Adsorption of nucleic acid bases on metal surface of nanoparticles has received much attention recently in bio- and nano- science, while there still remains a controversy that how adenine is adsorbed onto metal surface.

As the nitrogen in adenine plays an important role in the molecular recognition and interaction, the molecular spectral feature related to the nitrogen is the key to analysis of the adsorption configuration.

Rencently, the research group led by Prof. HUANG Qing from Institute of Technical Biology & Agriculture Engineering, Hefei Institutes of Physical Science reported a novel approach to investigate the interaction of adenine with noble metals.

According to the report, the team demonstrated an effective approach by applying the combination of density functional theory (DFT) and surface enhanced Raman spectroscopy (SERS) tools in isotopic molecules.

Figure 1. SERS spectra of adenine in (left) silver and (right) gold colloids: (a) ¹⁵N full-labeld (c) non-labeld experimental spectra, (b) ¹⁵N full-labeld (d) non-labeld simulated spectra (Image by YAO Guohua) 

In the study, they employed DFT calculations at B3LYP/6-311+G(d,p) level for the simulation of adsorption configurations, and in the meantime checked the corresponding SERS of isotopic ¹⁵N fully-labeled adenine adsorbed on the surfaces of silver and gold nanoparticles.

The agreement of spectral positions, intensities, and isotopic shifts of the SERS bands (Figure 1), suggests that adenine adsorbed on either silver or gold surface takes the same adsorption configuration (Figure 2) in which N7H adenine interacts with Ag₄⁺/Au₄⁺ cluster through both N3 and N9 sites.

Figure 2. The adsorption configuration in which N7H adenine interacts with Ag₄⁺/Au₄⁺ cluster through both N3 and N9 sites (Image by YAO Guohua) 

This study may not only shed new light on interaction of adenine with noble metals, but also demonstrate an effective new approach which combines both experimental isotopic SERS and quantum theoretical calculation for the research of biomolecules adsorption on the metal surface.

The study was published in the Journal of Physical Chemistry C with the title of "DFT and SERS Study of 15N Full-labeled Adenine Adsorption on Silver and Gold Surfaces".

The computation was conducted at Supercomputer Centers of University of Science and Technology of China, and the project was supported by the National Natural Science Foundation of China, the Anhui Provincial Natural Science Foundation and the National Basic Research Program of China.