MODIFICATION OF THE STRUCTURE OF WATER IN AGAR GELS

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Abstract
The proton signal of the water in agar gels, studied in high resolution NMR, differs from that of pure water in that the line width is significantly broadened and the amplitude is de-creased; T1 is not influenced but T2 is decreased. This effect in agar is not shown by a variety of other gels and viscous solutions studied. The signal of the methyl protons from tetramethylammonium chloride is essentially equivalent when studied in agar gels or in pure water in marked contrast to the proton signal from water. These findings dem-onstrate that a possible heterogeneity of the internal field, resulting from compartmentalization of water, diamagnetic anisotropy, or the presence of paramagnetic impurities, are not responsible for the NMR changes observed in the water of agar gels. The NMR data can best be explained at present on the basis that water in an agar gel is in a modified state with properties of structural rigidity and mobility inter-mediate between "free" water and ice.