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Highlighting radical sites in enzymes
What is it about?
Polarised neutron scattering from dynamically polarised protons operates on a nanometric scale. It relies on the creation of a short-lived local accumulation of polarized nuclei in hydrogenous material within a sphere of about 1 nm diameter centered at a paramagnetic impurity. The result of Dynamic Nuclear Polarisation (DNP) is modified by the selective reversal of the proton polarisation using the method of Adiabatic Fast Passage (AFP).
Why is it important?
The combined use of DNP and AFP in experiments of time-resolved polarised neutron scattering allows a differentiation between polarised protons close to a radical site and those of the bulk. Radical sites show up more clearly. The conversion of the amino acid tyrosine-369 of bovine liver catalase into the radical tyrosyl has bee confirmed. Magnetic inhomogeneities show in the same enzyme molecule.