabetic metal complexes, focusing on their action mechanism in terms of regulation of the insulin signaling pathway and inhibition of lipolysis signaling in adipocyte cells.

Arsenic and lead can induce genetic injuries and epigenetic signaling pathways in cultured mammalian cells. To test whether signaling pathways affect the extent of genetic injuries, we explored the impacts of extracellular signal-regulated kinase 1 and 2 (ERK) on nucleotide excision repair (NER), cytotoxicity, and genotoxicity following sodium arsenite [As(III)] and lead acetate [Pb(II)]. Sustained ERK activation was observed in human cells exposed to As(III) and Pb(II). As(III) inhibited the cellular NER synthesis capability; conversely, Pb(II) stimulated it. ERK activation contributed to the As(III)-induced NER inhibition and micronucleus formation. In contrast, this signal was required for inducing cellular NER activity and preventing mutagenesis following Pb(II). ERK activation by Pb(II) was dependent on protein kinase C (PKCα) that also exhibited anti-mutagenicity. Enforced expression of ERK signaling markedly elevated the cellular NER activity, which was suppressed by As(III). Nonetheless, ERK activation could counteract the cytotoxicity caused by these two metals. Together, the results indicate that pro-survival ERK signaling exhibits dual and opposing impacts on NER process following As(III) and Pb(II) exposures. The findings also suggest that ERK is an important epigenetic signaling in the determination of metal genotoxicity.