Molecular Recognition Capabilities of a Nucleolipid Amphiphile (3‘,5‘-Distearoyl)-2‘-Deoxythymidine to Adenosine at the Air/Water Interface and Langmuir−Blodgett Films Studied by Molecular Spectroscopy

Monolayer behavior of a nucleolipid amphiphile, (3‘,5‘-distearoyl)-2‘-deoxythymidine, on pure water, aqueous 1 mM and 5 mM adenosine solutions was investigated by means of surface pressure−molecular area ( π − A ) isotherms, which indicate that both hydrogen-bonding and stacking interactions are present between the (3‘,5‘-distearoyl)-2‘-deoxythymidine monolayer and adenosine in subphase, and the recognition of this amphiphile to adenosine is more complete in higher subphase concentration. The ultraviolet−visible (UV−vis), Fourier transform infrared (FTIR) transmission, FTIR-attenuated total reflection (ATR), and Fourier transform surface-enhanced Raman scattering (FT-SERS) spectroscopic results indicate that the adenosine molecules in the subphase can be transferred onto solid substrates by Langmuir−Blodgett (LB) technique as a result of the formation of Watson−Crick base-pairing at the air/water interface. The regular and closed packing of the constituent molecules facilitates the photodimerization of the thymine moieties in the headgroup under ultraviolet irradiation even at room temperature. FT-SERS technique, for the first time, was introduced into the research area of molecular recognition occurring at an interface system. High-quality FT-SERS spectra of single LB monolayers obtained in the 1750−500 cm - 1 region, together with the FTIR-ATR results in the NH-stretching high-frequency region, provide direct evidences for the formation of multiple complementary hydrogen bonds between the base pairs.