Electronic structure of dipeptides in the gas-phase and as an adsorbed monolayer

Abstract

Peptide-based molecular electronic devices are promising due to the large diversity and unique electronic properties of biomolecules. These electronic properties can change considerably with peptide structure, allowing diverse design possibilities. In this work, we explore the effect of the side-chain of the peptide on its electronic properties, by using both experimental and computational tools to detect the electronic energy levels of two model peptides. The peptides include 2Ala and 2Trp as well as their 3-mercaptopropionic acid linker which is used to form monolayers on an Au surface. Specifically, we compare experimental ultraviolet photoemission spectroscopy measurements with density functional theory based computational results. By analyzing differences in frontier energy levels and molecular orbitals between peptides in gas-phase and in a monolayer on gold, we find that the electronic properties of the peptide side-chain are maintained during binding of the peptide to the gold substrate. This indicates that the energy barrier for the peptide electron transport can be tuned by the amino acid compositions, which suggests a route for structural design of peptide-based electronic devices.

n-Type Doping of Triethylenetetramine on Single-Wall Carbon Nanotubes for Transparent Conducting Cathodes

“…The significant reduction in the measured WF of the SWCNT network was mainly attributed to the transfer of electrons from TETA molecules attached to the SWCNTs’ surface. Furthermore, a permanent electric dipole was induced at the surface of the SWCNTs. , In the latter case, the amine groups of the adsorbed TETA molecules induced a positive dipole on the surface that caused a downshift in the vacuum level, which in turn reduced the measured WF.…”

Conformation-dependent charge transport through short peptides

“…Therefore, it is possible to imagine a peptide as composed of rigid rods (the amide groups) that can rotate around their connection points (the α-carbons). Peptide flexibility and the possible conformations it can have, 3 thus increase with the number of amino acids. Even in vacuum, linear (unfolded) 4Ala likely has several conformations and there will be additional ones in our experiments, considering the presence of multiple binding sites to Au.…”

Photoelectron Spectroscopy of Molecules Beyond the Electric Dipole Approximation

“…From a computational perspective, the comparison between calculated and measured PE spectra is widely used to asses the quality of a particular electronic structure method. , Usually, the computed electronic structure is directly compared to PE spectra measured at low photon energies. References − constitute several examples of this practice applied at different levels of theory, from density functional theory (DFT) and the GW approximation to Dynamical Mean Field Theory (DMFT).…”