Inelastic Neutron Scattering from Water in Biological Structures
The beryllium filter technique is used to measure rotational modes of water in wet DNA and rat muscle. Measurements are also presented of rotational modes of bound H2O in live leaves of Ficus elastica decora, Philodendron cordaturn, and Peperomia obtusifolia. Interpretation of data is based on the hypothesis that hindrance of rotational motion should result in shifts to higher frequency. Such shifts are verified by comparing the scattering from water with that from ice and cytosine monohydrate. Statistical analysis of the scattering from plant leaves is based on the assumption that least-squares fitting can be carried out using variable percentages of ice and water spectra to describe hydrate and free water fractions. It is found that the amount of water present as a 4-fold bonded hydrate is very small, a few percent or less. A comparison of the beryllium filter and quasielastic techniques is made.