Elucidating Protein Behavior on the Nanoscale By Using Synthetic Model Peptides To Investigate The Interactions of Proteins With Single Walled Carbon Nanotubes
Abstract
Proteins are the most versatile macromolecules of the cell. Their biochemical functions include binding, catalysis, operating as molecular switches and serving as structural components of cells and organisms. Since proteins are critical molecules for life, it is imperative that we investigate how different factors such as temperature, solvent and pH can alter the three dimensional structure and specific characteristics of these molecules. Another important factor that can be studied is the conjugation of proteins with specific nanomaterials.
Single walled carbon nanotubes are a class of nanomaterials that has gained a lot of interest because of potential biomedical applications. Of significant interest are the interactions of carbon nanotubes with proteins, which are related to the development of bioscale sensors and biocatalytic devices and cellular delivery of peptides and proteins. Single walled carbon nanotubes are single sheets of graphite rolled into seamless cylinders with diameters ranging from 0.5 to 5 nm and lengths that can exceed 1µm. Although many investigations have explored the nonspecific interactions between proteins and carbon single walled nanotubes, they have also revealed complexity. The extent to which the protein species are adsorbed on the nanotube surface needs to be evaluated.
With this in mind I will examine protein behavior on the nanoscale by adsorbing synthetic model peptides to carbon single wall nanotubes (SWNTs). It is a standard approach to study small model peptides in order to determine the factors that contribute to the conformational stability and chemical properties of proteins.3 For this investigation four model peptides: 4A, 4A mini, H1, and H19G will be used. Of particular interest is the fact that although 4A and 4A mini have amino acid sequence homology and H1 and H19G have a similar amino acid sequence, each peptide has a unique secondary structure. 4A is alpha helical, while 4A mini is random coil. H1 is primarily beta sheet and H19G is random coil.
For this project I will determine what are the major factors that determine how these model peptides adsorb to single walled carbon nanotubes. Model peptides will be synthesized using Solid Phase Peptide Synthesis. The efficiency of adsorption of peptides to SWNTs will be analyzed by protein quantification assays and peptide-nanotube conjugates will be characterized by Attenuated Total Reflection/Fourier Transform Infrared (ATR/FTIR) spectroscopy and Atomic Force Microscopy. Results indicate that the conformation or shape of a peptide in solution is more important in determining efficiency of adsorption to SWNTs than the physical characteristics of the peptide such as charge and polarity. This information may be useful for understanding factors that contribute to the adsorption of full proteins to SWNTs.
Description
Keywords
nanotubes, model, peptides