Research Article: Magnetic Resonance Water Proton Relaxation in Protein Solutions and Tissue: T1ρ Dispersion Characterization

Date Published: January 5, 2010

Publisher: Public Library of Science

Author(s): Enn-Ling Chen, Raymond J. Kim, Shaolin Yang.

Abstract: Image contrast in clinical MRI is often determined by differences in tissue water proton relaxation behavior. However, many aspects of water proton relaxation in complex biological media, such as protein solutions and tissue are not well understood, perhaps due to the limited empirical data.

Partial Text: Image contrast in clinical MRI is often determined by differences in tissue water relaxation behavior. Although the observed properties of proton relaxation in homogeneous liquids such as pure water, ethanol, and glycerol have been successfully explained by the theory of Bloembergen, Purcell, and Pound (BPP) [1], the mechanism of water relaxation in more complex environments such as tissues is still highly speculative. In part to gain insight into tissue relaxation, many studies have evaluated the relaxation characteristics of protein solutions, since for most tissue, relaxation behavior is dominated by the water-macromolecule interaction [2]. However, few studies have attempted to systematically investigate the relationship between the physico-chemical properties of macromolecules and bulk water relaxation, and there are diverse hypotheses concerning the mechanism of water proton relaxation in protein systems—perhaps due to the limited empirical data.

Table 1 summarizes the relaxation times and T1ρ dispersion characteristics for all samples. The standard error of the estimate for the relaxation time curvefits were on average less than 1.0% of the calculated relaxation time values for all protein samples and less than 2.2% for tissue samples. Unless specifically reported, pH was not measured.



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