Photo-CIDNP NMR capability to perform rapid analysis of 1 µM Trp in solution. (a) NMR spectra of 1 µM Trp (solution conditions as in the legend of Fig. 1, Hα resonance, 2.4 µM FL, 8 scans) collected either at 14.1 Tesla (600 MHz) with a room-temperature probe in the presence of photo-CIDNP (1D 13C PRINT), or at 21.2 Tesla (900 MHz) with a cryogenic probe (1H-13C SE-HSQC) in the absence of photo-CIDNP. (b) Same experiments as in panel a except that extensive signal averaging (15,872 scans) was carried out at 21.2 Tesla, until the S/N of the experiment at 21.2 Tesla became approximately the same as the S/N of the experiment at 14.1 Tesla.