Gelation studies method

The materials and methods used in this work have been described in detail in the original publications (1 3). Briefly, the DNA used in the gelation work was prepared by extensive sonication of calf thymus DNA it had a degree of polymerization of 200 30 base pairs (bp). The DNA used in the ordinary-extraordinary transition studies was prepared by nuclease digestion of chromatin from chicken erythrocytes it was an equimolar mixture of two sizes, 140 bp and 160 bp, averaged to 150 bp. 

Measurements of dielectric properties have been used to monitor chemical reactions in organic materials for more than fifty years. In 1934, Kienle and Race 11 reported the use of dielectric measurements to study polyesterification reactions. Remarkably, many of the major issues that are the subject of this review were identified in that early paper the fact that ionic conductivity often dominates the observed dielectric properties the equivalence between the conductivity measured with both DC and AC methods the correlation between viscosity and conductivity early in cure the fact that conductivity does not show an abrupt change at gelation the possible contribution of orientable dipoles and sample heterogeneities to measured dielectric properties and the importance of electrode polarization at low frequencies. 

All solutions were mixed by the first method and studied by means of gelation, light scattering and NMR experiments. Only potassium solutions (which seemed to be representative) were prepared by the second method of mixing and were studied by gelation and NMR experiments. 

Auty, M.A.E., Fenelon, M.A., Guinee, T.P., Mullins, C., Mulvihill, D.M. 1999. Dynamic confocal scanning laser microscopy methods for studying milk protein gelation and cheese melting. Scanning 21, 299-304. 

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