This paper describes the use of surface plasmon resonance (SPR) spectroscopy to measure the rates and extents of association of four detergents - sodium dodecyl sulfate (SDS), β-octyl glucoside, Triton X-100, and Tween 20 - to self-assembled monolayers (SAMs) of alkanethiolates on gold. SAMs presenting hexaethylene glycol groups resisted the adsorption of all four detergents. These same detergents associated with hydrophobic SAMs presenting methyl groups; the concentration of detergent molecules on the surface was 120-280 pmol/cm2. The associations of the detergents with the hydrophobic SAM were described well by the Langmuir adsorption isotherm. The dissociation constants Kd (M) for the desorption of the detergents from the surface correlated with the critical micelle concentration (cmc, M) of the detergents in solution, and followed the relationship cmc ≈ 7 (±2)Kd. The efficacy of SDS in removing the protein fibrinogen adsorbed on a hydrophobic SAM depended strongly on the concentration of detergent. SDS at a concentration three times greater than the cmc removed (or displaced) the adsorbed layer of protein in seconds; SDS at a concentration three times smaller than the cmc did not desorb it even after several minutes. This paper shows that SPR is a useful analytical technique for characterizing the interactions of detergents - and other molecules having low molecular weight - with the well-defined surfaces of SAMs.
|Original language||English (US)|
|Number of pages||7|
|State||Published - May 14 1997|
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Surfaces and Interfaces