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On the philosophy of optimizing contrast agents: an analysis of 1H NMRD profiles and ESR lineshapes of the Gd(III)complex MS-325 + HSA
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
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. Vol. 167, no 1, 147-160 p.
URN: urn:nbn:se:umu:diva-14778DOI: 10.1016/j.jmr.2003.12.006OAI: diva2:154450
Available from: 2007-06-18 Created: 2007-06-18 Last updated: 2011-04-15Bibliographically approved
In thesis
1. An Analysis of NMRD profiles and ESR lineshapes of MRI Contrast Agents
Open this publication in new window or tab >>An Analysis of NMRD profiles and ESR lineshapes of MRI Contrast Agents
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.
Physical chemistry, MRI contrast agent, MS-325, Spin relaxation, NMRD, ESR, Fysikalisk kemi
National Category
Physical Chemistry
Research subject
Physical Chemistry
urn:nbn:se:umu:diva-361 (URN)91-7305-777-0 (ISBN)
Public defence
2004-12-09, KB3A9, KBC, Umeå University, Umeå, 10:00
Available from: 2004-11-12 Created: 2004-11-12 Last updated: 2011-04-15Bibliographically approved

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Zhou, XiangzhiWestlund, Per-Olof
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