Effect of Urea and Glycerol on the Adsorption of Ribonuclease A at the Air−Water Interface

Abstract

This study reports on the influence of nonionic cosolvents on the interfacial structure of ribonuclease A (RNase) adsorbed at the air-water interface. We applied X-ray reflectometry to obtain detailed volume fraction profiles of the adsorbed layers and to follow the effect of glycerol and urea on the adsorbate structure as a function of cosolvent concentration. Under all conditions studied, the adsorbed RNase layer maintains its compact shape, and the adsorbed RNase molecules adopt a flat-on orientation at the interface. Both kosmotropic glycerol and chaotropic urea exert profound effects on the adsorbate: The surface excess decreases linearly with glycerol content and is also reduced at low urea concentration. However, at high urea concentration, parts of the adsorbed layer are dehydrated and become exposed to air. The electron density and volume fraction profiles of the adsorbed protein provide clear evidence that these effects are ruled by different mechanisms.

Urea-based gemini surfactants: Synthesis, aggregation behaviour and biological activity

“…The measured values are reported uncorrected. and T = 298.15 K. The value of the prefactor i = 3 which applies to ionic gemini surfactants, was used in the equation (1). The value i=3 is applied for the premicellar region of gemini surfactant concentrations where the gemini surfactant is completely ionized in the solution from which adsorption occurs [50].…”

“…It controls folding and unfolding of proteins [1,2], enhances solubility of hydrocarbons in water and inhibits aggregation of surfactants. Especially, the area of interactions between urea and surfactant molecules attract a significant research interest.…”

Interfacial Properties and Iron Binding to Bacterial Proteins That Promote the Growth of Magnetite Nanocrystals: X-ray Reflectivity and Surface Spectroscopy Studies

“…30 The amount and volume fraction of absorbed proteins at the air− water interface can be estimated based on ED profiles, assuming the adsorbed layer(s) is a mixture of the protein and subphase solution. 23,29,31,32 The volume fraction profile of adsorbed Mms6, Φ Mms6 (z), can be directly related to ρ(z) as follows 29 3 , MW ∼10 kDa). 33 The mass of adsorbed proteins per surface area, Γ s , can be derived from obtained volume fraction profile Φ Mms6 (z).…”

“…33 The mass of adsorbed proteins per surface area, Γ s , can be derived from obtained volume fraction profile Φ Mms6 (z). 29 X-ray fluorescence (XF) from the films as a function of the X-ray incident-angle α i (or corresponding Q z ), using a Vortex energy dispersive detector (EDD), is used to determine quantitatively the density of specific ions that accumulate at the interface. 34 The pencillike detector for collecting fluorescence is pointed directly at the surface separated by a Kapton window in an aluminum well protruding into the Langmuir trough container (about 2 cm away from the liquid surface).…”

Arginine Inhibits Adsorption of Proteins on Polystyrene Surface

“…In addition, various solution additives have been reported to suppress surface adsorption [5]–[8]. For example, more than 3.0 M glycerol and urea were required to reduce the adsorption of RNase A by half at silica-water [5] and air-water [6] interfaces. Salts [7] and sugars [8] also decreased the amount of adsorbed RNase A on polystyrene surfaces at molar concentrations.…”