On the Role of Poly-Glutamic Acid in the Early Stages of Iron(III) (Oxy)(hydr)oxide Formation
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MDPI
Materia
Pre-nucleation clusters Iron (III) hydrolysis Poly-L-glutamic acid Nucleation Additivecontrolled mineralization
Date
2021Referencia bibliográfica
Luki´c, M.J.; Lücke, F.; Ili´c, T.; Petrovi´c, K.; Gebauer, D. On the Role of Poly-Glutamic Acid in the Early Stages of Iron(III) (Oxy)(hydr)oxide Formation. Minerals 2021, 11, 715. https:// doi.org/10.3390/min11070715
Sponsorship
Institute of Technical Sciences of SASA - Ministry of Education, Science and Technological Development of the Republic of Serbia (451-03-9/2021-14/200175); IAESTE Belgrade organization and DAADAbstract
Nucleation of minerals in the presence of additives is critical for achieving control over the
formation of solids in biomineralization processes or during syntheses of advanced hybrid materials.
Herein, we investigated the early stages of Fe(III) (oxy)(hydr)oxide formation with/without polyglutamic acid (pGlu) at low driving force for phase separation (pH 2.0 to 3.0). We employed an advanced
pH-constant titration assay, X-ray diffraction, thermal analysis with mass spectrometry, Fourier
Transform infrared spectroscopy, and scanning electron microscopy. Three stages were observed:
initial binding, stabilization of Fe(III) pre-nucleation clusters (PNCs), and phase separation, yielding
Fe(III) (oxy)(hydr)oxide. The data suggest that organic–inorganic interactions occurred via binding of
olation Fe(III) PNC species. Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed a plausible interaction motif and a conformational adaptation of the polypeptide. The stabilization of the
aqueous Fe(III) system against nucleation by pGlu contrasts with the previously reported influence
of poly-aspartic acid (pAsp). While this is difficult to explain based on classical nucleation theory,
alternative notions such as the so-called PNC pathway provide a possible rationale. Developing a
nucleation theory that successfully explains and predicts distinct influences for chemically similar
additives like pAsp and pGlu is the Holy Grail toward advancing the knowledge of nucleation, early
growth, and structure formation.