<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>7</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Akim, L G</style></author><author><style face="normal" font="default" size="100%">Cordeiro, N</style></author><author><style face="normal" font="default" size="100%">Pascoal Neto, C</style></author><author><style face="normal" font="default" size="100%">Gandini, A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Comparative Analysis of the Lignins of Cork from Quercus suber L. and Wood from Eucalyptus globulus L. by Dry Hydrogen Iodide Cleavage</style></title><secondary-title><style face="normal" font="default" size="100%">Lignin: Historical, Biological, and Materials Perspectives</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">cross-linking (PG)</style></keyword><keyword><style  face="normal" font="default" size="100%">Eucalyptus globulus</style></keyword><keyword><style  face="normal" font="default" size="100%">Lignin</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus suber</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><publisher><style face="normal" font="default" size="100%">American Chemical Society</style></publisher><volume><style face="normal" font="default" size="100%">742</style></volume><pages><style face="normal" font="default" size="100%">14-291</style></pages><isbn><style face="normal" font="default" size="100%">0-8412-3611-9</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Lignin from cork (Quercus suber L.) was isolated by two procedures: organosolv extraction and dioxane-water (9:1) extraction in presence of HCl. These lignins were characterized using a mild hydrogen iodide-cleavage method followed by 1H NMR and GPC analysis. The results were compared with those for eucalyptus lignins (Eucalyptus globulus) isolated by the same procedures. The method used provided syringyl/guaiacyl ratios for the linear parts of the macromolecules and the degrees of crosslinking. The prevalence of guaiacyl units was demonstrated for cork lignin. Syringyl units were found to be minor components and present mainly in the linear parts of macromolecules. p-Hydroxyphenyl units were mainly condensed. Cork lignin was found to be significantly more cross-linked than eucalyptus lignin.</style></abstract><notes><style face="normal" font="default" size="100%">doi:10.1021/bk-2000-0742.ch014</style></notes><research-notes><style face="normal" font="default" size="100%">doi:10.1021/bk-2000-0742.ch014</style></research-notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gil, A M</style></author><author><style face="normal" font="default" size="100%">Lopes, M H</style></author><author><style face="normal" font="default" size="100%">Pascoal Neto, C</style></author><author><style face="normal" font="default" size="100%">Rocha, J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Very high-resolution 1H MAS NMR of a natural polymeric material</style></title><secondary-title><style face="normal" font="default" size="100%">Solid State Nuclear Magnetic Resonance</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">1H MAS NMR</style></keyword><keyword><style  face="normal" font="default" size="100%">Cellulose</style></keyword><keyword><style  face="normal" font="default" size="100%">Cork</style></keyword><keyword><style  face="normal" font="default" size="100%">Lignin</style></keyword><keyword><style  face="normal" font="default" size="100%">Relaxation</style></keyword><keyword><style  face="normal" font="default" size="100%">suberin</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><volume><style face="normal" font="default" size="100%">15</style></volume><pages><style face="normal" font="default" size="100%">59-67</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The use of ultrafast magic angle spinning (&amp;gt;30 kHz) in tandem with delayed echo acquisition is shown to yield very high-resolution 1H MAS NMR spectra of complex natural organic materials. For the first time, very high-resolution 1H MAS NMR spectra are reported for cork and wood components, two natural materials with great economic importance. The effect of the spinning rate on the 1H NMR spectra was evaluated with single-pulse acquisition and delayed-echo acquisition. The delayed-echo acquisition spectra presented linewidths as sharp as 67 and 25 Hz. The narrow peaks, characterised by proton spin–spin and spin–lattice relaxation, were assigned to the isotropic chemical shifts and the general spectral features were shown to correlate with the sample chemical structure. The tentative assignments of cork 1H MAS NMR signals were presented.</style></abstract></record></records></xml>