UV excimer laser chemically induced dynamic nuclear polarization of amino acids at 360 MHz.

A system has been developed which permits ultraviolet irradiation of samples in the probe of a 360 MHz nmr spectrometer using an excimer laser (A= 249 or 308 nm). This system is ideally suited for studying Chemically Induced Dynamic Nuclear Polarization (CIDNP) during photochemical reactions involving amino acids, proteins, and nucleic acids. The photoreagents quinoxaline and p-methoxyacetophenone prove to be the most promising for reactions witn His, Trp, and Tyr. Spin polarized spectra are presented and interpreted according the reaction mechanisms involved, the spin density distributions, and the relative g-factors of the radical intermediates. This system allows the use of a number of new photoreagents for studying protein structure and dynamics by laser CIDNP in solution.