EFFECTS OF FREE ELECTRON LASER FAR INFRARED RADIATION ON LARGE BIOMOLECULES

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The major objective of this program is to achieve unprecedented resolution in far-infrared (FIR) transmission studies of DNA and other biomolecular species utilizing the unique time dependence of the Rutgers' free electron laser (FEL). The ultimate goal of this research program is to demonstrate the enhancement of biochemical activity with FIR radiation. An important first step is to experimentally determine the existence of well defined FIR active collective modes in biologically important molecules such as DNA. Whether the natural line widths of these modes are small compared to their frequencies will be determined. Low frequency, large amplitude, collective modes in DNA involving large numbers of atoms have been proposed to be important in allowing the structural transitions in the DNA double helix that are required for processes such as replication and transcription. To date, FIR studies of oriented films using fourier-transform spectrometers have shown broad absorption bands which are inhomogeneously broadened due to the statistical distribution of the possible base pairs and imperfect structural periodicity along the helix axis. Photon echo techniques using the Rutgers' FEL will be applied to obtain significantly improved resolution for the FIR spectra of DNA. The term "photon echo" denotes the pulse of light which is emitted spontaneously from a system of atoms previously irradiated by two coherent light pulses and is observed at a time after the second pulse very nearly equal to the time between the two excitation pulses.