Search results for " Ions"
showing 10 items of 474 documents
Analytical insight into degradation processes of aminopolyphosphonates as potential factors that induce cyanobacterial blooms
2017
Aminopolyphosphonates (AAPs) are commonly used industrial complexones of metal ions, which upon the action of biotic and abiotic factors undergo a breakdown and release their substructures. Despite the low toxicity of AAPs towards vertebrates, products of their transformations, especially those that contain phosphorus and nitrogen, can affect algal communities. To verify whether such chemical entities are present in water ecosystems, much effort has been made in developing fast, inexpensive, and reliable methods for analyzing phosphonates. However, unfortunately, the methods described thus far require time-consuming sample pretreatment and offer relatively high values of the limit of detect…
Handling Metalloproteinases.
2016
Substrate cleavage by metalloproteinases involves nucleophilic attack on the scissile peptide bond by a water molecule that is polarized by a catalytic metal, usually a zinc ion, and a general base, usually the carboxyl group of a glutamic acid side chain. The zinc ion is most often complexed by imidazole nitrogens of histidine side chains. This arrangement suggests that the physiological pH optimum of most metalloproteinases is in the neutral range. In addition to their catalytic metal ion, many metalloproteinases contain additional transition metal or alkaline earth ions, which are structurally important or modulate the catalytic activity. As a consequence, these enzymes are generally sen…
Quantitative and Qualitative in vivo Analysis of Metal Residuals in the Saliva of Subjects with and without Fixed Orthodontic Appliances
2020
Aim of the Work: The aim of this work was to evaluate Ni e Cr ions in the saliva of subjects with and without fixed orthodontic appliances. Materials and Methods: This was a prospective, non-randomized study of 100 patients, so selected: 50 have undergone fixed orthodontic appliance at least from 24 months; others 50 subjects as control-group, without any fixed and/or removable orthodontic appliance It was conducted according to the Declaration of the World Medical Association of Helsinki. The two selected groups were compatible for age, sex, absence of restoration in amalgam or other metals in the oral cavity. The saliva of all the subjects was collected with standardized sterile methods. …
On the Antibacterial Activity of Azacarboxylate Ligands: Lowered Metal Ion Affinities for Bis-amide Derivatives of EDTA do not mean Reduced Activity.
2018
EDTA is widely used as an inhibitor of bacterial growth, affecting the uptake and control of metal ions by microorganisms. We describe the synthesis and characterisation of two symmetrical bis-amide derivatives of EDTA, featuring glycyl or pyridyl substituents: AmGly2 and AmPy2 . Metal ion affinities (logK) have been evaluated for a range of metals (Mg2+ , Ca2+ , Fe3+ , Mn2+ , Zn2+ ), revealing less avid binding compared to EDTA. The solid-state structures of AmGly2 and of its Mg2+ complex have been determined crystallographically. The latter shows an unusual 7-coordinate, capped octahedral Mg2+ centre. The antibacterial activities of the two ligands and of EDTA have been evaluated against …
Metal Ions and Metal Complexes in Alzheimer's Disease.
2015
Background: Alzheimer’s disease (AD) is the most common form of dementia that seriously affects daily life. Even if AD pathogenesis is still subject of debate, it is generally accepted that cerebral cortex plaques formed by aggregated amyloid-β (Aβ) peptides can be considered a characteristic pathological hallmark. It is well known that metal ions play an important role in the aggregation process of Aβ. Methods: This review focuses on the anti-Aβ aggregation activity of chelating ligands as well as on the use of metal complexes as diagnostic probes and as potential drugs. Conclusion: While chelating agents, such as curcumin or flavonoid derivatives, are currently used to capture metal ions …
Pb2+complexes of small-cavity azamacrocyclic ligands: thermodynamic and kinetic studies
2017
The synthesis, acid-base behavior and Pb2+ coordination chemistry of the new aza-scorpiand like ligand 5-[2-(N-2-fluorenyl)ethylamino]-2,5,8-triaza[9]-2,6-pyridinophane (L1) have been studied by potentiometry, NMR and spectrofluorimetric titrations, and the results are compared with those obtained for the related compounds L2, lacking the fluorenyl group, and L3, the macrocycle lacking the pendant arm. The crystal structures obtained for complexes [PbL1][PbL1Cl](NO3)Cl2·4H2O (1) and [PbL3](ClO4)2 (2) reveal that the metal ion is located over the plane defined by the nitrogen atoms of the macrocyclic core due to its inability to accommodate the large Pb2+ ion in the macrocyclic cavity. For L…
Antimicrobial peptide–metal ion interactions – a potential way of activity enhancement
2018
Increasing bacterial and fungal drug resistance requires novel, effective antimicrobial treatments to be actively sought. Because of a general lack of resistance towards antimicrobial peptides (AMPs), they are being relied on as a novel class of therapeutics aiming to conquer drug-resistant bacteria and fungi. There are numerous ways in which AMPs might interact with pathogens, such as membrane disruption, production of ROS, inhibition of cell wall, nucleic acid and protein synthesis or by the withdrawal of essential metal ions. Biologically indispensable metal ions have a dual effect on the activity of antimicrobial peptides: (i) AMPs bind them, so that microbes cannot get enough metals es…
Histidine tracts in human transcription factors: insight into metal ion coordination ability
2017
Consecutive histidine repeats are chosen both by nature and by molecular biologists due to their high affinity towards metal ions. Screening of the human genome showed that transcription factors are extremely rich in His tracts. In this work, we examine two of such His-rich regions from forkhead box and MAFA proteins—MB3 (contains 18 His) and MB6 (with 21 His residues), focusing on the affinity and binding modes of Cu2+ and Zn2+ towards the two His-rich regions. In the case of Zn2+ species, the availability of imidazole nitrogen donors enhances metal complex stability. Interestingly, an opposite tendency is observed for Cu2+ complexes at above physiological pH, in which amide nitrogens part…
Study of the polysemic term of minerality in wine: Segmentation of consumers based on their textual responses to an open-ended survey
2016
International audience; Over the past 20 years, the word "minerality" has been increasingly used in the description of wines. However, a precise definition of the concept of minerality appears to be inexistent, and no consensual meaning, even among wine professionals, can be identified. Although this word usage seems to spread out from wine professionals to consumers, research on what consumers assume about minerality is scarce. This paper aims to study the various concepts about minerality held-by consumers by using an open-ended questionnaire.A total of 1697 French-speaking consumers responded to an, online survey and their free answers were analysed using statistical textual methods. The…
Interaction of Novel Metal Complexes with DNA: Synthetic and Structural Aspects
2009
Metal ions bind to nucleic acids at various positions. This binding can be modulated by using metal complexes with appropriate ligands. Novel mono- and especially dinuclear metal complexes could be a powerful tool to detect rare, but still physiologically relevant, forms of DNA, e.g. the left-handed Z-DNA. In this review, our recent research activities in this area of bioinorganic chemistry are summarized. A special emphasis is laid on the synthetic challenges that arose upon the synthesis of the polyamine ligands. Further, some rather unusual approaches to elucidate the solution structure of copper bound to guanosine monophosphate with the help of pulsed EPR techniques like ENDOR and HYSC…