K. Potter et al., MAGNETIC-RESONANCE MICROSCOPY STUDIES OF CATION DIFFUSION IN CARTILAGE, Biochimica et biophysica acta (G). General subjects, 1334(2-3), 1997, pp. 129-139
The diffusion of copper ions in bovine nasal cartilage (BNC), a dense
connective tissue, was investigated to further the understanding of io
n transport in charged biopolymer systems. Using an inversion-recovery
null-point imaging technique, it was found that the diffusion rate of
divalent copper ions into cartilage was significantly lower in normal
BNC than in BNC in which the matrix fixed charges had been reduced by
enzymatic digestion or acid neutralization. In normal cartilage, coun
terion diffusion was not well described by a simple Fickian process, l
ikely owing to the high charge density of the constituent molecules. I
n contrast, in both digested and acid neutralized BNC, counterion diff
usion appeared Fickian. Features of the ion transport process were mod
eled using a diffusion equation which included a linear sorption term
to account for cation binding. The diffusion coefficient of copper in
cartilage increased with decreasing matrix fixed charge and was consta
nt for reservoir concentrations up to 30 mM. The activation energy for
the diffusion of copper into BNC was determined to be 34.5 kJ/mol.