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. Author manuscript; available in PMC: 2017 Aug 16.
Published in final edited form as: J Am Chem Soc. 2015 Jun 19;137(25):8294–8307. doi: 10.1021/jacs.5b04843

Figure 4.

Figure 4

DNP enhancements of ssNMR signals from Aβ40 assemblies in frozen, triradical-doped glycerol/water solutions. (A-D) One-dimensional, cross-polarized 13C spectra of high pH, neutral pH, fibril, protofibril, and high pH samples, respectively, prepared with isotopic labeling pattern I in Table 1. Spectra were obtained at 100.8 MHz 13C NMR frequency, 25 K sample temperatures, and 6.7 kHz MAS frequency. Spectra with (blue) and without (red) microwave irradiation at 264.0 GHz are plotted on the same vertical scale in each panel and with the indicated number of scans for each spectrum. DNP enhancement factors, defined as the ratio of signal amplitudes with and without microwave irradiation, are 80, 60, 32, and 18 in panels A-D, respectively. Recycle delays are 5.6 s, 5.0 s, 25.0 s, and 30.0 s.