Of protein molecules adsorbed

ELECTROCHEMICAL STUDIES OF PROTEIN MOLECULES ADSORBED ON ELECTRODES... 

Subtraction of Ab from the total measured radioactivity (At) gives the radioactivity of protein molecules adsorbed in excess at the interface (Aa ) for each of the protein concentrations studied (Figure 6). At low protein solution concentrations (< 0.005 mg/ml), Ab is very small and At represents almost entirely the adsorbed quantity (Aad) > or the adsorption at higher protein concentration (> 0.5 mg/ml), Ab represents about 50% of the adsorbed value. 

We believe that a realistic model for protein adsorption should contain a description of the dynamics of protein molecules adsorbed on surfaces, as suggested earlier [1]. We therefore develop this dynamic model further in the following. 

I- 02 according to this approximation is also plotted in figure 2. Even if the approximation is not good for small Cs it indicates that the adsorption isotherms have the same form for irreversible and reversible adsorption in the presented model. The adsorbed amount will naturally be smaller in the reversible case. An important parameter is then the relative magnitude of the desorption rate constant for the two types of protein molecules adsorbed on the surface. A small r2/ri means that relatively more molecules of type 2 will be found on the surface at large concentrations. 

Thin layers of protein molecules adsorbed on a clean gold surface produce a change in work function which in turn causes a change in the measured CPD. 

The electrical properties of protein molecules adsorbed onto a gold substrate are studied by Hong Huo, Larisa-Emilia Cheran, and Michael Thompson using a scanning Kelvin nanoprobe in a microarray format. 

Jackler, G., Czeslik, C., Steitz, R., Royer, C.A. Spatial distribution of protein molecules adsorbed at a polyelectrolyte multilayer. Phys. Rev. E 71, 041912 (2005)... 

Mesoporous silicas have characteristics of high specific surface areas and pores with defined dimensions and uniform distribution. These features make mesoporous systems ideal candidates as host materials to guest bio-molecules. Protein stability may be enhanced due to reduced autolysis in the case of protease enzymes, and more generally reduced protein aggregation, as a result of the separation of the molecules adsorbed on the surface. 

The tendency of proteins to adsorb at interfaces is determined by many variables, including the pH, the ionic strength, the properties of the protein molecules and the interfaces, and the nature of the solvent and other components present. The process of protein adsorption is complicated, and despite the great volume of work over the past decades, a unified theory is still far ahead. Yet, some principles may be indicated. 

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. 

Let v5 be the number or moles of solute molecules adsorbed per area of surface. The subscript on v refers to the case of adsorption on a solid surface as contrasted with v used in the case of protein-ligand equilibria 4-47 49). Let [A] be the equilibrium solute concentration. 

Lyophilic surfaces can be made lyophobic, and vice versa. For example, clean glass surfaces, which are hydrophilic, can be made hydrophobic by a coating of wax conversely, the droplets in a hydrocarbon oil-in-water emulsion, which are hydrophobic, can be made hydrophilic by the addition of protein to the emulsion, the protein molecules adsorbing on to the droplet surfaces. 

Proteins, which are also surface active, can be used to prepare food emulsions. The protein molecules adsorb at the O/W interface and they may remain in their native state (forming a rigid layer of unfolded molecules) or undergo unfolding, forming loops, tails, and trains. These protein molecules stabilize the emulsion droplets, either by a steric stabilization mechanism or by producing a mechanical barrier at the O/W interface. 

Figure 7 shows adsorption isotherms for this protein on the different sorbents. The adsorption plateau-values at PS-(EO)8, approximately 2.5 mg m 2, is compatible with a complete monolayer of side-on adsorbed a-chymotrypsin molecules. Adsorption saturation at the PS and, even more so, the Teflon surfaces, is beyond monolayer coverage suggesting that on these hydrophobic surfaces the protein molecules are severely perturbed as to accommodate more protein mass in the adsorbed layers and/or adsorption of a second layer of protein molecules (possibly triggered by structurally altered molecules in the... 

When a protein molecule adsorbs, an area of interface of the order of 100 A has to be cleared for adsorption to occur (Section III,B). It seems reasonable to assume that once an adsorbed molecule has been compressed until its area in the interface, due to pressure displacement of segments, falls below this critical value, it will be unstable in the adsorbed state and will desorb. This transition state for desorption may be reached in two ways (1) at constant interfacial pressure and total area, by fluctuations in energy of the adsorbed molecules about the mean value, resulting in certain molecules achieving the transition state configuration (2) by compression of the film, thus increasing the interfacial pressure and decreasing the molecular area until the latter has been reduced to the critical value. 

The phenomenon of viral adsorption to various surfaces was extensively studied from an environmental standpoint as reviewed by Daniels (14) and Gerba (15) for prevention of various waterborne viral transmissions. The problem of virus removal from complex protein solutions is very different from that of sewage and drinking water treatment processes because most protein molecules compete for the active sites of the adsorbents. Hence, both the adsorption rate and capacity diminish in the presence of protein molecules (16). It is the intention of this paper to demonstrate and to compare the antiviral activity of a surface-bonded QAC in aqueous solutions against 2 model viruses with and without the presence of proteins. The efficacy of the accepted antiviral thermo-inactivation was compared with the viral inactivation method by the surface-bonded QAC treatment. Beta-lactamase was used as a thermolabile model protein (17), and bacteriophage T2 and herpes simplex virus type 1 (HSV-1, an enveloped animal virus) were used as model hydrophilic and hydrophobic viruses to test these chemical inactivation methods. 

A detailed analysis of different contributions to the enthalpy and entropy changes, for a number of protein-adsorbent systems, was carried out by Norde. Lyklema, and others 117,103,118,119], They showed that the protein adsorption on solids is often endothermic and that the driving force of the process is the positive ASaiis. The main contributions to large positive values of entropy can arise from sorbent surface dehydration and from the conformational rearrangement of protein molecules upon adsorption [17]. 

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