| Summary: | <p>Sensitivity being one of the main hurdles of nuclear
magnetic resonance (NMR) can be gained by polarization techniques including
chemically induced dynamic nuclear polarization (CIDNP). Kaptein
demonstrated that the basic mechanism of the CIDNP arises from
spin sorting based on coherent electron–electron nuclear spin dynamics
during the formation and the recombination of a radical pair in a magnetic
field. In photo-CIDNP of interest here the radical pair is between a dye and
the molecule to be polarized. Here, we explore continuous-wave (CW)
photo-CIDNP (denoted CW-photo-CIDNP) with a set of 10 tryptophan and tyrosine analogues, many of
them newly identified to be photo-CIDNP active, and we observe not only signal
enhancement of 2 orders of magnitude for <span class="inline-formula"><sup>1</sup></span>H at 600 MHz (corresponding
to 10 000 times in measurement time) but also reveal that polarization
enhancement correlates with the hydrophobicity of the molecules.
Furthermore, the small chemical library established indicates the existence
of many photo-CIDNP-active molecules.</p>
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