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E.R. Andrew 《Polymer》1985,26(2):190-192
The dynamical behaviour of four solid polypeptides (α-chymotrypsin, insulin, lysozyme, ribonuclease A) has been investigated by proton magnetic relaxation. The interpretation was supplemented by measurements on the constituent amino acids, and on dipeptides, tripeptides and homopolypeptides. The following motions were identified and characterized: methyl group reorientation, segmental motion, sidechain motion, proline ring puckering, reorientation of water molecules in the structure. Slow motions were investigated through measurements of the dipolar relaxation time TID. 相似文献
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M.A.L.D.I.-T.O.F. mass spectrometry characterization of 4-alkyl substituted phenol-formaldehyde novalac type resins 总被引:1,自引:0,他引:1
Two methods of synthesis for 4-alkyl substituted phenol-formaldehyde resins are described. A common method for synthesis of novolac type phenol-formaldehyde resin uses sulfuric acid catalyst in the presence of xylene for azeotropic removal of water of reaction. By the use of M.A.L.D.I.-T.O.F. mass spectrometry we have demonstrated that m-xylene is incorporated into these polymers. Polymers free of impurities are best prepared using a cation exchange resin as catalyst in the presence of a less reactive solvent, e.g. chlorobenzene, or in the absence of solvents. © 1997 Elsevier Science Ltd. 相似文献
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