Speciation of trace elements in proteins in human and bovine serum by size exclusion chromatography and inductively coupled plasma-mass spectrometry with a magnetic sector mass spectrometer
Wang, J.; Houk, R.S.; Dreessen, D.; Wiederin, D.R.
Journal of Biological Inorganic Chemistry Jbic a Publication of the Society of Biological Inorganic Chemistry 4(5): 546-553
Proteins are separated by size exclusion chromatography while atomic ions from the inorganic elements are detected on-line by inductively coupled plasma-mass spectrometry. A double focusing mass analyzer provides very high sensitivity, low background, and sufficient spectral resolution to separate the atomic ions of interest from most polyatomic ions at the same nominal m/z value. The chromatograms show the distribution of the elements of interest between protein-bound and free fractions and provide the approximate molecular weights of those protein fractions that contain the elements monitored. The distribution of various elements, including V, Mo, Fe, Co, Mn, and lanthanides, in human or bovine serum samples are shown. Alkali metals and Tl are present primarily as free metal ions and are not bound to proteins. Inorganic elements spiked into the serum samples can be followed into various proteins. EDTA does not remove Fe, Pb, Sn, or Th from the proteins but does extract Mn from some proteins. Procedures for determining the effects of breaking disulfide linkages on the metal binding characteristics of proteins are also described.