Aggregate structure of hydroxyproline-rich glycoprotein (HRGP) and HRGP assisted dispersion of carbon nanotubes

Abstract

Hydroxyproline-rich glycoproteins (HRGP) comprise a super-family of extracellular structural glycoproteins whose precise roles in plant cell wall assembly and functioning remain to be elucidated. However, their extended structure and repetitive block co-polymer character of HRGPs may mediate their self-assembly as wall scaffolds by like-with-like alignment of their hydrophobic peptide and hydrophilic glycopeptide modules. Intermolecular crosslinking further stabilizes the scaffold. Thus the design of HRGP-based scaffolds may have practical applications in bionanotechnology and medicine. As a first step, we have used single-molecule or single-aggregate atomic force microscopy (AFM) to visualize the structure of YK20, an amphiphilic HRGP comprised entirely of 20 tandem repeats of: Ser-Hyp 4 -Ser-Hyp-Ser-Hyp 4 -TyrTyr-Tyr-Lys. YK20 formed tightly aggregated coils at low ionic strength, but networks of entangled chains with a porosity of~0.5-3 lm at higher ionic strength. As a second step we have begun to design HRGPcarbon nanotube composites. Single-walled carbon nanotubes (SWNTs) can be considered as seamless cylinders rolled up from graphene sheets. These unique all-carbon structures have extraordinary aromatic and hydrophobic properties and form aggregated bundles due to strong inter-tube van der Waals interactions. Sonicating aggregated SWNT bundles with aqueous YK20 solubilized them presumably by interaction with the repetitive, hydrophobic, Tyr-rich peptide modules of YK20 with retention of the extended polyproline-II character. This may allow YK20 to form extended structures that could potentially be used as scaffolds for site-directed assembly of nanomaterials.

Simulations of Peptide-Graphene Interactions in Explicit Water

“…The binding enthalpy contributions of X are plotted as a function of the Kyte-Doolittle hydropathy index in Figure , where a decrease in hydropathy is associated with stronger binding. These results are consistent with numerous studies on peptide surface interactions on several points. ,,,− First, the phenomenon of protein adsorption is known to occur on hydrophobic surfaces . Second, solvent effects have been shown to play a major role in protein adsorption due to the water structure at the biomaterial interface. , Further, many experimental studies have determined that hydrophilic molecules bind to graphitic surfaces. ,,,− Finally, experimental evidence exists demonstrating that hydrophilic proteins bind to graphitic surfaces more readily than hydrophobic proteins …”

Antibacterial action of dispersed single-walled carbon nanotubes on Escherichia coli and Bacillus subtilis investigated by atomic force microscopy

“…Cell surfaces may collide with SWCNTs millions of times during incubation. It has been reported that glycoproteins can disperse SWCNTs in aqueous solutions, 45 and SWCNTs also interact strongly with polysaccharides, such as chitosan. 46 Thus, individual nanotubes may adsorb on cell surfaces, and more nanotubes on the cell surface would bundle together owing to the strong van der Waals attractions between nanotubes.…”

Supramolecular Surface Modification and Solubilization of Single‐Walled Carbon Nanotubes with Cyclodextrin Complexation

“…Noncovalent surface functionalization has so far employed various natural biopolymers, such as polysaccharides (Gum Arabic (a highly branched arabinogalactan polysaccharide: 70-80 % arabingalactan, 20 % arabingalactan-protein complex), [7] starch, [8] amylose, [9] glycosylated polymers, [10] schizophyllan and curdlan (b-1,3-glucans), [11] alginic acid, [12] water-soluble chitosan [13] ), peptide, [14] DNA, [15] green tea (catechins), [16] natural lignosulfonate-based polyelectrolytes, [17] artificial conjugate polymers, [18] and pyrene-containing polymers. [19] Many polyaromatic, especially small pyrene-based molecules and ions (electrolytes), have also been used as surface modifiers of carbon nanotubes.…”