title: Membrane protein resistance of oligo(ethylene oxide) self-assembled monolayers.
abstract: As part of an effort to develop biointerfaces for structure-function studies of integral membrane proteins (IMPs) a series of oligo(ethylene oxide) self-assembled monolayers (OEO-SAMs) were evaluated for their resistance to protein adsorption (RPA) of IMPs on Au and Pt. Spectroscopic ellipsometry (SE) was used to determine SAM thicknesses and compare the RPA of HS(CH2)3O(CH2CH2O)6CH3 (1), HS(CH2)3O(CH2CH2O)6H (2), [HS(CH2)3]2CHO(CH2CH2O)6CH3 (3) and [HS(CH2)3]2CHO(CH2CH2O)6H (4), assembled from water. For both substrates, SAM thicknesses for 1 to 4 were found to be comparable indicating SAMs with similar surface coverages and OEO chain order and packing densities. Fibrinogen (Fb), a soluble plasma protein, and rhodopsin (Rd), an integral membrane G-protein coupled receptor, adsorbed to the SAMs of 1, as expected from previous reports, but not to the hydroxy-terminated SAMs of 2 and 4. The methoxy-terminated SAMs of 3 were resistant to Fb but, surprisingly, not to Rd. The stark difference between the adsorption of Rd to the SAMs of 3 and 4 clearly indicate that a hydroxy-terminus of the OEO chain is essential for high RPA of IMPs. The similar thicknesses and high RPA of the SAMs of 2 and 4 show the conditions of protein resistance (screening the underlying substrate, packing densities, SAM order, and conformational mobility of the OEO chains) defined from previous studies on Au are applicable to Pt. In addition, the SAMs of 4, exhibiting the highest resistance to Fb and Rd, were placed in contact with undiluted fetal bovine serum for 2h. Low protein adsorption (≈12.4ng/cm(2)), obtained under these more challenging conditions, denote a high potential of the SAMs of 4 for various applications requiring the suppression of non-specific protein adsorption.
authors.affiliation: National Institute of Standards and Technology (NIST) Center for Neutron Research, Gaithersburg, MD 20899, USA; Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Vaish
authors.affiliation: Biomolecular Measurement Division, Material Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA; Institute for Bioscience and Biotechnology Research (IBBR), Rockville, MD 20850, USA. Electronic address: vanderah@ibbr.umd.edu.
authors.forename: David J
authors.initials: DJ
authors.lastname: Vanderah
authors.affiliation: Biomolecular Measurement Division, Material Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA; Institute for Bioscience and Biotechnology Research (IBBR), Rockville, MD 20850, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Vierling
authors.affiliation: Biomolecular Measurement Division, Material Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA; Institute for Bioscience and Biotechnology Research (IBBR), Rockville, MD 20850, USA.
authors.forename: Fay
authors.initials: F
authors.lastname: Crawshaw
authors.affiliation: Biomolecular Measurement Division, Material Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA; Institute for Bioscience and Biotechnology Research (IBBR), Rockville, MD 20850, USA.
authors.forename: D Travis
authors.initials: DT
authors.lastname: Gallagher
authors.affiliation: Materials Measurement Science Division, Material Measurement Laboratory, NIST, Gaithersburg, MD 20899, USA. Electronic address: marlon.walker@nist.gov.
authors.forename: Marlon L
authors.initials: ML
authors.lastname: Walker
mesh_terms: D000327:Adsorption; D005027:Ethylene Oxide / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D058105:Polymerization; D013499:Surface Properties
chemical_list: D008565:Membrane Proteins; D005027:Ethylene Oxide
keywords: Membrane protein resistance; Oligo(ethylene oxide) self-assembled monolayers