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Biomimetic magnetite formation: from biocombinatorial approaches to mineralization effects.

Baumgartner J, Carillo MA, Eckes KM, Werner P, Faivre D - Langmuir (2014)

Bottom Line: Our results suggest that the identified proteins and biomimetic polypeptides influence nucleation in vitro.Even though the in vivo role cannot be directly determined from our experiments, we can rationalize the following design principles: proteins, larger complexes, or membrane components that promote nucleation in vivo are likely to expose positively charged residues to a negatively charged crystal surface.In turn, components with acidic (negatively charged) functionality are nucleation inhibitors, which stabilize an amorphous structure through the coordination of iron.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces , Science Park Golm, 14424 Potsdam, Germany.

ABSTRACT
Biological materials typically display complex morphologies and hierarchical architectures, properties that are hardly matched by synthetic materials. Understanding the biological control of mineral properties will enable the development of new synthetic approaches toward biomimetic functional materials. Here, we combine biocombinatorial approaches with a proteome homology search and in vitro mineralization assays to assess the role of biological determinants in biomimetic magnetite mineralization. Our results suggest that the identified proteins and biomimetic polypeptides influence nucleation in vitro. Even though the in vivo role cannot be directly determined from our experiments, we can rationalize the following design principles: proteins, larger complexes, or membrane components that promote nucleation in vivo are likely to expose positively charged residues to a negatively charged crystal surface. In turn, components with acidic (negatively charged) functionality are nucleation inhibitors, which stabilize an amorphous structure through the coordination of iron.

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Schematic method representation. A comparison of peptidesequencesobtained by phage display and magnetosomal proteins affords proteinsand peptides of interest for further study in Fe precipitation experiments.Depending on the additive characteristics, mineralization can be influencedto yield amorphous gels and magnetite in aggregates or self-assembledparticle chains.
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fig1: Schematic method representation. A comparison of peptidesequencesobtained by phage display and magnetosomal proteins affords proteinsand peptides of interest for further study in Fe precipitation experiments.Depending on the additive characteristics, mineralization can be influencedto yield amorphous gels and magnetite in aggregates or self-assembledparticle chains.

Mentions: Here we investigatedthe example of the iron oxide mineral magnetitethat is found in diverse organisms (bacteria, mollusks, birds, andfish) and where it serves geonavigational or mechanical purposes.Its biogenic formation is best studied in magnetotactic bacteria,which form chains of magnetic nanoparticles termed magnetosomes.16 Because of their size and high monodispersity,magnetosomes are envisioned for MRI contrast agents and cancer treatmentapplications.17 Furthermore, similarlystructured synthetic magnetic nanoparticle assemblies have recentlyattracted much attention.18−20 Simple magnetotactic organismshave turned into a model system for iron oxide biomineralization becausethe genomes of several strains have been sequenced21 and because molecular techniques have been developed fortheir genetic manipulation.22,23 In particular, a wholeset of deletion mutants has been studied in Magnetospirillum strains, with phenotypes ranging from size and morphology changesto the complete disappearance of biomineralization.24 It has been shown that about 20 genes are sufficient torestore magnetite formation in cells deficient of the whole magnetosomeisland, the gene cluster responsible for magnetite biomineralization.25,26 The encoded Mam, Mms, and Mtx proteins are therefore good potentialcandidates for comparison with synthetically selected molecules andsubsequent in vitro mineralization studies. Furthermore, biocombinatorialpeptide selection studies on magnetite have been reported earlier,which provide a basis for such a comparison (Figure 1). Using the biocombinatorial techniques of cell surface andphage display, Brown et al. and Barbas et al. had independently shownthat polycationic polypeptides attach to magnetite or possibly tothe very similar maghemite crystal surfaces.27,28


Biomimetic magnetite formation: from biocombinatorial approaches to mineralization effects.

Baumgartner J, Carillo MA, Eckes KM, Werner P, Faivre D - Langmuir (2014)

Schematic method representation. A comparison of peptidesequencesobtained by phage display and magnetosomal proteins affords proteinsand peptides of interest for further study in Fe precipitation experiments.Depending on the additive characteristics, mineralization can be influencedto yield amorphous gels and magnetite in aggregates or self-assembledparticle chains.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3958130&req=5

fig1: Schematic method representation. A comparison of peptidesequencesobtained by phage display and magnetosomal proteins affords proteinsand peptides of interest for further study in Fe precipitation experiments.Depending on the additive characteristics, mineralization can be influencedto yield amorphous gels and magnetite in aggregates or self-assembledparticle chains.
Mentions: Here we investigatedthe example of the iron oxide mineral magnetitethat is found in diverse organisms (bacteria, mollusks, birds, andfish) and where it serves geonavigational or mechanical purposes.Its biogenic formation is best studied in magnetotactic bacteria,which form chains of magnetic nanoparticles termed magnetosomes.16 Because of their size and high monodispersity,magnetosomes are envisioned for MRI contrast agents and cancer treatmentapplications.17 Furthermore, similarlystructured synthetic magnetic nanoparticle assemblies have recentlyattracted much attention.18−20 Simple magnetotactic organismshave turned into a model system for iron oxide biomineralization becausethe genomes of several strains have been sequenced21 and because molecular techniques have been developed fortheir genetic manipulation.22,23 In particular, a wholeset of deletion mutants has been studied in Magnetospirillum strains, with phenotypes ranging from size and morphology changesto the complete disappearance of biomineralization.24 It has been shown that about 20 genes are sufficient torestore magnetite formation in cells deficient of the whole magnetosomeisland, the gene cluster responsible for magnetite biomineralization.25,26 The encoded Mam, Mms, and Mtx proteins are therefore good potentialcandidates for comparison with synthetically selected molecules andsubsequent in vitro mineralization studies. Furthermore, biocombinatorialpeptide selection studies on magnetite have been reported earlier,which provide a basis for such a comparison (Figure 1). Using the biocombinatorial techniques of cell surface andphage display, Brown et al. and Barbas et al. had independently shownthat polycationic polypeptides attach to magnetite or possibly tothe very similar maghemite crystal surfaces.27,28

Bottom Line: Our results suggest that the identified proteins and biomimetic polypeptides influence nucleation in vitro.Even though the in vivo role cannot be directly determined from our experiments, we can rationalize the following design principles: proteins, larger complexes, or membrane components that promote nucleation in vivo are likely to expose positively charged residues to a negatively charged crystal surface.In turn, components with acidic (negatively charged) functionality are nucleation inhibitors, which stabilize an amorphous structure through the coordination of iron.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces , Science Park Golm, 14424 Potsdam, Germany.

ABSTRACT
Biological materials typically display complex morphologies and hierarchical architectures, properties that are hardly matched by synthetic materials. Understanding the biological control of mineral properties will enable the development of new synthetic approaches toward biomimetic functional materials. Here, we combine biocombinatorial approaches with a proteome homology search and in vitro mineralization assays to assess the role of biological determinants in biomimetic magnetite mineralization. Our results suggest that the identified proteins and biomimetic polypeptides influence nucleation in vitro. Even though the in vivo role cannot be directly determined from our experiments, we can rationalize the following design principles: proteins, larger complexes, or membrane components that promote nucleation in vivo are likely to expose positively charged residues to a negatively charged crystal surface. In turn, components with acidic (negatively charged) functionality are nucleation inhibitors, which stabilize an amorphous structure through the coordination of iron.

Show MeSH