Abstract
Cross-relaxation effects in the 360 MHz 1H photo-CIDNP (chemically induced dynamic nuclear polarization) spectra of N-acetyl tyrosine, N-acetyl tryptophan, and bovine pancreatic phospholipase A 2 are investigated. The buildup and decay of polarization, produced by cyclic photochemical reactions involving a flavin dye, are measured respectively during and after a pulse of laser irradiation. Results are analyzed using a simple relaxation model including CIDNP pumping of nuclear magnetizations. The model is also used to discuss various manifestations of cross relaxation in CIDNP spectra and to assess the possibilities for observing polarization transfer between amino acid residues in proteins. Information is obtained on molecular tumbling rates and hyperfine couplings of the free radicals involved in CIDNP production. In favorable circumstances internuclear distances in macromolecules can be derived.
Published Version
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