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Morphological Transformations in the Magnetite Biomineralizing Protein Mms6 in Iron Solutions: A Small-Angle X-ray Scattering Study
  • Honghu Zhang, Iowa State University
  • Xunpei Liu, Iowa State University
  • Shuren Feng, Iowa State University
  • Wenjie Wang, Iowa State University
  • Klaus Schmidt-Rohr, Iowa State University
  • Mufit Akinc, Iowa State University
  • Marit Nilsen-Hamilton, Iowa State University
  • David Vaknin, Iowa State University
  • Surya K. Mallapragada, Iowa State University
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Magnetotactic bacteria that produce magnetic nanocrystals of uniform size and well-defined morphologies have inspired the use of biomineralization protein Mms6 to promote formation of uniform magnetic nanocrystals in vitro. Small angle X-ray scattering (SAXS) studies in physiological solutions reveal that Mms6 forms compact globular three-dimensional (3D) micelles (approximately 10 nm in diameter) that are, to a large extent, independent of concentration. In the presence of iron ions in the solutions, the general micellar morphology is preserved, however, with associations among micelles that are induced by iron ions. Compared with Mms6, the m2Mms6 mutant (with the sequence of hydroxyl/carboxyl containing residues in the C-terminal domain shuffled) exhibits subtle morphological changes in the presence of iron ions in solutions. The analysis of the SAXS data is consistent with a hierarchical core–corona micellar structure similar to that found in amphiphilic polymers. The addition of ferric and ferrous iron ions to the protein solution induces morphological changes in the micellar structure by transforming the 3D micelles into objects of reduced dimensionality of 2, with fractal-like characteristics (including Gaussian-chain-like) or, alternatively, platelet-like structures.

Reprinted (adapted) with permission from Langmuir, 2015, 31 (9), pp 2818–2825, DOI: 10.1021/la5044377. Copyright (2015) American Chemical Society.

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Honghu Zhang, Xunpei Liu, Shuren Feng, Wenjie Wang, et al.. "Morphological Transformations in the Magnetite Biomineralizing Protein Mms6 in Iron Solutions: A Small-Angle X-ray Scattering Study" Langmuir Vol. 31 Iss. 9 (2015) p. 2818 - 2825
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