Characterization of human Urotensin II peptide adsorbed on silver electrode by surface-enhanced Raman scattering...

The cyclic human neuropeptide Urotensin II (hU-II) is an important regulatory peptide found in the central nervous system, cardiovascular system, kidney, etc., however, its conformational structure and dynamics in aqueous solutions have not been studied in detail experimentally. In the present study, the structure of hU-II and the mechanism of its adsorption on the electrochemically roughened Ag electrode are investigated using electrochemical surface-enhanced Raman scattering spectroscopy (EC-SERS) in the voltage range from -1.0 to 0.0 V. We show that the adsorption of the hU-II peptide on the roughened Ag surface without the applied potential occurs mainly through the Phe⁶ and Trp⁷ residues of the cyclic hexapeptide sequence c[Cys⁵-Phe⁶-Trp⁷-Lys⁸-Tyr⁹-Cys¹⁰]. Under the applied negative potentials, a rearrangement of the Phe⁶ and Trp⁷ residues relative to the Ag electrode surface occurs, changing the orientation of the ring plane from an angle to a vertical. This favors the approach of the Lys⁸ and Tyr⁹ residues to the Ag surface and the additional anchoring of the hU-II peptide to the surface. The results of the detailed analysis of the interaction of the hU-II peptide with the solid-liquid interface obtained with EC-SERS can contribute to the understanding of the mechanisms of hU-II interaction with its receptor and help in the development of pharmacological analogs of hU-II in the future.