AVS 47th International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuM

Paper BI-TuM3
Investigation of the Structure and Dynamic of Proteins on Surfaces by EPR Spectroscopy: Annexin XII as an Exploratory Example

Tuesday, October 3, 2000, 9:00 am, Room 202

Session: Protein-Surface Interactions
Presenter: T. Risse, University of California, Los Angeles
Authors: T. Risse, University of California, Los Angeles
W.L. Hubbell, University of California, Los Angeles
M. Isas, University of California, Irvine
H. Haigler, University of California, Irvine
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Site-directed spin labeling (SDSL) has become an important tool for the investigation of structure and dynamics in proteins. The SDSL strategy involves introduction of one or two nitroxide side chains (R1) at selected positions in the protein sequence, followed by analysis of the electron paramagnetic resonance (EPR) spectrum in terms of secondary and tertiary structure. To increase the information content of the SDSL experiment, and to examine protein structure and dynamics at interfaces, oriented arrays of spin-labeled proteins on surfaces are now under investigation. Initial experiments have employed the helical protein Annexin XII adsorbed to single lipid bilayers supported on glass or mica surfaces. For molecules oriented in 2-dimensions, the tensorial nature of the Hamilton operator gives rise to angular dependent EPR spectra which can be used to extract the orientation of the nitroxide relative to the surface. Such information is of paramount importance for determining the topography of proteins bound to surfaces. In addition, direct information on the structure and interactions of the protein at the surface is obtained from the dynamics of the side chains inferred from the spectral lineshape. Results for R1 residues at sites 213, 147, 148 and 154, 156 in oriented monolayers of Annexin XII will be discussed relative to these points.