Method for protein nanowire synthesis and tunable control of nanowire length

Abstract

Methods for synthesizing nanowires are provided. Modified PilA peptides are used as peptide building blocks for synthesizing the nanowires. The method places the peptide building blocks in an assembly buffer with a hydrophobe. Addition of a hydrophobe and molecular crowding by evaporation of the assembly buffer triggers the self-assembly of the peptide building blocks into fibers. Multiple elongation cycles of addition of peptide building blocks, mixing and evaporation are conducted to promote elongation of the fibers and synthesis of nanowires. Electronic characterization of the synthesized nanowires is provided.

What is claimed is: 
     
         1 . A method of synthesizing protein nanowires comprising:
 providing purified peptide building blocks;   suspending the purified peptide building blocks in an assembly buffer;   forming an assembly composition by addition of a hydrophobe to the assembly buffer with the purified peptide building blocks to trigger self-assembly of the peptide building blocks; and   increasing molecular crowding by evaporation of a volume of the assembly buffer in the assembly composition to facilitate hydrophobe guided assembly to conductive nanowires.   
     
     
         2 . The method of  claim 1  further comprising conducting one or more elongation cycles to promote fiber formation, wherein the elongation cycle comprises providing additional peptide building blocks and/or hydrophobe into the assembly composition, mixing the assembly composition and evaporating the assembly buffer from the assembly composition. 
     
     
         3 . The method of  claim 1  wherein about four elongation cycles are conducted. 
     
     
         4 . The method of  claim 1  wherein the hydrophobe is octadecane. 
     
     
         5 . The method of  claim 1  wherein the hydrophobe is added to the assembly composition by loading the peptide building blocks into a column comprising particles and eluting the peptide building blocks into the assembly buffer, wherein the elution results in the elution of a portion of the particles of the column and the peptide building blocks into the assembly buffer and wherein the particles of the column are the hydrophobes in the assembly composition. 
     
     
         6 . The method of  claim 5  wherein the hydrophobe is C18-silica particles. 
     
     
         7 . The method of  claim 1  wherein the peptide building blocks are modified pilin peptides. 
     
     
         8 . The method of  claim 1  wherein the peptide building blocks are recombinant truncated pilin peptides from  G. sulfurreducens.    
     
     
         9 . The method of  claim 1  wherein the peptide building blocks are PilA 19  peptides from  G. sulfurreducens.    
     
     
         10 . The method of  claim 1  wherein the nanowires formed have a length from about 0.3 μm to about 10 μm. 
     
     
         11 . A composition comprising synthesized protein nanowires wherein the nanowires comprise peptide building blocks derived from PilA peptides and the nanowires have a length of at least about 2 μM. 
     
     
         12 . The composition of  claim 11  wherein the peptide building blocks are modified PilA peptides. 
     
     
         13 . The composition of  claim 11  wherein the peptide building blocks are truncated PilA n  peptides, wherein the truncated PilA n  peptides have the amino acid sequences selected from the group consisting of SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, and SEQ ID NO:5. 
     
     
         14 . The composition of  claim 11  wherein the nanowires have a length from about 2 μM to about 10 μM. 
     
     
         15 . The composition of  claim 11  wherein the nanowires have a length of from about 5 μM to about 7 μM. 
     
     
         16 . The composition of  claim 11  wherein the nanowires have an average diameter of about 2 nm. 
     
     
         17 . The composition of  claim 11  wherein the nanowires have a Circular Dichroism (CD) profile with an intensity ratio of 222 nm/208 nm from about 0.7 to higher than 1. 
     
     
         18 . A device comprising synthesized protein nanowires wherein the nanowires comprise peptide building blocks derived from PilA peptides and the nanowires have a length of at least about 2 μM. 
     
     
         19 . The device of  claim 18  wherein the peptide building blocks are modified PilA peptides. 
     
     
         20 . The device of  claim 18  wherein the device is selected from antenna, attenuator, battery, brush, capacitor, condenser, conductor, circuit, electrode, fuel cell, generator, filter circuit breaker (fuse), inductor, coil, nanowire array, particle collector, precipitator, reactor, rectifier, relay, resistor, solar energy collector, spark generator, suppressor and/or terminal.