High-field pulsed EPR and ENDOR of Gd3+ complexes in glassy solutions

Raitsimring, Arnold M.; Astashkin, Andrei V.; Poluektov, Oleg G.; Caravan, Peter

doi:10.1007/bf03166762

Cited by 76 publications

(146 citation statements)

References 34 publications

Supporting

Mentioning

131

Contrasting

Order By: Relevance

“…In a preliminary analysis, simulations of the ENDOR spectra have been performed for complexes Na 3 [Gd(L1)(H 2 O)] and Na 2 -[Gd(L3)(H 2 O) 2 ] in the absence of HSA, explicitly considering their crystal field interactions which were obtained separately from their EPR spectra. [30] For those complexes, the hydration number determined using this elaborate approach turned out to be identical within experimental error to the values given above ( Figure 7).…”

Section: Extension Of the Methods To Complexes With Larger Hydration Nmentioning

confidence: 62%

“…The relationship between the shape of the EPR spectrum and parameters of the crystal field interaction has been discussed previously. [30,31] The ENDOR spectrum M (Figure 3 C), where the À 1 / 2 , + 1 / 2 transition does not significantly contribute to the ENDOR spectrum while the intensities of the transitions between all other electronic manifolds are practically the same as in position a. This allows a separation of the ENDOR transitions, that is, the difference between the two ENDOR spectra according to Equation (4):…”

Section: Epr and Endor Spectra Of [Gdmentioning

confidence: 99%

See 1 more Smart Citation

Probing the Water Coordination of Protein‐Targeted MRI Contrast Agents by Pulsed ENDOR Spectroscopy

Zech¹,

Sun²,

Jacques³

et al. 2005

ChemPhysChem

View full text Add to dashboard Cite

A novel methodology based on electron-nuclear double resonance (ENDOR) spectroscopy is used for the direct determination of the water coordination number (q) of gadolinium-based magnetic resonance imaging (MRI) contrast agents. Proton ENDOR spectra can be obtained at approximately physiological concentrations for metal complexes in frozen aqueous solutions either in the presence or absence of protein targets. It is shown that, depending on the structure of the co-ligand, the water hydration number of a complex in aqueous solution can be significantly different to when the complex is noncovalently bound to a protein. From the ENDOR spectra of the exchangeable protons, precise information on the metal-proton distance can be derived as well. These essential parameters directly correlate with the efficacy of MRI contrast agents and should therefore aid the development of novel, highly efficient compounds targeted to various proteins.

show abstract

Section: Extension Of the Methods To Complexes With Larger Hydration Nmentioning

confidence: 62%

Section: Epr and Endor Spectra Of [Gdmentioning

confidence: 99%

Probing the Water Coordination of Protein‐Targeted MRI Contrast Agents by Pulsed ENDOR Spectroscopy

Zech¹,

Sun²,

Jacques³

et al. 2005

ChemPhysChem

View full text Add to dashboard Cite

show abstract

“…For this purpose, V 0 and V ref were simulated for a broad range of D values from D = 0.15 GHz to D = 2.5 GHz. Here, each D value corresponds to an average over orientations and a polynomial distribution of E values (see [40]), as indicated in Fig. 5d for D = 1 GHz.…”

Section: Dependence Of Echo Intensity On Zfs Splittingmentioning

confidence: 99%

Gd(III)–Gd(III) distance measurements with chirp pump pulses

Doll

Wili

et al. 2015

Journal of Magnetic Resonance

110

View full text Add to dashboard Cite

The broad EPR spectrum of Gd(III) spin labels restricts the dipolar modulation depth in distance measurements between Gd(III) pairs to a few percent. To overcome this limitation, frequency-swept chirp pulses are utilized as pump pulses in the DEER experiment. Using a model system with 3.4 nm Gd-Gd distance, application of one single chirp pump pulse at Q-band frequencies leads to modulation depths beyond 10%. However, the larger modulation depth is counteracted by a reduction of the absolute echo intensity due to the pump pulse. As supported by spin dynamics simulations, this effect is primarily driven by signal loss to double-quantum coherence and specific to the Gd(III) high spin state of S = 7/2. In order to balance modulation depth and echo intensity for optimum sensitivity, a simple experimental procedure is proposed. An additional improvement by 25% in DEER sensitivity is achieved with two consecutive chirp pump pulses. These pulses pump the Gd(III) spectrum symmetrically around the observation position, therefore mutually compensating for dynamical Bloch-Siegert phase shifts at the observer spins. The improved sensitivity of the DEER data with modulation depths on the order of 20% is due to mitigation of the echo reduction effects by the consecutive pump pulses. In particular, the second pump pulse does not lead to additional signal loss if perfect inversion is assumed. Moreover, the compensation of the dynamical Bloch-Siegert phase prevents signal loss due to spatial dependence of the dynamical phase, which is caused by inhomogeneities in the driving field. The new methodology is combined with pre-polarization techniques to measure long distances up to 8.6 nm, where signal intensity and modulation depth become attenuated by long dipolar evolution windows. In addition, the influence of the zero-field splitting parameters on the echo intensity is studied with simulations. Herein, larger sensitivity is anticipated for Gd(III) complexes with zero-field splitting that is smaller than for the employed Gd-PyMTA complex.

show abstract

“…15 A single value of E/D is not capable to describe the experimentally observed bell-like shape of the Gd 3+ EPR spectrum. 19,20 We assumed for each value of D a distribution of E values according to a probability function 19,20 25 with nearly axial symmetry (E0) should be rather small, as it implies a special arrangement of ligands. As the glassy sample reflects a pattern of dynamic rearrangements of complexes in solution, it should contain mainly distorted ligand configurations with lowest (tetragonal) symmetries.…”

Section: Analysis Of Dipolar Frequencies: Numeric Simulationsmentioning

confidence: 99%

“…17 The Gd 3+ centres have the particular feature of broadly distributed strengths and orientations of the zero field splitting (ZFS). 19,20 This leads to the absence of orientation selection 40 effects in distance measurements and can be very valuable for high-field distance measurements. 14 Recently we reported the basic details about setup and performance of the DEER experiment in Gd 3+ -nitroxide radical spin pairs.…”

mentioning

confidence: 99%

Distance measurements in Au nanoparticles functionalized with nitroxide radicals and Gd3+–DTPA chelate complexes

Yulikov

Lueders

Warsi

et al. 2012

Phys. Chem. Chem. Phys.

102

View full text Add to dashboard Cite

Nanosized gold particles were functionalised with two types of paramagnetic surface tags, one having a nitroxide radical and the other one carrying a DTPA complex loaded with Gd 3+ . Selective measurements of nitroxide-nitroxide, Gd 3+ -nitroxide and Gd 3+ -Gd 3+ distances were performed on this system and information on the distance distribution in the three types of spin pairs was obtained. A numerical analysis of the dipolar frequency distributions is presented for Gd 3+ centres with moderate magnitudes of zero-field splitting, in the range of detection frequencies and resonance fields where the high-field approximation is only roughly valid. The dipolar frequency analysis confirms the applicability of DEER for distance measurements in such complexes and gives an estimate for the magnitudes of possible systematic errors due to the non-ideality of the measurement of the dipole-dipole interaction.

show abstract

High-field pulsed EPR and ENDOR of Gd3+ complexes in glassy solutions

Cited by 76 publications

References 34 publications

Probing the Water Coordination of Protein‐Targeted MRI Contrast Agents by Pulsed ENDOR Spectroscopy

Probing the Water Coordination of Protein‐Targeted MRI Contrast Agents by Pulsed ENDOR Spectroscopy

Gd(III)–Gd(III) distance measurements with chirp pump pulses

Distance measurements in Au nanoparticles functionalized with nitroxide radicals and Gd3+–DTPA chelate complexes

Contact Info

Product

Resources

About