| Popis: |
Soft x-ray microscopy is now routinely capable of imaging biological specimens with resolutions that are five times better than the best visible light microscopes (⩽50 nm). However, for biological labeling the only options developed for x-ray microscopy have been silver enhanced gold probes that can be used with both scanning and wide field CCD microscopes, such as XM-1 at the Advanced Light Source (ALS), and luminescent lanthanide probes that necessitate a scanning microscope (SXM). To add to the arsenal of useful x-ray biological probes, we have begun the development of labels that rely on the L-edge absorption lines of vanadium. Vanadium is especially attractive as a biological contrast reagent because it has two strong absorption lines at energies that range from ∼512 to 525 eV just below the oxygen K-edge, which makes it an ideal material for imaging in the water window. In this report, we present our initial findings on the application of vanadium for biological labeling. Fixed NIH 3T3 cells grown on silicon nitride windows were incubated with vanadyl sulfate and in some cases basified with triethylamine. After vanadium treatment of the cells, they were thoroughly rinsed and then imaged using XM-1 above and below the vanadium 516 eV resonance. Vanadium staining was clearly visible around and in the cells. These findings suggest that bioconjugated vanadium clusters could provide sufficient x-ray contrast to be used as biological probes. |
