COLL 533 |
| Thilak Kumara Mudalige, Brian Tripp, and Subra Muralidharan. Department of Chemistry, Western Michigan University, Kalamazoo, MI 49008 |
| An emerging area of research in nanotechnology is bionanotubes and their composites with nanoparticles, obtained from lipids, peptides and proteins through the process of either spontaneous or stimulated self-assembly. Protein nanotubes are found in nature as flagella, which bacteria use to propel themselves. Flagella are formed by the self-assembly of flagellin proteins exported outside the cell. The flagellin protein has four distinct domains D0, D1, D2, and D3 where the Do and D1 domains contain the N- and C-terminal regions critical for the self-assembly and the D3 domain the solvent accessible region that can be modified without affecting the self-assembly process. The flagellin is a nanotube where each section consists of 11 flagellin protein units and typical flagellin has an inner diameter of 3 nm and outer diameter of 20 nm. Our research program is focused on engineering the flagellin protein by site directed mutagenesis to have amino acids and peptides in the D3 domain to bind nanoparticles such as Au, TiO2, and quantum dots (undoped and doped ZnS, CdSe etc). We have used a flagellin genetic system, termed, FliTrx, which contains a 12 kDa thioredoxin protein inserted into an E. coli flagellin internal deletion variant. The chimeric flagellin-thioredoxin FliTrx protein has been specifically designed to allow rational insertion and extracellular display of arbitrary loop peptides fused onto the solvent-accessible D3 domain. A variety of loop peptides such as polyhistidine, polylysine, and polyarginie have been inserted into the thioredoxin active site of the FliTrx protein employing synthetic DNA oligonucleotides encoding peptides of interest. The flagellin proteins with the peptide loops have been over expressed employing E. Coli and harvested by shearing the flagella. SDS PAGE gel electrophoresis of the isolated flagellin proteins indicated that in the case of polyhistidine up to four histidine loops had been inserted into the D3 domain. Various nanoparticles such as thiolated Au nanoparticles with exposed COOH groups and ZnS quantum dots have been attached to the flagellin surface through the polypeptides. These flagellin nanotubes with an ordered array of nanoparticles have been characterized by TEM, uv-visible and fluorescence spectroscopy, and light scattering studies. These studies will be presented. |
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Nanoscience and Nanotechnology
2:00 PM-5:15 PM, Thursday, April 1, 2004 Marriott -- Orange County 5, Oral
Division of Colloid and Surface Chemistry |