Biomedical subjects

W P Skoczylas

Publications and source records attributed to W P Skoczylas.

4 recordsLinked to original sources

PubMed1991

Design and performance of a high-resolution photoelectron microscope.

The design of a high-resolution photoelectron microscope (photoelectron emission microscope) is described. It is an oil-free ultrahigh-vacuum instrument utilizing electrostatic electron optics. New designs are presented for a specimen translator, cathode stage, aperture stop control, electrostatic hexapole stigmator, beam shutter, and camera system. These components could also be used in a low-energy electron microscope (LEEM). The theoretical resolution of this instrument is 5 nm for UV illumination near the photoemission threshold. The photoelectron microscope is now in operation at the University of Oregon, and it is achieving results within a factor of two of this design limit.

Computer Terminals↗

PubMed1991

A computer-aided control, design and image-processing system for electron microscopes.

A computer-control system for electron microscopes is described. The aim is to reduce a complex series of vacuum-system controls to a menu-driven program that simplifies the operation of the microscope. The system also incorporates image processing, notebook, computer-aided design, and communication functions. It is designed around a commercially available computer workstation. This system has been implemented on an institute-built photoelectron microscope of ultrahigh-vacuum design.

Computer Graphics↗

PubMed1990

On the possibility of obtaining a physical map of genomes by photoelectron imaging.

Photoelectron imaging provides the possibility of a new method of mapping chromosomes. The basic concept is to cause DNA to emit electrons under the action of UV light. The criteria which must be met to map genomes by photoelectron imaging are set forth and discussed. Forming an image of the DNA by accelerating and focusing the electrons is a necessary but not sufficient condition for genome mapping. Equally important is to identify wavelengths of UV light which will cause selective emission from the base pairs, adenine-thymine and guanine-cytosine. The resulting image would then contain a modulation in the image brightness along the DNA duplex. By examining the photoelectron current from uniform films of homopolymers, a wavelength region is identified where marked differences in emission from base pairs is observed. At 160 nm, for example, the relative electron emission from a film of poly(dGdC) is approximately 5 times greater than for an equivalent film of poly(dAdT). Using the experimental data and known sequences, photoelectron gene maps are calculated for the bacteriophage lambda and for a short interspersed repetitive DNA sequence (an Alu repeat) of the human genome. The results suggest that a 5-nm physical map of chromosomes generated by photoelectron imaging would be informative and useful in mapping human and other large genomes.

Bacteriophage lambda↗

PubMed1989

Biological photocathodes.

Biological surfaces emit electrons when subjected to UV light. This emission is increased greatly after exposure to cesium vapor. Increases from 2 to 3 orders of magnitude are observed, depending on the biochemicals present. Heme and chlorophyll exhibit unusually high photoemission currents, which are increased further after cesiation. Photoemission from proteins and lipids is much less but also is increased by exposure to cesium. The formation of photocathodes with cesium greatly increases the practical magnifications attainable in photoelectron microscopy of organic and biological specimens. Photoelectron micrographs taken at magnifications greater than or equal to X 100,000 of chlorophyll-rich thylakoid membranes and of colloidal gold-labeled cytoskeleton preparations of cultured epithelial cells demonstrate the improvement in magnification. The selectivity and stability of the photocathodes suggest the possibility of detecting chromophore binding proteins in membranes and the design of photoelectron labels for tagging specific sites on biological surfaces.

Animals↗