AVS 46th International Symposium
    Biomaterial Interfaces Group Monday Sessions
       Session BI-MoA

Paper BI-MoA9
1-Thiaoligo(Ethylene Oxide) SAMs: Biomimetic Matrix Structure Tuned via Hydrophilic Spacer Length & Packing Density

Monday, October 25, 1999, 4:40 pm, Room 613/614

Session: Protein Solid-Surface Interactions I
Presenter: T. Petralli-Mallow, National Institute of Standards and Technology
Authors: T. Petralli-Mallow, National Institute of Standards and Technology
D.J. Vanderah, National Institute of Standards and Technology
C.W. Meuse, National Institute of Standards and Technology
A.L. Plant, National Institute of Standards and Technology
Correspondent: Click to Email
Interest in reconstituting transmembrane proteins into supported cell membrane mimics has led to development of novel tethering molecules. In order to introduce a flexible and fluid hydrophilic region at the proximal side of a supported lipid bilayer, oligo(ethylene oxide) moieties have been used as spacers between the sulfur and the alkane chain of alkanethiols. Our group has previously shown that the ethylene oxide moiety adopts a 7/2 helical conformation in self-assembled monolayers (SAM)s of both 1-thiahexa(ethylene oxide) (HS(EO)@sub 6@) decane and HS(EO)@sub 6@ octadecane on gold, indicating that the alkane chain is not the driving force for the helical conformation. Ethylene oxide structure may be controlled by packing density. For example, infrared analysis of mixed monolayers of HS(EO)@sub 6@-decane and phospholipids transferred from the air/water interface indicate that at low packing densities the EO region is disordered, but at higher packing densities the EO segment can assume the helical structure. For a series of decane-terminated 1-thiaoligo(ethylene oxide) SAMs with varying lengths of ethylene oxide spacers, infrared spectroscopy and sum frequency generation indicate that the conformation of the ethyleneoxide moieties may be controlled by their length. The conformation of the ethylene oxide segment is an extended all-trans chain in HS(EO)@sub 4@ SAM, a 7/2 helix in HS(EO)@sub 5-7@ SAM, and a less ordered conformation in the HS(EO)@sub 8@ SAM. The ability to control order via spacer length and packing suggests that HS(EO)@sub n@ SAMs may be successful platforms for biomimetic materials incorporating transmembrane proteins.