Selective detection of the antigenic polar heads of model lipid membranes supported on metals from their vibrational nonlinear optical response

We have investigated a metal-supported lipid film by using a sum frequency generation (SFG) spectrometer coupled to a free electron laser (FEL). DFT calculations on a molecular model have enabled to assign the vibrational signatures. The SFG vibrations detected in the backbone region, between 1375 cm−1 and 1000 cm−1, originate from the vibrational motions of the 2,4-dinitrophenyl polar head of the lipid, which holds antigenic properties, and can therefore be used to selectively study the biological interactions with complementary antibodies. Theses results strengthen the role of SFG spectroscopy as a highly sensitive tool for biological detection.