Creating Long-Lived Spin States at Variable Magnetic Field by Means of Photochemically Induced Dynamic Nuclear Polarization

We have shown that long-lived spin states (LLS) can be selectively populated by photogenerated chemically induced dynamic nuclear polarization (CIDNP) over a wide range of magnetic fields. Relaxation times of LLS of the beta-CH2 protons in N-acetyl histidine and partially deuterated histidine have been measured Our experiments demonstrate that CIDNP enables creating LLS in the amino acid in a field range of up to a few Tesla and that their lifetimes can be 45 times longer than T-1. The advantage of the method is thus two-fold: it allows one to accumulate high levels of spin hyperpolarization and to preserve them for periods of time far exceeding T-1. Therefore, photo-CIDNP is a technique suitable for creating long-lived spin order in biologically relevant molecules.