Carey K. Johnson

Professor

1251 Wescoe Hall Drive Malott Hall Room B039 University of Kansas Lawrence, KS 66045 Phone: (785) 864-4219 Fax: (785) 864-5396 Email: ckjohnson@ku.edu

Physical, biophysical, and bioanalytical chemistry: single-molecule and time-resolved investigations of dynamics and function of biomolecules, fluorescence detection of biomolecules.

The high sensitivity in single-molecule fluorescence spectroscopy is opening new doors to understanding the structure, dynamics, and interactions of biomolecules. Conventional methods measure the average properties of many molecules, often missing important information about the distributions of structures, dynamics, and interactions. By probing single-molecules, the properties of individual members of a distribution can be measured, thus recovering lost information. The applications are profound for biophysical properties (structure and dynamics) and bioanalysis (e.g. detection of protein-protein interactions). The newest frontier, to detect and track the dynamics and interactions of single molecules inside live cells, bridges the fields of chemistry, biology, and physics.

My laboratory is particularly interested in calcium signaling proteins. The protein calmodulin functions as a molecular switch by detecting calcium signals and relaying the signal to dozens of other proteins in the cell. By detecting single molecules we obtain unique information that helps us unravel the mechanisms by which proteins like calmodulin function.  Our single-molecule studies focus on calmodulin at three levels. 

First, we have detected conformational states and dynamics of calmodulin freely diffusing in solution.  Second, we have detected binding of calmodulin to target peptides with single-molecule sensitivity.  Third, we have detected binding of calmodulin to target enzymes such as a calcium pump. In each case, single-molecule methods have revealed new intermediate states and dynamics, providing insight into how these molecules function. New projects are aimed at applying these methods in living cells.

Other research in my laboratory is aimed at detecting domain motions in proteins and peptides. Ultrafast laser pulses and high time-resolution detection are used to detect reorientational dynamics on the time scales of molecular tumbling, intramolecular motions, or fast protein domain motions. We are also using time-resolved fluorescence methods to develop new techniques for ultrasensitive fluorescence detection of substrate binding to DNA or proteins.

Michael W. Allen, Ramona J. Bieber Urbauer, and Carey K. Johnson, Single-Molecule Assays of Calmodulin Target Binding Detected with a Calmodulin Energy-Transfer Construct, Anal. Chem.76, 3630-3637 (2004).

Brian D. Slaughter, Michael W. Allen, Jay R. Unruh, Ramona J. Bieber Urbauer, and Carey K. Johnson, Single-Molecule Resonance Energy Transfer and Fluorescence Correlation Spectroscopy of Calmodulin in Solution, J. Phys. Chem. B108 (G.J. Small Special Issue), 10388-10397 (2004).

Kenneth D. Osborn, Asma Zaidi, Abhijit Mandal, Ramona J. Bieber Urbauer, and Carey K. Johnson, Single-Molecule Dynamics of the Calcium-Dependent Activation of Plasma-Membrane Ca 2+-ATPase by Calmodulin, Biophys. J. 87, 1892-1899 (2004).

Kenneth D. Osborn, Ryan K. Bartlett, Abhijit Mandal, Asma Zaidi, Ramona J. Bieber Urbauer, Nadya Galeva, Todd D. Williams, and Carey K. Johnson, Single Molecule Dynamics Reveal an Altered Conformation for the Autoinhibitory Domain of Plasma-Membrane Ca 2+-ATPase Bound to Oxidized Calmodulin, Biochemistry43, 12937-12944 (2004).

Carey K. Johnson, Kenneth D. Osborn, Michael W. Allen, and Brian D. Slaughter, Single-Molecule Fluorescence Spectroscopy: New Probes of Protein Function and Dynamics, Physiology (Emerging Topics/Tools invited review) 20, 10-14 (2005).

Brian D. Slaughter, Jay R. Unruh, Michael W. Allen, Ramona J. Bieber Urbauer, and Carey K. Johnson, Conformational Substates of Calmodulin Revealed by Single-pair Fluorescence Resonance Energy Transfer: Influence of Solution Conditions and Oxidative Modification, Biochemistry44, 3694-3707 (2005).

Giridharan Gokulrangan, Jay R. Unruh, Douglas F. Holub, Brian Ingram, Carey K. Johnson, and George S. Wilson, DNA Aptamer Based Bioanalysis of IgE by Fluorescence Polarization Anisotropy, Anal. Chem.77, 1963-1970 (2005).

Jay R. Unruh, Giridharan Gokulrangan, G.H. Lushington, Carey K. Johnson, and George S. Wilson, Orientational Dynamics and Dye-DNA Interactions in a DNA Aptamer, Biophys. J.88, 3455-3465 (2005).

Brian D. Slaughter, Ramona J. Bieber-Urbauer, and Carey K. Johnson, Single-Molecule Tracking of Sub-millisecond Domain Motion in Calmodulin, J. Phys. Chem. B109, 12658-12662 (2005).

Brian D. Slaughter, Jay R. Unruh, E. Shane Price, Jason L. Huynh, Ramona J. Bieber-Urbauer, and Carey K. Johnson, Sampling Unfolding Intermediates in Calmodulin by Single-Molecule Spectroscopy, J. Am. Chem. Soc.127, 12107-12114 (2005).

Carey K. Johnson, Brian D. Slaughter, Jay R. Unruh, and E. Shane Price, Fluorescence Probes of Protein Dynamics and Conformations in Freely Diffusing Molecules. Single-Molecule Resonance Energy Transfer and Time-Resolved Fluorescence Methods, in Reviews in Fluorescence, Vol. 3, C. D. Geddes and J. R. Lakowicz, eds., invited book chapter, (Springer, New York, 2006) 239-259.

Carey K. Johnson, Calmodulin, Conformational States, and Calcium Signaling. A Single-Molecule Perspective, Biochemistry invited Current Topics article, ASAP publication (2006).