AVS 51st International Symposium
    Surface Science Thursday Sessions
       Session SS1-ThA

Paper SS1-ThA10
The Reaction of DL-Proline on TiO@sub2@(110) Single Crystal Surfaces.

Thursday, November 18, 2004, 5:00 pm, Room 210B

Session: Metal Oxides and Clusters IV: Oxide Surface Chemistry
Presenter: H. Idriss, University of Auckland, New Zealand
Authors: K. Adib, Brookhaven National Laboratory
G. Fleming, University of Auckland, New Zealand
J.A. Rodriguez, Brookhaven National Laboratory
H. Idriss, University of Auckland, New Zealand
M.A. Barteau, University of Delaware
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Titanium metal is widely used as a medical implant in the aiding of healing fractures in teeth and bone. The choice of titanium as an implant material is based on both its mechanical properties and on its relative chemical inertness. Once placed in the body's aqueous environment, the implant undergoes an oxidation process where the formation of a thin oxide layer in the range of 10 to 100 nm thick occurs. This layer is crucial since it prevents the Ti metal from further reacting with the biological molecules. However, the nature of interaction of the bio-molecule with this thin TiO@sub2@ surface will ultimately determines its conformation. If the conformation of the bio-molecule is altered from its naturally occurring state, it may cause the body to undergo an auto immune response and reject the implant. Surface science studies can address the nature of interaction of prototype amino acids with TiO@sub2@. In this work we study the reaction of DL-Proline on the surface of a model TiO@sub2@ surface, the rutile (110) surface. Proline was chosen as it is a constituent of collagen I, a major high tensile structural protein found in teeth, bone and cartilage. The reaction of DL-Proline on stoichiometric and O-defected surfaces has been investigated by temperature programmed desorption while the surface species at different reaction temperatures were monitored by X-ray core level shifts and by their valence band. Proline binds to the surface via its COO group. The presence of two N(1s) lines upon adsorption at 300 K indicates the presence of two distinct species that are tentatively assigned to -NH@sub2@@super+@- and -NH- attributed to the zwitterionic and non-zwitterionic forms of the amino acid, respectively. Complex reactions are seen for Proline upon heating the surface, and products such as CH@sub2@=C=O and HCN are seen in the gas phase. In addition, large amounts of organic species containing O and N are still present on the surface even after heating to 600 K.