Chu says that the ability to move the stage of a microscope small distances and calculate the geometric center (centroid) of the image makes it possible to not only measure the photo-response non-uniformity between pixels, but also to measure the non-uniformity within each individual pixel.
"Knowing this non-uniformity then allows us to make corrections between the apparent position and the real position of the image's centroid," says Chu. "Since this non-uniform response is built into the CCD array and does not change from day to day, our active feedback system allows us to image repeatedly at the same position of the CCD array."
Pertsinidis is continuing to work with Chu and others in the group on the further development and application of this super-resolution technique. In addition to the human RNA polymerase II system, he and the group are using it to determine the structure of the Epithelial cadherin molecules that are responsible for the cell-to-cell adhesion that holds tissue and other biological materials together. Pertsinidis, Zhang, and another postdoc in Chu's research group, Sang Ryul Park, are also using this technique to create 3D measurements of the molecular organization inside brain cells.
"The idea is to determine the structure and dynamics of the vesicle fusion process that releases the neurotransmitter molecules used by neurons to communicate with one another," Pertsinidis says. "Right now we are getting in situ measurements with a resolution of about 10 nanometers, but we think we can push this resolution to within two nanometers."
In a collaboration with Joe Gray, Berkeley Lab's Associate Director for Life Sciences and a leading cancer researcher, postdocs in Chu's research group are also using the super-resolution technique to stud
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory