期刊
MOLECULES
卷 28, 期 13, 页码 -出版社
MDPI
DOI: 10.3390/molecules28135200
关键词
beta-casein; A2 milk; thermolysin; liquid chromatography; tandem mass spectrometry
Beta-casein, a protein found in milk and dairy products, has two variants called A1 and A2. A1 beta-casein is believed to have negative effects on human health. Distinguishing between A1 and A2 beta-casein is challenging due to only a single amino acid variation at the 67th position. This study developed a novel method using thermolytic peptides to determine the presence of A1 and A2 beta-casein in milk samples, offering high specificity, sensitivity, and efficiency.
beta-casein, a protein in milk and dairy products, has two main variant forms termed as A1 and A2. A1 beta-casein may have adverse effects on humans. The fact that there is only one amino acid variation at the 67th position between A1 and A2 beta-casein makes it difficult to distinguish between them. In this study, a novel method using characteristic thermolytic peptides is developed for the determination of A1 and A2 beta-casein in milk. Firstly, caseins extracted from milk samples are thermolytic digested at 60 degrees C without any denaturing reagents required for unfolding proteins, which simplifies the sample pretreatment procedure. The characteristic thermolytic peptides (i.e., fragments 66-76 and 59-76 for A1 and A2 beta-casein, respectively) selected to specifically distinguish A1 and A2 beta-casein only have eleven or eighteen amino acid moieties. Compared with tryptic characteristic peptides with a length of 49 amino acid moieties, these shorter thermolytic characteristic peptides are more suitable for LC-MS analysis. This novel method, with the advantages of high specificity, high sensitivity, and high efficiency, was successfully applied for the analysis of six milk samples collected from a local supermarket. After further investigation, it is found that this method would contribute to the development of A2 dairy products for a company and the quality inspection of A2 dairy products for a government.
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