Electron transfer in monolayer films of designed heme proteins / Xiaoxi Chen.

Format:

Book

Manuscript

Microformat

Thesis/Dissertation

Author/Creator:

Chen, Xiaoxi.

Contributor:

Dutton, P. Leslie, advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Biochemistry.

Biochemistry--Penn dissertations.

Penn dissertations--Molecular biophysics.

Molecular biophysics--Penn dissertations.

Biochemistry and Molecular Biophysics.

Academic Dissertations as Topic.

Medical Subjects:

Biochemistry and Molecular Biophysics.

Academic Dissertations as Topic.

Local Subjects:

Penn dissertations--Biochemistry.

Biochemistry--Penn dissertations.

Penn dissertations--Molecular biophysics.

Molecular biophysics--Penn dissertations.

Physical Description:

x, 138 pages : illustrations ; 29 cm

Production:

1999.

Summary:

Experimental explorations of functional mechanisms in natural electron transfer proteins are often frustrated by their fragility and their extreme complexity. We have designed and synthesized four-alpha-helix-bundle proteins which accommodate heme groups in a much simplified protein and robust setting. With the idea to start delineating guidelines to create synthetic redox proteins capable of catalysis and tunneling, these heme protein models, "maquettes", have been designed to bind and orient on solid surfaces to facilitate the systematic investigation of factors that govern biological electron transfer kinetics and coupled reactions. Both the Langmuir-Blodgett (LB) technique and self-assembled monolayer (SAM) approach were used to prepare monolayer films of these proteins on solid surfaces. The structural conservation on transfer from solution to surface and the orientations of the four-alpha-helix-bundles in the films were characterized by circular dichroism (CD), ultraviolet-visible (UV-vis) and Fourier-transformed-infrared (FTIR) spectroscopy. The electron transfer properties of the bundles in the films were characterized by cyclic voltammetry (CV). Control of the protein density and orientation in the monolayer films has been achieved using the following strategies: (1) In LB films, attaching hydrophobic tails to the bundles caused the orientation of the bundles to change from parallel to perpendicular to the air-water interface at high surface pressure; (2) In LB films, segregation of positively and negatively charged amino acids on different helices of the four-alpha-helix-bundle preserved the bundle integrity and promoted a perpendicular orientation in the presence of heme at the air-water interface; and (3) In SAMs, choosing the distribution of charged amino acids along the surfaces of the bundles promoted desired density and orientation of the bundles on a charged substrate surface. With these structures, electron tunneling between the electrode and the hemes through spacers and protein matrix has been quantitated, and redox coupled events including proton exchange and CO binding/release have been demonstrated. Our original goal of establishing guidelines for constructing viable structures that reflect not only physical and chemical events common to natural proteins, but also basic elements of catalysis in synthetic proteins has been achieved.

Notes:

Supervisor: P. Leslie Dutton.

Thesis (Ph.D. in Biochemistry and Molecular biophysics) -- University of Pennsylvania, 1999.

Includes bibliographical references.

Local Notes:

University Microfilms order no.: 99-53512 .

OCLC:

187483600