Protein adsorption/desorption

In conclusion, TIRF promises to be exceedingly useful in the study of protein-substrate interactions. It gives in situ, possibly remote, real-time information about protein adsorption-desorption parameters, conformational changes upon adsorption and hopefully, nanosecond time-resolved fluorescence lifetime information about adsorbed proteins 156). 

Sharma C.P and Chandy. T, Influence of L-asootbic add, blood cdlls and components on protein adsorption/desorption on polycartxmate. Haemostasis, 17,70-78(1987). 

Interfacial protein fluorescence is an in situ method that can provide real time data with a resolution of 0.1 s. This technique is a major advantage in that the protein adsorption-desorption dynamics may be determined without resorting to sample manipulation prior to analysis. Figure 9 illustrates adsorption-desorption dynamics for both BSA and 7-globulin at bulk equimolar concentrations of 6.671xM/L. The 7-globulin required 40 min to reach... 

A dual-channel ATR flow cell has been fabricated and tested in a variety of protein adsorption/desorption studies, permitting the direct comparison of two surfaces or two flowing solutions under otherwise identical conditions. 

Studies on polymer monolayers spread at the air-water interface are now in progress in our laboratory. Biocompatible and biodegradable polymers used as nanoparticles carrying biologically active substances are characterized using the surface balance, surface potential and protein adsorption/desorption measurements. The combined data of all these measurements provide information on drug and protein penetration/delivery with these polymers. 

In the most elementary formulation, there is no relaxation and protein adsorption-desorption is described in terms of Langmuir s kinetics ... 

FIGURE 9.27 Schematic representation of protein adsorption desorption as a function of temperature. 

In the past few decades, a significant number of engineering stimuli-responsive surfaces have been developed for modulating surface interactions with proteins in response to external factors including temperature, pH, ionic strength, light, and electrical field. Switching on and off protein adsorption/desorption on surfaces enables... 

Protein adsorption has been studied with a variety of techniques such as ellipsome-try [107,108], ESCA [109], surface forces measurements [102], total internal reflection fluorescence (TIRE) [103,110], electron microscopy [111], and electrokinetic measurement of latex particles [112,113] and capillaries [114], The TIRE technique has recently been adapted to observe surface diffusion [106] and orientation [IIS] in adsorbed layers. These experiments point toward the significant influence of the protein-surface interaction on the adsorption characteristics [105,108,110]. A very important interaction is due to the hydrophobic interaction between parts of the protein and polymeric surfaces [18], although often electrostatic interactions are also influential [ 116]. Protein desorption can be affected by altering the pH [117] or by the introduction of a complexing agent [118]. 

Kakiuehi et al. [84] studied the adsorption properties of two types of nonionic surfactants, sorbitan fatty acid esters and sucrose alkanoate, at the water-nitrobenzene interface. These surfactants lower the interfacial capacity in the range of the applied potential with no sign of desorption. On the other hand, the remarkable adsorption-desorption capacity peak analogous to the adsorption peak seen for organic molecules at the mercury-electrolyte interface can be observed in the presence of ionic surfactants, such as triazine dye ligands for proteins [85]. 

Two investigations have combined TIR with FCS thus far. The first(126) adapted TIR/FCS to measure the absolute concentration of virions in solution. The other(127) measured the adsorption/desorption kinetics of immunoglobulin on a protein-coated surface on the millisecond time scale. 

This proposal describes the development of a new, systematic approach for qualitatively and quantitatively studying surface-biomolecule interactions by matrix-assisted laser desorption ionization (MALDl) mass spectrometry (MS). This methodology is being developed because of the profound importance that surface-biomolecule interactions play in applications where biomaterials come into contact with complex biological fluids, it can readily be shown that undesired reactions occurring in response to surface-biomolecule contact (protein adsorption, biofouling, immune response activation, etc.) lead to enormous economic and human costs. Thus, the development of analytical methodologies that allow for efficient assessment of the properties of new biomaterials and/or the study of detailed fundamental processes initiated upon surface-biomolecule contact are of critical value ... 

Problems of desorption and loss of activity encountered with natural heparin have led numerous workers to explore synthetic heparin-like polymers or heparinoids, as reviewed by Gebelein and Murphy [475, 514, 515]. The blood compatibility of 5% blended polyelectrolyte/polyfvinly alcohol) membranes was studied by Aleyamma and Sharma [516,517]. The membranes were modified with synthetic heparinoid polyelectrolytes, and surface properties (platelet adhesion, water contact angle, protein adsorption) and bulk properties such as permeability and mechanical characteristics were evaluated. The blended membrane had a lower tendency to adhere platelets than standard cellulose membranes and were useful as dialysis grade materials. 

In contrast, on the surface of the amino-containing polymeric materials, protonated amino groups introduced in a small proportion under physiological conditions, destroy their surrounding hydrogen bonds to produce, here and there, gaps in the network [127, 128]. Thus, the network structures are considered to become more or less unstable. As a consequence, the residence time of protein molecules trapped by these defective networks will be shorter than in the case of polyHEMA or cellulose. On the surface of these amino-containing materials, reversible protein adsorption and desorption, and also replacement (Vroman effect) - or even protein rejection - will become possible. 

Fig. 12. Hypothetical 3-D plot of protein adsorption isotherm (D plotted against [P]B) as a function of surface ligand concentration, [A]s. Note that the system is reversible only up to a critical [A]s and then behaves irreversibly for higher ligand surface concentrations. The right arrows (— ) denote adsorption the left-facing ones ( -), desorption...

Fig. 13. Most of the kinetic models which might be applicable to protein adsorption (see Refs.70 73)) k is rate constant, subscript a and d are adsorption and desorption respectively, 1 and 2 are adsorption states — usually native and denatured...

Fig. 24. Matsuda, et al. s model of the protein adsorption/denaturation/aggregation/desorption/ delamination process involved in the blood interactions of materials (from Ref. 127 , p. 357)...

Chapter 15 focuses mainly on antibody purification by chromatographic means. Numerous sorbents have been developed for protein separation, and they are based on a variety of adsorption-desorption principles. Selection of suitable materials and principles depends on the properties of the particular immunoglobulins to be separated and on the composition of the impurities that constitute the feedstock. 

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