Publications by Lothar Helm | EPFL Graph Search

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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 ...

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 ...

We performed an ab initio mol. dynamics simulation of the paramagnetic transition metal ion Cr3+ in aq. soln. Isotropic hyperfine coupling consts. between the electron spin of the chromium ion and nuclear spins of all water mols. have been detd. for instan ...

To study the influence of hydrazine functions in the ligand skeleton, we designed the heptadentate HYD ligand (2,2',2 '',2 ''-(2,2'-(pyridine-2,6-diyl)bis(2-methylhydrazine-2,1,1-triyl)) tetraacetic acid) and compared the thermodynamic, kinetic, and relaxa ...

Understanding radiation-induced defect formation in carbon materials is crucial for nuclear technology and for the manufacturing of nanostructures with desired properties. Using first-principles molecular dynamics, we perform a systematic study of the none ...

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 ...

The zero,-field splitting (ZFS) parameters of the Mn(EDTA)(H2O).2H(2)O. and [Mn(MeNO(2)A)(H2O)].2H(2)O systems were estimated by using DFT and ab initio CASSCF/NEVPT2 calculations (EDTA = (ethane-1,2-41bis(azanetriy1))tetraatetate; MeNO2A = 2,2'-(7-m ...

Medium sized molecules endowed with multiple Gd3+ complexes are efficient high magnetic field MRI contrast agents. The novel ligand Mes(DO3A)3, presenting three DO3A (1,4,7,10-tetraazacyclododecane-N,N′,N′′-triacetatic acid) units grafted on the methyl pos ...

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 ...

The search for higher spatial resolution and better sensitivity stimulates the development of high-field (3 T) and ultrahigh field (>3 T) MRI scanners. Gadolinium-based MRI contrast agents, commercial ones used in clinics, as well as recently developed mor ...

Water exchange kinetics on [Ln(AAZTAPh–NO2)(H2O)q]− (Ln = Gd3+, Dy3+, or Tm3+) were determined by 1H nuclear magnetic resonance (NMR) measurements. The number of inner-sphere water molecules was found to change from two to one when going from Dy3+ to Tm3+. ...

A combined variable-temp. and multiple field 17O NMR, EPR and NMRD study was performed for the 1st time on Gd(III) complexes of cryptand ligands, L1 and L2, where L1 contains three 2,2'-bipyridine units ([bpy.bpy.bpy]) and L2 is the disubstituted Me ester ...

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 ...

{Fe[Gd2bpy(DTTA)2(H2O)4]3}4- is a self-assembled, metallostar-structured potential MRI contrast agent, with six efficiently relaxing Gd3+ centers confined into a small mol. space. Its proton relaxivity is particularly remarkable at very high magnetic field ...

We applied first principles molecular dynamics (MD) technique to study structure, dynamics, and magnetic interactions of the

Gd^{3+}

aqua ion dissolved in liquid water, a prototypical system for Gd-based complexes used as contrast agents for magnetic res ...

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 ...

The water-soluble endohedral gadofullerene derivatives, Gd@C60(OH)x and Gd@C60[C(COOH)2]10, have been characterized with regard to their MRI contrast agent properties. Water-proton relaxivities have been measured in aqueous solution at variable temperature ...

Hyperpolarization by dissolution dynamic nuclear polarization (DNP) enhances Y-89 spin magnetization by 3 to 4 orders of magnitude and provides a way to monitor yttrium-ligand complexation "on the fly" by means of Y-89 NMR. In this communication, we show a ...

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 ...

The need for magnetic resonance imaging (MRI) contrast agents with improved relaxivity maintains the development of new Gd-III chelates as an intensive and demanding field of research. In this work, we introduce the new dimeric chelators bis{1,4,7,10-tetra ...

Lothar Helm

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

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

Hyperfine interactions in aqueous solution of Cr3+: an ab initio molecular dynamics study

A Pyridine-Based Ligand with Two Hydrazine Functions for Lanthanide Chelation: Remarkable Kinetic Inertness for a Linear, Bishydrated Complex

Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study

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

Transient versus Static Electron Spin Relaxation in Mn2+ Complexes Relevant as MRI Contrast Agents

Synthesis, complexation and NMR relaxation properties of Gd3+ complexes of Mes(DO3A)3

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

Optimization of gadolinium-based MRI contrast agents for high magnetic‑field applications

Evaluation of Water Exchange Kinetics on [Ln(AAZTAPh–NO2)(H2O)q]x Complexes Using Proton Nuclear Magnetic Resonance

Positively Charged GdIII Cryptates: Slow, Associative Water Exchange

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

First in vivo MRI assessment of a self-assembled metallostar compound endowed with a remarkable high field relaxivity

Gadolinium(III) ion in liquid water: structure, dynamics and magnetic interactions from first principles

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

Water-Soluble Gadofullerenes: Toward High-Relaxivity, pH-Responsive MRI Contrast Agents

Kinetics of Yttrium-Ligand Complexation Monitored Using Hyperpolarized 89Y as a Model for Gadolinium in Contrast Agents

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

Dinuclear DOTA-Based Gd-III Chelates - Revisiting a Straightforward Strategy for Relaxivity Improvement