 Professor, Born 1952
B.S. 1974, Michigan State University
Ph.D. 1979, University of California - Berkeley
Room: 4211a
Phone: 608-262-0266
Email: weisshaa@chem.wisc.edu
Position: Professor
T. Wang, C. Ingram, and J.C. Weisshaar, Model Lipid Bilayer with Facile Diffusion of Lipids and Integral Membrane Proteins, submitted to Langmuir, January, 2010. M.C. Konopka, K.A. Sochacki B.P. Bratton, I.A. Shkel, M.T. Record, and J.C. Weisshaar, Cytoplasmic Protein Mobility in Osmotically Stressed Escherichia coli, J. Bacteriology 191, 231-237 (2009). T. Wang, E. Smith, E.R. Chapman, and J.C. Weisshaar, Lipid Mixing and Content Release in Single-Vesicle, SNARE-driven Fusion Assay with 1–5 ms Resolution, Biophys. J. 96, 4122-31 (2009). T. Liu, E.R. Chapman, and J.C. Weisshaar, Productive Hemifusion Intermediates in Fast Vesicle Fusion Driven by Neuronal SNAREs, Biophys. J. 94, 1303-1314 (2008). M. Konopka, J.C. Weisshaar, and M. T. Record, Methods of Changing Biopolymer Volume Fraction and Cytoplasmic Solute Concentrations for In Vivo Biophysical Studies, Methods in Enzymology, 428, 487-504 (2007). A. Yethiraj and J.C. Weisshaar, Why are lipid rafts not observed in vivo?, Biophys. J., 93, 3113-9 (2007); chosen as "New and Noteworthy". M. Konopka, I. Shkel, S. Cayley, M. T. Record, and J.C. Weisshaar, Crowding and Confinement Effects on Protein Diffusion In Vivo, J. Bacteriology, 188, 6115-6123 (2006). T. Liu, W. Tucker, E.R. Chapman, and J.C. Weisshaar, Fast, SNARE-dependent vesicle fusion in vitro, Biophys. J. 89, 2458-72 (2005); chosen as "New and Noteworthy". M. Konopka and J.C. Weisshaar, Heterogeneous motion of secretory vesicles in the actin cortex of live cells: 3D tracking to 5-nm accuracy, J. Phys. Chem., 108, 9814-9826 (2004) M. Konopka and J.C. Weisshaar, Heterogeneous motion of secretory vesicles in the actin cortex of live cells: 3D tracking to 5-nm accuracy, J. Phys. Chem., 108, 9814-9826 (2004)
| Research Description
Quantitative fluorescence microscopy in vivo and in vitro
Principal Investigator: James C. Weisshaar
(608)262-0266, weisshaar@chem.wisc.edu
Graduate Students: Colin Ingram, Ben Bratton, Kem Sochacki, Izzy Smith, Renee Dalrymple, Somenath Bakshi, Ken Barns
Research Interests: Fluorescence microscopy of biological systems. Design and characterization of a fast, SNARE-driven in vitro single-vesicle
fusion assay. Tracking of single proteins in live cells with 10 nm spatial resolution. Architecture of vesicle fusion machinery. Spatial biology of the transcription and translation systems in bacterial cells. Direct observation of the attack of antimicrobial agents on bacterial cell membranes.
We participate in the revolution in the fluorescence microscopy of biological systems. It is increasingly possible to observe the motion of proteins and DNA with single-molecule precision in live cells and in contexts approximating natural conditions. The result is an unprecedented, high resolution view of biological structure and activity. Areas of current focus include:
(1) The structure and function of the proteins responsible for Ca2+-triggered synaptic vesicle fusion, the elementary step in neuron-neuron communication. The new PALM methodology enables us to track single copies of Syntaxin in live PC-12 cells with ~20-nm spatial resolution and 20-ms time resolution, for example.
(2) The diffusive motion and spatial distribution of GFP-labeled proteins in live E. coli cells. Species of interest include RNA polymerase, architectural proteins, and 30S ribosomal subunits. FRAP (Fig. 2) and single-molecule tracking (Fig. 3) enable us to directly observe the motion and spatial distributions of key elements of the transcription/translation machinery.
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| Fig. 2. RNAP image in live E. coli (inset) and time-dependent recovery of the fluorescence asymmetry after one lobe is photobleached. Blue line is pre-bleach value. |
The ribosomes, the nucleoid, and RNAP all exhibit a remarkable level of time-varying spatial organization. Simple “toy models” developed with the Yethiraj group may help understand the organization based on excluded volume and entropic effects alone (Fig. 4).
(3) The time-resolved attack of antimicrobial agents on bacterial cell membranes. Examples include LL-37 (Fig. 5), a human antimicrobial peptide, and synthetic random copolymers designed by the Gellman group. Simultaneous two-color imaging of the antimicrobial and cytoplasmic or periplasmic GFP yields unprecedented insight into the mechanism of attack.
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| Periplasmic GFP and rhodamine-LL-37 images vs time. Axial intensity plots at right. The attack comes as three waves, the second of which spreads outward from mid-cell and lyses the outer membrane, releasing GFP. |
Last Updated: February 10, 2010
American Association for the Advancement of Science Fellow, 2009 Fellow, American Physical Society, 2001 Wisconsin Alumni Research Foundation Kellett Mid-Career Research Award, 1998-2003 Vilas Associate Award, UW-Chemistry, 1997-1998 Evan P. Helfaer Professor of Chemistry, 1996-2001 Upjohn Award for Teaching Excellence in Chemistry, 1995 Hilldale Undergraduate Research Awards, 1993, 1995, 1999, 2001, 2002 (with undergraduates K. Haug , W.-K. Woo, V. Chen, T. Huppert, L. Klein) Romnes Faculty Research Fellowship, UW-Madison, 1991-1996 Dreyfus Research Grant for Newly Appointed Faculty in Chemistry, 1981 - ACS Nobel Laureate Signature Award, 1980
- NSF Predoctoral Fellow, 1974-77
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