David DeRosier
Professor Emeritus of Biology
Research Description
The generation and interpretation of cryogenic electron microscope tomograms (cryo-ET) has become the cutting edge of structural cell biology. The three dimensional (3D) cryo-ET images of cells at 2 to 5 nm resolution allow us to see molecules in situ. Using clever averaging techniques, we can extend the resolution of individual molecules to better than 1 nm.
To generate a tomogram by cryo-ET, we collect a series of tilted images of a sample by tilting it from + 60 degrees to -60 degrees in 2 degree steps. Tilts above 60 degrees or below -60 degrees are not possible because of the physical size of the device holding the sample. As a result, tomograms are missing views in these forbidden tilt directions. The effect of the missing views is to make the resolution in the 3D images worse along the direction of the electron beam (the z direction).
Over the years, there have been many attempts to compensate for the missing views in order to improve the resolution in the z-direction. Success has been limited. When pushing the resolution in the z-direction, we find that the errors in the set of tilted images are amplified in the 3D image we generate. I am analyzing the extent to which we can improve the 3D images without amplifying the errors. Key to this effort may be inserting additional knowledge (such as the limited thickness of the sample) into the generation of the 3D images.
I carry out these studies in San Diego, CA where I now reside.
Selected Publications
Wolanin PM, Baker MD, Francis NR, Thomas DR, DeRosier DJ, Stock JB. (2006) Self-assembly of receptor/signaling complexes in bacterial chemotaxis. Proc Natl Acad Sci U S A 103, 14313-8.
Mercogliano, CP and DeRosier, DJ. (2006). Gold nanocluster formation using metallothionein: mass spectrometry and electron microscopy. J. Mol. Biol. 355, 211-23.
Wolf, M. DeRosier, D. J. and Grigorieff, N. (2006) Ewald sphere correction for single-particle electron microscopy. Ultramicroscopy 106, pp 376-82.
Tilney, LG and DeRosier, DJ (2006) How to make a curved Drosophila bristle using straight actin bundles. Proc Natl Acad Sci USA 102, 18785-92.
Thomas DR, Francis NR, Xu C, DeRosier DJ. (2006) The three-dimensional structure of the flagellar rotor from a clockwise-locked mutant of Salmonella enterica serovar Typhimurium. J. Bact. 188, 7039-48.
DeRosier, D. (2006) Bacterial flagellum: visualizing the complete machine in situ. Curr. Biol. 16, R928-30.
Mercogliano, C. and DeRosier, D.J. (2007) Concatenated Metallothionein as a Clonable Gold Label for Electron Microscopy. J Struct Biol. 2007 Oct;160(1):70-82.
Wolfberg AJ, DeRosier, D, Roberts T, Syed Z., Acker D, and du Plessis A. (2008) A comparison of subjective and mathematical estimations of fetal heart rate variability. Journal of Maternal-Fetal and Neonatal Medicine. 21, 101-104. [abstract]
Lattman, E and DeRosier, D. (2008) Why Phase Errors Affect the Electron Density Function More than Amplitude Errors. Acta Crystallographica A. 64(Pt 2):341-4.
Hampton, CM, Liu, J, Taylor, DW, Ouyang, G, DeRosier, DJ and Taylor, KA. (2008) The 3D Structure of Villin as a Unique F-actin Cross-Linker. Structure. 16(12):1882-91.
DeRosier, DJ. (2010) 3D Reconstruction from Electron Micrographs: a Personal Account of its Development. Methods Enzymol. 481:1-24.