Modeling of DNA Base Interactions with Carbon Nanotubes: ab initio Calculations and SEIRA Data

摘要

SEIRA spectroscopy data was compared with ab initio calculations for thymine and adenine adsorbed on carbon nanotubes. Numerous changes in spectral features of thymine and adenine adsorbed on carbon nanotubes in comparison with spectra of thymine and adenine adsorbed on neutral substrate (CaF2) and gold substrate were observed. The changes occur in the region of C=O stretching vibrations for thymine and NH2 and C=C for adenine, and they are evidence of protonation of nitrogenous bases and redistribution of H-bond net under interaction with carbon nanotubes. We have registered the enhancement of intensity of vibration of thymine and adenine adsorbed on gold and nanotube surface (about 3-5) for some bands as well as a several stable states of the thymine and adenine adsorbed on the nanotubes. These partially coincide with the calculated results. Based on IR data we suppose that thymine forms monolayer and multi-layer films on the nanotube surface with tilted to the surface of nanotube, adenine forms separate molecules and island films on the nanotubes rather than layers. Energy of interaction between bases and nanotubes estimated from spectra was less than energy calculated with ab initio.