Characterization of macromolecule resonances in the ¹H NMR spectrum of rat brain

Abstract

The 1H NMR spectrum of the macromolecule fraction of rat brain cytosol was investigated following centrifugation and dialysis to remove low molecular weight metabolites and peptides (< 3500 daltons). At least seven well resolved resonances were detected between 0.9 and 3.0 ppm in the 1H NMR spectrum of rat brain cytosol after dialysis, several of which cannot be observed in vivo due to overlap with N-acetylaspartate, glutamate, glutamine, creatine, and gamma-aminobutyric acid. Several cross-peaks detected in 2D COSY spectra of the cytosolic macromolecule fraction coincided with those measured in a previous study of rat brain tissue in vitro and in situ (K. L. Behar, T. Ogino, Magn. Reson. Med. 17, 285 (1991)). Treatment of the cytosolic macromolecule fraction with a nonspecific protease permitted partial assignments of resonances in the 1H NMR spectrum to specific amino acids. Fractionation of the dialyzed cytosol of rat brain by gel filtration yielded qualitatively similar 1H NMR spectra for elution volumes corresponding to molecular masses from 12.5 kDa to over 100 kDa. The results indicate that many of the background nonmetabolite resonances observed in the 1H NMR spectrum of normal brain tissue arise from cytosolic proteins.

Toward an in Vivo Neurochemical Profile: Quantification of 18 Metabolites in Short-Echo-Time 1H NMR Spectra of the Rat Brain

“…The apparent structure of the spline baseline suggested the presence of biological signals underlying the narrow metabolite peaks, consistent with previous reports of large molecular weight compounds contributing to the spectrum of brain extracts (14) with relatively short T 1 and T 2 compared with acid-extracted metabolites. We therefore further assessed potential macromolecule contributions to the in vivo spectrum and the effect on the quantification of including a measured macromolecule spectrum to the LCModel approach.…”

“…The spectra acquired with TE ϭ 2 ms and TE ϭ 20 ms using this t IR null ( Fig. 3) represent mostly macromolecule signals which have been reported with short T 1 (14). Major resonances were observed at 0.916 ppm (labeled M1, which was used as reference), 1.21 (M2), 1.39 (M3), 1.67 (M4), 2.04 (M5), 2.26 (M6), and 2.99 ppm (M7).…”

1H NMR spectroscopy of rat brain in vivo at 14.1Tesla: Improvements in quantification of the neurochemical profile

“…Spectra measured at short echo-times are further complicated by broad signals ascribed mainly to cytosolic proteins [10]. At high magnetic fields the largely field-independent linewidth of the signals of macromolecules increasingly approaches that of metabolites and an experimental assessment of macromolecular contribution to the proton spectrum may become crucial for accurate metabolite quantification.…”

1H-NMR detectable fatty acyl chain unsaturation in excised leiomyosarcoma correlate with grade and mitotic activity.

“…H-NMR spectroscopy can provide unique and important structural information about plasma membrane composition and function in cells and tissues with the additional advantage of being nondestructive to the system under study (9)(10)(11)(12). Correlation spectroscopy (COSY) 1 experiments, a standard method for establishing proton coupling networks, have been used to detect and identify amino acids, phospholipids, plasma membrane triglycerides and cell surface carbohydrates in cancer cells and tissues (13)(14)(15). From these studies, NMR measurable changes in triglycerides and carbohydrates were found to correlate with cancer cell tumorigenesis and metastatic potential.…”