Applications of PIXE in the life sciences.

During the last decade, particle-induced X-ray emission spectrometry (PIXE) has been accepted by the analytical chemistry community as a standard method. Instead of routine bulk analysis of biomedical samples where several competing analytical techniques are available, the full strength of PIXE could be exploited in special applications where also location of the detected ions is desirable. In this article, two different approaches for this purpose are discussed and illustrated: (1) nuclear microscopy, where micro-PIXE utilizing a proton beam spot of approx 1 micron 2 or less promises unique perspectives to obtain elemental maps at the cellular level, and (2) in situ PIXE analysis of the minute metalloprotein volumes concentrated in thin-layer electrophoretograms.

Determination of hair trace elements in childhood celiac disease and in cystic fibrosis.

Applying proton-induced X-ray emission authors investigated the hair trace element contents in 10 children with acute celiac disease after 3 to 6 and 12 months long gluten-free diet; in 9 children with cystic fibrosis and in a control group (6 children) of the same age. There was no difference in Cu, Fe, Ca, Cl values between the examined groups. The Zn contents of the hair are significantly low in the group with acute celiac disease after a short-term diet and also in the group with cystic fibrosis, the data approach the normal range only after a year's diet. The significant rise of hair potassium contents is well indicated in patients with acute celiac disease and this rise may be due to the destruction of cell cuticles. In case of cystic fibrosis there is no significant rise of hair potassium value.

Location and quantification of metal ions in enzymes combining polyacrylamide gel electrophoresis and particle-induced X-ray emission.

A method is presented to identify and determine the relative amounts of protein-bound metal ions in situ. Proteins or their subunits are separated by SDS-PAGE, the appropriately dried gel sections are directly scanned by a collimated proton beam of 3 MeV energy, and the characteristic X-rays produced are detected. The determination of Fe content of an iron-sulfur protein (HiPiP), as well as the Fe and Ni analysis of the hydrogenase from Thiocapsa reseopersicina, have shown the feasibility of this technique.

Metal composition analysis of hydrogenase from Thiocapsa roseopersicina by proton induced X-ray emission spectroscopy.

Polyacrylamide gel electrophoresis combined with proton induced X-ray emission spectroscopy is suitable to identify and to determine the relative amounts of protein bound metals in situ. An analysis of the hydrogenase from Thiocapsa roseopersicina has shown the feasibility of the technique and provides new insight into the relative amount as well as the intramolecular location of Fe and Ni metal atoms in this enzyme.

Elemental analysis of samples of biological origin relative to their protein content by means of charged particle bombardment.

The particle-induced X-ray emission (PIXE) method and the 14N(d,p)15N nuclear reaction are combined for simultaneous trace element and nitrogen determination. Measurement of nitrogen content often allows the relating of the elemental concentrations determined by PIXE to the protein content of the sample. For the measurements only a small amount of sample material is needed; therefore, it is possible to keep track of the quantity of a certain element in the successive steps of a biomedical separation process. In about 10 min, trace element concentrations in the ppm range can be determined with a statistical accuracy of about 10%.