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Metal-Mediated Functionalization of Natural Peptides and Proteins: Panning for Bioconjugation Gold.
Ohata, J, Martin, SC, Ball, ZT
Angewandte Chemie (International ed. in English). 2019;(19):6176-6199
Abstract
Selective modification of natural proteins is a daunting methodological challenge and a stringent test of selectivity and reaction scope. There is a continued need for new reactivity and new selectivity concepts. Transition metals exhibit a wealth of unique reactivity that is orthogonal to biological reactions and processes. As such, metal-based methods play an increasingly important role in bioconjugation. This Review examines metal-based methods as well as their reactivity and selectivity for the functionalization of natural proteins and peptides.
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Additive manufacturing of biodegradable metals: Current research status and future perspectives.
Qin, Y, Wen, P, Guo, H, Xia, D, Zheng, Y, Jauer, L, Poprawe, R, Voshage, M, Schleifenbaum, JH
Acta biomaterialia. 2019;:3-22
Abstract
The combination of biodegradable metals and additive manufacturing (AM) leads to a revolutionary change of metal implants in many aspects including materials, design, manufacturing, and clinical applications. The AM of nondegradable metals such as titanium and CoCr alloys has proven to be a tremendous success in clinical applications. The AM of biodegradable metals including magnesium (Mg), iron (Fe), and zinc (Zn) is still in its infancy, although much progress has been made in the research field. Element loss and porosity are common processing problems for AM of biodegradable metals like Zn and Mg, which are mainly caused by evaporation during melting under a high-energy beam. The resulting formation quality and properties are closely related to material, design, and processing, making AM of biodegradable metals a typical interdisciplinary subject involving biomaterials, mechanical engineering, and medicine. This work reviews the state of research and future perspective on AM of biodegradable metals from extensive viewpoints such as material, processing, formation quality, design, microstructure, and properties. Effects of powder properties and processing parameters on formation quality are characterized in detail. The microstructure and metallurgical defects encountered in the AM parts are described. Mechanical and biodegradable properties of AM samples are introduced. Design principles and potential applications of biodegradable metal implants produced by AM are discussed. Finally, current research status is summarized together with some proposed future perspectives for advancing knowledge about AM of biodegradable metals. STATEMENT OF SIGNIFICANCE Rapid development of research and applications on biodegradable metals and additive manufacturing (AM) has been made in recent years. Customized geometric shapes of medical metals with porous structure can be realized accurately and efficiently by laser powder bed fusion (L-PBF), which is beneficial to achieve reliable stress conduction and balanced properties. This review introduces the development history and current status of AM of biodegradable metals and then critically surveys L-PBF of Mg-, Fe-, and Zn-based metals from multiple viewpoints including materials, processing, formation quality, structural design, microstructure, and mechanical and biological properties. The present findings are summarized together with some proposed future challenges for advancing AM of biodegradable metals into real clinical applications.
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3.
Metal-responsive RNA polymerase extracytoplasmic function (ECF) sigma factors.
Moraleda-Muñoz, A, Marcos-Torres, FJ, Pérez, J, Muñoz-Dorado, J
Molecular microbiology. 2019;(2):385-398
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Abstract
In order to survive, bacteria must adapt to multiple fluctuations in their environment, including coping with changes in metal concentrations. Many metals are essential for viability, since they act as cofactors of indispensable enzymes. But on the other hand, they are potentially toxic because they generate reactive oxygen species or displace other metals from proteins, turning them inactive. This dual effect of metals forces cells to maintain homeostasis using a variety of systems to import and export them. These systems are usually inducible, and their expression is regulated by metal sensors and signal-transduction mechanisms, one of which is mediated by extracytoplasmic function (ECF) sigma factors. In this review, we have focused on the metal-responsive ECF sigma factors, several of which are activated by iron depletion (FecI, FpvI and PvdS), while others are activated by excess of metals such as nickel and cobalt (CnrH), copper (CarQ and CorE) or cadmium and zinc (CorE2). We focus particularly on their physiological roles, mechanisms of action and signal transduction pathways.
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Metal ligands in micronutrient acquisition and homeostasis.
Clemens, S
Plant, cell & environment. 2019;(10):2902-2912
Abstract
Acquisition and homeostasis of micronutrients such as iron (Fe) and zinc (Zn) pose specific challenges. Poor solubility and high reactivity require controlled synthesis and supply of ligands to complex these metals extracellularly and intracellularly. Cytosolic labile pools represent only a minute fraction of the total cellular content. Several low-molecular-weight ligands are known in plants, including sulfur ligands (cysteine and peptides), nitrogen/oxygen ligands (S-adenosyl-l-methionine-derived molecules and histidine), and oxygen ligands (phenolics and organic acids). Some ligands are secreted into the extracellular space and influence the phytoavailability of metal ions. A second principal function is the intracellular buffering of micronutrients as well as the facilitation of long-distance transport in xylem and phloem. Furthermore, low-molecular-weight ligands are involved in the storage of metals, predominantly in vacuoles. A detailed molecular understanding is hampered by technical limitations, in particular the difficulty to detect and quantify cellular metal-ligand complexes. More, but still too little, is known about ligand synthesis and the transport across membranes, either with or without a complexed metal. Metal ligands have an immediate impact on human well-being. Engineering metal ligand synthesis and distribution in crops has tremendous potential to improve the nutritional quality of food and to tackle major human health risks.
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Transition metal transporters in rhizobia: tuning the inorganic micronutrient requirements to different living styles.
Abreu, I, Mihelj, P, Raimunda, D
Metallomics : integrated biometal science. 2019;(4):735-755
Abstract
A group of bacteria known as rhizobia are key players in symbiotic nitrogen fixation (SNF) in partnership with legumes. After a molecular exchange, the bacteria end surrounded by a plant membrane forming symbiosomes, organelle-like structures, where they differentiate to bacteroids and fix nitrogen. This symbiotic process is highly dependent on dynamic nutrient exchanges between the partners. Among these are transition metals (TM) participating as inorganic and organic cofactors of fundamental enzymes. While the understanding of how plant transporters facilitate TMs to the very near environment of the bacteroid is expanding, our knowledge on how bacteroid transporters integrate to TM homeostasis mechanisms in the plant host is still limited. This is significantly relevant considering the low solubility and scarcity of TMs in soils, and the in crescendo gradient of TM bioavailability rhizobia faces during the infection and bacteroid differentiation processes. In the present work, we review the main metal transporter families found in rhizobia, their role in free-living conditions and, when known, in symbiosis. We focus on discussing those transporters which could play a significant role in TM-dependent biochemical and physiological processes in the bacteroid, thus paving the way towards an optimized SNF.
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A Review of Biomarkers Used for Assessing Human Exposure to Metals from E-Waste.
Arain, AL, Neitzel, RL
International journal of environmental research and public health. 2019;(10)
Abstract
Electronic waste recycling presents workers and communities with a potential for exposures to dangerous chemicals, including metals. This review examines studies that report on blood, hair, and urine biomarkers of communities and workers exposed to metals from e-waste. Our results from the evaluation of 19 publications found that there are consistently elevated levels of lead found in occupationally and non-occupationally exposed populations, in both the formal and the informal e-waste recycling sectors. Various other metals were found to be elevated in different exposure groups assessed using various types of biomarkers, but with less consistency than found in lead. Antimony and cadmium generally showed higher concentrations in exposed groups compared to reference group(s). Mercury and arsenic did not show a trend among exposure groups due to the dietary and environmental considerations. Observed variations in trends amongst exposure groups within studies using multiple biomarkers highlights the need to carefully select appropriate biomarkers. Our study concludes that there is a need for more rigorous research that moves past cross-sectional study designs, involves more thoughtful and methodical selection of biomarkers, and a systematic reporting standard for exposure studies to ensure that results can be compared across studies.
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Switching on Endogenous Metal Binding Proteins in Parkinson's Disease.
McLeary, FA, Rcom-H'cheo-Gauthier, AN, Goulding, M, Radford, RAW, Okita, Y, Faller, P, Chung, RS, Pountney, DL
Cells. 2019;(2)
Abstract
The formation of cytotoxic intracellular protein aggregates is a pathological signature of multiple neurodegenerative diseases. The principle aggregating protein in Parkinson's disease (PD) and atypical Parkinson's diseases is α-synuclein (α-syn), which occurs in neural cytoplasmic inclusions. Several factors have been found to trigger α-syn aggregation, including raised calcium, iron, and copper. Transcriptional inducers have been explored to upregulate expression of endogenous metal-binding proteins as a potential neuroprotective strategy. The vitamin-D analogue, calcipotriol, induced increased expression of the neuronal vitamin D-dependent calcium-binding protein, calbindin-D28k, and this significantly decreased the occurrence of α-syn aggregates in cells with transiently raised intracellular free Ca, thereby increasing viability. More recently, the induction of endogenous expression of the Zn and Cu binding protein, metallothionein, by the glucocorticoid analogue, dexamethasone, gave a specific reduction in Cu-dependent α-syn aggregates. Fe accumulation has long been associated with PD. Intracellularly, Fe is regulated by interactions between the Fe storage protein ferritin and Fe transporters, such as poly(C)-binding protein 1. Analysis of the transcriptional regulation of Fe binding proteins may reveal potential inducers that could modulate Fe homoeostasis in disease. The current review highlights recent studies that suggest that transcriptional inducers may have potential as novel mechanism-based drugs against metal overload in PD.
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Metals in Medicine: The Therapeutic Use of Metal Ions in the Clinic.
Carver, PL
Metal ions in life sciences. 2019
Abstract
Metal ions are indispensable for living organisms. However, the roles of metal ions in humans is complex, and remains poorly understood. Imbalances in metal ion levels, due to genetic or environmental sources, are associated with a number of significant health issues. However, in clinical medicine, the role of metal ions and metal-based drugs is notable in three major areas: as metal-related diseases; as metal-based medicines (including drugs, imaging agents, and metal chelators); and as agents of metal-based toxicity.
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Emergence of metal selectivity and promiscuity in metalloenzymes.
Eom, H, Song, WJ
Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry. 2019;(4):517-531
Abstract
Metal coordination with proteinaceous ligands has greatly expanded the chemical toolbox of proteins and their biological roles. The structure and function of natural metalloproteins have been determined according to the physicochemical properties of metal ions bound to the active sites. Concurrently, amino acid sequences are optimized for metal coordination geometry and/or dedicated action of metal ions in proteinaceous environments. In some occasions, however, natural enzymes exhibit promiscuous reactivity with more than one designated metal ion, under in vitro and/or in vivo conditions. In this review, we discuss selected examples of metalloenzymes that bind various first-row, mid- to late-transition metal ions for their native catalytic activities. From these examples, we suggest that environmental, inorganic, and biochemical factors, such as bioavailability, native organism, cellular compartment, reaction mechanism, binding affinity, protein sequence, and structure, might be responsible for determining metal selectivity or promiscuity. The current work proposes how natural metalloproteins might have emerged and adapted for specific metal incorporation under the given circumstances and may provide insights into the design and engineering of de novo metalloproteins.
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An overview on the exponential growth of non-invasive diagnosis of diabetes mellitus from exhaled breath by nanostructured metal oxide Chemi-resistive gas sensors and μ-preconcentrator.
Kalidoss, R, Umapathy, S
Biomedical microdevices. 2019;(1):2
Abstract
The characterization of acetone in exhaled breath reflects the internal metabolism of glucose in bloodstream and airways. This phenomenon provides a great potential for non-invasive diagnosis of diabetes mellitus and has inspired medical sodalities as an alternative diagnostic tool. This review discusses about the origination of acetone in breath, its correlation with blood glucose level along with the ways to collect breath sample. Furthermore, we also discuss the detection of acetone by chemical sensors with emphasis on the use of pre-concentrators on a single lab-on-chip for the diagnosis of diabetes mellitus. Finally, this review outlines the future directions for the detection of acetone from exhaled breath. The first part of the review introduces the biochemistry and prevalence of diabetes in India along with the existing techniques to estimate the concentration of acetone. The second part focuses on the semiconducting metal oxide and polymer gas sensors which discusses about tailoring the dynamic sensitivity range and selectivity towards acetone in breath. The third part elaborates on the ways to pre-concentrate the target biomarkers along with future perspectives for non-invasive diabetes diagnosis. Finally we also provide the perspectives on future challenges to make it to clinical practice. Graphical abstract .