Effect of potential on temperature-dependent SERS spectra of neuromedin B on Cu electrode

Adsorption of decapeptide neuromedin B (NMB) on copper electrode has been investigated by in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry in the temperature interval from 12 to 72 1 Cat 0.600 and 1.000 V potentials. It was found that intensities of peptide bands decrease at temperatures above 30 1 C with higher decrease slope at 1.000 V. Frequency of F12 mode (1004 cm 1 ) of non-surface-interactive phenylalanine residue was found to be insensitive to temperature variation at both studied electrode potentials, while frequency–temperature curves for surface-interactive groups (Amide-III, methylene) were found to be controlled by the potential. In particular, opposite frequency–temperature trends were detected for Amide-III (Am-III) mode indicating decrease in H-bonding interaction strength of amide C Q O and N–H groups above 38 1 Cfor 0.600 V, and increase in H-bonding interaction strength between 12 and 72 1 Cfor 1.000 V. Anomalous Am-III temperature- dependence of the frequency at 1.000 V was explained by temperature-induced transformation of a disordered secondary structure to a helix-like conformation. The potential-difference spectrum revealed interaction of methylene groups with Cu surface at sufficiently negative potential values because of the appearance of a soft C–H stretching band near 2825 cm 1 and a broad band near 2904 cm 1 assigned to vibration of a distal C–H bond of the surface-confined methylene group. Consequently, a rapid decrease in frequency of CH 2 -stretching band with temperature was observed at 1.000 V, while no essential frequency changes were detected for this mode at 0.600 V. The results show that electrode potential controls the temperature-dependence of the frequency for vibrations associated with surface- interactive molecular group

Phe-MetNH_2 terminal bombesin subfamily peptides : potential induced changes in adsorption on Ag, Au, and Cu electrodes monitored by SERS

Surface-enhanced Raman scattering, electro- chemistry, and generalized two-dimensional correlation analysis methods were used to characterize phyllolitorin and a peptide derived from Pseudophryne guntheri (PG-L). Phyllolitorin and PG-L were deposited onto Ag, Au, and Cu electrode surfaces at different applied electrode potentials in an aqueous solution at physiological pH, and the orientations and adsorption mechanisms of peptides were determined based on the enhancement, broadening, and shifts in the wavenumbers of specific bands. On the basis of these analyses, specific conclusions were drawn regarding the peptide geometry and changes in the geometry that occurred when the electrode type and applied electrode potential were varied. The phyllolitorin and PG-L deposited onto the Ag, Au, and Cu electrode surfaces showed bands that were due to the vibrations of moieties in contact with or in close proximity to the electrode surfaces and were thus located on the same side of the polypeptide backbone. These moieties included the Phe and Trp rings, the sulfur atom of Met, and the amide bond. Variations in the arrangement of these fragments were observed with changes in the metal surface and the applied electrode potential

Computational Modeling of the Electrochemical System of Lipase Activity Detection

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Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy for Probing Riboflavin on Graphene

Graphene research and technology development requires to reveal adsorption processes and understand how the defects change the physicochemical properties of the graphene-based systems. In this study, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and graphene-enhanced Raman spectroscopy (GERS) coupled with density functional theory (DFT) modeling were applied for probing the structure of riboflavin adsorbed on single-layer graphene substrate grown on copper. Intense and detailed vibrational signatures of the adsorbed riboflavin were revealed by SHINERS method. Based on DFT modeling and detected downshift of prominent riboflavin band at 1349 cm−1 comparing with the solution Raman spectrum, π-stacking interaction between the adsorbate and graphene was confirmed. Different spectral patterns from graphene-riboflavin surface were revealed by SHINERS and GERS techniques. Contrary to GERS method, SHINERS spectra revealed not only ring stretching bands but also vibrational features associated with ribityl group of riboflavin and D-band of graphene. Based on DFT modeling it was suggested that activation of D-band took place due to riboflavin induced tilt and distortion of graphene plane. The ability to explore local perturbations by the SHINERS method was highlighted. We demonstrated that SHINERS spectroscopy has a great potential to probe adsorbed molecules at graphene

Influence of applied potential on bradykinin adsorption onto Ag, Au, and Cu electrodes

Surface-enhanced Raman scattering, electrochemistry, and generalized two-dimensional correlation analysis (G2DCA) methods were used to characterize bradykinin (BK), a hormone which is known to be involved in small-cell and non-small-cell lung carcinoma and prostate cancer. BK was deposited onto Ag, Au, and Cu electrode surfaces under different applied electrode potentials ( 1.000V to 0.200V) in aqueous solutions. Based on the analysis of the enhancement, the broadening, and the shifts in the wavenumbers of individual bands, speci fi c conclusions were drawn regarding the peptide geometry and changes in this geometry that occurred when the electrode type and applied electrode potential were varied. Brie fl y, BK deposited onto the Ag, Au, and Cu electrode surfaces showed bands that were due to the vibrations of moieties in contact with or in close proximity to the electrode surfaces and were thus located on the same side of the polypeptide backbone. These moieties included the Phe, Arg, and Pro residues. The fi ndingsfor adsorbed BKwere fully supportedbyG2DCA,which also allowed ustodeterminethe order in which changes occurred when the electrode potential was changed. In addition, it was found that at negative electrode potentials, the Phe rings and methylene groups interact with Ag electrode surface. No such interaction was observed for Au and Cu electrodes

Phe-MetNH₂ Terminal Bombesin Subfamily Peptides: Potential Induced Changes in Adsorption on Ag, Au, and Cu Electrodes Monitored by SERS

Surface-enhanced Raman scattering, electrochemistry, and generalized two-dimensional correlation analysis methods were used to characterize phyllolitorin and a peptide derived from <i>Pseudophryne guntheri</i> (PG-L). Phyllolitorin and PG-L were deposited onto Ag, Au, and Cu electrode surfaces at different applied electrode potentials in an aqueous solution at physiological pH, and the orientations and adsorption mechanisms of peptides were determined based on the enhancement, broadening, and shifts in the wavenumbers of specific bands. On the basis of these analyses, specific conclusions were drawn regarding the peptide geometry and changes in the geometry that occurred when the electrode type and applied electrode potential were varied. The phyllolitorin and PG-L deposited onto the Ag, Au, and Cu electrode surfaces showed bands that were due to the vibrations of moieties in contact with or in close proximity to the electrode surfaces and were thus located on the same side of the polypeptide backbone. These moieties included the Phe and Trp rings, the sulfur atom of Met, and the amide bond. Variations in the arrangement of these fragments were observed with changes in the metal surface and the applied electrode potential