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Fast screening and quantitative evaluation of internally deleted goat α s1 ‐casein variants by mass spectrometric detection of the signature peptides
Author(s) -
Picariello Gianluca,
Ferranti Pasquale,
Caira Simonetta,
Fierro Olga,
Chianese Lina,
Addeo Francesco
Publication year - 2009
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3944
Subject(s) - chemistry , chromatography , mass spectrometry , electrospray ionization , casein , peptide , ionization , detection limit , analytical chemistry (journal) , ion , biochemistry , organic chemistry
Currently, the internally deleted caprine α s1 ‐casein ( α s1 ‐CN) variants F and G, associated with low casein expression, are detected by means of ordinary descriptive techniques. No relevant procedure is available to detect internally deleted goat α s1 ‐CN in bulk milks. The availability of full‐length and α s1 ‐CN F and G variants allowed us to further investigate this issue. Using matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectrometry (MS) and high‐performance liquid chromatography (HPLC)/electrospray ionization (ESI)‐MS and ESI‐MS/MS, tryptic signature peptides α s1 ‐CN F f59‐63/f43‐63, α s1 ‐CN G f4‐20/f4‐21, α s1 ‐CN B 2 f4‐22 Pro 16 and α s1 ‐CN A f4‐22 Leu 16 were identified. This also helped to solve the interesting question of how the casein variants contribute to the composition of goat's bulk milk. Synthetic peptide analogues with ionization efficiency equivalent to that of tryptic junction peptides were used as internal standards to evaluate α s1 ‐CN variants, either individually or globally, using bulk milk from a single goat breed as a model system. Here, α s1 ‐CN F accounted for 0.15 ± 0.08% and the α s1 ‐CN G variant was missing or below the 0.10% detection limit. The analysis of six samples confirmed that α s1 ‐CN G was missing and that α s1 ‐CN F occurred at a low frequency in hybrid and local breed bulk milks from Mediterranean areas. In conclusion, a quantitative MS‐based application of the signature peptides for full‐length and internally deleted variants in goat's casein is provided. The strategy is also suggested for the determination of splice variants in any biological sample. Copyright © 2009 John Wiley & Sons, Ltd.