A QUASIELASTIC NEUTRON SCATTERING STUDY OF WATER DIFFUSION IN FROG MUSCLE
HEIDORN, DOUGLAS BRUCE
Doctor of Philosophy
The microscopic structure and dynamics of cytoplasmic water in the cells of organs and tissues are not well-understood. Much work has been done using various experimental techniques to study the properties of water in living systems, yet there is no generally accepted model describing the interaction of water with cellular constituents. Quasi-elastic neutron scattering (QNS) is a technique capable of a spatial resolution of 1-10 (ANGSTROM) and a frequency resolution of 10('9) to 10('13) sec('-1) which is suitable for the study of the diffusive motion of water in biological systems. A monochromatic beam of 0.95 THz neutrons was used to obtain QNS spectra within an energy window of (+OR-)0.2 THz for momentum transfer values in the ranges of 0.5 (ANGSTROM)('-1) to 1.9 (ANGSTROM)('-1). We have obtained QNS spectra for water in sartorius and gracilis major muscles of green leopard frogs (Rana pipiens pipiens) at 30(DEGREES)C and comparison spectra for a .15 molar solution of KCl at 3(DEGREES)C. The spectra were interpreted with a jump-diffusion model for translational water motion in both systems and a bound-free model for water in the muscle. The measured diffusion parameters of these two systems indicate that the water motion is more restricted in the frog muscle than in the aqueous KCl solution. We estimate the bound fraction of water in muscle to be 15.0 (+OR-) 4.1%. Our results for the bound water fraction in muscle and diffusion coefficients and correlation times of water in muscle and in a .15 m KCl solution agree well with the QNS and NMR results of others.
Condensed matter physics