. 2023 Jan 26;123(4):1417–1551. doi: 10.1021/acs.chemrev.2c00534

Table 3. Summary of NMR Sensitivity Advantages Achievable via Photo-CIDNP Nuclear Polarization.

Molecule of interest	Enhanced/detected nucleus	Photosensitizer dye	Pulse sequence type^a	Percent polarization p, %^d	Enhancementfactor ε^g	Sensitivity enhancement	Lowest detected conc. (amount)^k	Ref
Tryptophan (U-¹³C, ¹⁵N)^b	¹³C^α/¹H^α	FMN	¹³C-¹H rev-INEPT (¹³C PRINT)	0.016%^e	13.5 ± 0.6	22 ± 3^h	1.0 mM (0.14 mg)	(490)
Tryptophan (U-¹³C, ¹⁵N)^b	¹H^ε1/¹H^ε1	FMN	¹H-¹⁵N HSQC	0.031%^e	6.0 ± 0.3	6.0 ± 0.3^h	2.0 mM (0.29 mg)	(492)
Tryptophan (U-¹³C, ¹⁵N)^b	¹³C^η2/¹H^η2	FMN	¹³C-¹H rev-INEPT (¹³C PRINT)	0.033%^e	41 ± 2	11.8 ± 20.7^h	1.0 mM (0.14 mg)	(490)
Tryptophan (U-¹³C, ¹⁵N)^b	¹⁵N^ε1, ¹H^ε1/¹H^ε1	FMN	¹H-¹⁵N HSQC	0.048%^e	100 ± 15	100 ± 15^h	2.0 mM (0.29 mg)	(492)
Tryptophan (¹⁵N₂-Trp)^b	¹⁵N^ε1/¹H^ε1	FMN	¹H-¹⁵N HSQC	0.15%^e	30.9 ± 0.8	30.9 ± 0.8^h	2.0 mM (0.29 mg)	(491)
Tryptophan (U-¹³C, ¹⁵N)^c	¹³C^α/¹H^α	Fluorescein	¹³C-¹H rev-INEPT (¹³C PREPRINT)	0.353%^e	292	1,800^h, 73ⁱ	200 nM (28 ng)	(475)
Tryptophan (U-¹³C, ¹⁵N)^c	¹³C^α/¹H^α	Fluorescein	¹³C-¹H rev-INEPT (¹³C RASPRINT)	0.375%^e	310 ± 16	832 ± 44^h,208 ± 11ⁱ	500 nM (76 ng)	(472)
Tryptophan (α-¹³C)	¹³C^α/¹H^α	Fluorescein	¹³C-¹H rev-INEPT (¹³C RASPRINT)	0.496%^e	410 ± 2	1,168 ± 61^h, 292 ± 15^j	n.a. (est. <28 ng)ⁱ	(484)
Tryptophan (α-¹³C-β, β,2,4,5,6,7-d₇)	¹³C^α/¹H^α	Fluorescein	¹³C-¹H rev-INEPT (¹³C RASPRINT)	0.568%^e	470 ± 13	1,306 ± 69^h, 327 ± 17^j	20 nM (2.8 ng)	(484)
Tyrosine	¹H/¹H	Atto Thio 12	Pulse-acquire	0.30%^e	59	59^h	10 μM	(499)
N-Acetyl-l-tyrosine	¹H/¹H	FMN	Pulse-acquire	0.019%^f	6	6^h	5 mM (1.1 μg)	(43)
Nucleotide (GMP)	¹H/¹H	FMN	Pulse-acquire	0.023%^f	7	7^h	20 mM (7.3 μg)	(43)
p-Fluorophenol	¹⁹F/¹⁹F	FMN	Pulse-acquire	n.a.^l	n.a. (>500)	n.a. (>500)^h	0.8 μM (90 pg)	(43)

Rev-INEPT denotes a reverse-INEPT pulse sequence type.

Can be detected both in its free form or as a residue within proteins. The tyrosine (Tyr) and histidine (His) amino acids can also be detected, though the sensitivity is somewhat lower.

Can be detected both in its free form or as a residue within proteins. The tyrosine (Tyr) amino acid can also be detected, though the sensitivity is somewhat lower.

p is defined according to eq 1 and is expressed in percent. These values were not explicitly reported in the original references and were assessed here according to the reported enhancement factor, experimental methods and thermal polarization (according to the Boltzmann distribution).

Polarization values calculated at 600 MHz, consistent with the original reference.

Percent polarization values were assessed at 400 MHz, consistent with the original reference.

The enhancement factor ε defined as the ratio between photo-CIDNP polarization and thermal polarization: ε = p/p_therm, where p_therm is the polarization at thermal equilibrium.

Sensitivity enhancement factor relative to the same pulse sequence under dark conditions (sensitivity enhancement = (SNR)_t. light/(SNR)_t, dark).

ⁱ

Sensitivity enhancement factor relative to ¹H-¹³C CT-SE-HSQC (constant-time sensitivity-enhanced HSQC). Sensitivity enhancement = (SNR)_t,light/(SNR)_t,HSQC.

Approximate estimate from comparisons between SE-HSQC and dark-state ¹³C RASPRINT data.

Smallest amount of detectable material according to the corresponding reference. The true detection limit is lower or equal to the reported value.

Not available (i.e., not quantified in the original publication).