Energetic Basis of Single-Wall Carbon Nanotube Enantiomer Recognition by Single-Stranded DNA

Hybrids of single-stranded DNA and single-walled carbon nanotubes (SWCNTs) have proven to be very successful in separating various chiralities and, recently, enantiomers of carbon nanotubes using aqueous two-phase separation. This technique sorts objects based on small differences in hydration energy, which is related to corresponding small differences in structure. Separation by handedness requires that a given ssDNA sequence adopt different structures on the two SWCNT enantiomers. Here we study the physical basis of such selectivity using a coarse-grained model to compute the energetics of ssDNA wrapped around an SWCNT. Our model suggests that difference by handedness of the SWCNT requires spontaneous twist of the ssDNA backbone. We also show that differences depend sensitively on the choice of DNA sequence