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Patrik R. CallisChemistry & Biochemistry

Physical Chemistry, Quantum Chemistry, Biophysical Chemistry

Patrik R. Callis Contact Information:
MSU Dept. of Chemistry and Biochemistry
55 Chemistry and Biochemistry Bldg.
Bozeman, MT 59717-3400
phone: (406) 994-5414

B.S. Oregon State University, 1960; Ph.D., University of Washington, 1965; Postdoctoral, Cal Tech, 1966-68.

Wiley Award for Meritorious Research, 1990; Cox Award for Teaching and Scholarship, 1992; Phi Kappa Phi Anna Krueger Fridley Award for Distinguished Teaching, 1994; Letters and Science Meritorious Research and Creativity Award, 2015

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.


Understanding the Variable Quenching of Tryptophan Fluorescence in Proteins: Modulation of Electron Transfer Rates by Electrostatics   

Selected Publications

P.R. Callis, Simulating Electrostatic Effects on Electronic Transitions in Proteins. Molecular Simulation, (2015) 41, 190–204, Published online: 13 Jun 2014

P.R. Callis, Binding Phenomena and Fluorescence Quenching. I: Descriptive Quantum Principles of Fluorescence Quenching using a Supermolecule Approach, J. Mol. Struct. 1077 (2014) 14-21

P.R. Callis, Binding Phenomena and Fluorescence Quenching. II: Photophysics of Aromatic Residues and Dependence of Fluorescence Spectra on Protein Conformation, J. Mol. Struct. 1077 (2014) 22–29

P.R. Callis, J.R. Tusell, MD + QM Correlations with Tryptophan Fluorescence Spectral Shifts and Lifetimes, Methods Mol. Biol. (Clifton NJ) 1076 (2014), p. 171-214.

Biesso, J.H. Xu, P.L. Muiño, P.R. Callis, J.R. Knutson, Charge Invariant Protein-Water Relaxation in GB1 via Ultrafast Tryptophan Fluorescence, J. Am. Chem. Soc. 136 (2014), p. 2739-2747.

Xu,J.H.; Chen,B.B.; Callis,P.; Rozeboom,H.; Broos,J.; Knutson,J. Femtosecond Fluorescence Dynamics of Tryptophan and 5-Fluorotryptophan in Monellin: Slow Water Relaxation Unmasked, Biophys. J. (2013), 104, 681A.

J.N. Scott, P.R. Callis, Insensitivity of Tryptophan Fluorescence to Local Charge Mutations, J. Phys. Chem. B 117 (2013), p. 9598-9605.

Scott,J.N.; Callis,P.R., "MD plus QM Calculations Explore the Origins of Differences amongst the Red Fluorescent Proteins",Biophys. J. 2013, 104, 684A.

Drobizhev,M.; Scott,J.N.; Callis,P.R.; Rebane,A. All-Optical Sensing of the Components of the Internal Local Electric Field in ProteinsIeee Photonics Journal (2012), 4, 1996-2001.

Drobizhev,M.; Hughes,T.E.; Stepanenko,Y.; Wnuk,P.; O'Donnell,K.; Scott,J.N.; Callis,P.R.; Mikhaylov,A.; Dokken,L.; Rebane,A., "Primary Role of the Chromophore Bond Length Alternation in Reversible Photoconversion of Red Fluorescence Proteins:, Scientific Reports (2012),2 Article Number: 688 DOI: 10.1038/srep00688 Published: SEP 24 2012

Tusell,J.R.; Callis,P.R. Simulations of Tryptophan Fluorescence Dynamics during Folding of the Villin Headpiece, J. Phys. Chem. B (2012), 116, 2586-94.

"Correlation of Tryptophan Fluorescence Spectral Shifts and Lifetimes Arising Directly from Heterogeneous Environment", C.-P. Pan, Pedro L. Muino, M.D. Barkley, and P.R. Callis, J. Phys. Chem. B (2011), 115, 3245-3253.

"Predicting Fluorescence Lifetimes and Spectra of Biopolymers", P.R. Callis, Methods in Enzymology (2010), 487,1-38 .

"Electrochromism and solvatochromism in fluorescence response of organic dyes. A nanoscopic view", P.R. Callis, in Advanced Fluorescence Reporters in Chemistry and Biology I (2010),A. Demchenko, Ed. , Springer-Verlag, Heidelberg, pp 309-330.

"Exploring the Electrostatic Landscape of Proteins with Tryptophan Fluorescence", P. R. Callis, in Reviews in Fluorescence 2007 (2009), C. D. Geddes (ed.), Vol. 4, Springer, NY, pp 199-248.

"Femtosecond Fluorescence Spectra of Tryptophan in Human gamma-Crystallin Mutants: Site-Dependent Ultrafast Quenching", J. Xu, J. Chen, D. Toptygin, O. Tcherkasskaya, P.R. Callis, J. King, L. Brand and J.R. Knutson, J.Am.Chem.Soc. (2009), 131, 16751-16757.

"Mechanism of the Very Efficient Quenching of Tryptophan Fluorescence in Human .D- and .S-Crystallins: The gamma-Crystallin Fold May Have Evolved To Protect Tryptophan Residues from Ultraviolet Photodamage", J. Chen, P.R. Callis, and J. King, Biochemistry (2009), 48, 3708-3716.

"Solvent Effects on the Fluorescence Quenching of Tryptophan by Amides via Electron Transfer. Experimental and Computational Studies", P. R. Callis and P. L. Muino, J. Phys. Chem. B (2009), 113, 2572-2577.

"Molecular dynamics simulations of perylene and tetracene libratio\ ns: Comparison withfemtosecond upconversion data", Rosales T , Xu JH , Wu XW, Hodoseek M, Callis P, Brooks BR, Knutson JR, J. Phys. Chem. A (2008), 112, 5593-5597.

"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

Quantitative prediction of fluorescence quenching rates

"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.

Web Release Date: March 1, 2005

  "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) 994-4802 | Fax (406) 994-5407

Last modified February 15, 2015