Steven F. Tanner

Solid-state 13C-N.M.R. and electron microscopy study on the reversible cellulose I→cellulose IIII transformation in Valonia

An electron microscopy and a high-resolution 13C-n.m.r. study of cellulose is described and a previously unreported solid-state 13C-n.m.r. spectrum of cellulose III is presented. It is shown that a cyclic transformation of highly crystalline cellulose I (Valonia) into cellulose III and back to cellulose I results in a material whose crystallites have a reduced lateral dimension similar to that in cotton and whose electron-diffraction patterns and 13C-n.m.r. spectra are very close to that of cotton. In addition, some new features in the 13C-n.m.r. spectrum of Valonia cellulose are reported.

Interaction of group I cations with iota, kappa and lambda carrageenans studied by multinuclear n.m.r.

Abstract Results are reported for 23 Na, 39 K, 87 Rb and 133 Cs n.m.r. on kappa and iota carrageenans over a range of temperatures. Results for 23 Na and 39 K n.m.r. for lambda carrageenan are also given over the same range of temperatures. A variety of behaviour is observed which, in general, does not correlate with the rheological behaviour in these systems. It is concluded that non-specific ion interactions are of importance in determining rheological behaviour.

High resolution solid state 13C n.m.r. study of some α(1–4) linked glucans: the influence of water on structure and spectra

Abstract High resolution solid state 13 C spectra have been obtained for a number of well characterized α(1–4) linked glucans. These include various cyclodextrins and their complexes with small organic molecules, potato starch and also a highly crystalline amylose sample. The spectra are very well resolved and show peak multiplicities which are a source of information on solid state structure. The appearance of the spectra of the starch sample and some of the cyclodextrin hydrates depends on the amount of water present in those samples. Cross-polarization magic-angle spinning can cause loss of water and thus change the spectra of certain samples during the course of the experiment.

Effects of group I cations on the gelation of iota carrageenan

N.m.r. and rheological measurements have been used to study the gelation of iota carrageenan. Gelation has been found to occur only at polymer concentrations above the critical entanglement concentration. The high temperature sol state above the gel-sol transition appears to be an entangled polymer network. Although Li+ and Na+ ions are less effective at gelling the polymer than K+, Rb+ and Cs+ all cationic forms studied gel at sufficiently high polymer concentration and ionic strength. 7Li+, 23Na, 39K, 87Rb and 133Cs n.m.r. studies have been made as a function of temperature. The lithium salt form (2.2% w/w concentration) formed a viscoelastic solution at room temperature. The other salt forms gelled on cooling. The spectra of Li, Na and Cs carrageenan showed little change on heating whereas K and Rb spectra showed marked changes in apparent intensity. The nature of the cation interaction with the juntion zones is discussed.

Crystal and molecular structure of potassium β-d-glucopyranose 6-sulphate

Abstract The crystal and molecular structure of potassium β- d -glucopyranose 6-sulphate has been determined by direct methods. The sugar ring has the expected 4C1 conformation although the sulphate group causes flattening of the ring. The potassium ion has octahedral co-ordination involving oxygen atoms of five independent β- d -glucopyranose 6-sulphate molecules. The n.m.r. spectrum of the 6-sulphate in the solid state is consistent with the occurrence of two molecules in the unit cell related by a 21 symmetry axis.

Determination of the moisture content of starch using near infrared photoacoustic spectroscopy

Near infrared photoacoustic spectroscopy has been used to measure the water content of wet starch samples (over the range 0–30% of water). The relationship between moisture content and observed intensity of the photoacoustic signal is analysed in terms of the theory of the photoacoustic effect. It is shown that the non-linear dependence of signal intensity on moisture content is consistent with theory and that this non-linearity is to be generally expected in high water content systems. A method of linearising the data is described.

Multinuclear n.m.r. studies of group I cations in furcellaran gels

Multinuclear n.m.r. experiments were carried out in order to study the possible selective interaction between group I cations and furcellaran. It has been shown that the intensity of the 39K, 87Rb and 133Cs spectra show a change in the vicinity of the sol-gel transition. However, the intensity of the 23Na spectrum showed no singularity at the sol-gel transition. These studies suggest that the selective interactions of the group I cations upon gelation of furcellaran resemble those observed for the structurally related kappa-carrageenan.

A 13C cross-polarisation magic-angle-spinning nuclear magnetic resonance study of some well characterised crown ethers and their complexes

Solid crown ethers and crown ether complexes with well determined crystal structures have been examined by 13C cross-polarisation magic-angle-spinning (CPMAS) n.m.r. Certain carbon atoms in most of the compounds studied gave single lines in the solution-state spectra, but produced multiplets in the spectra of the solids. Such multiplicities depend on the conformation and packing adopted by the molecules in the solid state and a qualitative discussion is presented of the origins of such splittings in these compounds. The sensitivity of 13C CPMAS spectra to subtle structural differences is reflected in the differences between the spectra of two isomorphous complexes.