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Characterization of chiral amino acids from different milk origins using ultra-performance liquid chromatography coupled to ion-mobility mass spectrometry

View Article: PubMed Central - PubMed

ABSTRACT

Milk contains free amino acids (AAs) that play essential roles in maintaining the growth and health of infants, and D-AA isomers are increasingly being recognized as important signalling molecules. However, there are no studies of the different characteristics of chiral AA (C-AA) from different milk origins. Here, UPLC coupled to ion-mobility high-resolution MS (IM-HRMS) was employed to characterize 18 pairs of C-AAs in human, cow, yak, buffalo, goat, and camel milk. The results proved that milk origins can be differentiated based on the D- to L- AA ratio-based projection scores by principal component analysis. The present study gives a deeper understanding of the D- to L- AA ratio underlying the biological functions of different animal milks, and provide a new strategy for the study of AA metabolic pathways.

No MeSH data available.


Related in: MedlinePlus

Two peaks from single L-Phe in IM and their MS/MS spectra and putative fragmentation.(A) MS/MS spectra of the peak 1 ion. (B) MS/MS spectra of the peak 2 ion. (C) MS/MS spectra of the peak 2 ions, respectively. (D) Putative fragmentation of derivatized L-Phe.
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f2: Two peaks from single L-Phe in IM and their MS/MS spectra and putative fragmentation.(A) MS/MS spectra of the peak 1 ion. (B) MS/MS spectra of the peak 2 ion. (C) MS/MS spectra of the peak 2 ions, respectively. (D) Putative fragmentation of derivatized L-Phe.

Mentions: The selectivity of the method was assessed using 10 underivatized milk samples from each milk origin. The lack of a signal greater than 3 times the signal-to-noise ratio at the same elution time as the target compound indicated the absence of a false positive signal from matrix interference. An interesting discovery was found that the detection of derivatized L-phenylalanine (L-Phe) using UPLC-IMMS displayed peaks in different drift time (dt), see Fig. 2A. It has been reported that small ions may have multiple conformers in the gas phase to produce multiple peaks in IM38. The production of multiple peaks is thought to be the result of protonation site isomers. Further MS/MS analysis of these two ions showed that their product ion spectra was almost the same (Fig. 2B,C), and Fig. 2D is the putative fragmentations of derivatized L-Phe. Thereby, it is proved that these two peaks came from a single analyte.


Characterization of chiral amino acids from different milk origins using ultra-performance liquid chromatography coupled to ion-mobility mass spectrometry
Two peaks from single L-Phe in IM and their MS/MS spectra and putative fragmentation.(A) MS/MS spectra of the peak 1 ion. (B) MS/MS spectra of the peak 2 ion. (C) MS/MS spectra of the peak 2 ions, respectively. (D) Putative fragmentation of derivatized L-Phe.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385494&req=5

f2: Two peaks from single L-Phe in IM and their MS/MS spectra and putative fragmentation.(A) MS/MS spectra of the peak 1 ion. (B) MS/MS spectra of the peak 2 ion. (C) MS/MS spectra of the peak 2 ions, respectively. (D) Putative fragmentation of derivatized L-Phe.
Mentions: The selectivity of the method was assessed using 10 underivatized milk samples from each milk origin. The lack of a signal greater than 3 times the signal-to-noise ratio at the same elution time as the target compound indicated the absence of a false positive signal from matrix interference. An interesting discovery was found that the detection of derivatized L-phenylalanine (L-Phe) using UPLC-IMMS displayed peaks in different drift time (dt), see Fig. 2A. It has been reported that small ions may have multiple conformers in the gas phase to produce multiple peaks in IM38. The production of multiple peaks is thought to be the result of protonation site isomers. Further MS/MS analysis of these two ions showed that their product ion spectra was almost the same (Fig. 2B,C), and Fig. 2D is the putative fragmentations of derivatized L-Phe. Thereby, it is proved that these two peaks came from a single analyte.

View Article: PubMed Central - PubMed

ABSTRACT

Milk contains free amino acids (AAs) that play essential roles in maintaining the growth and health of infants, and D-AA isomers are increasingly being recognized as important signalling molecules. However, there are no studies of the different characteristics of chiral AA (C-AA) from different milk origins. Here, UPLC coupled to ion-mobility high-resolution MS (IM-HRMS) was employed to characterize 18 pairs of C-AAs in human, cow, yak, buffalo, goat, and camel milk. The results proved that milk origins can be differentiated based on the D- to L- AA ratio-based projection scores by principal component analysis. The present study gives a deeper understanding of the D- to L- AA ratio underlying the biological functions of different animal milks, and provide a new strategy for the study of AA metabolic pathways.

No MeSH data available.


Related in: MedlinePlus