Propofol adsorption at the air/water interface : a combined vibrational sum frequency spectroscopy, nuclear magnetic resonance and neutron reflectometry study

• Propofol interaction with cell membrane has remarkable influence on neuronal function, yet data regarding its behaviour at an interface is still scarce. Here we present the results of propofol adsorption at the air/water interface studied by means of vibrational sum frequency spectroscopy (VSFS), neutron reflectometry (NR), and surface tensiometry. VSFS was utilized to elucidate the orientation change of propofol at the surface as a function of concentration, and the water of hydration was studied by probing the OH vibrational region of the spectrum in two different polarisation combinations. Data show that propofol adsorbs at the air/water interface in an ordered fashion showing strong interactions with the water of hydration, as well as weak interactions with water in the proximity of the hydrocarbon parts of the molecule. In the concentration range studied (0 – 0.89 mM) there is almost no change in the orientation adopted at the interface. NR shows that propofol forms a dense monolayer with a thickness of 4.8 Å, and this result is consistent with a limiting area per molecule equivalent to a close-packed monolayer as demonstrated by surface tensiometry. The possibility that islands or multilayers of propofol form at the air/water interface is therefore excluded. Additionally, the ability of propofol to form associations/multimeric structures in water was studied using nuclear magnetic resonance (NMR). The 1H NMR chemical shifts recorded indicate that propofol does not form dimers or multimers in bulk water (D2O).

Ämnesord

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)