Baker, Timothy
Macromolecular, cryoelectron microscopy and three-dimensional, image-reconstruction techniques.

Contact Information
Professor Emeritus

Office: Natural Sciences Bldg 4105
Phone: 858-534-5845
Group: View group members
1976 Ph.D., University of California, Los Angeles
1974 C.Phil., University of California, Los Angeles
1971 B.S., Duke University
Awards and Academic Honors
Fellow, Microscopy Society of America
Distinguished Biological Scientist, Microscopy Society of America
Session Chair, Symposium on Electron Microscopy in NanoMedicine, UCLA
Editorial Board, Journal of Structural Biology
Session Chair, Gordon Conference on 3D Electron Microscopy of Mcaromolecules, New London, NH
NIH NIGMS Method to Extend Research in Time (MERIT) award
Appointed to the Faculty, UCSD
Herbert Newby McCoy Award for Scientific Achievement
Charles A. King Trust Postdoctoral Fellow, Rosenstiel Research Center, Brandeis University; Structural Biology
NIH Postdoctoral Fellow ; Rosenstiel Research Center, Brandeis University; Structural Biology
Jane Coffin Childs Post-doctoral Fellow; MRC Lab of Molecular Biology, Cambridge, UK; Structural Biology
Research Interests
Viruses are one of natures smallest (nano), most efficient, machines, whose primary function is to infect and replicate in host cells. The predominant thrust of our research over the past 25 years has been to image and determine the three-dimensional (3D) structures of viruses to gain insights about the mechanisms they use to interact with their hosts so they can replicate and assemble a new set of mature, infectious particles. To accomplish this, we use cryo-electron microscopy (CryoEM) and 3D image-reconstruction methods to study viruses and various kinds of virus-complexes (e.g. virus-antibody or virus-receptor) and virus-like particles at sub-nanometer (< 10-Å) resolutions. At this level of resolution, we can discern and distinguish viral components (protein, nucleic acid, lipid, carbohydrate) and secondary structural details such as a-helices and b-sheets in proteins.

CryoEM is a powerful tool because it permits the structures of biological samples to be preserved in a near native state. Samples are flash-frozen (vitrified) in liquid ethane in a sub-millisecond time frame, which prevents ice crystal formation that would damage the specimen. This technique uses no chemical fixatives or stains and thereby helps preserve the hydrated structure of the virus (or any macromolecular complex). Specimens are then loaded into one of two, computer-controlled, transmission electron microscopes housed in Bonner Hall, both of which are able to maintain specimens at liquid nitrogen or lower temperature. These microscopes are used to collect upwards of tens of thousands or more virus images that are needed to obtain high-resolution 3D reconstructions. Such large numbers are required because each individual virus image is extremely noisy owing to radiation-induced damage to the sample caused by the high voltage electron beam and because the contrast in unstained samples is extremely low.

In house, computer reconstruction techniques are continuously being developed and tested to more reliably and efficiently extract usable information from the noisy image data. We have developed a processing pipeline, called Auto3DEM, which automates nearly all of the tedious steps in the 3D reconstruction process. In favorable cases, we are able to obtain reconstructions at sub-nanometer resolution in a day or less after the images are recorded. In addition, we are developing tools designed to provide real time, 3D reconstruction feedback (i.e. in a few minutes or less) to the microscopist to further improve success of data collection.

Viral pathogens from many different families are currently under investigation. These infect a wide range of hosts and include: human parvoviruses (bocavirus and several serotypes of adeno-associated viruses both as native virions and complexed with neutralizing antibodies and receptor molecules); human papilloma viruses that cause cancer (HPV-16) or genital warts (HPV -6 and HPV-11) or are listed as high risk (HPV-52); four distinct totiviruses (the invertebrate IMNV, the fungal HvV190S, and the protozoan TVV1 and GLV); the alphavirus group of small, enveloped, ssRNA viruses (e.g. Sindbis virus) that are human and insect pathogens, some of which are listed as possible agents of bio-terrorism; two large, dsDNA viruses (the insect CIV and frog FV3); three fungal partitiviruses (PsV-S, PsV-F, FpV-01); four bacteriophages (P22, Sf6, CUS-3, and f29); and an insect tetravirus (NwV).

Primary Research Area
Interdisciplinary interests
Macromolecular Structure

Outreach Activities
I enthusiastically support efforts to promote diversity at all levels within the University, including attracting undergraduate, graduate student, postdoc, research and administrative staff, and faculty minority candidates. I frequently participate in these efforts, for example, while serving on ad hoc committees for faculty hires, when hiring staff and postdoc candidates, when interviewing prospective graduate students, meeting with students at conferences and during seminar trips, and so forth.

Selected Publications