Screening of metal-chelating peptides and hydrolysates using surface plasmon resonance and switch sense

Lipid oxidation is, among other factors, catalyzed by the presence of metal ions and efficient metal chelators are therefore highly sought after in the food industry. Among these, natural metal chelators are gaining interest as opposed to their synthetic counterparts such as EDTA. Traditional screening for metal chelation capacity is time consuming and non-specific. The aim of this study was to screen potato protein hydrolysate and synthetic peptides derived from potato protein sequences for their metal-chelating capacity. Seven peptides and two hydrolysates (raw and ultra-filtrated) were studied. Peptides were selected using two different models: an empirical-based bioinformatics approach (AnOxPePred) and a theoretically based model for metal chelation. Surface Plasmon Resonance (SPR) is a label-free, optical technique used to determine the dissociation constant (KD) of a complex formed between immobilized Ni2+ and peptides. The SwitchSENSE technology is another approach used to study Ni2+/peptide affinity. It utilizes the quenching of fluorescence of a fluorophore upon Ni2+ immobilization and the inverse fluorescence increase upon peptide binding onto Ni2+. Both analyses were carried out at pH 7.4. In this study, we successfully determined the dissociation constants (KD) of two peptides (ASH and DHGPKIFEPS) using SPR. These values compare favorably with previous results indicating metal chelating potential. The association rate constant (kon) of all peptides were determined using switchSENSE. Yet, due to bad fitting of the kinetics data obtained with switchSENSE, the KDs of the hydrolysates were only determined with low accuracy.