Metabolism of choline and deuterated choline detected by 1H-14N 2D heteronuclear single-quantum coherence (HSQC) NMR

Motivation: Standard MRS allows the detection of total choline but has insufficient resolution to separate choline from phosphocholine and glycerophosphocholine. Goal(s): To develop 1H-14N 2D HSQC methods to allow separate detection of all 1H and 2H cholines. Approach: 1H detection of choline methylene protons provides high detection sensitivity and chemical shift separation of choline types. 14N provides high sensitivity towards methyl group deuteration. All features can be combined in 2D HSQC through scalar coupling between 1H and 14N. Results: 2D HSQC allows the detection of all six forms of protonated and deuterated choline forms as demonstrated on RG2 cells and rat brain extracts. Impact: A single 1H-14N 2D HSQC scan can quantitatively map all forms of protonated and deuterated choline, phosphocholine and glycerophosphocholine, opening the possibility of comprehensive study of dynamic 2H-choline transport, turnover and metabolism.