Table 1.

Summary of ¹⁹F and ¹H signal enhancements in 14.1 T DNP MAS NMR spectra of 5F-Trp,U-¹³C,¹⁵N CA tubular assemblies under different experimental conditions.^*

Biradical concentration (mM)	T (K)	MAS frequency (kHz)	Microwave power (mA / W**)	19F DNP polarization buildup time, Tb (s)	19F DNP signal enhancement		1H DNP polarization buildup time, Tb (s)	1H DNP signal enhancement
					integrated intensity (isotropic peak)	integrated intensity (all side bands)		integrated intensity
4.3	120	24	120 / 8.4	11.8	29	37	4.3	63
			130 / 10.2		34	45		71
			140 / 12.0		38	48		76
			150 / 13.8		40	51		77
			160 / 15.6		41	53		76
12	120	15	150 / 13.8	11.1	32	36
		20	130 / 10.2		68	70
			150 / 13.8		77	82
		22	130 / 10.2		50	60
			150 / 13.8		66	72
15	106	24	110 / 6.6	18.9	37	46
	120		140 / 12.0		58.4	72		49
			150 / 13.8				1.4	50
	125	25	120 / 8.4	14.4	30	36
			130 / 10.2		33	39
			140 / 12.0		36	43
			150 / 13.8		43	51
			160 / 15.6		38	44
	130	25	130 / 10.2		33	38
	160	25	130 / 10.2	12.1	7	8
	185	30	130 / 10.2		7	7
22.2	120	24	150 / 13.8	10.9	79	100	1.2	72
28.5	120	24	150 / 13.8	9.5	80	98.5	0.9	65

^*The DNP enhancement factors were calculated as ratios of the integrated peak intensities for maximum peak intensities with and without the microwave irradiation.

^**Microwave power at the end of the waveguide.