Comparison of adsorption mechanism on colloidal silver surface of alafosfalin and its analogs

Abstract

The equilibrium geometries and vibrational wavenumbers are calculated using density functional theory (DFT) at the B3LYP; 6-31++G * * level of theory using Gaussian'03, GaussSum 0.8, and GAR2PED software. We briefly compare and analyze the experimental and calculated vibrational wavenumbers in the range of 3600-400 cm −1 . In addition, Raman wavenumbers are compared to those from surface-enhanced Raman scattering (SERS) for the phosphonodipeptides of alanine (Ala) adsorbed on a colloidal silver surface. The geometry of these molecules etched on the silver surface is deduce from the observed changes in both the intensity and breadth of Raman bands in the spectra of the bound vs free species. For example, A7, A8, A1, A3, and A4 appear to adsorb onto the colloidal silver particles mainly through the phosphonate terminus, and for A3 and A4, through the -C-NH 2 and -CONH-fragments. The most dominant SERS bands of A5, A6, A9, A10, and A11 are due to the amide bond vibrations, as well as to the vibrations of the -C-NH 2 group (A9 and A10) and the C-C group (A6 and A11). The differences recorded for the A5, A6, A9, A10, and A11 and those of A2 and A12 are due to interactions between the amine and methyl groups with the silver surface, and they reflect vibrational characteristic of these groups.alafosfalin) is approved for treatment of urinary tract infections, 5 and it is used in diagnostic testing 6 and for isolation of Salmonella from clinical samples. 7 In this work, we have studied the mechanism of adsorption of alafosfalin and its 11 analogs on the surface of colloidal silver. The set of compounds studied are L-Ala-L-NH-CH(Me)-PO 3 H 2 (alafosfalin, A1),

Effect of Pb2+ on L‐glutathione monolayers on a silver surface investigated by surface‐enhanced Raman scattering spectroscopy

“…Also, the mixed band of O6H wagging and N11H wagging can be found at 832 cm −1 . The assignments of NH vibrations in the range of 606-1577 cm −1 made by Podstawka et al [40,41] coincide with the above attributions. The SERS technique in the confocal fashion is able to obtain information just from the molecules bound to the metallic surface because of the high spatial resolution.…”

Nociceptin and its natural and specifically‐modified fragments: Structural studies

“…30 This technique can thus be employed to investigate ligand-receptor binding for drugprotein complexes and differences in individual molecules. 20,25 The enormous Raman scattering enhancement results from the strong increase of local electromagnetic fields in close vicinity to metal (i.e., silver, gold, or copper) surfaces that accompanies the excitation of surface plasmon resonances in the metals. 31 The most popular and universal substrate used for SERS is silver, which is usually used as in colloidal suspension.…”

Surface‐enhanced Raman difference between bombesin and its modified analogues on the colloidal and electrochemically roughen silver surfaces

“…37 The observed SERS signals we correlated with the contribution of the structural components to the ability of these peptides to interact with the rGRP-R. For example, we showed that the first five amino acids of the BN N-terminus do not influence the adsorption mechanism on the silver roughen electrode similar as they are not essential for interaction with rGRP-R. 19 Also, based on almost exclusively enhancement of the Trp 8 bands in the SERS spectra of BN, its modified analogues, and 6-14 fragments, we encouraged the conclusion that Trp 8 is responsible for receptor recognition. 37,38 The strong enhancement of the C¼ ¼O vibrations for BN, [Tyr amide bond. This is in agreement with the biological activity studies showing that such modifications are not particularly important in expression of biological activity at rGRP-R. 24 The aim of this work is to elucidate the nature of interaction of abovementioned peptides with the colloidal silver surface.…”

“…Both these facts are in agreement with our earlier studies of the adsorption mechanism of BN and its modified analogues and fragments on the electrochemically roughen silver surface. 37,38 Phenylalanine Side Chain…”