Overview
Irankunda and co-authors review the experimental methodology of Immobilized Metal Ion Affinity Chromatography (IMAC) for separating metal-chelating peptides (MCPs) from enzymatic protein hydrolysates and propose a chromatography-modelling and simulation workflow in which sorption-isotherm parameters measured by Surface Plasmon Resonance (SPR) are used as input data for a transport-dispersive model of IMAC. The review’s framing is functional-food and nutraceutical manufacturing — MCPs as carriers for nutritionally essential metals (Ca²⁺, Fe²⁺, Zn²⁺, Cu²⁺) and as antioxidants — not contamination of food by toxic heavy metals. The paper notes in passing that MCPs can also remove heavy metals such as Cd²⁺, Ni²⁺, As³⁺ and Pb²⁺ from the environment for decontamination applications, but reports no measurements on such removal. This source is recorded here for its coordination-chemistry background — HSAB classification of metal ions and amino-acid donor groups, complexing-agent denticity, and the parameters controlling peptide–metal binding — which underpins primary studies in the HMI corpus that quantify binding of toxic heavy metals to food protein hydrolysates. No occurrence values for HMI’s regulated heavy metals (Pb, cadmium (Cd), inorganic arsenic (iAs), total arsenic (tAs), methylmercury (MeHg), total mercury (tHg), nickel (Ni), aluminum (Al), chromium (Cr), hexavalent chromium (Cr-VI), tin (Sn), Sb, U) appear.
Key numbers
The review reports method parameters, chemical classifications, and modelling equations. None are HMI heavy-metal occurrence values; the most directly HMI-relevant content is the Table 2 HSAB classification, which places several HMI-regulated metal ions on the hard/borderline/soft acid continuum that governs their preferential donor-atom binding.
| Item | Detail as reported |
|---|---|
| HSAB hard acids (Table 2) | H⁺, Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Sn²⁺, Cr³⁺, Co³⁺, Fe³⁺, As³⁺, Ir³⁺, Al³⁺, Sc³⁺, Ga³⁺, In³⁺, La³⁺, Si⁴⁺, Ti⁴⁺, Zr⁴⁺, Th⁴⁺, Pu⁴⁺ |
| HSAB borderline acids (Table 2) | Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Mn²⁺ |
| HSAB soft acids (Table 2) | Cu⁺, Ag⁺, Au⁺, Tl⁺, Hg⁺, Cs⁺, Pd²⁺, Cd²⁺, Pt²⁺, Hg²⁺ |
| HSAB hard bases (Table 2) | Carboxylate group (Asp, Glu), hydroxyl group (Ser, Thr, Tyr), phosphorylated amino acids |
| HSAB borderline bases (Table 2) | Aromatic nitrogen (His, Trp), amides (Asn, Gln), aliphatic nitrogen |
| HSAB soft bases (Table 2) | Cyanides, sulphur groups (Cys, Met) |
| IMAC loading-buffer NaCl range | 0.1–3 M to reduce non-specific interactions |
| Glycerol additive | up to 50% v/v to limit hydrophobic interactions |
| Ethanol additive | up to 20% v/v |
| Acetonitrile additive | 1:1 v/v ratio reported |
| Tween 80 additive | 0.01% v/v |
| Triton X-100 additive | 1% |
| EDTA column-stripping concentration | 10–50 mM |
| Common complexing agents | bidentate (α-aminohydroxamic acid, salicylaldehyde, 8-hydroxyquinoline); tridentate (iminodiacetic acid IDA, orthophospho-DL-serine OPS, dipicolylamine DPA, N-(2-pyridylmethyl)aminoacetate, 2,6-diaminomethylpyridine); tetradentate (nitrilotriacetic acid NTA, carboxymethylated aspartic acid CM-Asp); pentadentate (N,N,N′-tris(carboxymethyl) ethylene diamine TED) |
| Most-used complexing agents | NTA, IDA, TED |
| Frequently immobilized metal ions | Ni²⁺, Cu²⁺, Fe²⁺, Co²⁺ |
| Cu²⁺ binding requirement | one exposed histidine residue |
| Ni²⁺ and Zn²⁺ binding requirement | two exposed vicinal histidine residues |
| Co²⁺ binding requirement | at least two adjacent exposed histidine residues |
| Biacore SPR conversion | response of 100 RU represents a protein concentration of 1 g/L; q_max,SPR = R_max / 100 |
| SPR–IMAC flow rates (Table 3) | IMAC 1 mL/min per 1 mL bed volume; SPR 20 µL/min |
| Modelled isotherm | Mono-component Langmuir q = q_max·K_A·C / (1 + K_A·C); multi-component form given for imidazole-elution competition |
| SPR–IMAC affinity conversion | K_A,IMAC ≈ K_A,SPR / MW (peptide molecular weight, g/mol) |
Representative peptide sequences with metal-chelating activity tabulated by the authors from cited primary literature (Table 1) include — from sesame (Zn²⁺ and Fe²⁺): SM, NCS; from Alaska pollock skin (Fe²⁺): SCH; from soybean (Ca²⁺): DEGEQPFFPF; from tilapia scales (Ca²⁺): NGNNGEAGKIG; from Antarctic krill (Ca²⁺): VLGYIQIR; from oyster (Zn²⁺): HLRQEEKEEVTV, GSLK; from rapeseed (Zn²⁺): AR, NSM, EPSH; from defatted walnut flake (Fe³⁺): LAGNPDDEFRPQ, VEDELVAVV; from Pacific cod skin gelatin (Fe²⁺): GPAGPHGPPGKDGR, AGPHGPPGKDGR; from scad (Decapterus maruadsi) by-products (Fe³⁺): QKGTYDDYVEGL; from casein (Fe²⁺): EDVPSER, HKEMPFPK, NMAINPSK, AVPYPQR; from peony seed (Fe²⁺): SMRKPPG. These are tabulated from primary literature and are not original measurements of this review.
Methods (brief)
This is a narrative methodological review with simulation discussion. The authors compile primary literature on MCP production by enzymatic proteolysis (Alcalase, Flavourzyme, trypsin, pepsin, papain, Protamex, Neutrase, Pancreatin, Chymotrypsin, Thermolysin), on peptide–metal-ion coordination chemistry organized around Pearson’s HSAB framework, on IMAC constituents (matrix, complexing-agent denticity, immobilized metal ion), on column operation (equilibration, loading, washing, elution by pH variation, competitive elution with imidazole, chelate destruction with EDTA, column stripping, regeneration), and on parameters affecting separation (pH, ionic strength, organic-solvent and detergent additives, reducing agents). The simulation section develops a transport-dispersive model — a mass-balance partial differential equation with axial-dispersion and convective transport terms, an LDF mass-transfer relation, and a Langmuir or multi-component Langmuir isotherm — and proposes using SPR-measured sorption-isotherm parameters (K_D, R_max) as inputs, on the analogy that SPR and IMAC share the same complexing agent (NTA), immobilized metal ion, and a comparable surface chemistry on dextran (SPR) or agarose (IMAC). The authors generate no primary analytical data. Compiled instrument and reagent names function as scientific-method identifiers (Biacore chip, Cytiva product code BR100407, IMAC column resins, named protease preparations) and are not attributions of contamination values to brands.
Related evidence
Update history
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git.
| Commit | Date | Change | Description |
|---|---|---|---|
| b01ec52c31 | 2026-08-04 | major | 1 section added |
| 3171d069e3 | 2026-08-02 | major | 1 section added |
| 90a2f9a38e | 2026-07-30 | major | 1 section added and 1 removed |
| eaa8eeeedf | 2026-07-27 | major | 1 section added and 1 removed |
| aca5e2155a | 2026-06-09 | major | 1 section added |