Development of High Resolution X-ray Microscopy A scanning soft x-ray microscope has been built and put into operation at the National Synchrotron Light Source at Brookhaven National Laboratory. The instrument makes use of the bright, tuneable undulator source at the XlA beamline. It uses zone plates to form a 55 nm beam spot, and is well suited to the study of wet, unstained specimens. New imaging modes will be developed further to map particular chemical states using the resonances present near elemental absorption edges (XANES), and to use the detection of visible light excited in luminescent tags for immunolabelling. The instrument will be modified to accept frozen hydrated specimens. This will minimize specimen damage due to radiolytical etching; such a step is necessary to reach higher resolution in wet biological specimens, and for studies where multiple images of hydrated specimens are required, such as in tomography and chemical mapping. Whereas electron microscopes can view thin cryosections at high resolution, our instrument will be better suited to examining thick (1-10 ,m water layer) whole specimens, without the need for sectioning. The instrumental resolution will be improved to the 20-30 nm level using higher resolution zone plates. With the planned brightness upgrade of the Light Source, the microscope will remain the premier instrument of its type through the proposed grant period. These instrumentation developments will be undertaken to aid research involving the following systems: chromosomes and chromosome folding, malarial erythrocytes, the distribution of protein and DNA in sperms, and spine formation in sea urchin embryo differentiation. These collaborative biological investigations will be continued and expanded, especially by the addition of a postdoc with biological rather than x-ray physics background. The team also welcomes inquiries by investigators interested in using the instrument to solve additional biological problems mat ched to its unique capabilities.
