The chapter presents the results of one-dimensional NMR methods in
studying molecular anisotropy and microstructure of collagen fibers from two
connective tissues with different cross-linking level (fibers from adult steer and young
calf) at humidity level (HL) of 0.6 g water per g dry mass. The apparent diffusion
coefficients (Dapp) have been studied in oriented collagen fibers (along the static
magnetic field B0) for two experimental cases: (1) the gradient was applied along the
static magnetic field B0 and (2) the gradient was switched on perpendicular to the
magnetic field B0. The dependences of Dapp on diffusion time discovered a restriction
diffusion of water for both gradient directions. A model of equally spaced parallel
planes with permeable barriers, has been used to estimate a restricted distance and
permeability coefficient. For both types of collagen fibers (adult and young)
anisotropic diffusion of water has been discovered. Moreover, self-diffusion of water in
fibers of natural silk (Bombyx mori) with HL=0.18 g H2O per g dry mass has been
studied by pulsed field gradient NMR stimulated echo at various diffusion times Δ
between 10 and 200 ms. The analysis showed that the decrease in Dapp with the
increasing Δ due to the restricted diffusion. The results obtained were compared with
published data on restricted diffusion in natural macromolecular systems with low
water content.
Keywords: Apparent diffusion coefficient Dapp, Free induction decay (FID),
Natural Biopolymers, Pulsed Field Gradient (PFG) NMR, Spin-echo (SE), Spinlattice
(longitudinal) relaxation time T1, Spin-spin (transverse) relaxation time T2,
Stimulated echo (STE).
