title: Water magnetic relaxation dispersion in biological systems: the contribution of proton exchange and implications for the noninvasive detection of cartilage degradation.
abstract: Magnetic relaxation has been used extensively to study and characterize biological tissues. In particular, spin-lattice relaxation in the rotating frame (T(1rho)) of water in protein solutions has been demonstrated to be sensitive to macromolecular weight and composition. However, the nature of the contribution from low frequency processes to water relaxation remains unclear. We have examined this problem by studying the water T(1rho) dispersion in peptide solutions ((14)N- and (15)N-labeled), glycosaminoglycan solutions, and samples of bovine articular cartilage before and after proteoglycan degradation. We find in model systems and tissue that hydrogen exchange from NH and OH groups to water dominates the low frequency water T(1rho) dispersion, in the context of the model used to interpret the relaxation data. Further, low frequency dispersion changes are correlated with loss of proteoglycan from the extra-cellular matrix of articular cartilage. This finding has significance for the noninvasive detection of matrix degradation.
authors.affiliation: Department of Radiology, Metabolic Magnetic Resonance Research and Computing Center, University of Pennsylvania, Philadelphia, PA 19104, USA. uduvvuri@mail.med.upenn.edu
authors.forename: U
authors.initials: U
authors.lastname: Duvvuri
authors.forename: A D
authors.initials: AD
authors.lastname: Goldberg
authors.forename: J K
authors.initials: JK
authors.lastname: Kranz
authors.forename: L
authors.initials: L
authors.lastname: Hoang
authors.forename: R
authors.initials: R
authors.lastname: Reddy
authors.forename: F W
authors.initials: FW
authors.lastname: Wehrli
authors.forename: A J
authors.initials: AJ
authors.lastname: Wand
authors.forename: S W
authors.initials: SW
authors.lastname: Englander
authors.forename: J S
authors.initials: JS
authors.lastname: Leigh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism*; D002417:Cattle; D003094:Collagen / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011509:Proteoglycans / Q000378:metabolism; D011522:Protons; D014867:Water
chemical_list: D011509:Proteoglycans; D011522:Protons; D014867:Water; D003094:Collagen