scholarly journals Expanding the Ligand Classes Used for Mn(II) Complexation: Oxa-aza Macrocycles Make the Difference

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1524
Author(s):  
Ferenc K. Kálmán ◽  
Viktória Nagy ◽  
Rocío Uzal-Varela ◽  
Paulo Pérez-Lourido ◽  
David Esteban-Gómez ◽  
...  
Keyword(s):  
Water Molecule ◽  
Metal Ion ◽  
Macrocyclic Ligand ◽  
Relaxation Dispersion ◽  
Metal Exchange ◽  
Relaxation Rates ◽  
Exchange Reactions ◽  
Biologically Relevant ◽  
The Difference ◽  
Nuclear Magnetic

We report two macrocyclic ligands based on a 1,7-diaza-12-crown-4 platform functionalized with acetate (tO2DO2A2−) or piperidineacetamide (tO2DO2AMPip) pendant arms and a detailed characterization of the corresponding Mn(II) complexes. The X−ray structure of [Mn(tO2DO2A)(H2O)]·2H2O shows that the metal ion is coordinated by six donor atoms of the macrocyclic ligand and one water molecule, to result in seven-coordination. The Cu(II) analogue presents a distorted octahedral coordination environment. The protonation constants of the ligands and the stability constants of the complexes formed with Mn(II) and other biologically relevant metal ions (Mg(II), Ca(II), Cu(II) and Zn(II)) were determined using potentiometric titrations (I = 0.15 M NaCl, T = 25 °C). The conditional stabilities of Mn(II) complexes at pH 7.4 are comparable to those reported for the cyclen-based tDO2A2− ligand. The dissociation of the Mn(II) chelates were investigated by evaluating the rate constants of metal exchange reactions with Cu(II) under acidic conditions (I = 0.15 M NaCl, T = 25 °C). Dissociation of the [Mn(tO2DO2A)(H2O)] complex occurs through both proton− and metal−assisted pathways, while the [Mn(tO2DO2AMPip)(H2O)] analogue dissociates through spontaneous and proton-assisted mechanisms. The Mn(II) complex of tO2DO2A2− is remarkably inert with respect to its dissociation, while the amide analogue is significantly more labile. The presence of a water molecule coordinated to Mn(II) imparts relatively high relaxivities to the complexes. The parameters determining this key property were investigated using 17O NMR (Nuclear Magnetic Resonance) transverse relaxation rates and 1H nuclear magnetic relaxation dispersion (NMRD) profiles.

scholarly journals Gd3+ Complexes Conjugated to Cyclodextrins: Hydroxyl Functions Influence the Relaxation Properties

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 269
Author(s):  
Anais Biscotti ◽  
François Estour ◽  
Berthe-Sandra Sembo-Backonly ◽  
Sébastien Balieu ◽  
Michaël Bosco ◽  
...  
Keyword(s):  
Water Molecule ◽  
Bound Water ◽  
Relaxation Dispersion ◽  
Amide Bond ◽  
Hydroxyl Groups ◽  
Relaxation Rates ◽  
Transverse Relaxation ◽  
Relaxation Properties ◽  
Hydrogen Bound ◽  
The Impact

In the search for improvement in the properties of gadolinium-based contrast agents, cyclodextrins (CDs) are interesting hydrophilic scaffolds with high molecular weight. The impact of the hydrophilicity of these systems on the MRI efficacy has been studied using five β-CDs substituted with DOTA or TTHA ligands which, respectively, allow for one (q = 1) or no water molecule (q = 0) in the inner coordination sphere of the Gd3+ ion. Original synthetic pathways were developed to immobilize the ligands at C-6 position of various hydroxylated and permethylated β-CDs via an amide bond. To describe the influence of alcohol and ether oxide functions of the CD macrocycle on the relaxation properties of the Gd3+ complexes, 1H Nuclear Magnetic Relaxation Dispersion (NMRD) profiles, and 17O transverse relaxation rates have been measured at various temperatures. The differences observed between the hydroxylated and permethylated β-CDs bearing non-hydrated GdTTHA complexes can be rationalized by a second sphere contribution to the relaxivity in the case of the hydroxylated derivatives, induced by hydrogen-bound water molecules around the hydroxyl groups. In contrast, for the DOTA analogs the exchange rate of the water molecule directly coordinated to the Gd3+ is clearly influenced by the number of hydroxyl groups present on the CD, which in turn influences the relaxivity and gives rise to a very complex behavior of these hydrophilic systems.

Metallothionein-protein interactions

2013 ◽  
Vol 4 (2) ◽  
pp. 143-160 ◽  
Author(s):  
Sílvia Atrian ◽  
Mercè Capdevila
Keyword(s):  
Protein Interactions ◽  
Stress Responses ◽  
Metal Ion ◽  
Physical Contact ◽  
Metal Exchange ◽  
Exchange Reactions ◽  
Spongiform Encephalopathies ◽  
Small Proteins ◽  
Parkinson’S Diseases ◽  
Wide Range

AbstractMetallothioneins (MTs) are a family of universal, small proteins, sharing a high cysteine content and an optimal capacity for metal ion coordination. They take part in a plethora of metal ion-related events (from detoxification to homeostasis, storage, and delivery), in a wide range of stress responses, and in different pathological processes (tumorigenesis, neurodegeneration, and inflammation). The information on both intracellular and extracellular interactions of MTs with other proteins is here comprehensively reviewed. In mammalian kidney, MT1/MT2 interact with megalin and related receptors, and with the transporter transthyretin. Most of the mammalian MT partners identified concern interactions with central nervous system (mainly brain) proteins, both through physical contact or metal exchange reactions. Physical interactions mainly involve neuronal secretion multimers. Regarding metal swap events, brain MT3 appears to control the metal ion load in peptides whose aggregation leads to neurodegenerative disorders, such as Aβ peptide, α-synuclein, and prion proteins (Alzheimer’s and Parkinson’s diseases, and spongiform encephalopathies, respectively). Interaction with ferritin and bovine serum albumin are also documented. The intercourse of MTs with zinc-dependent enzymes and transcription factors is capable to activate/deactivate them, thus conferring MTs the role of metabolic and gene expression regulators. As some of these proteins are involved in cell cycle and proliferation control (p53, nuclear factor κB, and PKCμ), they are considered in the context of oncogenesis and tumor progression. Only one non-mammalian MT interaction, involving Drosophila MtnA and MtnB major isoforms and peroxiredoxins, has been reported. The prospective use for biomedical applications of the MT-interaction information is finally discussed.

The Interaction of Cobalt(II), Nickel(II), Copper(II) and Zinc(II) With Oxygen-Nitrogen Donor Macrocycles Immobilized on a Polystyrene Matrix

1986 ◽  
Vol 39 (7) ◽  
pp. 1071 ◽  
Author(s):  
RS Paredes ◽  
NS Valera ◽  
LF Lindoy
Keyword(s):  
Metal Ion ◽  
Matrix Effects ◽  
Aqueous Media ◽  
Solvent Mixture ◽  
Ion Binding ◽  
Metal Exchange ◽  
Metal Ion Binding ◽  
Exchange Reactions ◽  
Binding Properties ◽  
Crosslinked Polystyrene

Five macrocyclic ligands incorporating O2N2 or O2N3 donor sets have been appended to 2% crosslinked polystyrene, and the metal-ion-binding properties of the resulting functionalized polymers towards CoII , NiII, CuII and ZnII have been investigated. Loading studies were undertaken in ethyl acetate/methanol (9 : 1), and, under similar conditions, the degree of loading was found to be metal-dependent. In addition, in some cases metal uptake was found to exceed that required for 1:1 complexation of metal to cyclic ligand . In the above solvent mixture, metal-exchange reactions were found to be relatively facile. However, attempts to leach metal ions from the loaded polymers with either acid or ammonia in aqueous media were less successful due to poor swelling of the polymer beads in such media. Matrix effects associated with the polystyrene backbone appear to be the cause of the significant modification in metal-ion-binding properties of the immobilized macrocycles relative to those of their detached analogues.

Metal exchange reactions between divalent metal ions and their dithiocarbamate complexes in dimethyl sulfoxide: a kinetic and mechanistic study

1981 ◽  
Vol 34 (10) ◽  
pp. 2195 ◽  
Author(s):  
J Sachinidis ◽  
MW Grant
Keyword(s):  
Dimethyl Sulfoxide ◽  
Metal Ion ◽  
Mechanistic Study ◽  
Metal Exchange ◽  
Divalent Metal Ions ◽  
Exchange Reactions ◽  
Electrophilic Attack ◽  
The Stability ◽  
Ligand Transfer ◽  
Electrophilic Character

The kinetics and mechanism of metal exchange between NiII, CuII, ZnII, CdII, PbII and HgII and their dithiocarbamate complexes have been studied in dimethyl sulfoxide. Two pathways for ligand transfer are observed. The first involves dissociation of dithiocarbamate from the metal complex followed by substitution at the metal ion, while the second involves direct electrophilic attack by the metal ion on the dithiocarbamate complex. The relative importance of the pathways depends on the stability of the complex and the substitution lability and electrophilic character of the metal ion. The stability of the dithiocarbamate complexes in dimethyl sulfoxide is in the order Hg > Cu > Ni > Pb ≈ Cd > Zn.

scholarly journals Fast-field-cycling ultralow-field nuclear magnetic relaxation dispersion

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sven Bodenstedt ◽  
Morgan W. Mitchell ◽  
Michael C. D. Tayler
Keyword(s):  
High Resolution ◽  
Magnetic Relaxation ◽  
Magnetic Measurements ◽  
Nuclear Magnetic Relaxation ◽  
Relaxation Dispersion ◽  
Relaxation Rates ◽  
Field Range ◽  
Field Cycling ◽  
Fast Field ◽  
Nuclear Magnetic

AbstractOptically pumped magnetometers (OPMs) based on alkali-atom vapors are ultra-sensitive devices for dc and low-frequency ac magnetic measurements. Here, in combination with fast-field-cycling hardware and high-resolution spectroscopic detection, we demonstrate applicability of OPMs in quantifying nuclear magnetic relaxation phenomena. Relaxation rate dispersion across the nT to mT field range enables quantitative investigation of extremely slow molecular motion correlations in the liquid state, with time constants > 1 ms, and insight into the corresponding relaxation mechanisms. The 10-20 fT/$$\sqrt{{\rm{H}}}{\rm{z}}$$ H z sensitivity of an OPM between 10 Hz and 5.5 kHz 1H Larmor frequency suffices to detect magnetic resonance signals from ~ 0.1 mL liquid volumes imbibed in simple mesoporous materials, or inside metal tubing, following nuclear spin prepolarization adjacent to the OPM. High-resolution spectroscopic detection can resolve inter-nucleus spin-spin couplings, further widening the scope of application to chemical systems. Expected limits of the technique regarding measurement of relaxation rates above 100 s−1 are discussed.

scholarly journals Nuclear Magnetic Relaxation Dispersion in Protein Solutions

1970 ◽  
Vol 245 (17) ◽  
pp. 4251-4255
Author(s):  
Bruce P. Gaber ◽  
Walter E. Schillinger ◽  
Seymour H. Koenig ◽  
Philip Aisen
Keyword(s):  
Magnetic Relaxation ◽  
Nuclear Magnetic Relaxation ◽  
Relaxation Dispersion ◽  
Protein Solutions ◽  
Nuclear Magnetic Relaxation Dispersion ◽  
Nuclear Magnetic

Understanding and Practical Use of Ligand and Metal Exchange Reactions in Thiolate-Protected Metal Clusters to Synthesize Controlled Metal Clusters

2017 ◽  
Vol 17 (5) ◽  
pp. 473-484 ◽  
Author(s):  
Yoshiki Niihori ◽  
Sakiat Hossain ◽  
Sachil Sharma ◽  
Bharat Kumar ◽  
Wataru Kurashige ◽  
...  
Keyword(s):  
Metal Clusters ◽  
Metal Exchange ◽  
Exchange Reactions
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