A new field of solid-state NMR by very fast MAS：sub-micro-litter sample ¹⁴N NMR collection in a few minutes

Rapid observations of ¹⁴N NMR for sub-micro-litter samples are presented. ¹⁴N is  rarely observed by NMR despite its high natural abundance (99.6%) and its  importance in bio and material sciences. The difficulties in observing ¹⁴N resonances  are due to its integer spin quantum number (I=1) and quadrupolar interactions.  Because of these difficulties ¹⁵N NMR with expensive ¹⁵N isotopic-labeling is usually  applied. Very fast MAS by 1 mm MAS system, which we recently developed, realizes  quick observation of ¹⁴N NMR resonances of sub-micro liter samples within a few  minutes, combining ¹H-¹⁴N solid-state HMQC methods. The ¹H-¹⁴N D-HMQC of dipeptide (glycyl-L-alanine) of 0.8 uL gives clearly separated peaks of two distinct  nitrogens. Slightly different ¹H shifts for each peak can also be obtained. No isotopic  labeling methods are applied to the sample.

This work has been supported by JST-SENTAN(JAPAN).