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An Analysis of NMRD profiles and ESR lineshapes of MRI Contrast Agents
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

To optimize contrast agent in MRI scan region, e.g. to enhance paramagnetic relaxation in the MRI scan fields(0.1T-3T), one possible way is to slow down the tumbling of the paramagnetic complex. The effect of slowing down the reorientational motion of the complex to increase relaxivity is obvious and this strategy has already been employed in producing MRI contrast agent that can bind to specific proteins. An example is MS-325 binds to human serum albumin(HSA). The slow down effects on the ligands around paramagnetic ion, and on the zero field splitting(ZFS) interaction are under studies and the physics behind is still not clear. In this thesis, a generalized Solomon-Bloembergen-Morgan(GSBM) theory together with stochastic Liouville approach(SLA), is applied to investigate the mechanism behind the slow down effects. Two gadolinium complexes, MS-325+HSA and Gd(H2O)83++glycerol are studied by means of NMRD and ESR experiments.

GSBM is a second order perturbation theory with closed analytical form. The computation based on this theory is fast, but it has its limitation and in the case of Gd(S=7/2) the ZFS strength times its correlation time(Δt.τƒ) should be less than 0.1. In comparison, the SLA is an "exact" theory that can evaluate the validity of GSBM calculation. However, the calculation in SLA is time consuming due to the large matrix it constructed. The major model used in GSBM is a two dynamic model, characterized by transient ZFS Δt and static ZFS Δs and their corresponding correlation time τƒ and τR, while in SLA the model is only described by Δt and τƒ. A combined NMRD and ESR analysis is used to understand the details of ZFS interaction. Both models can reproduce experimental NMRD profiles and model parameters are similar; for ESR linewidths the model parameters are quite different. The fitting results indicate the NMRD profiles are less sensitive to the detail expression of ZFS correlation function. In order to interpret both NMRD and ESR experiments with identical parameters, a more complex ZFS interaction model should be developed.

Place, publisher, year, edition, pages
Umeå: Kemi , 2004. , 40 p.
Keyword [en]
Physical chemistry, MRI contrast agent, MS-325, Spin relaxation, NMRD, ESR
Keyword [sv]
Fysikalisk kemi
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-361ISBN: 91-7305-777-0 (print)OAI: oai:DiVA.org:umu-361DiVA: diva2:143243
Public defence
2004-12-09, KB3A9, KBC, Umeå University, Umeå, 10:00
Opponent
Supervisors
Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2017-05-04Bibliographically approved
List of papers
1. On the philosophy of optimizing contrast agents: an analysis of 1H NMRD profiles and ESR lineshapes of the Gd(III)complex MS-325 + HSA
Open this publication in new window or tab >>On the philosophy of optimizing contrast agents: an analysis of 1H NMRD profiles and ESR lineshapes of the Gd(III)complex MS-325 + HSA
2004 (English)In: Journal of magnetic resonance (San Diego, Calif. 1997: Print), ISSN 1090-7807, E-ISSN 1096-0856, Vol. 167, no 1, 147-160 p.Article in journal (Refereed) Published
Abstract [en]

A generalization of the modified SBM theory is developed in closed analytical form. The theory is applied to describe the paramagnetically enhanced water proton spin–lattice relaxation rates of the aqueous-systems containing a gadolinium(S=7/2) complex(MS-325) in the presence or absence of human serum albumin (HSA). MS-325 binds to HSA: in the absence of the protein the reorientational time, τR, is short, but when HSA is added τR becomes much longer. In this way, the effect of reorientational motion, static (Δs), and transient (Δt) zero-field splitting (ZFS) interactions on both the water proton relaxivity and the Gd ESR lineshapes are investigated.

Two dynamic models of electron spin relaxation are presented, characterized by transient and static ZFS-interactions. X-, Q-, and W-bands ESR spectra of MS-325+HSA are analyzed in order to describe the effect on the electron spin system upon binding to a macromolecule. A computer program based on this theory is developed which calculates solvent water proton T1 NMRD profiles and the corresponding X-, Q-, U-, and W-bands ESR lineshapes.

Place, publisher, year, edition, pages
San Diego: Academic Press, 2004
Identifiers
urn:nbn:se:umu:diva-14778 (URN)10.1016/j.jmr.2003.12.006 (DOI)
Available from: 2007-06-18 Created: 2007-06-18 Last updated: 2011-04-15Bibliographically approved
2. 1H NMRD profiles and ESR lineshapes of Gd(III) complexes: a comparison between the generalized SBM and the stochastic Liouville approach
Open this publication in new window or tab >>1H NMRD profiles and ESR lineshapes of Gd(III) complexes: a comparison between the generalized SBM and the stochastic Liouville approach
2005 (English)In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 173, no 1, 75-83 p.Article in journal (Refereed) Published
Abstract [en]

A complete description of the T1-NMRD profiles and the ESR lineshape of Gd(III) complexes (S = 7/2) was presented using second-order perturbation theory (GSBM) by Zhou et al. [J. Magn. Reson. 167 (2004) 147]. This report compares the GSBM with the stochastic Liouville approach (SLA) to determine the validity of the closed analytical expressions of NMRD and the ESR lineshape functions. Both approaches give the same results at high fields while a very small divergence is observed for X- and W-band ESR lineshapes when the magnitude of the perturbation term times the correlation time approaches the limit of the perturbation regime, ΔZFSτf ≈ 0.1. There was a clear discrepancy between the theoretical GSBM X-band spectrum and the recorded ESR spectrum of the Gd(III) MS-325 + HSA complex. This is probably due to a slow-motion effect caused by a slow modulation of the ZFS interaction. The characteristic correlation time of this slow modulation is in the range of 150 ps, which therefore cannot be due to the reorientational motion of the whole MS-325 + HSA complex.

Place, publisher, year, edition, pages
San Diego: Academic Press, 2005
Keyword
GSBM, SLA, NMRD, ESR, MS-325
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-14677 (URN)10.1016/j.jmr.2004.10.014 (DOI)000227103500010 ()
Available from: 2008-03-31 Created: 2008-03-31 Last updated: 2017-05-04Bibliographically approved
3. The Viscosity and Temperature dependence of X-band ESR lineshapes of Gd(III) Aqueous Complex
Open this publication in new window or tab >>The Viscosity and Temperature dependence of X-band ESR lineshapes of Gd(III) Aqueous Complex
In: Spectrochimica Acta Part AArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:umu:diva-4233 (URN)
Available from: 2004-11-12 Created: 2004-11-12Bibliographically approved
4. The Viscosity and Temperature dependence of 1H T_1-NMRD of the Gd(H_2O)_8^{3+} Complex
Open this publication in new window or tab >>The Viscosity and Temperature dependence of 1H T_1-NMRD of the Gd(H_2O)_8^{3+} Complex
In: Spectrochimica Acta Part AArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:umu:diva-4234 (URN)
Available from: 2004-11-12 Created: 2004-11-12Bibliographically approved

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