title: Speciation analysis of calcium, iron, and zinc in casein phosphopeptide fractions from toddler milk-based formula by anion exchange and reversed-phase high-performance liquid chromatography-mass spectrometry/flame atomic-absorption spectroscopy.
abstract: Casein phosphopeptides (CPP) are phosphorylated casein-derived peptides that can be released by in-vitro or in-vivo enzymatic hydrolysis of alpha(s1)-casein, alpha(s2)-casein, and beta-casein (CN). Many of these peptides contain a highly polar acidic sequence of three phosphoseryl groups followed by two glutamic acid residues. These domains are binding sites for minerals such as calcium, iron, and zinc and play an important role in mineral bioavailability. The aim of this study was speciation analysis of calcium, iron, and zinc in CPP fractions from the soluble fraction of a toddler milk-based formula. Methods for CPP separation by anion-exchange high-performance liquid chromatography (AE-HPLC) were combined with CPP identification by reversed-phase high performance liquid chromatography-electrospray ionization mass spectrometry and determination of the calcium, iron, zinc, and phosphorus content of the fractions obtained by AE-HPLC. Calcium and phosphorus were detected in all the analyzed AE-HPLC fractions. Calcium and zinc could be bound to CPP derived from alpha(s1)-CN and alpha(s2)-CN in fraction 3. Iron could be bound to CPP in fraction 4 in which beta-CN(15-34)4P was present with the cluster sequence S(P)S(P)S(P)EE. The results obtained prove the different distribution of calcium, iron, and zinc in heterogeneous CPP fractions.
authors.affiliation: Nutrition and Food Chemistry, Faculty of Pharmacy, University of Valencia, Av. Vicent Andrés Estellés s/n, 46100, Burjassot, Valencia, Spain. rosaura.farre@uv.es
authors.forename: Esther
authors.initials: E
authors.lastname: Miquel
authors.forename: Amparo
authors.initials: A
authors.lastname: Alegría
authors.forename: Reyes
authors.initials: R
authors.lastname: Barberá
authors.forename: Rosaura
authors.initials: R
authors.lastname: Farré
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000032:analysis; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D002852:Chromatography, Ion Exchange; D006801:Humans; D007223:Infant; D041943:Infant Formula / Q000737:chemistry*; D007231:Infant, Newborn; D007501:Iron / Q000032:analysis; D008903:Minerals / Q000032:analysis*; D008969:Molecular Sequence Data; D010748:Phosphopeptides / Q000737:chemistry* / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013054:Spectrophotometry, Atomic; D015032:Zinc / Q000032:analysis
chemical_list: D002364:Caseins; D008903:Minerals; D010748:Phosphopeptides; D007501:Iron; D015032:Zinc; D002118:Calcium