Bonding of Histidine to Cerium Oxide

Abstract

Adsorption of histidine on cerium oxide model surfaces was investigated by synchrotron radiation photoemission, resonant photoemission, and near edge X-ray absorption fine structure spectroscopies. Histidine was evaporated in a vacuum onto ordered stoichiometric CeO2(111) and partially reduced CeO1.9 thin films grown on Cu(111). Histidine binds to CeO2 in anionic form via the carboxylate group and all three nitrogen atoms, with the imidazole ring parallel to the surface. The amino nitrogen atom of the imidazole ring (IM) is deprotonated, and both IM nitrogen atoms form strong bonds via π orbitals, while the α-amino nitrogen interacts with the oxide via its hydrogen atoms. In the case of CeO1.9, the deprotonation of the amino nitrogen of the imidazole ring is less pronounced and N K-edge spectra do not show a clear orientation of the ring with respect to the surface. A minor reduction of the cerium surface on adsorption of histidine was observed and explained by charge exchange as a result of hybridization of the π orbitals of the IM ring with the f and d orbitals of ceria. Knowledge of histidine adsorption on the cerium oxide surface can be used for design of mediator-less biosensors where the histidine-containing proteins can be strongly bound to the oxide surface via the imidazole side chain of this residue.

Functionalization of nanostructured cerium oxide films with histidine

“…27, i.e. The molecular adlayer thickness on polycrystalline CeO 2 was estimated by comparison of absolute C 1s and N 1s intensities of the histidine saturated coverage on the Cu(111) reference surface.…”

“…The C 1s, N 1s and O 1s core levels were acquired with photon energies 410, 475 and 630 eV and the total resolutions of 350, 500 and 700 meV, respectively. 27,31 The corrected positions of core levels were then used as the reference for lines measured under the synchrotron radiation. Spectra recorded at 121.4 and 124.8 eV correspond to the D(Ce 3+ ) resonance enhancements in Ce 3+ cations (emission from Ce 4f states located at a binding energy (BE) of about 1.4 eV) and D(Ce 4+ ) -in Ce 4+ cations (emission from hybridized oxygen cerium states at about 4.0 eV), respectively.…”

“…27 The local pressure during deposition was about 3 Â 10 À8 mbar. Histidine was deposited by evaporation from a Knudsen cell under vacuum.…”

“…27 Histidine, one of the principal amino acids, was chosen with the aim to model the bonding of proteins and other complex biomolecules with the cerium oxide surface. 27 Histidine, one of the principal amino acids, was chosen with the aim to model the bonding of proteins and other complex biomolecules with the cerium oxide surface.…”

“…27 Histidine, one of the principal amino acids, was chosen with the aim to model the bonding of proteins and other complex biomolecules with the cerium oxide surface. 27 Here we present the continuation of this line of research. 1, and it has three important chemical groups: carboxylic acid, a-amino and imidazole.…”