Frederick G. Morin

Degree of deacetylation of chitosan using conductometric titration and solid-state NMR

Chitosan is composed primarily of 2-amino-2-deoxy-o-glucose residues and is produced by the deacetylation of chitin (2acetamido-2-deoxy-o-glucose) by methods that include alkaline hydrolysis’ and thermo-mechano-chemical technology’. This biopolymer has applications in industries ranging from cosmetics to water clarification and waste management. Accurate determination of the degree of deacetylation of chitosan is essential when studying structure-properties relations and possible industrial uses3. Infrared4 and NMR spectroscopy’, potentiometric5, argentometric5 and colloid titration6, mass spectrometry’, ultraviolet spectrometry’, and gel-permeation chromatography7 have been proposed as methods for the determination of the acetyl content of chitosan samples. For low acetyl contents, such methods as the IR technique, which depend on deconvoluting the amide I band (1655 cm-‘), show inherent resolution difficulties4. The need for a reliable technique to determine low acetyl contents, which are typical of commercial chitosan, is evident. Conductometric titration is a well known analytical tool for quantifying acidic functional groups. It was popularized by the well known text “pH and Electra Titrations” by Kolthoff and Laitinen8. Numerous applications, such as measuring the number of carboxylic and sulfonic acid groups in wood pulps’, quantifying strong and weak acids bound to latexes”, and characterizing heparin” are known. In fact, it is probably the most accurate technique for analyzing multifunctional polysaccharides and should prove invaluable for characterizing glycosaminoglycans. In this study, the degree of deacetylation of chitosan samples was determined by the conductometric approach and solid-state NMR. The results were compared to those obtained by ultraviolet spectrophotometry, a frequently used technique for these determinations. Also included in this study are results on a water-insoluble film of chitin crystallites (hydrochitin)‘2T13, which exemplifies a high level of acetyl content.

Chemical composition change of bamboo accompanying its growth

Chemical Composition Change of Bamboo Accompanying its Growth ByYasuyo Fujii, Jun-ichi Azuma, Robert H. Marchessault, Frederick G. Morin, Shigeo Aibara and Keizo Okamura 1 Department of Wood Science and Technology, Faculty of Agriculture, Kyoto University, Kyoto 606-01, Japan 2 Chemistry Department and Pulp and Paper Research Center, McGill University, 3420 University Street, Montreal, Que. H3A2A7, Canada 3 Division of Food Processing and Preservation, Research Institute for Food Science, Kyoto University, Gokasho, Uji, Kyoto 611, Japan

Characterization of polyacrylamide-stabilized Pf1 phage liquid crystals for protein NMR spectroscopy

A new polymer-stabilized nematic liquid crystal has been characterized for the measurement of biomolecular residual dipolar couplings. Filamentous Pf1 phage were embedded in a polyacrylamide matrix that fixes the orientation of the particles. The alignment was characterized by the quadrupolar splitting of the 2H NMR water signal and by the measurement of 1H-15N residual dipolar couplings (RDC) in the archeal translation elongation factor 1β. Protein dissolved in the polymer-stabilized medium orients quantitatively as in media without polyacrylamide. We show that the quadrupolar splitting and RDCs are zero in media in which the Pf1 phage particles are aligned at the magic angle. This allows measurement of J and dipolar couplings in a single sample.

Magnetic Field and Temperature Effects on the Solid State Proton Spin-Lattice Relaxation Time Measurements of Wood and Pulps

The proton spin-lattice relaxation times (T 1 ) for a series of progressively sulphonated black spruce pulps were measured at two static magnetic fields and at a variety of temperatures. These determinations showed that the frequency of the anisotropic molecular motions of carbohydrates and lignin responsible for spin relaxation on wood and pulps is of the order of 10 -9 s. For cross-polarization measurements with a 300 MHz solid state NMR spectrometer, room temperature seems to be close to the T 1 versus correlation time minimum

Probing the macromolecular structure of wood and pulps with proton spin-lattice relaxation time measurements in the solid state

SummaryBy measuring the proton spin-lattice relaxation times (T1) in the solid state, for a series of progressively sulphonated and methylated black spruce pulps, the molecular mobilities of carbohydrates and lignin have been evaluated as a function of chemical treatment. These measurements were made possible only after the paramagnetic metal ion impurities were removed from the samples. For untreated wood the proton T1 values of carbohydrates and lignin were virtually undistinguishable, irrespective of the applied magnetic field strength. The introduction of sodium salts of carboxylic and sulphonic acid groups in softwood pulps and the introduction of methoxyl groups, seem to very significantly increase the molecular mobilities of carbohydrates and lignin. The opposite was true when calcium were the counterions of the acidic groups. These observations have been attributed to the disruption of associative lignin-carbohydrate hydrogen bonding interactions otherwise operating within untreated wood.

Structural and spectroscopic studies of bis(pentacarbonylmanganese)diphenyltin(IV) and bis(pentacarbonylmanganese)diphenyllead(IV)

Solid-state nuclear magnetic resonance and vibrational spectroscopic studies are reported for bis(pentacarbonylmanganese)diphenyltin(IV) and bis(pentacarbonylmanganese)diphenyllead(IV). The solid-state, CP-MAS, 119 Sn and 207 Pb NMR spectra of these complexes each reveal a single asymmetric undecet due to the 1 J 119 Sn‐ 55 Mn and 207 Pb‐ 55 Mn spin‐spin couplings and second-order quadrupole‐dipole effects. The 1 JSn‐Mn and 1 JPb,-Mn values are 139 ^ 1a nd 228^ 1H z; respectively. The 119 Sn and 207 Pb chemical shift anisotropies have been determined. The crystal structure of the tin compound has been re-examined. q 2001 Elsevier Science B.V. All rights reserved.