Characterization of leukemic and normal white blood cells by Curie-point pyrolysis—mass spectrometry: II. Biochemical interpretation of some of the differences in the pyrolysis patterns

Abstract

Differences found in nucleotide and lipid related mass peaks in the Curie-point pyrolysis—mass spectra of leukemic and normal white blood cells were further investigated using several different pyrolysis-mass spectrometric (Py—MS) modes. Time-resolved pyrolysis profiles of mass peaks 114 and 116 in the white blood cell spectra were found to match the time profiles of the corresponding peaks in the pyrolysis—mass spectra of RNA and DNA respectively. Visual comparison of spectra from standard samples of RNA, DNA, lecithin and cholesterol with the white blood cell spectra further defined the mass peaks contributed by these compounds. Direct probe MS of low-volatile pyrolysis condensates from white blood cells and standard compounds demonstrated the presence of characteristic mass peaks representing nucleic acid components, e.g. bases and nucleoside fragments, as well as of phospholipids and cholesterol. The strong changes observed in the relative abundance of these components between leukemic and normal white blood cells paralleled changes seen in the Curie-point pyrolysis—mass spectra. Finally, the use of collision induced dissociation. MS (MS/MS) enabled confirmation of the identity of individual compounds, e.g. thymine, in white blood cells pyrolyzates. This finding appears to indicate the possibility of direct measurement of DNA content of whole cells by Py-MS/MS techniques.