Photo of Keiderling, Tim

Tim Keiderling

Emeritus Professor



5407B SES, MC 111

Office Phone:

(312) 996-3156


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Our research is primarily focused on the use of spectroscopic techniques to determine biomolecular structure and follow its dynamic changes. My group is recognized for developing new IR and vibrational circular dichroism (VCD) based optical spectroscopic methods and applying them to the study of peptide and protein conformation and folding. We have developed ab initio QM methods to model and interpret our peptide IR, Raman and VCD spectra. Our spectral studies probe equilibrium and thermodynamic changes, as well as microsec dynamics using IR and fluorescence detected T-jump methods. Most of these studies address model peptide systems to exemplify fundamental secondary structure types and to model small folding units in proteins. Our studies also use NMR structure determination to generate models for folded structures and MD methods to develop models for folding processes and intermediate structures on the pathway. Recently we have begun a number of studies related to protein and peptide aggregation and fibril formation, processes important in many biomedical conditions.

Additionally, the group studies larger protein folding problems, with a particular emphasis on b-sheet dominant structures and aggregates, model systems for protein membrane interaction and folding studies. Perturbation effects on protein and protein complex structures, such as disulfide reduction, surface binding, pH and thermal variation are studied with equilibrium and dynamic (stop-flow) IR, CD and fluorescence methods.

Previous work allowed us to refine protein structure determination in terms of fractional secondary structure with using various pattern recognition and statistical methods to interpret optical spectra, which can correlate with NMR studies, H-D exchange, as well as kinetically based fluorescence and electronic CD spectral measurements. All of these are useful for dynamic study of structural changes such as occur during the protein folding process.

A figure that shows how isotopically labeling a protein affects its infrared spectrum.
Figure 1. For three isotopically labeled (13C on amide C=O) hairpin peptides, (a) schematically indicated on left, comparison of (b) simulated IR spectra and (c) experimental IR spectra at T = 5 C for TZ2C (black), A1A10 (green), A3A8 (red) and A3A10 (blue). Simulations are presented for a full DFT calculation at the BPW91/6-31G** level of the Ala-substituted (Trpzip2C ) sequence in vacuum constrained to the experimental backbone structure.

Selected Publications

  1. “Geometry and efficacy of cross-strand Trp/Trp, Trp/Tyr and Tyr/Tyr aromatic interaction in a -hairpin peptide” Ling Wu, Dan McElheny,Takahiro Takekiyo, and Timothy A. Keiderling, Biochemistry 49, 4705-4714 (2010) DOI: 10.1021/bi100491s
  2. “Spiral Superstructures of Amyloid-Like Fibrils of Polyglutamic Acid: An Infrared Absorption and Vibrational Circular Dichroism Study” Aleksandra Fulara, Ahmed Lakhani, Sławomir Wójcik, Hanna Nieznańska, Timothy A. Keiderling, Wojciech Dzwolak, Journal of Physical Chemistry B 115 , 11010–11016 (2011) DOI: 10.1021/jp206271e
  3. “Inter-residue Coupling and Equlibrium Unfolding of PPII Helical peptides. Vibrational spectra enhanced with 13C isotopic labeling,” Heng Chi, Ahmed Lakhani, Anjan Roy, Marcelo Nakaema, Timothy A. Keiderling, Journal of Physical Chemistry B, 114,12744-12753 (2010) DOI: 10.1021/jp106095q
  4. “Comparison of isotopic substitution methods for equilibrium and T-jump infrared studies of b-hairpin peptide conformation”, Karin Hauser, Oliver Ridderbusch, Anjan Roy, Alexandra Hellerbach, Rong Huang, Timothy A. Keiderling, Journal of Physical Chemistry B, 114, 11628–11637 (2010) DOI: 10.1021/jp1028245
  5. “Kinetic Studies of the Interaction of β-Lactoglobulin with Model Membranes: Stopped Flow CD/Fluorescence studies,” Ning Ge, Xiuqi Zhang and Timothy A. Keiderling Biochemistry 49, 8831-8838 (2010) DOI: 10.1021/bi1008936


BS, Loras College, 1969
PhD, Princeton University, 1974
Postdoctoral Fellow University of Southern California,1973-76
Fulbright Senior Research Fellow, Max Planck Institute for Quantum Optics, Munich, 1984
University of Illinois Scholar, 1991-1994
Senior Visitor, Oxford Centre for Molecular Sciences, Oxford University, 1994
Guggenheim Fellow and Guest Professor, University of Freiburg, Germany, 2004-05, University of Padova, Italy,. 2005