Tri- and dipeptides identification in whey protein and porcine liver protein hydrolysates by fast LC-MS/MS neutral loss screening and de novo sequencing.

We describe a fast (5 min) liquid chromatography tandem mass spectrometry method (LC-MS/MS) based on a 46 Da neutral loss of formic acid (H O and CO) to identify tri- and dipeptides (DIPEP) in whey protein and porcine liver protein hydrolysates and confirmed by further de novo sequencing. Sample solutions were acidified to favor [dipep + H] ions, and a m/z range of 50-300 was used to improve sensitivity. All dipeptide candidates were selected based on all possibilities of the 20 amino acid combinations, and their collision-induced dissociation fragments were screened via de novo sequencing.

Anthocyanidins structural study using positive electrospray ionization triple quadrupole mass spectrometry and H/D exchange.

We report herein a detailed structural study by collision-induced dissociation (CID) of nonglycosylated anthocyanins (anthocyanidins) using electrospray ionization triple quadrupole mass spectrometry (ESI-QqQ) and isotope labeling experiments to understand the fragmentation process often used in mass spectrometry analysis of this class of compounds. Tandem mass spectrometric product ion spectra for three anthocyanidins (cyanidin, delphynidin, and pelargonin) were evaluated to propose fragmentation mechanisms to this natural colorant class of organic compounds. The proposed rearrangements, retro Diels-Alder reaction, water loss, CO losses, and stable acylium ion formation, were evaluated based on tandem mass spectrometric experiments of normal and labeled precursor ions together to computational thermochemistry.