Search results for "spin resonance"

Bioinspired manganese(II) complexes with a clickable ligand for immobilisation on a solid support.

2014

International audience; Clickable ligands like N,N′-bis((pyridin-2-yl)methyl)prop-2-yn-1-amine (L1) and N-((1-methyl-1H-imidazol-2-yl)methyl)-N-(pyridin-2-ylmethyl)prop-2-yn-1-amine (L2) have been used to synthesise a series of manganese(II) complexes for grafting onto appropriate solid supports. These ligands mimic the 2-His-1-carboxylate facial chelation present in the active site of the manganese-dependent dioxygenase (MndD), while the alkyne side function allows grafting of the ligand onto an azido-functionalised support using “click chemistry” methodologies. Such synthetic analogues of the MndD crystallise in the solid state as double halide or pseudohalide-bridged dinuclear manganese(…

The first unpaired electron placed inside a C3-symmetry P-chirogenic cluster

2010

The Pd(3)(dppm*)(3)(CO)(n+) enantiomers (n = 2 (2), 1 (3)) were prepared either from (R,R)- or (S,S)-P-chirogenic bis(phenyl-m-xylylphosphino)methane (dppm*; 1) and Pd(OAc)(2) in the presence of CF(3)CO(2)H, CO and water (n = 2), and then by reductive electrolysis (n = 1). The stable enantiomeric [Pd(3)((S,S)-dppm*)(3)(CO)](+)˙ (3), is the first C(3)-symmetry radical-cation M-M bonded cluster, therefore the odd electron is delocalized onto the Pd(3) frame within this symmetry. The novel chiral species have been characterized by circular dichroism (CD) of both enantiomers of the Pd(3)(dppm*)(3)(CO)(2+) clusters (2) and by EPR spectroscopy for the Pd(3)((S,S)-dppm*)(3)(CO)(+)˙ paramagnetic co…

Effect of tin and lead chlorotriphenyl analogues on selected living cells.

2010

Three kinds of living cells, human embryonic kidney cells, Saccharomyces cerevisiae, and Escherichia coli, were tested for their sensitivity to chlorotriphenyltin and chlorotriphenyllead. The tin compound proved definitely more toxic than the lead derivative, particularly in the case of the human embryonic kidney cells devoid of any protective cell wall. Electron paramagnetic resonance (EPR) comparative studies carried out by using a natural model liposome system (egg yolk lecithin) confirmed considerable changes within the lipid bilayer upon doping by the aforementioned additives, which may be crucial to the mechanism of the observed cell cleavage. The individual dopants revealed diverse i…

Copper Uptake Induces Self-Assembly of 18.5 kDa Myelin Basic Protein (MBP)

2010

Myelin basic protein (MBP) is predominantly found in the membranes of the myelin sheath of the central nervous system and is involved in important protein-protein and protein-lipid interactions in vivo and in vitro. Furthermore, divalent transition metal ions, especially Zn(2+) and Cu(2+), seem to directly affect the MBP-mediated formation and stabilization of the myelin sheath of the central nervous system. MBP belongs to the realm of intrinsically disordered proteins, and only fragmentary information is available regarding its partial structure(s) or supramolecular arrangements. Here, using standard continuous wave and modern pulse electron paramagnetic resonance methods, as well as dynam…

When two become one: Integrating FRET and EPR into one structural model

2021

Dynamic nuclear polarisation of biological matter

1986

Polarised targets as used in high energy physics experiments may be of considerable interest in biological structure research using polarized neutrons. So far, this promising method has been facing difficulties in getting reasonable polarization of the target nuclei. We report on a polarized "frozen spin" target which has been prepared from an enzyme dissolved in a mixture of heavy water and deuterated propanediol doped with a completely deuterated paramagnetic radical. Clusters of 700 protons defined by the structure of lysozyme embedded in a fully deuterated matrix were polarized to 75% within an hour by 4 mm microwave irradiation in a magnetic field of 2.5 tesla at a temperature of 0.3 K…

Heparin–polynitroxides: Synthesis and preliminary evaluation as cardiovascular EPR/MR imaging probes and extracellular space-targeted antioxidants

2011

We report here the synthesis of heparin-polynitroxide derivatives (HPNs) in which nitroxide moieties are linked either to uronic acid or glycosamine residues of the heparin macromolecule. HPNs have low anticoagulant activity, possess superoxide scavenging properties, bind to the vascular endothelium/extra-cellular matrix and can be detected by EPR and MRI techniques. As the vascular wall-targeted redox-active paramagnetic compounds, HPNs may have both diagnostic (molecular MRI) and therapeutic (ecSOD mimics) applications.

ENDOR Spectroscopic and Molecular Orbital Study of the Dynamical Properties of the Side Chain in Radical Anions of Ubiquinones Q-1, Q-2, Q-6, and Q-10

2000

Abstract The dynamics of the side chain of the radical anions of ubiquinones Q-1 (2,3-dimethoxy-5-methyl-6-[3-methyl-2-butenyl]-1,4-benzoquinone), Q-2, Q-6, and Q-10 have been investigated using electron nuclear double-resonance (ENDOR) spectroscopy. When radicals are produced in the liquid phase, secondary radicals are also formed. The EPR spectra of these additional radicals overlap with the radical of interest. ENDOR spectroscopy was found to be capable for studying the dynamical properties of such conditions. The temperature dependence of the isotropic hyperfine coupling constants of the β- and γ-protons of the side chain was measured. The activation energy of the rotation and other dyn…

Sensitivity enhancement in pulse EPR distance measurements

2004

Established pulse EPR approaches to the measurement of small dipole-dipole couplings between electron spins rely on constant-time echo experiments to separate relaxational contributions from dipolar time evolution. This requires a compromise between sensitivity and resolution to be made prior to the measurement, so that optimum data are only obtained if the magnitude of the dipole-dipole coupling is known beforehand to a good approximation. Moreover, the whole dipolar evolution function is measured with relatively low sensitivity. These problems are overcome by a variable-time experiment that achieves suppression of the relaxation contribution by reference deconvolution. Theoretical and exp…

ESR response of phenol compounds for dosimetry of gamma photon beams

2014

Abstract In the present paper we investigate the features of IRGANOX® 1076 phenols as a material for electron spin resonance (ESR) dosimetry. We experimentally analyzed the ESR response of pellets of IRGANOX® 1076 phenols irradiated with 60Co photons. The best experimental parameters (modulation amplitude and microwave power) for dosimetric applications have been obtained. The dependence of ESR signal as function of γ dose is found to be linear in the dose range studied (12–60 Gy) and the lowest measurable dose is found to be of the order of 1 Gy. The signal after irradiation is very stable in the first thirty days. From the point of view of the tissue equivalence, these materials have mass…