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Lothar Helm

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Publications associées (91)

Lanthanide chelates of (bis)-hydroxymethyl-substituted DTTA with potential application as contrast agents in magnetic resonance imaging

Lothar Helm

A novel bis-hydroxymethyl-substituted DTTA chelator N¢-Bz-C4,4¢-(CH2OH)2-DTTA (1) and its DTPA analogue C4,4¢-(CH2OH)2-DTPA (2) were synthesized and characterized. A variable-temperature 1H NMR spectroscopy study of the solution dynamics of their diamagnet ...

2009

Aqueous solubility and speciation of Te(IV) at elevated temperatures

Lothar Helm, Pascal Grundler

2009

Multiple Frequency and Variable Temperature EPR study of Gd(III) polyaminocarboxylates: analysis and comparison of the magnetically dilute powder and the frozen solution spectra

André Merbach, Lothar Helm, Alain Borel

An Electron Paramagnetic Resonance (EPR) study of glasses and magnetically dilute powders of [Gd(DTPA)(H2O)]2−, [Gd(DOTA)(H2O)]-, and macromolecular Gd-P792 complexes was carried out at X-, Q-band and 240 GHz DTPA=diethylenetriaminepentaacetato; DOTA=1,4,7 ...

Wiley-VHCA AG2009

Synthesis, structures and characterisations of truly homoleptic acetonitrile Ln3+ complexes in solid state and in solution

Lothar Helm, Rosario Scopelliti, Gabriella Eva Bodizs, Ines Raabe

Total halide abstraction from LnCl3 by Ag[Al(OC(CF3)3)4]/CH3CN has been confirmed for a series of lanthanide metal ions by the structural characterization of [Ln(CH3CN)n][Al(OC(CF3)3)4]3 (n = 9, Ln3+ = Nd, Eu, Gd, Dy; n = 8, Ln3+ = Tm) complexes. Evidence ...

2009

A ruthenium-based metallostar: synthesis, sensitized luminescence and 1H relaxivity

Jean-Claude Bünzli, Loïck Moriggi, Lothar Helm, Alain Borel, Annina Aebischer

Ru-based metallostars Na4{Ru[Ln2bpy-DTTA2(H2O)4]3} (Ln = Y, Gd, and Eu) have been self-assembled in aqueous solution and their relaxivity and optical properties unravelled. The ynthesis and the purification of the new, highly stable heptametallic entities ...

2009

Multivalent bombesin analogues conjugated to DOTA-based chelators for targeted multimodal imaging of GRP-receptor positive tumors

Lothar Helm

2008

Nuclear Spin Relaxation Parameters of MRI Contrast Agents – Insight from Quantum Mechanical Calculations

Lothar Helm, Oleg Yazyev

Nuclear magnetic relaxation in the presence of paramagnetic centres has gained increasing interest in recent years partly due to its importance for contrast agents in magnetic resonance imaging. Rational design of new more efficient agents is possible as a ...

Wiley-Blackwell2008

Ligand exchange and complex formation kinetics studied by NMR exemplified on fac-[(CO)3M(H2O)]+ (M = Mn, Tc, Re)

Lothar Helm

In this review ligand exchange and complex formation reactions on fac-[(CO)3M(H2O)3]+ (M = Mn, Tc, Re) and on fac-[(CO)2(NO)Re(H2O)3]2+ are presented. A variety of experimental NMR techniques are described and it is shown that sometimes combinations of tec ...

2008

Novel DOTA-based prochelator for divalent peptide vectorization: synthesis of dimeric bombesin analogues for multimodality tumor imaging and therapy

Hugues Jaccard, Lothar Helm

Dimeric peptidic vectors, obtained by the divalent grafting of bombesin analogues on a newly synthesized DOTA-based prochelator, showed improved qualities as tumor targeted imaging probes in comparison to their monomeric analogues. ...

Royal Society of Chemistry2008

Gadonanotubes as Ultrasensitive pH-Smart Probes for Magnetic Resonance Imaging

André Merbach, Lothar Helm, Eva Jakab Toth, Sabrina Laus

With their nanoscalar, superparamagnetic Gd3+-ion clusters (1 ´ 5 nm) confined within ultrashort (20-80 nm) single- walled carbon nanotube capsules, gadonanotubes are high- performance T1-weighted contrast agents for magnetic resonance imaging (MRI). At 1. ...

American Chemical Society (ACS)2008

A benzene-core trinuclear GdIII complex: towards the optimization of relaxivity for MRI contrast agent applications at high magnetic field

André Merbach, Lothar Helm, Eva Jakab Toth, Joao Bruno Livramento Fig.

A novel ligand, H12L, based on a trimethylbenzene core bearing three methylenediethylenetriamine-N,N,N,N- tetraacetate moieties (–CH2DTTA4–) for Gd3+ chelation has been synthesized, and its trinuclear Gd3+ complex [Gd3L(H2O) 6]3– investigated with respect ...

2008

In vivo MRI assessment of a novel GdIII-based contrast agent designed for high magnetic field applications

André Merbach, Lothar Helm, Eva Jakab Toth, Joao Bruno Livramento Fig.

Gd3L is a trinuclear Gd3R complex of intermediate size, designed for contrast agent applications in high field magnetic resonance imaging (H12L is based on a trimethylbenzene core bearing three methylene-diethylenetriamine-N,N,N00,N00-tetraacetate moieties ...

2008

Comparison of different methods for calculating the paramagnetic relaxation enhancement of nuclear spins as a function of the magnetic field

Lothar Helm

The enhancement of the spin-lattice relaxation rate for nuclear spins in a ligand bound to a paramagnetic metal ion [known as the paramagnetic relaxation enhancement (PRE)] arises primarily through the dipole-dipole (DD) interaction between the nuclear spi ...

2008

Mechanism of Pyridine-Ligand Exchanges at the Different Labile Sites of 3d Heterometallic and Mixed Valence μ3-oxo Trinuclear Clusters

André Merbach, Lothar Helm, Rosario Scopelliti, Fabrice Riblet

The syntheses and single crystal X-ray structural analysis of five novel hetero- and homometallic μ3-oxo trinuclear cluster with the formula [FeIII2MII(μ3-O)(μ-O2CCH3)6(4-Rpy)3] · x(4-Rpy) · y(CH3CN) where R ) Ph for 1(Fe2Mn),2(Fe2Fe), 3(Fe2Co), 4(Fe2Ni) a ...

2008

Towards the Rational Design of MRI Contrast Agents: Electron Spin Relaxation Is Largely Unaffected by the Coordination Geometry of Gadolinium(III)-DOTA-Type Complexes

Loïck Moriggi, Lothar Helm, Alain Borel

Electron-spin relaxation is one of the determining factors in the efficacy of MRI contrast agents. Of all the parameters involved in determining relaxivity it remains the least well understood, particularly as it relates to the structure of the complex. On ...

2008

Spectroscopic investigation of Tellurium in chloride brines

Lothar Helm, Pascal Grundler

2008

Physicochemical Properties of the High-Field MRI-Relevant [Gd(DTTA-Me)(H2O)2]− Complex

Loïck Moriggi, Lothar Helm, Cora Prestinari

To study the physicochemical properties of the DTTA chelating moiety (H4DTTA = diethylenetriaminetetraacetic acid = N,N′-[iminobis(ethane-2,1-diyl)]bis[N-(carboxymethyl)glycine]), used in several compounds proposed as magnetic resonance imaging (MRI) contr ...

2008

Gd(III)-EPTPAC16, a new self-assembling potential liver MRI contrast agent: in vitro characterization and in vivo animal imaging studies

Lothar Helm

The recently reported amphiphilic chelate,

[Gd(EPTPAC_{16})(H_2O)]^{2-}

, forms supramolecular aggregates in aqueous solution by self-assembly of the monomers with a relaxometrically determined critical micellar concentration (CMC) of 0.34 mM. The effect ...

2008

Physicochemical and MRI characterization of Gd3+-loaded polyamidoamine and hyperbranched dendrimers

André Merbach, Loïck Moriggi, Lothar Helm, Eva Jakab Toth

Springer, Springer-Verlag2007

H5EPTPACH2OH: Synthesis, Relaxometric Characterization and 1H NMR Spectroscopic Studies on the Solution Dynamics of Its LnIII Complexes

Lothar Helm, Eva Jakab Toth

The synthesis and characterization of a new metal chelator, 4-(S)-hydroxymethyl-3,6,10-tri(carboxymethyl)-3,6,10-triazadodecanedioic acid (H5EPTPACH2OH), is reported. Protonation constants for the ligand H5EPTPACH2OH and for the previously reported H5EPTPA ...

2007

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