Role of $Phe-D_5$ isotopically labeled analogues of bradykinin on elucidation of its adsorption mode on Ag, Au, and Cu electrodes : surface- enhanced Raman spectroscopy studies

Raman (RS), surface-enhanced Raman scattering (SERS), electrochemistry, and isotopic effect methods were used to characterize selective adsorption of two isotopically labeled bradykinin analogues, [(Phe-D 5 ) 5 ]BK and [(Phe-D 5 ) 8 ]BK, a hormone which is known to be involved in small-cell and non-small-cell lung carcinoma and prostate cancer. The investigated analogues contain Phe residue, at position 5 or 8 in the amino acid sequence, substituted by Phe-D 5 ( fi ve protons of L-phenylalanine ring substituted by deuterium). [(Phe-D 5 ) 5 ]BK and [(Phe-D 5 ) 8 ]BK were immobilized onto electrochemically roughened Ag, Au, and Cu electrode surfaces under different applied electrode potentials ( 1.000 V to 0.200 V) in an aqueous solution containing 0.01 M phosphate buffer (pH=7.0) and 0.1 M Na 2 SO 4 . Based on the analyses of the spectral pro fi les in the 920 – 1050 cm 1 spectral range, speci fi c conclusions were drawn with respect to the Phe metal interactions and changes in the interaction that occurred when the adsorption conditions were varied.