A study on ATR-FUV spectroscopy for investigation of electronic structure and transitions of various biological molecules

This study aims at exploring the potential of ATR-far-ultraviolet (FUV) spectroscopy in investigating electronic structure and transitions of various kinds of biological molecules. For this purpose, ATR-FUV spectra were measured for several kinds of proteins with the different secondary structures, several kinds of carbohydrates, nucleic acids, and lipids. Band assignments have been made for all kinds of biological molecules investigated based on our previous ATR-FUV studies on n-alkanes, alcohols, esters, and amides. For example, the proteins show a characteristic band near 200 nm due to π-π* transition of amide groups. The position of this band varies a little with the secondary structure of proteins but its intensity changes significantly depending on the secondary structure and solutions. All the carbohydrates studied yielded a band near 170 nm due to n-Rydberg transition of ether. In addition, acetylcarbohydrates give an additional band near 190 nm originating from π-π* transition of amide at 2’ carbon. The present study has demonstrated that ATR-FUV spectroscopy is a new powerful technique in exploring electronic structure and transitions of biological molecules, in general. It is also possible to use ATR-FUV spectroscopy for quantitative and qualitative analysis of biological molecules. Moreover, it is of note that information regarding electronic transitions collected by ATR-FUV spectroscopy is useful for UV resonance Raman (UVRR) spectroscopy studies of biological molecules. A combined ATR-FUV spectroscopy and UVRR spectroscopy method may provide a novel analytical tool for molecular and electronic structure of biological molecules.