Proton nuclear magnetic resonance moment and relaxation study of cellulose morphology

Abstract

Proton magnetic resonance pH NMR) has been used to determine the second moment (M2) of the line shape, solid echo decay, and dipolar (Tld), rotating frame (Tlp) and spin-lattice (Tt) relaxation times of unaltered, crystallite-enriched, and gelled-reprecipitated samples of cotton and filter paper cellulose.For all samples, the measured M2 was within 30% of that for the rigid lattice, indicating that cellulose microfibrils are almost rigid on the NMR time scale of 10"5 s. Measurements of 7\ as a function of frequency indicated the presence of a low amplitude but important motion occurring in cellulose at about 10-15 MHz which may be methylol group reorientation. Measurements of Tld, Tlp, and the solid echo decay revealed the presence of two types of domains which we assign to crystalline and paracrystalline cellulose. Crystallite-enriched cellulose contained material of only one domain type. Cellulose of reduced crystallinity (gelled-reprecipitated) contained a corresponding increase in the domain we assigned to paracrystalline cellulose. Our results are in agreement with a model in which the crystalline cellulose domains consist of rigid crystalline microfibrils with cross-sectional widths of 100-400 Á and the paracrystalline cellulose domains consist of smaller elementary fibrils with lower packing density.

The physical mechanism of “inhomogeneous” magnetization transfer MRI

“…As with lipid bilayers, dipolar order in the non-aqueous protons of hair, wood, and tendon is destroyed at the aqueous/non-aqueous proton interface due to proton exchange. When there is no exchange, the dipolar order can evolve for much longer: crystalline cellulose prepared in D 2 O has T 1D $ 50 ms, for example [55].…”

Use of Chemical Fractionation and Proton Nuclear Magnetic Resonance to Probe the Physical Structure of the Primary Plant Cell Wall

“…In cell wall preparations (14), we have assigned the TID component with the longer TID to the crystalline cellulose, and that with the shorter TID to paracrystalline cellulose and other polysaccharides. We point out that the proportions of the crystalline components reported here should be interpreted as lower limits due to the possibility of spin diffusion between the two components (13,14). The Jeener echo measurements are less accurate than the solid echo measurements since the two TID components differed by only a factor of 3 (Table III).…”

“…Jeener echo studies on preparations of cellulose (13) and cell walls ( 14) have been interpreted in terms of contributions from paracrystalline and crystalline components. It has been demonstrated (13) that crystalline cellulose has a TID value of 30 to 60 ms and a second moment corresponding to the rigid lattice M2 value, and paracrystalline cellulose has a TID value of 10 ms or less and an M2 value that is about 70% of the rigid lattice value.…”

“…We have used the 'H-NMR methods reported earlier (12)(13)(14)20) to describe the properties of P. vulgaris etiolated hypocotyl cell wall fragments before and after each stage of the commonly used chemical fractionation with ammonium oxalate and KOH (10). The aims ofthis work were to discover whether the physical properties of the remaining materials were affected by the chemical fractionation of the cell walls and to assess the implications of fractionation studies for models of in vivo cell wall structure.…”

Molecular Dynamics of Polycrystalline Cellobiose Studied by Solid-State NMR

“…So far, the 1 H relaxation studies have been limited to showing the relative rigidity of cellulose [23][24][25][26] and distinguishing molecules in the crystalline and paracrystalline domains of the microfibrils [25,26]. We report, in this paper, results on polycrystalline TANG AND BELTON cellobiose, in both protonated and deuterated forms.…”