Complete proton magnetic resonance in whole cells

Abstract

The proton magnetic resonance spectrum of whole cells is a complex, composite spectrum with a myriad of dipolar broadened (“broadline”) and non-dipolar-broadened (“high-resolution”) contributions. Methods of separating and characterizing the different types of components are described and developed using a phospholipid bilayer model membrane and the R13762 rat mammary adenocarcinoma cell line. It was found that 35 ± 2% of the protons in the 1H NMR spectrum of the R13762 cells are associated with the high-resolution spectrum. Of the remaining 65%, approximately 40% can be assigned to the characteristic fluid membrane dipolar-broadened, super-Lorentzian lines. A further 20% can be assigned to dipolar-broadened lines from membrane proteins and the last 5% to non-dipolar-broadened lines of width several hundred hertz, from rigid parts of cytoplasmic proteins. Quantitative analysis of the narrow methylene peak, which has been used to characterize the metastatic properties of R13762 cells, shows that it contains 7.3 ± 1.6% of all the protons in the cell. The introduction of spectroscopic selection methods such as the CPMG pulse sequence and the Jeener-Broekaert echo sequence has made it possible to simultaneously analyze the broadline and high-resolution characteristics of an intact viable cell.