13C-Detection

13C-detection in biomolecular NMR

The availability of ¹³C-observe CryoProbes™ has made it possible to develop ¹³C-observe methods for paramagnetic proteins and large deuterated proteins - which are otherwise difficult to study by NMR due to rapid relaxation and the absence of proton signals.
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The use of CryoProbes helps to alleviate the major disadvantage of ¹³C-detection, that is, the lack of sensitivity. Although ¹³C-detection, compared to ¹H-detection, suffers from lower sensitivity, it also has a number of advantages.

Some of these include:

Favorable relaxation behavior due to shorter pulse sequences
Detection of non-protonated carbons
High dispersion of ¹³C chemical shifts
Absence of dominant signals from the solvent or buffer
High salt tolerance

These properties make the ¹³C-detected experiments a potentially useful complement to the traditional proton detection.

2D constant time ¹³C-¹³C-TOCSY spectrum (above diagonal) and 2D real time ¹³C-¹³C-TOCSY spectrum (below diagonal) of the uniformly ²H,¹³C,¹⁵N-labeled trimeric 44kDa enzyme chorismate mutase from Bacillus subtilis. The measuring time for the constant time experiment was 96 hours and that of the real time experiment was 36 hours. CryoProbe optimized for ¹³C-detection at 500MHz was used.

Courtesy: Alexander Eletsky, Osvaldo Moreira, Helena Kovacs and Konstantin Pervushin, J. Biomol. NMR 26 (2003) 167-179.A novel strategy for the assignment of side-chain resonances in completely deuterated large proteins using 13C spectroscopy