Zeller Wayne E, Sullivan Michael L, Mueller-Harvey Irene, Grabber John H, Ramsay Aina, Drake Chris, Brown Ronald H
U.S. Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture , 1925 Linden Drive, Madison, Wisconsin 53706, United States.
Chemistry and Biochemistry Laboratory, Food Production and Quality Division, School of Agriculture, Policy and Development, University of Reading , P.O. Box 236, 1 Earley Gate, Reading RG6 6AT, United Kingdom.
J Agric Food Chem. 2015 Feb 4;63(4):1160-1168. doi: 10.1021/jf504715p. Epub 2015 Jan 22.
The precipitation of bovine serum albumin (BSA), lysozyme (LYS), and alfalfa leaf protein (ALF) by two large- and two medium-sized condensed tannin (CT) fractions of similar flavan-3-ol subunit composition is described. CT fractions isolated from white clover flowers and big trefoil leaves exhibited high-purity profiles by 1D/2D NMR and purities >90% (determined by thiolysis). At pH 6.5, large CTs with a mean degree of polymerization (mDP) of ∼18 exhibited similar protein precipitation behaviors and were significantly more effective than medium CTs (mDP ∼9). Medium CTs exhibited similar capacities to precipitate ALF or BSA, but showed small but significant differences in their capacity to precipitate LYS. All CTs precipitated ALF more effectively than BSA or LYS. Aggregation of CT-protein complexes likely aided precipitation of ALF and BSA, but not LYS. This study, one of the first to use CTs of confirmed high purity, demonstrates that the mDP of CTs influences protein precipitation efficacy.
本文描述了两种具有相似黄烷-3-醇亚基组成的大型和两种中型缩合单宁（CT）组分对牛血清白蛋白（BSA）、溶菌酶（LYS）和苜蓿叶蛋白（ALF）的沉淀作用。从白三叶草花和大三叶叶中分离得到的CT组分通过一维/二维核磁共振显示出高纯度图谱，纯度>90%（通过硫解测定）。在pH 6.5时，平均聚合度（mDP）约为18的大型CT表现出相似的蛋白质沉淀行为，并且比中型CT（mDP约为9）显著更有效。中型CT在沉淀ALF或BSA方面表现出相似的能力，但在沉淀LYS的能力上显示出微小但显著的差异。所有CT对ALF的沉淀效果均比对BSA或LYS更有效。CT-蛋白质复合物的聚集可能有助于ALF和BSA的沉淀，但对LYS无效。本研究是最早使用经确认具有高纯度的CT的研究之一，表明CT的mDP会影响蛋白质沉淀效果。
