“…For example, the 99% of carbon is 12 C with spin quantum number, I = 0 (NMR inactive) and 99.6% of nitrogen is quadrupolar ( 14 N) with I = 1, while only 1.1% ( 13 C) and 0.37% ( 15 N) are NMR active nuclei with I = 1/2. Therefore, there is a significant reduction of the sensitivity in ssNMR spectra of 13 There are many excellent research articles and reviews that highlight the role of fast 4 MAS for biomolecular NMR applications 21,23,25,26,27,28,29,30,31,32 .…”