2D
two-dimensional

3D
three-dimensional

Double Labelled
Shorthand for protein which has been uniformly ¹⁵N- and ¹³C-labelled.

Double Resonance
NMR spectroscopy using two NMR-active nuclei. For proteins this usually means ¹H hydrogen and ¹⁵N nitrogen. To do this the protein must be ¹⁵N-labelled.

COSY
Correlation Spectroscopy

HSQC
Heteronuclear Single-Quantum Correlation

MAS
Magic Angle Spinning. Solid-state NMR samples are often rotated/spun at high speeds (8-25 kHz or more) around the so-called magic angle (54.7 degrees) relative to the static magnetic field of the NMR spectrometer. This eliminates strong dipolar couplings and sharpens the resonance lines. The alternative is to use samples in which the molecules are all aligned the same way relative to the static magnetic field (which can be done relatively straight forwardly for membrane proteins).

NMR
Nuclear Magnetic Resonance (spectroscopy)

NOE
Nuclear Overhauser Effect (or Enhancement)

NOESY
Nuclear Overhauser Effect (or Enhancement) Spectroscopy, usually refers to an NMR experiment which incorporates an element using the NOE

RDC
Residual Dipolar Coupling

Spin System
All the spins belonging to the same residue

Triple Labelled
Shorthand for protein which has been uniformly ¹⁵N-, ¹³C- and ²H-labelled.

Triple Resonance
NMR spectroscopy using three NMR-active nuclei. For proteins this usually means ¹H hydrogen, ¹⁵N nitrogen and ¹³C carbon. To do this the protein must be ¹⁵N- and ¹³C-labelled. Note that for triple resonance spectroscopy you need double labelled protein!