The synthesis of protein-based polymers with controlled conformational properties and functional group placement offers many opportunities for the design of advanced materials. In this work, protein engineering methods have been used to produce repetitive alanine-rich protein polymers with the sequence [(AAAQ) 5 -(AAAE)(AAAQ) 5 ] x (x = 2 and 6); these macromolecules may mimic architectural features of certain alanine-rich helical sequences found in natural proteins. Various proteins from this family can be readily expressed and purified from Escherichia coli. Circular dichroic spectroscopy (CD) characterization demonstrates that the purified proteins are highly helical under a variety of conditions. Thermal analysis of [(AAAQ) 5 (AAAE)-(AAAQ) 5 ] 2 via differential scanning calorimetry (DSC) and CD indicates that the protein undergoes a reversible helix-coil transition at approximately 45 °C and that the protein conformation can be manipulated at elevated temperatures depending on solution conditions. The demonstrated conformational properties of these artificial proteins suggest that they may be excellent candidates for elucidating structure-function relationships in biopolymers for nanotechnology and biological applications.

Micrometer and submicrometer diameter fibers of recombinant dragline spider silk analogues, synthesized via protein engineering strategies, have been electrospun from 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and compared with cast films via Raman spectroscopy in order to assess changes in protein conformation that may result from the electrospinning process. Although the solvent casting process was shown to result in predominantly beta-sheet conformation similar to that observed in the bulk, the electrospinning process causes a major change in conformation from beta-sheet to alpha-helix. A possible mechanism involving electric field-induced stabilization of alpha-helical segments in HFIP solution during the electrospinning process is discussed.

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