Abstract:

The objective of this study was to investigate the effect of extraction methods on two-dimensional electrophoresis (2-
DE) maps of whey proteome in cow milk and to explore an optimal extraction method. Samples were extracted from cow milk
by different isoelectric precipitations and ultracentrifugation methods. 2-DE maps were analyzed by PDQuest 8.0 software. The
results of 2-DE maps showed that milk whey protein could be effectively extracted by the above methods with less background,
no significant strips and good repeatability. However, there were still some residual caseins appearing in each map. 2-DE maps
of whey protein refined by isoelectric precipitations were relatively informative when compared with the gel maps obtained by
ultracentrifugation. Moreover, the richness of different whey proteins in various maps extracted by adjusting pH to 4.6 as isoelectric
point was slightly higher than adjusting pH to 4.8. The results indicated that adjusting pH to 4.6 as isoelectric point to extract whey
protein had some advantages than adjusting pH to 4.8 and ultracentrifugation. However, all the methods used in this study could
effectively remove high abundant casein to improve the detection sensitivity of low abundance proteins.

Key words: cow milk, whey protein, isoelectric precipitation, ultracentrifugation, extraction methods, two-dimensional electrophoresis map