Richardson Sara, Nilsson Gunilla, Cohen Arieh, Momcilovic Dane, Brinkmalm Gunnar, Gorton Lo
Department of Analytical Chemistry, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Anal Chem. 2003 Dec 1;75(23):6499-508. doi: 10.1021/ac0300688.
The distribution of substituents along the polymer chain in cationic potato amylopectin starch, modified in solution, granular slurry, or dry state, was investigated. The starch derivatives were successively hydrolyzed by different enzymes, followed by characterization of the hydrolysis products obtained by means of electrospray mass spectrometry (ESI-MS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). ESI-MS and MALDI-MS were proved to be appropriate techniques for identification of the substituted hydrolysis products, for which there are no standard compounds available. No highly substituted oligomers were found in the hydrolysates, which was taken as an indication of a more or less homogeneous distribution of cationic groups in the amylopectin molecules. Furthermore, from the results obtained it was suggested that the enzymes cleave glucosidic linkages only between unsubstituted glucose units and, preferentially, linkages in sequences containing more than two adjacent unsubstituted units. The determination of the amount of unsubstituted glucose produced from every successive hydrolysis step revealed slight differences between the different starch samples with respect to the homogeneity of the substitution pattern. Among the three samples under investigation, starch cationized in solution was found to have the most and dry-cationized starch the least homogeneous distribution of substituents.
研究了在溶液、颗粒浆液或干燥状态下改性的阳离子马铃薯支链淀粉中取代基沿聚合物链的分布情况。淀粉衍生物先后用不同的酶进行水解，然后通过电喷雾质谱（ESI-MS）和基质辅助激光解吸/电离质谱（MALDI-MS）对所得水解产物进行表征。ESI-MS和MALDI-MS被证明是鉴定取代水解产物的合适技术，因为没有可用的标准化合物。在水解产物中未发现高度取代的低聚物，这表明支链淀粉分子中阳离子基团的分布或多或少是均匀的。此外，从所得结果表明，酶仅在未取代的葡萄糖单元之间切割糖苷键，并且优先切割含有两个以上相邻未取代单元的序列中的键。对每个连续水解步骤产生的未取代葡萄糖量的测定揭示了不同淀粉样品在取代模式均匀性方面的细微差异。在所研究的三个样品中，发现溶液中阳离子化的淀粉取代基分布最不均匀，而干燥阳离子化的淀粉取代基分布最均匀。
