Spectroscopic characterization of Au-complexation and nanoparticle formation on S-layer protein of L. sphaericus JG-A12


Spectroscopic characterization of Au-complexation and nanoparticle formation on S-layer protein of L. sphaericus JG-A12

Jankowski, U.; Fahmy, K.; Selenska-Pobell, S.; Merroun, M.

The strain Lysinibacillus sphaericus JG-A12, isolated from the uranium mining waste pile “Haberland” in Saxony (Germany), is capable of selective and reversible accumulation of radionuclides and toxic metals. It was demonstrated that metal binding is caused generally by the surface layer of the protein. This S-layer possesses a highly ordered lattice structure and can serve as a template spatially confined metal nanoparticle growth.
Our aim was to elucidate binding modes of Au to S-layer protein from L. sphaericus JG-A12.
In this study Au-complexes were produced by sorption of Au(III) on S-layer and reduction of these complexes to Au(0) nanoparticles. Au(III) complexes and Au(0) nanoparticles were studied by means of FTIR and EXAFS techniques.
EXAFS reveals the short range environment of the metal. No significant differences between the Au(III) and Au(0) were observed. Furthermore, EXAFS can only distinguish between elements in the short range order around the metal, the detected elements N, O and C cannot further be assigned to specific chemical groups.
FTIR measurements have shown that side chain carboxylates play a different role in Au(0) complex formation as compared to the complexation of Pd(II) or Pt(II).
For Au a weakening of asymmetric (1560 cm-1) and symmetric (1400 cm-1) carboxylate stretching mode indicates a different binding mode of Au to protein, probably involving stabilization of the protonated state of the carboxyls.
Hypothesize that Au causes hydrophobic burial, and thus protonation of carboxylic side chains rather than ionic interactions as found for Pd.
The results let us conclude that the binding mode of Au to S-layer from L. sphaericus JG-A12 is remarkably different from that of Pt or Pd.

  • Poster
    The European conference on the Spectroscopy of Biological Molecules, 28.08.-02.09.2009, Palermo, Italien

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Publ.-Id: 12726