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The uptake of Fe(III) by living cells of unicellular green algae Dunaliella salina ions is investigated. The effects of operational conditions such as contact time, biomass concentration, initial pH, and initial Fe(III) concentration on iron uptake are studied. The time profile of the Fe(III) uptake by living cells of D. salina shows a time lag in the first 15 min, which is associated with the production of metal chelating agents. In addition, it is found that the optimum pH for maximal iron uptake is 8. At optimal conditions, the uptake is increasing gradually along with the increase of biomass concentration. Furthermore, the uptake increased with the rising of the initial metal ion concentration. Dry samples of iron free and iron containing biomass of D. salina are analyzed using Fourier‐transform infrared (FTIR) spectroscopy. Comparison of the obtained FTIR spectra revealed the presence of amino, carboxylic, hydroxylic, phosphate and sulphonate groups of the lipids, proteins and polysaccharides localized at the cell surface, which are involved in the process of Fe(III) acquisition.

Abstract. Lactoferrin is a non-heme protein known for its ability to bind tightly Fe(III) ions in various physiological environments. Due to this feature lactoferrin plays an important role in the processes of iron regulation at the cellular level preventing the body from damages produced by high levels of free iron ions. The X-ray crystal structure of human lactoferrin shows that the iron-binding process leads to conformational changes within the protein structure. The present study was addressed to conformation stability of human lactoferrin in solution. Using molecular dynamics simulations, it was shown that Arg121 is the key amino acid in the stabilization of the Fe(III) ion in the N-lobe of human lactoferrin. The small-angle neutron scattering method allowed us to detect the structural differences between the open and closed conformation of human lactoferrin in solution. Our results indicate that the radius of gyration of apolactoferrin appears to be smaller than that of the hololactoferrin, $R_{g}=24.16(\pm 0.707)$ R g = 24 . 16 ( ± 0 . 707 ) Å and $R_{g}= 26.20(\pm 1.191)$ R g = 26 . 20 ( ± 1 . 191 ) Å, respectively. The low-resolution three-dimensional models computed for both forms of human lactoferrin in solution also show visible differences, both having a more compact conformation compared to the high-resolution structure. Graphical abstract