Analysis of macromolecule resonances in ¹H NMR spectra of human brain

TLDR

Macromolecule resonances that overlap with metabolite signals in 1H NMR spectra were studied in temporal lobe biopsies from epilepsy patients and in localized spectra from healthy volunteers. The authors prepared brain tissue spectra, compared them with cytosol and dialyzed cytosol, and used a J‑editing method based on spectral parameters and 2D experiments to assign specific macromolecule resonances, exploiting the large T1 differences to acquire metabolite‑nulled macromolecule spectra. J‑editing revealed two prominent macromolecule resonances (0.93–2.05 ppm and 1.6–3.00 ppm) in vivo, and the metabolite‑nulled spectra matched those of isolated macromolecules in vitro.

Abstract

Abstract Macromolecule resonances underlying metabolites in 1 H NMR spectra were investigated in temporal lobe biopsy tissue from epilepsy patients and from localized 1 H spectra of the brains of healthy volunteers. The 1 H NMR spectrum of brain tissue was cornpared with that of cytosol and dialyzed cytosol after removal of low molecular weight molecules (4500 daltons) at 8.4 and 2.1 Tesla. The assignment of specific resonances to macromolecules in 2.1 Tesla, short‐ TE , localized human brain 1 H NMR spectra in vivo was made on the basis of a J‐editing method using the spectral parameters (δ, J ) and connectivities determined from 2D experiments in vitro . Two prominent corinectivities associated with macromolecules in vitro (0.93–2.05 δ and 1.6–3.00 δ) were also detected in vivo by the J ‐editing method. Advantage was taken of the large difference in measured T 1 relaxation times between macromolecule and metabolite resonances in the brain spectrum to acquire ‘metabolite‐nulled’ macromolecule spectra. These spectra appear identical to the spectra of macromolecules isolated in vitro .