Abstract
We report osmotic swelling pressure and small angle neutron scattering (SANS) measurements made on DNA gels prepared in 40 mM NaCl solution. Two series of gels were made: in the first the crosslinks were introduced in the absence of CaCl2, while in the second the DNA was crosslinked in solutions containing 40 mM NaCl with different amounts of CaCl2. The swelling pressure of the gels was determined as a function of the DNA concentration at constant salt concentrations. It was found that gels prepared in the presence of CaCl2 exhibited significantly lower swelling pressure than the corresponding gels made in CaCl2 free solutions. SANS revealed the presence of large clusters (>1000 Å) dominating the scattering signal at low values of q. In the intermediate q‐range the SANS intensity varied as q−1, in agreement with the linear character of the DNA chains. From the SANS response in the high q region the thermodynamic component of the concentration fluctuations, Idyn(0), was estimated. It was shown that Idyn(0) determined from SANS was in good agreement with the intensity calculated from osmotic swelling pressure measurements.
Published Version
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