AVS 53rd International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuP

Paper BI-TuP5
Characterization of Nitrilotriacetic Acid-Terminated Self-Assembled Monolayers for Orientation-Controlled Immobilization of Proteins

Tuesday, November 14, 2006, 6:00 pm, Room 3rd Floor Lobby

Session: Biomaterial Interfaces Poster Session
Presenter: F. Cheng, University of Washington
Authors: F. Cheng, University of Washington
L.J. Gamble, University of Washington
D. Graham, University of Washington
D.G. Castner, University of Washington
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In recent studies of orientation and conformation in adsorbed protein films, it is essential step to immobilize proteins onto surfaces in a controlled and well-defined manner. The oriented immobilization of genetically engineered histidine-tagged proteins onto nitrilotriacetic acid (NTA)-terminated self-assembled monolayers (SAMs) on gold has been a widely used model system. X-ray photoelectron spectroscopy (XPS), angle-resolved XPS (ARXPS) and surface plasmon resonance (SPR) have been used to characterize monolayers generated via self-assembly of the NTA thiol onto gold and backfill of methyl-terminated thiol (mercaptoundecane, MUD) into the loosely-packed NTA SAMs. In pure NTA SAMs, self-assembly conditions can significantly affect lateral packing density and nickel-activation efficiency. In mixed NTA SAMs, the correlation between the MUD backfill time and surface compositions indicates a two-step backfill process: 1) at short backfill times (@footnote 1@1h), MUD binds to unoccupied gold sites in NTA monolayer; 2) at long backfill times (@footnote 2@1h), MUD displaces NTA from the gold surface. ARXPS analysis shows that the MUD backfill method can optimize the vertical distribution of NTA endgroup and enrich NTA endgroup in the outmost layer of the films. The binding constants of oligo (histidine) onto the NTA surfaces were determined by SPR.