DNA-Binding Properties of Peptide-Functionalized Graphene Quantum Dots

Abstract

We present here the synthesis and characterization of nanoscale materials with DNA binding properties. We have functionalized graphene quantum dots (GQDs) with graphite-binding peptides to obtain graphene/peptide conjugates. The conjugates form stable 2D crystalline beta-sheet domains on the graphene surface. Upon incubation with DNA, we observe that DNA binding to the domain is directional, and the DNA preferentially aligns to the peptide direction. Upon binding the peptide-functionalized GQDs to DNA we observe an architectural role of GQDs in global and local flexibility, looping, and compacting of DNA. We use worm like chain (WLC) model to determine the persistence length of DNA in the absence and in the presence of GQDs, confirming a decreased persistence length upon GQD binding. Further, we find that the presence of peptide augments the number of DNA binding sites, as compared with exposure of bare GQDs to DNA. Our results show that peptide-modified GQDs can be a potentially ideal nanomaterial mimic of DNA-binding proteins similar to nucleosomal structures and other DNA-metabolic enzymes.