| Research Associate, University of Pittsburgh | 07/70 - 05/71 |
| Research Chemist, VA Medical Center, Pittsburgh, PA | 05/71 - 04/86 |
| Assistant Professor (Adjunct), University of Pittsburgh | 10/74 - 12/78 |
| Assistant Chief, Biocrystallography Laboratory, VA Medical Center, Pittsburgh, PA | 01/76 - 04/86 |
| Associate Professor (Adjunct), University of Pittsburgh | 01/79 - 05/85 |
| Professor (Adjunct), University of Pittsburgh | 06/85 - 04/86 |
| Professor, Department of Crystallography and Department of Biological Sciences, University of Pittsburgh | 05/86 - 04/95 |
| Professor (Adjunct), Institute of Molecular Biology, Academia Sinica, Taiwan, R.O.C. | 04/90 - present |
| Professor (Adjunct), University of Pittsburgh | 05/95 - 05/00 |
| Professor of Biochemistry and Molecular Biology, University of Georgia | 05/95 - present |
| Eminent Scholar in Structural Biology (X-ray Crystallography), Georgia Research Alliance and University of Georgia | 05/95 - present |
| Director, Southeast Regional Collaborative Access Team for Synchrotron beam lines at APS | 10/97- present |
| Director, Southeast Collaboratory for Structural Genomics | 09/00 - present |
| Professor (Visiting), Tainjin Medical University | 11/05 - present |
| Professor (Adjunct), Institute of Biophysics, Chinese Academy of Sciences | 11/05 - present |
| Director (Joint), Joint Center for Structural Genomics and Proteomics, Institute of Biophysics, CAS | 11/05 - present |
