- B.A., 1973, Tabor College
- Ph.D., 1981, Iowa State University
- National Institutes of Health Postdoctoral Fellow, University of Pennsylvania, 1982-84
Areas of Specialization
Biophysics, spectroscopy, bioanalytical chemistry, protein interactions and dynamics, single-molecule spectroscopy
Single-molecule and time-resolved investigations of dynamics and function of biomolecules; multiphoton imaging; fluorescence detection of biomolecules.
The high sensitivity in single-molecule fluorescence spectroscopy opens new avenues to understanding the structure, dynamics, and interactions of biomolecules. Experiments on single molecules can recover information about conformations and dynamics not available by conventional spectroscopies. 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.
One project in my lab focuses particularly on calcium signaling proteins. The protein calmodulin functions as a molecular switch, responding to 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. We detect conformational states and dynamics of calmodulin freely diffusing in solution, and we detect binding of calmodulin to target enzymes such as nitric oxide synthase. 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 developing new methods of microscopy based on multiphoton imaging methods such as two-photon excitation and coherent Raman spectroscopy. We have built new fiber-laser excitation (FLEx) sources for multiphoton microscopy based on fiber-lasers and photonic-crystal fibers. We also use time-resolved fluorescence methods to detect conformations and dynamics of peptides and proteins.
Carey K. Johnson, Calmodulin, Conformational States, and Calcium Signaling. A Single-Molecule Perspective, Biochemistry 45, 14233-14246 (2006) invited Current Topics article.
Carey K. Johnson, “Fluorescence Techniques for Proteins,” in Wiley Encyclopedia of Chemical Biology, ed. T.P. Begley, invited article (Wiley, 2008).
Jay R. Unruh, Krzysztof Kuczera, and Carey K. Johnson, Conformational Heterogeneity of a Leucine Enkephalin Analog in Aqueous Solution and SDS Micelles: Comparison of Time-Resolved FRET and Molecular Dynamics Simulations, J. Phys. Chem. B 113, 14381-14392 (2009).
Carey K. Johnson, Mangala R. Liyanage, Kenneth D. Osborn, and Asma Zaidi, Single-protein dynamics and the regulation of the plasma-membrane Ca2+ pump, in Cell Signaling Reactions: Single-Molecular Kinetic Analysis, Y. Sako and M. Ueda, eds. (Springer, Dordrecht, 2011) pp 121 – 151 (invited contribution).
E. Shane Price, Marek Aleksiejew, and Carey K. Johnson, FRET-FCS Detection of Intra-lobe Dynamics in Calmodulin, J. Phys. Chem. B 115, 9320-9326 (2011).
Mihailo Backović, E. Shane Price, Carey K. Johnson, and John P. Ralston, A Distribution-Based Method to Resolve Single-Molecule FRET Observations, J. Chem. Phys. 134, 145101-1 – 145101-15 (2011).
Peter Adany, David C. Arnett, Carey K. Johnson, and Rongqing Hui, Tunable Excitation Source for Coherent Raman Spectroscopy Based on a Single Fiber Laser, Appl. Phys. Lett. 99, 181112-1 – 1881112-3 (2011).
Matthew S. DeVore, Stephen F. Gull, and Carey K. Johnson, Classic Maximum Entropy Recovery of the Average Joint Distribution of Apparent FRET Efficiency and Fluorescence Photons for Single-Molecule Burst Measurements, J. Phys. Chem. B 116, 4006−4015 (2012).
Matthew S. DeVore, Stephen F. Gull, and Carey K. Johnson, MultiNest and Classic Maximum Entropy Characterization of Calmodulin Single-Molecule FRET States, Dye-Interactions, and CaMKII Peptide Binding, Chem. Phys. 422, 238-245 (2013). (Special Issue in honor of Robin Hochstrasser.)
Jue Su, Ruxin Xie, Carey K. Johnson, and Rongqing Hui, Single Fiber Laser Based Wavelength Tunable Excitation for CRS Spectroscopy, J. Opt. Soc. Am. B 30, 1671-1682 (2013).
Gouri S. Jas, Wendy A. Hegefeld, C. Russell Middaugh, Carey K. Johnson, and Krzysztof Kuczera, Detailed Microscopic Unfolding Pathways of an α-Helix and a β-Hairpin: Direct Observation and Molecular Dynamics, J. Phys. Chem. B 118, 7233-7246. (2014).
David C. Arnett, Anthony Persechini, Quang-Kim Tran, D.J. Black, and Carey K. Johnson, Fluorescence Quenching Studies of Structure and Dynamics in Calmodulin-eNOS Complexes, FEBS Lett. 589, 1173-1178 (2015).