TY - BOOK

T1 - Metal binding by food components

AU - Tang, Ning

PY - 2017

Y1 - 2017

N2 - For calcium binding: Electrochemical method (calcium ion selective electrode) combined with quantum mechanicalcalculations (density functional theory) were used to investigate the calcium binding affinity of the amino acids and smallglycine peptides. The effects of the ionic strength and pH on calcium binding affinity of the investigated amino acids werediscussed. It was found that only charged amino acids would be affected by ionic strength. The calcium binding affinity wasconsiderably improved by high pH inducted protonation of amino group. Moreover, a model was established to describe thispH effect. Optimized structures of calcium amino acids or peptides complexes were obtained through density functionaltheory calculations. The calculated calcium binding affinity is in agreement with the obtained experimental data. Theseoptimized structures provide the possible calcium binding mechanism by amino acids and peptides. In addition, amino acidswith strong calcium binding ability at high pH was found to have a calcium binding site shift from carboxylate binding tochelation by α-amino group and carboxylate oxygen. Compared with calcium binding ability of the single amino acid,synergistic effect in calcium binding was found for the small glycine peptide rather than amino acids mixtures with theenhanced driving force up to -6 kJ/mol. Such study provides useful information for the future development of calciumsupplements.For zinc binding: Isothermal titration calorimetry was applied to investigate the zinc binding affinity of amino acids,peptides and whey proteins. Cysteine and histidine are strong zinc binders, while aspartic acid and glutamic acid need tocombine nitrogen donor or sulfur donor to facilitate zinc binding. Enthalpy entropy compensation effect was observed forzinc binding by the investigated amino acids, peptides and proteins. The thiol group or imidazole group containing aminoacids, peptides and proteins which exhibited strong zinc binding ability were further selected for interacting with zinc saltsin relation to zinc absorption. The interactions between the above selected food components and zinc citrate or zinc phytatewill lead to the enhanced solubility of zinc citrate or zinc phytate. The main driving force for this observed solubilityenhancement is the complex formation between zinc and investigated food components as revealed by isothermal titrationcalorimetry and quantum mechanical calculations. This is due to the zinc binding affinity of the relatively softer ligands(investigated food components) will become much stronger than citrate or phytate when they present together in aqueoussolution. This mechanism indicates these food components induced solubility enhancement will improve the zinc bioavailability. Moreover, a mathematical model established from the studies of human absorption of zinc was applied toquantify the effect of the enhanced zinc phytate solubility on zinc absorption. Histidine and citrate are very promisingligands for improving zinc absorption from phytate rich foods. Such study provides a better understanding of zinc bindingby the food components which can be used for improving zinc absorption.For iron binding: The iron(IV) binding protein, ferrylmyoglobin, was investigated for the iron binding study. Tyrosinebased food components were selected to reduce the ferrylmyoglobin. Different reaction pathways were proposed accordingto the multivariate curve resolution analysis. The reduction kinetics was obtained through hard modelling of the spectraldata obtained from stopped flow spectroscopy. The pH was found to affect the reaction kinetics considerably. In addition,the reaction mechanism was investigated through quantum mechanical calculations. According to the density functionaltheory calculated quantity descriptors, sequential proton loss electron transfer seems to be the reaction mechanism for thereduction of ferrylmyoglobin by tyrosine based food components. Moreover, based on the obtained thermodynamicparameters that relevant for reduction of ferrylmyoglobin, the quantitative structure activity relationship model for reducingferrylmyoglobin by tyrosine based food components were established by applying partial least square regression. Suchstudy provides useful information for developing muscle foods.

AB - For calcium binding: Electrochemical method (calcium ion selective electrode) combined with quantum mechanicalcalculations (density functional theory) were used to investigate the calcium binding affinity of the amino acids and smallglycine peptides. The effects of the ionic strength and pH on calcium binding affinity of the investigated amino acids werediscussed. It was found that only charged amino acids would be affected by ionic strength. The calcium binding affinity wasconsiderably improved by high pH inducted protonation of amino group. Moreover, a model was established to describe thispH effect. Optimized structures of calcium amino acids or peptides complexes were obtained through density functionaltheory calculations. The calculated calcium binding affinity is in agreement with the obtained experimental data. Theseoptimized structures provide the possible calcium binding mechanism by amino acids and peptides. In addition, amino acidswith strong calcium binding ability at high pH was found to have a calcium binding site shift from carboxylate binding tochelation by α-amino group and carboxylate oxygen. Compared with calcium binding ability of the single amino acid,synergistic effect in calcium binding was found for the small glycine peptide rather than amino acids mixtures with theenhanced driving force up to -6 kJ/mol. Such study provides useful information for the future development of calciumsupplements.For zinc binding: Isothermal titration calorimetry was applied to investigate the zinc binding affinity of amino acids,peptides and whey proteins. Cysteine and histidine are strong zinc binders, while aspartic acid and glutamic acid need tocombine nitrogen donor or sulfur donor to facilitate zinc binding. Enthalpy entropy compensation effect was observed forzinc binding by the investigated amino acids, peptides and proteins. The thiol group or imidazole group containing aminoacids, peptides and proteins which exhibited strong zinc binding ability were further selected for interacting with zinc saltsin relation to zinc absorption. The interactions between the above selected food components and zinc citrate or zinc phytatewill lead to the enhanced solubility of zinc citrate or zinc phytate. The main driving force for this observed solubilityenhancement is the complex formation between zinc and investigated food components as revealed by isothermal titrationcalorimetry and quantum mechanical calculations. This is due to the zinc binding affinity of the relatively softer ligands(investigated food components) will become much stronger than citrate or phytate when they present together in aqueoussolution. This mechanism indicates these food components induced solubility enhancement will improve the zinc bioavailability. Moreover, a mathematical model established from the studies of human absorption of zinc was applied toquantify the effect of the enhanced zinc phytate solubility on zinc absorption. Histidine and citrate are very promisingligands for improving zinc absorption from phytate rich foods. Such study provides a better understanding of zinc bindingby the food components which can be used for improving zinc absorption.For iron binding: The iron(IV) binding protein, ferrylmyoglobin, was investigated for the iron binding study. Tyrosinebased food components were selected to reduce the ferrylmyoglobin. Different reaction pathways were proposed accordingto the multivariate curve resolution analysis. The reduction kinetics was obtained through hard modelling of the spectraldata obtained from stopped flow spectroscopy. The pH was found to affect the reaction kinetics considerably. In addition,the reaction mechanism was investigated through quantum mechanical calculations. According to the density functionaltheory calculated quantity descriptors, sequential proton loss electron transfer seems to be the reaction mechanism for thereduction of ferrylmyoglobin by tyrosine based food components. Moreover, based on the obtained thermodynamicparameters that relevant for reduction of ferrylmyoglobin, the quantitative structure activity relationship model for reducingferrylmyoglobin by tyrosine based food components were established by applying partial least square regression. Suchstudy provides useful information for developing muscle foods.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122982880105763

M3 - Ph.D. thesis

BT - Metal binding by food components

PB - Department of Food Science, Faculty of Science, University of Copenhagen

ER -