COMPARATIVE DENSITY FUNCTIONAL THEORY, DENSITY FUNCTIONAL TIGHT BINDING AND FORCE FIELD STUDIES OF AMINOACIDS, PEPTIDES AND PEPTIDE-TITANIA INTERFACES: BRINGING AB INITIO ACCURACY TO BIOMOLECULAR SIMULATIONS

Abstract

The performance of the density functional tight binding (DFTB) method is compared with a common force field (FF) for simulation of a large cell penetrating peptide (CPP) Lycosine-I, and with density functional theory (DFT) for simulation of aminoacids and a small CPP TAT. I also present a comparative DFT-DFTB study of bio-inorganic interfaces: arginine, arginine dipeptide, and the arginine-rich TAT cell-penetrating peptide on TiO2. For Lycosine-I, good agreement between DFTB and FF is found. While there is good agreement in the structures and relative energies of aminoacids and of TAT conformers between DFT and DFTB, the agreement does not hold for the interfaces. I relate this difference to the difference in electronic structures and argue that DFTB (with is an approximation to DFT but with which the correct band structure can be effectively obtained) - performs better than the DFT itself with functionals feasible for bio-inorganic interfaces.