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Article
Calcium binding to amino acids and small glycine peptides in aqueous solution: Towards peptide design for better calcium bioavailability Ning Tang, and Leif H. Skibsted J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b01534 • Publication Date (Web): 09 May 2016 Downloaded from http://pubs.acs.org on May 9, 2016
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Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
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Journal of Agricultural and Food Chemistry
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Calcium Binding to Amino Acids and Small Glycine Peptides in Aqueous Solution: Towards Peptide Design for
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Better Calcium Bioavailability
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Ning Tang and Leif H. Skibsted*
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Food Chemistry, Department of Food Science, University of Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark
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*Corresponding Author:
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Tel: 45-3533 3221; Fax: 45-3528 3344; E-mail:
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1 ACS Paragon Plus Environment
Journal of Agricultural and Food Chemistry
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Abstract
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Deprotonation of amino acids as occurring during transfer from stomach to intestines during food digestion was found by
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comparison of complex formation constants as determined electrochemically for increasing pH to increase calcium binding
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(i) by a factor of around 6 for the neutral amino acids; (ii) by a factor of around 4 for anions of the acidic amino acids
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aspartic and glutamic acid; and (iii) by a factor of around 5.5 for basic amino acids. Optimized structures of the 1:1
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complexes and ∆Hbinding for calcium binding as calculated by Density Functional Theory (DFT) confirmed in all complexes
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a stronger calcium binding and shorter calcium oxygen bond length in the deprotonated form. In addition, the stronger
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calcium binding was also accompanied by a binding site shift from carboxylate binding to chelation by α-amino group and
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carboxylate oxygen for leucine, aspartate, glutamate, alanine and asparagine. For binary amino acid mixtures, calcium
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binding constant was close to the predicted geometric mean of the individual amino acid binding constants indicating
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separate binding of calcium to two amino acids when present together in solution. At high pH, corresponding to conditions
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for calcium absorption, the binding affinity increased along the series: Lys < Arg < Cys < Gln < Gly ~ Ala < Asn < His
