Joe Strzalka's Research Page

University of Pennsylvania
Department of Chemistry
Box 141
Philadelphia, PA 19104-6323
Voice: (215) 573-7995
Fax: (215) 573-2112
strzalka@sas.upenn.edu

As a research associate in the laboratory of Prof. J. Kent. Blasie, I investigate protein thin films (molecular monolayers) chiefly by means of x-ray and neutron scattering. The thin film geometry enables the sructural characterization of proteins in an environment that allows them to function, making it convenient for studying basic biophysical questions as well as for the development of synthetic proteins as components of novel materials. My work involves the synthesis of proteins, the fabrication of monolayer and multilayer samples by various techniques, and the development of new techniques in scattering.

For my dissertation, I made and characterized thin films (molecular monolayers) of a synthetic peptide designed to be a useful model system for studying electron transfer in naturally occurring proteins. I applied x-ray scattering techniques (reflectivity, GID, interferometry and holography) to characterize the structure of these films, both at the air/water interface and on solid supports.

Take a look at the homepages of my collaborators, Prof. P. Leslie Dutton and the Dutton group, who have designed the peptides that I am studying.

Here are two idealized representations of the maquette peptide based on model atomic coordinates courtesy of Dr. Brian Gibney. Click on the images to see them full-size. Or click for some VRML images that you can manipulate yourself!

The basic unit synthesized is a 31-mer that is mostly alpha-helical, except for a flexible region of three glycine residues that connects the alpha-helix to the cysteine residue at the N-terminus (In the schematic representation on the right, the peptide is indicated in cyan). Under basic conditions, disulfide bridges (yellow) form, creating homodimers of the peptide: (alpha-S-S-alpha). The apposed histidine residues of the two alpha-helices (green) form two bis-His binding sites for heme groups (magenta). In solution, two dimers associate into a four-helix bundle: (alpha-S-S-alpha)₂ (Robertson, 1994). More recently, hydrophobic moieties (palmitic acid, shown in gray) were added to the peptide by means of a peptide bond between the carboxyl group of the fatty acid and the N-terminal cysteine residue. This enhances the stability of monolayers formed from the peptide. (Chen, 1998). In the groups shown explicitly, oxygen atoms appear red, nitrogen appears blue and sulfur appears yellow.

The Experimental Progress Report Summary that we submitted for 1997-1998 provides a brief overview of our work on maquette peptide Langmuir films at Beamline X22B of the National Synchrotron Light Source. It gives you an idea of the information we obtain from studying monolayers of these proteins at the air/water interface using the liquid surface spectrometer.

I have been involved with commissioning the new liquid surface spectrometer and Langmuir trough that are part of the facilities at CMC-CAT at the Advanced Photon Source, a third generation synchrotron source at Argonne National Lab. We have expanded the capabilities of the instrument for Grazing-Incidence Diffraction through the use of a CCD-based area detector and developed resonant x-ray reflectivity at the air-water interface. I am currently working on interferometric techniques for Langmuir monoalyers and on in situ methods for further characterization of the monolayers that complement our scattering techniques.

I have prepared a partial bibliography about maquette peptides (with links to the full texts).

A full(er) bibliography of the Dutton group's papers on maquettes and other topics is available from their homepage. Click here to go there.

PUBLICATIONS

"Three-Dimensional Structure and Dynamics of a de novo Designed, Amphiphilic Metallo-Porphyrin-Binding Protein Maquette at Soft Interfaces by Molecular Dynamics Simulations," Hongling Zou, Joseph Strzalka, Ting Xu, Andrey Tronin, J. Kent Blasie, J. Phys. Chem. B: 111(7): 1823-1833 (2007).

"Structural Studies of Amphiphilic 4-Helix Bundle Peptides Incorporating Designed Extended Chromophores for Nonlinear Optical Biomolecular Materials," Joseph Strzalka, Ting Xu, Andrey Tronin, Sophia P. Wu, Ivan Miloradovic, Ivan Kuzmenko, Thomas Gog, Michael J. Therien and J. Kent Blasie, Nano Letters: 6 2395-2405 (2006).

"Monolayers of a Model Anesthetic-Binding Membrane Protein. Formation, Characterization and Halothane-Binding Affinity," Inna Y Churbanova, Andrey Tronin, Joseph Strzalka, Thomas Gog, Ivan Kuzmenko, Jonas S Johansson and J. Kent Blasie, Biophys. J. 90(9): 3255-3266 (2006).

"Amphiphilic Four-Helix Bundle Peptides Designed for Light-Induced Electron Transfer across a Soft Interface," S. Ye, B. M. Discher, J. Strzalka, T. Xu, S. P. Wu, D. Noy, I. Kuzmenko, T. Gog, M. J. Therien, P. L. Dutton and J. K. Blasie, Nano Letters 5(9): 1658-1667 (2005).

"Design of Amphiphilic Protein Maquettes: Controlling Assembly, Membrane Insertion, and Cofactor Interactions," B. M. Discher, D. Noy, J. Strzalka, S. Ye, C. C. Moser, J. D. Lear, J. K. Blasie, and P. L. Dutton, Biochemistry, 44(37): 12329-12343 (2005).

"Resonant x-ray reflectivity from a bromine-labeled fatty acid Langmuir monolayer," Joseph Strzalka, Elaine DiMasi, Ivan Kuzmenko, Thomas Gog and J. Kent Blasie, Phys. Rev. E, 70:051603 (2004).

"Specular neutron reflectivity and the structure of artificial protein maquettes vectorially oriented at interfaces," Joseph Strzalka, Brian R. Gibney, Sushil Satija, J. Kent Blasie, Physical Review E 70: 061905 (2004)

"A Model Membrane Protein for Binding Volatile Anesthetics," Shixin Ye, Joseph Strzalka, Inna Y. Churbanova, Songyan Zheng, Jonas S. Johansson, J. Kent Blasie, Biophys. J. 87:4065-4074.

"Amphiphilic 4-Helix Bundles Designed for Biomolecular Materials Applications," Shixin Ye, Joseph W. Strzalka, Bohdana M. Discher, Dror Noy, Songyan Zheng, P. Leslie Dutton, and J. Kent Blasie, Langmuir, 20, 5897-5904 (2004).
correction

"Solution to the Phase Problem for Specular X-Ray or Neutron Reflectivity from Thin Films on Liquid Surfaces," J. Kent Blasie, Songyan Zheng and Joseph Strzalka, Phys. Rev. B, 67 224201 (2003).

"Comparative Structural Studies of Vpu Peptides in Phospholipid Monolayers by X-Ray Scattering," Songyan Zheng, Joseph Strzalka, David H. Jones, Stanley J. Opella, and J. Kent Blasie, Biophys. J., 84 2393-2415.

" Assembly of a Vectorially Oriented Four-Helix Bundle at the Air/Water Interface via Directed Electrostatic Interactions," S. Ye, J. Strzalka, X. Chen, C. C. Moser, P. L. Dutton, and J. K. Blasie, Langmuir, electronic edition, 2002.

" Orientational Distributions of the Di-alpha-helical Synthetic Peptide ZnPPIX-BBC16 in Langmuir Monolayers by X-ray Reflectivity and Polarized Epifluorescence," A. Tronin, J. Strzalka, X. Chen, P. L. Dutton, B. M. Ocko, and J. K. Blasie, Langmuir, 17, 3061-3066, 2001.

" Structural Studies of the HIV-1 Accessory Protein Vpu in Langmuir Monolayers: Synchrotron X-Ray Reflectivity," S. Zheng, J. Strzalka, C. Ma, S. J. Opella, B. M. Ocko, and J. K. Blasie, Biophysical Journal, 80, 1837-1850, 2001.

" Positional order and thermal expansion of surface crystalline N-alkane monolayers," B. M. Ocko, E. B. Sirota, M. Deutsch, E. DiMasi, S. Coburn, Joe Strzalka, Songyan Zheng, Andrey Tronin, Thomas Gog, and Chitra Venkataraman, Phys. Rev. E, 63, 032602, 2001.

"X-ray Structural Studies of Maquette Peptide Monolayers 1. Reflectivity and GID at the Air/Water Interface," J. Strzalka, Xiaoxi Chen, Christopher C. Moser, P. Leslie Dutton, Benjamin M. Ocko, J. Kent Blasie, Langmuir, 16, 10404-10418, 2000.

"X-ray Structural Studies of Maquette Peptide Monolayers 2. Interferometry at the Vapor/Solid Interface," J. Strzalka, Xiaoxi Chen, Christopher C. Moser, P. Leslie Dutton, John C. Bean, J. Kent Blasie, Langmuir, 17, 1193-1199, 2001.

"Determination of the Porphyrin Orientation Distribution in Langmuir Monolayers by Polarized Epifluorescence," A. Tronin, J. Strzalka, X. Chen, P. L. Dutton and J. K. Blasie, Langmuir, 16, 9878-9886, 2000.

"Structure of Discotic Liquid Crystalline Compounds at the Air-Water Interface," D. Gidalevitz, O. Y. Mindyuk, P. A. Heiney, B. M. Ocko, P. Henderson, H. Ringsdorf, N. Boden, R. J. Bushby, P. S. Martin, J. Strzalka, J. P. McCauley Jr; A. B. Smith III, Journal of Physical Chemistry B, 101, #50, 10870-10875, 1997.

PRESENTATIONS
"Artificial Integral Membrane Proteins for Vectorial Electron Transfer Across Soft Interfaces," Joseph Strzalka, Shixin Ye, Bohdana M. Discher, Christopher C. Moser, J. Kent Blasie, Fall Meeting of the Materials Research Society, Boston, MA, November 2004 (29 Nov-03 Dec, Symposium Z: Bio-Inspired and Bio-Derived Materials and Processes).

"Single-Residue Sensitivity in Neutron Reflectivity and Resonant X-ray Reflectivity from Langmuir Monolayers of Synthetic Peptides," Joseph Strzalka, Sushil Satija, Elaine DiMasi, Ivan Kuzmenko, Thomas Gog and J. Kent Blasie, March Meeting of the American Physical Society, Montreal, Canada, March, 2004 (22-26 March 2004, Session A8: Neutron Scattering and Other Studies of Phospholipids).

"Resonance X-ray Reflectivity to Probe the Profile Structure of Langmuir Monolayers of Lipids and Peptides," Joseph Strzalka, Elaine DiMasi, Ivan Kuzmenko, Thomas Gog and J. Kent Blasie, Annual Meeting of the Biophysical Society, Baltimore, MD, February, 2004 (17 Feb 2004, Platform Session AS: X-ray Analysis of Membrane Structure, 10:45-12:45 AM). Abstract published in Biophysical Journal 86(1): 349A, Part 2 (2004).

"Assembly of a Vectorially-Oriented Four-Helix Bundle at the Air/Water Interface," Joseph Strzalka, S. Ye, A. Tronin, X. Chen, C.C. Moser, P.L. Dutton, B.M. Ocko and J.K. Blasie, March Meeting of the American Physical Society, Indianapolis, Indiana, March 2002.

"Neutron Reflectivity Can Probe the Secondary Structure of Selectively Deuterated Peptides in a Langmuir Monolayer," Joseph Strzalka, B. R. Gibney, X. Chen, C. C. Moser, P. L. Dutton, S. K. Satija, B. M. Ocko, J. K. Blasie, Annual Meeting of the Biophysical Society, New Orleans, LA, February 2000 (Biophysical Journal 78, No. 1, pt. 2, Abstract 1924).

"X-Ray Reflectivity Studies of Mixed Langmuir Monolayers of a Lipopeptide Maquette and a Phospholipid," J. Strzalka, X. Chen, B. R. Gibney, C. C. Moser, P. L. Dutton, B. M. Ocko, J. K. Blasie, Annual Meeting of the Biophysical Society, Baltimore, MD, February 1999 (Biophysical Journal, 76, No. 1, pt. 2, A18, Su.-AM-I1).

"Structural Studies of Model Metalloprotein Maquettes Vectorially Oriented at a Soft Interface," J. Strzalka, X. Chen, C. C. Moser, P. L. Dutton, B. M. Ocko, J. K. Blasie, Annual Meeting of the Biophysical Society, Kansas City, MO, February 1988.

"Unique Phasing of X-Ray Reflectivity Data from Organic Overlayers on Solid Substrates via Interferometry and Holography," J. Strzalka, J. K. Blasie, J. C. Bean, Annual Meeting of the American Physical Society, Kansas City, MO, March 1997.