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Metal binding novel flaxseed peptides (linusorbs)

Jadhav, Pramodkumar D., Zuo, Yang, Shim, Youn Young, Shen, Jianheng, Reaney, Martin J. T., Zhang, Ning, Wang, Yong
International journal of food science & technology 2018 v.53 no.8 pp. 1972-1982
acetates, cadmium, lead, linseed, mass spectrometry, metal ions, methionine, moieties, molecular weight, nitrates, nuclear magnetic resonance spectroscopy, oxidation, peptides, toxicity, zinc, zinc sulfate
Linusorbs (LOs; a.k.a. cyclolinopeptides) are naturally occurring orbitides derived from flaxseed. These compounds consist of 8–10 amino acid residues, which are linked via an N‐ to C‐terminal peptide bond with molecular masses of approximately 1 kDa. The LO circular structure makes them candidates for metal binding studies. Flaxseed extracts are known to suppress Pb and Cd toxicity. Hence, four metal salts surveyed include Zn(CH₃COO)₂, ZnSO₄, Pb(CH₃COO)₂ and Cd(NO₃)₂ with pure LOs 1–5. Proton NMR spectra indicated interaction of LOs with metal salts in solution and were used to determine impacts of methionine oxidation on interactions with metal ions. The methyl group of methionine S,S‐dioxide of related LOs did not show the same shift in the presence of Zn(CH₃COO)₂ and Pb(CH₃COO)₂ observed in their methionine S‐oxide analogues. Metal complexes were observed forming at 10⁻² m to 10⁻⁴ m but not at lower concentrations (10⁻⁵ m to 10⁻⁸ m). Mass spectrometry data confirmed that metal binding strength varied by metal in the order Zn(CH₃COO)₂<Pb(CH₃COO)₂<ZnSO₄<Cd(NO₃)₂.