Sep 30, 2011
Metallized recombinant S-layer protein nanotubes prepared for nanobiotechnology applications
Self-assembling bacterial surface layer (S-layer) proteins, which can be genetically engineered on demand, are strong candidates for building nanoscale devices via bottom-up approaches. Tagged with a protein of choice (for example, the green fluorescent protein – eGFP), recombinant S-layer proteins can be synthesized in suitable host cells such as yeasts, isolated in their monomeric form, and self-assembled on user-defined surfaces into structures that can then be further modified. In a recent study, scientists from Dresden have explored metallized tubular assemblies of the S-layer protein SbsC, fused to eGFP (mSbsC-eGFP), for possible applications in nanobiotechnology by investigating the contact potential and conductivity of test samples.
As shown in the figure, isolated mSbsC-eGFP forms fluorescent tubular assemblies. Electroless metal plating with 150 mM Pt salt solution resulted in the formation of S-layer assemblies decorated with Pt nanoparticles (Ø > 3 nm) that were closely packed and aggregated into metal clusters. Metallized nanotubes were monitored with a high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX). The contact potential differences (CPD) of metallized and unmetallized samples with respect to the silicon surface were determined by Kelvin probe force microscopy (KPFM) measurements.
Metallized and unmetallized S-layer tubes differ in their surface potential, indicating that Pt deposition changes the electrostatic surface characteristics of the protein assemblies. Finally, in situ conductivity measurements were performed with a scanning tunnelling microscopy (STM) holder in a TEM (upper image). While unmetallized S-layer assemblies were not conductive, metallized samples showed linear I–V dependence between –1 and +1 V with a conductivity of ~103 S/m.
Conductive S-layer tubes may be applied in nanobiotechnology. For example, to scale down electronic devices.
The researchers presented their work in the journal Nanotechnology.
About the author
This study is a collaborative work of research teams of the Institute for Genetics (IFG, Technische Universität Dresden, TUD), Institute for General Photophysics (IAPP, TUD) and Leibniz Institute for Solid State and Materials Research (IFW, Dresden). Nuriye Korkmaz, currently a postdoctoral researcher in the Interdisciplinary Human Biotechnology group at Korea Institute of Science and Technology (KIST-Europe, Saarbrücken), is working on self-assembling biomolecules and their applications. Felix Börrnert, a PhD student in the Molecular Structures group at IFW, has expertise in in situ conductivity measurements of nanoscale materials. Denny Köhler is a postdoctoral researcher in the Scanning Probe Microscopy and Manipulation group at IAPP. PhD student Rafael G Mendes of the Molecular Structures group at IFW specializes in HRTEM imaging. Alicja Bachmatiuk is an Alexander von Humboldt postdoctoral researcher in the Molecular Structures group at IFW. Mark H. Rümmeli leads the Molecular Structures group at IFW. Bernd Büchner is a professor at TUD and director of the Institute for Solid State Research at IFW. Lukas Eng, a professor at TUD, is head of the Scanning Probe Microscopy and Manipulation group at IAPP. Gerhard Rödel is a professor at TUD, head of IFG, Dean of the Dresden International Graduate School for Biomedicine and Bioengineering (DIGS-BB) and currently Vice-Rector for research of the Technische Universität Dresden. This work was partially supported by Research Training Group Nano- and Biotechnologies for Packaging of Electronic Systems (German Research Foundation, DFG 1401/1).