Structural Characterization and Chelation Mechanism of Corn Peptide Calcium Chelate
To investigate the structure characteristics of the corn peptide calcium chelate and the binding sites of peptides with calcium ions,corn peptide calcium chelate was prepared using corn peptides and calcium chloride as raw materials.The structures of corn peptide calcium chelate were characterized by Fourier transform infrared spectrometer(FTIR),nuclear magnetic resonance(NMR),thermogravimetry analysis(TG),and mass spectrometry,and the binding sites of peptides and calcium ions were simulated by molecular docking technique.FTIR indicated that after the chelation of corn peptides with calcium ions,the amide Ⅰ and amide Ⅱ bands exhibited the red-shift and the N-H bond showed the blue-shift,and exhibited the red-shift at around 1 400 cm-1 because of stretching vibration of COO-.NMR showed that the absorption peak of corn peptide calcium chelate generally weakened and disappeared.The TG result showed that the degradation rates during the degradation stage were 43.26％and 65.05％,respectively,and the residual rate significantly increased from 19％to 38.6％.Seven peptide sequences were identified through mass spectrometry analysis.Two peptide segments with more hydrophobic amino acids were selected for molecular docking with calcium ions to simulate binding sites.The binding energies of Asn-Gln-Phe-Ser-Leu-Ile-Asn-Pro-Val-Leu-Ser-Arg(NQFSLINPVLSR)and Ser-Leu-Ile-Asn-Pro-Val-Leu-Ser-Arg-Gln-Gln-Pro-Ile-Val-Gly-Gly-Ala(SLINPVLSRQQPIVGGA)with calcium ions were-68.08 kJ/mol and-67.56 kJ/mol,respectively.It is speculated that the carboxyl oxygen atom and the amino groups on the amino acid residues of peptides were the main binding sites for chelating calcium ions.The thermal stability of corn peptide calcium chelate was significantly enhanced compared to corn peptides.
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