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College Park, Maryland      June 6 - 10 , 2004

T1-B4 (9:30 AM): Analysis of Myoglobin Adsorption to Cu(II)-IDA and Ni(II)-IDA Functionalized Langmuir Monolayers by Grazing Incidence Neutron and X-ray Techniques

M. S. Kent, H. Yim, D. Y. Sasaki (Sandia National Laboratories, Albuquerque, NM 87123), S. Satija (National Institute of Standards and Technology), J. Majewski (Argonne National Laboratory), T. Gog (Los Alamos National Laboratory)

The adsorption of myoglobin to Langmuir monolayers of a metal-chelating lipid in crystalline phase was studied using neutron and X-ray reflectivity and grazing incidence X-ray diffraction (GIXD). In this system adsorption is due to the interaction between chelated Cu2+ and Ni2+ ions and the histidine moieties at the outer surface of the protein. Cu2+ is known to interact much more strongly with histidine than Ni2+. Adsorption was examined by NR and XR under conditions of constant surface area with an initial pressure of 40 mN/m as well as under constant pressure at 40 mN/m. The adsorbed layer structure in the final state was examined for a variety of bulk concentrations on and below the adsorption plateau. In addition, since the adsorption process is rather slow for this system, the layer characteristics were obtained as a function of time during the adsorption process. Finally, corresponding GIXD experiments were performed under the same conditions to follow changes in the packing of the lipid tails upon protein adsorption. Significant differences in the evolution of the adsorbed protein layer are observed for chelated Cu2+ and Ni2+ ions that may indicated differing extents of protein denaturation in the two cases. In addition, the disruption of the lipid packing is found to occur for the constant pressure case (40 mN/m) but not for constant area (initial pressure - 40 mN/m).

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