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Multiexponential proton relaxation processes of compartmentalized water in gels
Author(s) -
Watanabe Tokuko,
Murase Norio,
Staemmler Martin,
Gersonde Klaus
Publication year - 1992
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910270112
Subject(s) - relaxation (psychology) , proton , chemistry , magnetic relaxation , dipole , matrix (chemical analysis) , chemical physics , analytical chemistry (journal) , thermodynamics , nuclear magnetic resonance , chromatography , organic chemistry , psychology , social psychology , physics , magnetization , quantum mechanics , magnetic field
The proton relaxation times, T 1 and T 2 , of water in Sephadex gels, exhibiting pores of varying size (i.e., with exclusion limits of molecular weight between l0 3 and 10 5 ) and water contents in the range 30 to 70% (w/w, weight of water to total weight), were measured at 20 MHz in the temperature range 5 to 50°C. Multiexponential analysis of the relaxation curves revealed the existence of two relaxation components in all gel systems. A component with long T 1 and T 2 ( T 1,1 and T 2,1 ) is associated with a large water fraction α 1,1 and α 2,1 and a component with short T 1 and T 2 ( T 1,2 and T 2,2 with a small water fraction α 1,2 and α 2,2 An analysis of the temperature behavior of the relaxation components gives insight into the relaxation mechanisms. The relaxation process in water, compartmentalized in the gel matrix, is mainly controlled by dipole‐dipole interactions. In addition, proton exchange processes between hydration water and hydroxyl groups of the matrix chain contribute under specific conditions and lead to a dramatic enhancement of the relaxation rate. In particular, for gels with small pores and with low water content proton exchange is observed. Compartments of water in gels could be models for compartments of water in biological tissues.