Adenine− and Adenosine Monophosphate (AMP)−Gold Binding Interactions Studied by Surface-Enhanced Raman and Infrared Spectroscopies

Abstract

Understanding the interactions of biomolecules with noble metal surfaces is critical to our development of functional biomedical nanodevices and accurate biosensors. Here we use surface enhanced Raman spectroscopy (SERS) and surface enhanced infrared absorption spectroscopy (SEIRA) on Au nanoshell substrates to study the interactions of adenine and two adenine derivatives, thiolated polyadenine single-stranded DNA (polyA) and adenosine monophosphate (AMP), with Au surfaces. pH-dependent conformational changes of these molecular species adsorbed on Au nanoshell surfaces were observed using SERS, and confirmed with SEIRA. The combined SERS-SEIRA spectra show significant pH dependence, consistent with adenine protonation and reduced Au-adenine binding at low pH. The spectra are also consistent with adenine binding "end-on" to the Au surface via a ring nitrogen, with the bond to the external NH 2 group aligned near the surface normal. For AMP, spectral evidence indicates binding through either a ring nitrogen and/or the external NH 2 group. Density functional calculations on adenine and comparisons with the literature allow us to assign the observed spectral features and to gain insight to the local binding geometry of the adsorbates.

A DFT Investigation of Surface‐Enhanced Raman Scattering of Adenine and 2′‐Deoxyadenosine 5′‐Monophosphate on Ag20 Nanoclusters

“…All complexes are formed by linkage of Ag atoms to nitrogen atoms in a side-on orientation, which implies that adenine prefers to adopt an end-on adsorption mode on silver nanoparticles. As reported by many experimental and computational studies, [9,12,18,19] Figure 2 shows that adenine is bound to the cluster through N1, N3, or N7 in an upright orientation for the S complexes (a, b, c, and e), in a slightly tilted orientation for the V complexes (a1, b1, c1, and e1), and in an orientation perpendicular to one edge for the E complexes (a2, b2, c2, and e2). Furthermore, adenine could be adsorbed on the silver cluster through the external amino group in complex f1, which is a model of flat-on adsorption on silver surfaces.…”

“…[8][9][10][11][12][13][14][15][16][17][18] Of the four nucleobases, adenine ( Figure 1) is an extremely important molecule with which to study chemisorption to Ag or Au nanoparticle surfaces in detail. Adsorption of adenine on noble metal surfaces has been studied by SERS experimentally and theoretically.…”

“…Adsorption of adenine on noble metal surfaces has been studied by SERS experimentally and theoretically. [9,16,[18][19][20][21][22] In a SERS measurement, adenine was reported to bind to silver surfaces through three modes: flat "face-on" adsorption through the adenine p system, "end-on" coordination to a ring nitrogen atom, and binding via the external amino group. For example, on the basis of SERS measurements on adenine on silver sol, Suh and Moskovits [22] suggested that adenine is bound flat to the metal surface.…”

New Surface-Enhanced Raman Sensing Chip Designed for On-Site Detection of Active Ricin in Complex Matrices Based on Specific Depurination

“…35 However, they are absent in the characteristic peaks from phosphate and sugar moieties on ssODN as a result of the small Raman cross-section of them. 36 Moreover, we also evaluated the signal performance of the SERS chip fabricated with different sizes of poly(21dA)−AuNPs (∼60, ∼75, ∼90, and ∼100 nm). It is found that the SERS chip fabricated with poly(21dA)−AuNPs of ∼100 nm possesses the most sensitive SERS signal ( Figure S5 of the Supporting Information), which is optimal for "turn-off" SERS detection.…”

Adsorption of Cytosine and AZA Derivatives of Cytidine on Au Single Crystal Surfaces

“…Both 6-azaC and 5-azaC nucleosides have a wide spectrum of biological properties that result in pharmacological activity, primarily antitumor and antiviral effects [1][2][3][4][5][6][7] . There have been extensive experimental [8][9][10][11][12][13][14][15][16][17] and theoretical [18][19][20] studies of biomolecules on gold and other Group 11 metal surfaces, to a large extent focused on amino acids, nucleobases, and their polymers -oligonucleotides, peptides, proteins, etc. We have chosen the present set of compounds based on (and including) the nucleobase cytosine as they are a representative set containing a standard nucleobase, as well as novel functional groups in the derivatives, such as one would expect to find in new pharmaceuticals, for example.…”