Thickness adsorbed protein layers

The 3D structure of a native protein (in aqueous solution) is only marginally thermodynamically stable and it is sensitive to changes in its environment. It is, therefore, not surprising that adsorption is often accompanied by rearrangements in the protein s 3D structure. It is commonly observed experimentally that the thickness of an adsorbed protein layer is comparable to the dimensions of the protein molecule in solution. It indicates that the adsorbed protein molecules remain compactly structured. 

Thickness of Adsorbed Protein Layers on Glass Adsorption of Proteins in Multilayers... 

When the thickness of the draining film is less than twice the thickness of the adsorbed protein layer, (i.e. TLs), the approaching faces of the film experience a steric interaction because of the overlap of the adsorbed protein layers. 

From the above equation, the variation of equilibrium disjoining pressure and the radius of curvature of plateau border with position for a concentrated emulsion can be obtained. If the polarizabilities of the oil, water and the adsorbed protein layer (the effective Hamaker constants), the net charge of protein molecule, ionic strength, protein-solvent interaction and the thickness of the adsorbed protein layer are known, the disjoining pressure II(x/7) can be related to the film thickness using equations 9 -20. The variation of equilitnium film thickness with position in the emulsion can then be calculated. From the knowledge of r and Xp, the variation of cross sectional area of plateau border Qp and the continuous phase liquid holdup e with position can then be calculated using equations 7 and 21 respectively. The results of such calculations for different parameters are presented in the next session. 

FIGURE 2. Continuous phase liquid holdup profiles (CPLHP) for different centrifugal accelerations for droplet size R = 5jc10 /w, surface concentration r=5jcl0 il g//n, ionic strength m =0.1M,thickness of adsorbed protein layer L, = 12xl(T /n and zeta potential = 12mV. 

FIGURE 7. Continuous phase liquid holdup profiles (CPLHP) for different zeta potentials for droplet size / =50bcl0" /n, centrifugal acceleration Qc = 10 m lsec, ionic strength m=0.1Af, thickness of adsorbed protein layer Lg = 12xl(T m and surface concentration r = 5jc IQT kglnr. 

Tween 20 was considerably more effective at reducing the stability of foams of a-la than was the case with /3-lg. There was a significant decrease in a-la foam stability in the presence of Tween, at R values as low as 0.05. Minimal foam stability was observed at R = 0.15. There was no observed change in film drainage behavior or onset of surface diffusion in the adsorbed protein layer up to this R value. The only observed change was a progressive decrease in film thickness. Therefore, it is likely that disruption of adsorbed multilayers is responsible for a reduction in the structural integrity of the adsorbed protein layer and that this increases the probability of film rupture. 

Surface shear viscosity (and modulus) may thus tell us something about conformation and thickness of adsorbed protein layers, and especially about changes with time and with composition. The latter may involve the addition of small quantities of an amphiphile, which tends to greatly reduce t]ls, or partial displacement of an adsorbed protein by another one. However, a clear and simple theory is not available combination with the... 

The two parameters of the adsorption process that are the easiest to quantify and are therefore most frequently reported are the thickness of the adsorbed protein layer and the density of the protein on the surface. The increase in the thickness of the adsorbed protein layer and in surface coverage as a function of added protein are shown schematically in Figs. 2A and 2B, respectively. 

FIG. 6 The displacement of bovine p-casein from the surface of a negatively charged PS latex by the nonionic detergent Tween 20, showing that protein displacement is accompanied by a decrease in the thickness of the adsorbed protein layer. (O) Protein coverage ( ) hydrodynamic layer thickness. R is the molar ratio of detergent to protein. 

Tissue response is determined by a sequence of events that occurs at several different time and length scales. After hydration of the implanted surface, which occurs on a microsecond timescale, small molecules migrate toward the surface in milliseconds, and protein over a timescale of minutes. Subsequent cell attachment that occurs over the adsorbed protein layers determines the long term tissue response of the implanted material. Each of these processes needs to be characterized and understood when designing the surface to elicit the required tissue response. Some features of the surface layer that are typically monitored include macroscopic characteristics such as the thickness and the surface energy of the layer, the hydration state of the surface layer, the structure and conformation of... 

ELM is an optical method widely used to measme the thickness and surface roughness of ultrathin films in the semiconductor industry. It measures changes in the polarization of a light beam reflected from a surface, which can be related to the characteristics of the surface layer, such as an adsorbed protein layer or a layer of cells attached to a surface (Elwing, 1998 Theeten, 1981 Tompkins and Irene, 2005). When a linearly... 

The thickness and the refractive index of the adsorbed protein layer were determined by ellipsometry [7]. The adsorbed mass, r, was calculated according to Cuypers et al. (81. The values used for the molar weight/molar refractivity were 4.10 and 4.17 g/ml and for the partial specific volume 0.751 and 0.750 ml/g for jS-lactoglobulin and ovalbumin, respectively. The change in electrode potential, AE, was... 

Protein-adsorption behavior tvas also investigated by in situ spectroscopic ellips-ometry using a rotating compensator apparatus [56]. A fixed angle of incidence of 75° tvas used over a spectrum range of 191 to 1690 nm. The refractive indices of the polymer and the adsorbed protein layer as transparent materials were described using the Cauchy relationship. The thickness (d) and refractive index (n) of the adsorbed protein determined were used to calculate the surface concentration of protein (F) using De Feijter s formula ... 

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