Center for Functional Nanomaterials Seminar

An E. coli flagellin protein, termed FliTrx, was investigated for use as a novel form of self-assembling protein nanotube. This protein was genetically engineered to surface display constrained peptide loops with a series of different thiol, cationic, anionic, and imidazole functional groups. Various metal ions such as Co(II), Cu(II), Cd(II), Ag(I), Au(I), were bound to histidine and aspartic acid-glutamic acid peptide loops and reduced in a controlled manner to generate nanoparticle arrays and nanotubes. Silicate and titanate ions were bound to arginine-lysine and tyrosine-serine-glycine peptide loops respectively and polymerized to obtained silica and titania nanotubes. Hydroxyapatite nanoparticles were also generated on aspartic acid-glutamic acid peptide loops. The CdTe quantum dots of (3±0.3) nm diameter were bound to histidine peptide loops to generate an ordered array of quantum dots on the flagella. Exciton energy transfer between small (donor) and large (acceptor) CdTe quantum dots was demonstrated from a 5 nm (18 meV) red shift in the emission maximum for the flagella bound quantum dots compared to those free in solution. The flagella with cysteine loops aggregated through disulfide bond formation to form bundles which could be dissociated into single flagella nanotubes employing a reducing agent such as TCEP. These nanotube bundles exhibited an interesting behavior in optical traps generated with 1064 nm laser. They were repelled by the laser beam instead of being trapped resulting in their escape. Significant results of these studies will be presented.