Increasing the Coverage of a Mass Spectral Library of Milk Oligosaccharides Using a Hybrid- Search-Based Bootstrapping Method and Milks from a Wide Variety of Mammals
Concepcion A. Remoroza, Tytus D. Mak, Yuri A. Mirokhin, Sergey L. Sheetlin, Xiaoyu Yang, Stephen E. Stein, Power L. Michael, San Andres V. Joice, Yuxue Liang
This study significantly expands both the scope and method of identification for construction of a previously reported tandem mass spectral library of 74 human milk oligosaccharides (HMOs) derived from results of LC-MS/MS experiments. In the present work, a hybrid search bootstrap identification method was employed. This involved hybrid searching of the previous library, which was itself constructed using the hybrid search of oligosaccharide spectra in the NIST 17 tandem library. The general approach appears applicable to library construction of other classes of compounds. The coverage of oligosaccharides was also significantly extended using milks from a variety of mammals, including bovine, Asian buffalo, African lion and goat. This new method led to the identification of another 145 oligosaccharides, including an additional 80 HMOs from reanalysis of human milk. The newly identified compounds were added to a freely available mass spectral reference database of 219 milk oligosaccharides. We also provide suggestions to overcome several limitations and pitfalls in the interpretation of spectra of unknown oligosaccharides.