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Patrik R. Callis
Physical Chemistry, Quantum Chemistry, Biophysical Chemistry
Contact
Information:MSU Dept. of Chemistry and Biochemistry
108 Gaines Hall
Bozeman, MT 59717
phone: (406) 994-5414
E-mail: pcallis@montana.edu
B.S. Oregon State University, 1960; Ph.D., University of Washington, 1965; Postdoctoral, Cal Tech, 1966-68.
Awards
Wiley Award for Meritorious Research, 1990; Cox Award for Teaching and Scholarship, 1992; Phi Kappa Phi Anna Krueger Fridley Award for Distinguished Teaching, 1994.
We are currently studying the internal structure and dynamics of
proteins through a combination of molecular modeling, quantum mechanics, and ultraviolet spectroscopy. We are primarily exploiting the amino acid tryptophan, whose spectra are sensitive to the internal electric field caused by the surrounding protein scaffolding and solvent. We have already a good quantum mechanical understanding of the tryptophan excited states, one that strongly suggests that the wavelength of the fluorescence emitted from the excited state after excitation with UV light depends almost entirely on the magnitude and direction of the electric field caused by charges and dipoles of the protein and solvent. Current focus is on the more challenging problem of understanding the basis of the 30-fold variation in fluorescence quantum yield found for tryptophans in different protein environments. By combining quantum mechanics and molecular dynamics simulations to generate parameters for electron transfer rate theory, we have found a promising correlation between quantum yield and the computed energy gap between the emitting state and a higher lying charge transfer excited state. The significance of this work lies in the fact that hundreds of experiments are published every year exploiting the changes in tryptophan fluorescence in proteins for a variety of studies, including protein folding pathways and dynamics, enzyme action, and molecular recognition. It is essential that this probe be understood at a fundamental level, because the ultimate detailed pictures of proteins cannot be established from conventional structure methods alone. In addition, if the electrostatic model we have proposed proves correct, tryptophan fluorescence wavelengths will provide excellent tests for the important task of accurately predicting electrostatic fields and potentials in proteins.
Presentation
Understanding the Variable Quenching of Tryptophan Fluorescence in Proteins: Modulation of Electron Transfer Rates by Electrostatics
Selected Publications
Quantitative prediction of fluorescence quenching rates
Web Release Date: 16-Aug-2007; (Letter) DOI: 10.1021/jp0744883
"Ab Initio Prediction of Tryptophan Fluorescence Quenching by Protein Electric Field Enabled Electron Transfer", Patrik R. Callis, Alexander Petrenko, Pedro L. Muino, and Jose R. Tusell. J. Phys. Chem. B (Letter); 2007;111(35) 10335-10339. DOI: 10.1021/jp0
"The Emitting State of Tryptophan in Proteins With Extremely Blue Fluorescence", Jaap Broos*, Karina Tveen-Jensen, Ellen de Waal, Ben H. Hesp, J. Baz Jackson*, Gerard W. Canters, and Patrik R. Callis,Angew. Chem. Int. Ed. (2007), 46, 5137
"Mechanism of the Highly Efficient Quenching of Tryptophan Fluorescence in Human gammaD-Crystallin", Jiejin Chen, Shannon Flaugh, Patrik R. Callis*, and Jonathan King*, Biochemistry (2006), 45, 11552-11563.
"Dependence of Tryptophan Emission Wavelength on Conformation in Cyclic Hexapeptides", Chia-Pin Pan, Patrik R. Callis,*, and Mary D. Barkley*, 5139 J. Phys. Chem. B (2006), 110, 7009-7016.
"Short Range Photoinduced Electron Transfer in Proteins: QM-MM Simulations of Tryptophan and Flavin Fluorescence Quenching in Proteins", Patrik R. Callis and Tiqing Liu, Chem. Phys. (2006), 326, 230-239.
"Ultrafast Fluorescence Dynamics of Tryptophan in the Proteins Monellin and IIAGlc", Jianhua Xu, Dmitri Toptygin, Karen J. Graver, Rebecca A. Albertini, Regina S. Savtchenko, Norman D. Meadow, Saul Roseman, Patrik R. Callis, Ludwig Brand, and Jay R. Knutson*, J. Am. Chem. Soc. (2006), 128, 1214-1221.
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"Ionization Potentials of Fluoroindoles and the Origin of Non-Exponential Tryptophan Fluorescence Decay in Proteins", Tiqing Liu, Patrik R. Callis, Ben H. Hesp, Mattijs de Groot, Wybren Jan Buma, and Jaap Broos, J. Am. Chem. Soc 127, 4104-4113(2005).
"Photophysics of Tryptophan Fluorescence: Link with the Catalytic Strategy of the Citrate Synthase from Thermoplasma acidophilum", Linda C. Kurz, Brett Fite, John Jean, Jung Park, Tim Erpelding and Patrik Callis, Biochemistry (2005), 44, 1394-1413.
"Quantitative predictions of fluorescence quantum yields for tryptophan in proteins", by Patrik R. Callis and Tiqing Liu. J. Phys. Chem. B 108, 4248-4259 (2004).
"Experimental and theoretical investigations of environmentally sensitive single-molecule fluorophores", Katherine A. Willets, Patrik R. Callis, W.E. Moerner, J. Phys. Chem. B (2004), 108, 10465-10473.
Understanding the variable fluorescence quantum yield of tryptophan in proteins using QM-MM simulations. Quenching by charge transfer to the peptide backbone," P. R. Callis and J. T. Vivian. Chem. Phys. Lett. 369, 409-414 (2003).
Quantitative prediction of fluorescence wavelengths
"Mechanisms of tryptophan fluorescence shifts in proteins", J. T. Vivian and P. R. Callis, Biophys. J., 80, 2093-2109 (2001).
"Tryptophan Fluorescence Shifts in Proteins From Hybrid Simulations: An Electrostatic Approach," Callis, P.R. and Burgess, B.K., J. Phys. Chem. B, 101, 9429-9432 (1997).
Electronic structure of indoles and related systems
"One- and two-photon spectra of jet-cooled 2,3-dimethylindole: 1 Lb and 1La assignments," K. W. Short and P. R. Callis, Chemical Physics 283, 269-278 (2002).
"Electronic structure and hyperfine interactions in thioether-substituted tyrosyl radicals," A. M. Boulet, E. D. Walter, D. A. Schwartz, G. J. Gerfen, P. R. Callis, and D. J. Singel Chem. Phys. Lett., 331, 108-114 (2000).
"Evidence for 1La fluorescence from jet-cooled 3-methylindole-polar solvent complexes," K. W. Short and P. R. Callis, J. Chem. Phys., 113, 5235-5244 (2000).
"Fluorescence properties of benz[f]indole, a wavelength and quenching selective tryptophan analog," B. Liu, M. D. Barkley, G. A. Morales, M. L. McLaughlin, and P. R. Callis, J. Phys. Chem. B,, 104, 1837-1843 (2000).
"Ground-State Proton-Transfer tautomer of the Salicylate Anion," D. M. Friedrich, Z. Wang, A. G. Joly, K. A. Peterson, and P. R. Callis, J. Phys. Chem., 103, 9644-9653 (1999).
"Vibrational Assignments for Indole with the Aid of Ultra-Sharp Phosphorescence Spectra," B. J. Fender, K. W. Short, D. K. Hahn and P .R. Callis, Int. J. Quantum Chem., 72, 347-356 (1999).
"Evidence of Pure 1Lb Fluorescence From Redshifted Indole-polar Solvent Complexes in a Supersonic Jet," Short, K.W. and Callis, P.R., J. Chem. Phys., 108, 10189-10196 (1998).
"Two-photon Induced Fluorescence," Callis, P.R. Annual Reviews of Physical Chem., 48, 271-297 (1997).
"1La and 1Lb Transitions of Tryptophan: Applications of Theory and Experimental Observations to Fluorescence of Proteins," Callis, P.R., Methods in Enzymology, 278, 113-151 (1997).
"The Triplet State of Indole: An ab initio Study," Hahn, D.K. and Callis, P.R., J. Chem. Phys., 101, 2686-2691 (1997).
"Ab initio Calculations of Vibronic Spectra for Indole," Callis, P.R., Vivian, J.T., and Slater, L.S., Chem. Phys. Letters, 244, 53-58 (1995).
"Site Selective Photoselection Study of Indole in Argon Matrix: Location of the 1La Origin," Fender, B.J., Sammeth, D.M., and Callis, P.R., Chem. Phys. Letters,, 239 31-37 (1995).
"Fluorescence Anisotropy of Tyrosine Using one-and two-photon Excitation," Lakowicz, J.R., Kierdaszuk, B., Callis, P.R., Malak, H., and Grycznski, I., Biophysical Chemistry, 56, 263-271 (1995).
Department of Chemistry and Biochemistry
Montana State University
PO Box 173400
Bozeman, MT 59717-3400
(406) 994-4801 | Fax (406) 994-5407
Last modified October 22, 2007