Use of 1H NMR-determined diffusion coefficients to characterize lipoprotein fractions in human blood plasma

The H-1 NMR spectra of human blood plasma show, inter alia, prominent resonances from the methyl and methylene groups of the fatty acyl chains from the triglycerides, phospholipids and cholesteryl esters of lipoproteins. Each band shows some degree of peak resolution due to chemical shift differences between the lipoprotein fractions, namely very low-density lipoprotein (VLDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL). In order to assign resonances within the NMR bands to individual lipoproteins, previous studies relied upon the measurement of pure fractions obtained by ultracentrifugation. Here a new approach was used where the lipoprotein peaks in the NMR spectrum were deconvolved mathematically and the area of each sub-peak was monitored using an NMR pulse sequence to yield the diffusion coefficient relating to each sub-peak and hence to each type of lipoprotein. The validity of the deconvolution results was confirmed by comparison of 1H NMR spectra measured at 600 and 800 MHz. The diffusion coefficient is directly related to the hydrodynamic radius of the particle and hence provides an unambiguous assignment. The derived diffusion coefficients of the lipoprotein fractions therefore provide a direct assignment of the NMR bands and also give a measure of lipoprotein particle size, the results being in agreement with those from conventional measurements. Copyright (C) 2002 John Wiley Sons, Ltd.