title: Mixed self-assembled monolayers in chemical separations.
abstract: Chemical separations of many biomolecules and pharmaceuticals are limited by their electrostatic interaction with the surfaces of the separation medium. Mixed self-assembled monolayers of octadecyl and methyl chains organize into a dense, two-dimensionally cross-linked network over the chromatographic silica surface to reduce acid dissociation of the surface silanols. Molecular models predict that two-dimensional cross-linking is sterically possible for pure methylsiloxane monolayers, silicon-29 nuclear magnetic resonance measurements show that cross-linking predominates for mixed monolayers of primarily methylsiloxane, and chromatographic measurements confirm that electrostatic interactions are reduced when the monolayer is primarily methylsiloxane. Chromatographic separation of genetic variants of a highly charged protein, cytochrome c, demonstrates the promise of self-assembled monolayers in separations of biomolecules.
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Wirth
authors.forename: R W
authors.initials: RW
authors.lastname: Fairbank
authors.forename: H O
authors.initials: HO
authors.lastname: Fatunmbi
mesh_terms: D000818:Animals; D002845:Chromatography / Q000379:methods*; D003574:Cytochrome c Group / Q000302:isolation & purification; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D011506:Proteins / Q000302:isolation & purification*; D058428:Silica Gel; D012822:Silicon Dioxide; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003574:Cytochrome c Group; D011506:Proteins; D012833:Siloxanes; D058428:Silica Gel; D012822:Silicon Dioxide