MEASUREMENT OF BOUND WATER IN AN AQUEOUS DNA SOLUTION USING NUCLEAR-MAGNETIC-RESONANCE AND TIME DOMAIN REFLECTOMETRY

Nuclear magnetic resonance (NMR) and time domain reflectometry (TDR) were employed to investigate the bound water of deoxyribonucleic acid (DNA) in aqueous solution. The NMR transverse magnetization of the water protons decays in the manner described by a monoexponential function which gives a single magnetic relaxation time (T2). However, this fact does not mean that the correlation times for rotational reorientation of both bound and free water molecules are identical. On the other hand, two different dielectric relaxation times (tau(d)) associated with bound and free water molecules were observed in the same solution. Substituting the dielectric relaxation times into the fast exchange model for the NMR relaxation, we could evaluate the amount of bound water as 0.3 g of water/g of DNA.