The construction of a dynamic nuclear polarization/nuclear magnetic resonance (DNP/NMR) spectrometer operating at high magnetic fields (approximately 100W 4.7T) is proposed. The instrument will also be employed for high field pulsed and CW electron paramagnetic resonance (EPR) spectroscopy. The problem of a high frequency, hig power microwave source, which has been the limiting factor in applying these techniques at high fields, will be solved by employing a gyrotron - a long lifetime microwave oscillator -which will supply a power of approximately 100W 102W at 140 GHz. This instrument will permit us to apply these magnetic resonance techniques to solve a number of outstanding problems which have resisted solution by presently available techiques. DNP/NMR experiments discussed in this proposal include improved 2D dipolar/chemical shift spectroscopy, determination of the NH Schiff base bond distrance in bacteriorhodopsin (bR), the elucidation of the mechanism of the opsin shift in this protein, the determination of molecular structure in the vicinity of the B-ionone ring of the retinal chromophore, and finally, chain tracing experiments analogous to solution state NOESY and COSY experiments. Planned high frequency EPR experiments include high resolution spectroscopy and orientation-selection/electron-nuclear double resonance investigations of free radicals, in particular spin-labeled bR, as well as spin-echo modulation experiments targeted to enable the investigation of the first coordination sphere of Cu++ in copper- metalloproteins.
