Measurement of protein adsorption

Nystrom, M. and Vaisanen, P., Contact angle measurements of protein adsorption onto membrane polymer films, Acta Polytech. Scand., Chem. Technol. Ser., N273, 5, 2000. 

The application of infrared difference spectrometry to the measurement of protein adsorption at solid/liquid interfaces is potentially... 

In our laboratory, two techniques have been extensively used for studying protein behavior at various interfaces. The first technique censists of in situ measurement of protein adsorption with labeled proteins the second technique based on multiple-beam interferometry measures surface forces between two mica sheets with adsorbed proteins (Tabor-Israelachvili technique). While the in situ measurements enable quantitation of protein adsorption, force-distance measurements provide direct experimental data on the extension of adsorbed protein layers towards the solution and on their conformation. 

Davies, J., Nunnerley, C.S., Paul, A.J. (1996) A correlative study of the measurement of protein adsorption to steel, glass, polypropylene, and silicone surfaces using ToF-SIMS and dynamic contact angle analyses. Colloids Surf B, 6,181-190. 

Ellipsometry is one of widely spread method for direct measurements of protein adsorption. Prior to adsorption ellipsometry measurements require determination of the optical properties of the solid surface [68-69]. For obtaining the amount of adsorbed protein the method described in [70] is applied using the values of the refractive index increments of the protein. The optical technique reflectometry is a simplified version of ellipsometry [71]. Reflectometry is especially suited to study adsorption kinetics because it can rapidly monitor the rates of adsorption using relatively simple and cheap instruments. During the experiment the protein layer is adsorbed on top of the sorbent surface and the... 

Mrksich, M., Signal, G. and Whitesides, G. M., Surface plasmon resonance permits in situ measurements of protein adsorption on self-assembled monolayers of alkanethiolates on gold, Langmuir, 11, 4383-4385 (1995). 

The extended repulsion boundary not only obstructs bilayer-bilayer approach, but also inhibits molecular adsorption to the surface. Measurements of protein adsorption and cell adhesion versus the surface concentration of PEG-DSPE on the phospholipid surface verify the inhibition effect of the surface-grafted PEG (Figure 16.5 [13]). The continuous line in each panel is calculated from the... 

To conclude, a strong correlation was found to exist between the net charge of the proteins in solution, the net charge of the SUM surface, and the extent of protein adsorption, which was expressed in terms of flux losses measured after filtration of the different protein solutions. Moreover, in the case of charge-neutral SUMs, flux losses increased with the hydrophobicity of the nucleophiles bound to the S-layer lattice. All proteins caused higher flux losses on SUMs modified with HDA than on those modified with GME or... 

In contrast to other analytical methods, ion-selective electrodes respond to an ion activity, not concentration, which makes them especially attractive for clinical applications as health disorders are usually correlated to ion activity. While most ISEs are used in vitro, the possibility to perform measurements in vivo and continuously with implanted sensors could arm a physician with a valuable diagnostic tool. In-vivo detection is still a challenge, as sensors must meet two strict requirements first, minimally perturb the in-vivo environment, which could be problematic due to injuries and inflammation often created by an implanted sensor and also due to leaching of sensing materials second, the sensor must not be susceptible to this environment, and effects of protein adsorption, cell adhesion, and extraction of lipophilic species on a sensor response must be diminished [13], Nevertheless, direct electrolyte measurements in situ in rabbit muscles and in a porcine beating heart were successfully performed with microfabricated sensor arrays [18],... 

As a technique for selective surface illumination at liquid/solid interfaces, TIRF was first introduced by Hirschfeld(1) in 1965. Other important early applications were pioneered by Harrick and Loeb(2) in 1973 for detecting fluorescence from a surface coated with dansyl-labeled bovine serum allbumin, by Kronick and Little(3) in 1975 for measuring the equilibrium constant between soluble fluorescent-labeled antibodies and surface-immobilized antigens, and by Watkins and Robertson(4) in 1977 for measuring kinetics of protein adsorption following a concentration jump. Previous rcvicws(5 7) contain additional references to some important early work. Section 7.5 presents a literature review of recent work. 

At the plateau region direct calorimetric measurements of AadsH (adsorption enthalpy) showed that for a number of protein-surface combinations there is a part of the pH range where AadsH > O. Since AadsG < O for the process to occur, TAadsS... 

An important hypothesis related to interface energetics is that of Nyilas, who said that the free energy of adsorption basically drives conformational change 132>. He probed this approach by measuring the enthalpy of adsorption using micro calorimetry and attempted to relate surfaces with low heats of protein adsorption with increased blood compatibility. 

The major advantage of protein adsorption studies on high surface area materials is that changes of some extensive properties which accompany the process of adsorption are large enough to be directly measured heat of adsorption through microcalorimetry 141), uptake or release of small ions by a combination of electrokinetic methods and titration 142), thickness of adsorbed layer or an increase of the volume fraction of solid phase by a hydrodynamic method like viscometry 143). Chromatographiclike analysis can also be applied to protein adsorption 144). 

It has recently been shown that the inverted setup is better suited to measurement of the adsorption kinetics of protein samples at, e.g., the oil/water interface since it prevents reservoir depletion. Reservoir depletion can occur if the concentration of surfactant in the solvent phase is low. If the protein is present in the drop-forming phase, then the concentration within the drop itself may decrease during the adsorption process. This in turn would affect the measured rate of adsorption. In this case, it is preferable to form an inverted oil droplet in the protein solvent. 

An excellent comprehensive review of all theoretical and practical aspects of dynamic and static interfacial tension measurements written by the most prolific authors in the field of protein adsorption. Contains a wealth of additional references that the interested reader may consult to gain additional understanding of the field of research. 

L. E. Locascio, C.E. Perso and C.S. Lee, Measurement of electroosmotic flow in plastic imprinted microfluid devices and the effect of protein adsorption on flow rate, J. Chromatogr. A, 857 (1999) 275-284. 

Interestingly, protein adsorption is also a field of biological interfacial chemistry which parallels that of synthetic materials at the solid - liquid interface. A number of spectroscopic advances have been made which allow FT-IR to be used in kinetic monitoring of protein adsorption on metals and "biocompatible" polymers. In addition to providing in - situ measurements of total adsorbed protein, FT-IR can also yield information about perturbation of protein secondary structure in adsorbed layers. 

Polymer Adsorption. A review of the theory and measurement of polymer adsorption points out succinctly the distinquishing features of the behavior of macromolecules at solid - liquid interfaces (118). Polymer adsoiption and desorption kinetics are more complex than those of small molecules, mainly because of the lower diffusion rates of polymer chains in solution and the "rearrangement" of adsorbed chains on a solid surface, characterized by slowly formed, multi-point attachments. The latter point is one which is of special interest in protein adsoiption from aqueous solutions. In the case of proteins, initial adsoiption kinetics may be quite rapid. However, the slow rearrangement step may be much more important in terms of the function of the adsorbed layer in natural processes, such as thrombogenesis or biocorrosion / biofouling caused by cell adhesion. 

Kim, et al., ( ) have utilized radioiodinated (I proteins to measure adsorption of individual proteins and protein mixtures on LTI carbon surfaces. Their results indicate a very rapid adsorption of albumin onto the LTI carbon surface, consistent with Kim s model of blood interactions via a platelet-adhesion mechanism (.8). Microcalorimetric and electrophoretic mobility studies of protein adsorption on LTI carbon surfaces have been done by Chiu, et al., ( 5). The extension of the adsorbed protein layers have been directly measured by Fenstermaker, et al., ( ) and Stromberg et al., 7) at NBS using ellipsometric methods. 

Increasing levels of emulsification significantly depleted protein from the fat globule in the mix. The adsorbed protein content in the mix (mg m of fat surface area) correlated with major characteristic analyses describing the fat structure in ice cream (fat agglomerate size, fat agglomeration index, solvent extractable fat Fig. 6). Thus, the measurement of protein load in the mix can be used to predict ice-cream-fat stability and related structure. Structural analyses indicated enhanced interaction between fat and air as protein adsorption decreased. It was also observed that the fat content in the dripped portion collected from a meltdown test correlated well with other indices of fat destabilization. 

Tomberg, E. The application of the drop volume technique to measurements of the adsorption of proteins at interfaces, /. Colloid Interface Sci., 154, 316, 1978. 

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