Macromolecules adsorption

It is commonly stated that the first readily observable event at the interface between a material and a biological Quid is protein or macromolecule adsorption. Clearly other interactions precede protein adsorption water adsorption and possibly absorption (hydration effects), ion bonding and electrical double layer formation, and the adsorption and absorption of low molecular weight solutes — such as amino acids. The protein adsorption event must result in major perturbation of the interfacial boundary layer which initially consists of water, ions, and other solutes. 

Ognier, S., Wisniewski, C. and Grasmick, A. (2002) Influence of macromolecule adsorption during filtration of a membrane bioreactor mixed liquor suspension. Journal of Membrane Science, 209, 27-37. 

As for other macromolecules, adsorption takes place only with segments of the whole chain molecule, whereas the connecting parts in between form loops into the bulk of the solution. The surface density of segments " at a given potential depends on the flexibility of the whole chain and on the time necessary to reach saturation, which is a rather irreversible process. Therefore one has to distinguish between the d.m.e. and the h.m.d.e. (cf. Table 3). In this section, only results obtained by a.c. polarography in alkaline medium, where electron uptake is suppressed, will be discussed. 

Adsorption of macromolecules Ifom solution into the saturated adsorption layer occurs only on sites where the concentration of monomer links of macromolecule in adsorption layer is less than their concentration in the globula of solved macromolecule (Fig. 5). In this case, the possibility of macromolecule adsorption from solution is determined by the time of existence of the macromolecule near the adsorption layer, which depends on the macromolecule concentration in solution. 

The theoretical and experimental results obtained for model colloid systems can be used effectively as reference states for analyzing protein and macromolecule adsorption at heterogeneous surfaces. 

We also attempt to distinguish between surface physical chemistry and colloid and polymer physical chemistry. This distinction is not always possible, and clearly many of the features of physical chemistry of surfaces, such as the electrostatic interactions and adsorption of macromolecules, have a significant... 

Proteins, like other macromolecules, can be made into monolayers at the air-water interface either by spreading, adsorption, or specific binding. Proteins, while complex polymers, are interesting because of their inherent surface activity and amphiphilicity. There is an increasing body of literature on proteins at liquid interfaces, and here we only briefly discuss a few highlights. 

Most LB-forming amphiphiles have hydrophobic tails, leaving a very hydrophobic surface. In order to introduce polarity to the final surface, one needs to incorporate bipolar components that would not normally form LB films on their own. Berg and co-workers have partly surmounted this problem with two- and three-component mixtures of fatty acids, amines, and bipolar alcohols [175, 176]. Interestingly, the type of deposition depends on the contact angle of the substrate, and, thus, when relatively polar monolayers are formed, they are deposited as Z-type multilayers. Phase-separated LB films of hydrocarbon-fluorocarbon mixtures provide selective adsorption sites for macromolecules, due to the formation of a step site at the domain boundary [177]. 

Stouffer J M and McCarthy T J 1988 Polymer monolayers prepared by the spontaneous adsorption of sulphur-functionalized polystyrene on gold surfaces Macromolecules 2 1204-8... 

Biomaterials with Low Thrombogenicity. Poly(ethylene oxide) exhibits extraordinary inertness toward most proteins and biological macromolecules. The polymer is therefore used in bulk and surface modification of biomaterials to develop antithrombogenic surfaces for blood contacting materials. Such modified surfaces result in reduced concentrations of ceU adhesion and protein adsorption when compared to the nonmodifted surfaces. 

Select mobile phases for HPSEC based on their ability to dissolve the sample and their compatibility with the column. Zorbax PSM columns are compatible with a wide variety of organic and aqueous mobile phases (Table 3.4), but analysts should avoid aqueous mobile phases with a pH greater than 8.5. As mentioned earlier, select mobile phases that minimize adsorption between samples and silica-based packings. Sample elution from the column after the permeation volume indicates that adsorption has occurred. If adsorption is observed or suspected, select a mobile phase that will be more strongly adsorbed onto the silica surface than the sample. For example, N,N-dimethyl-formamide (DMF) is often used for polyurethanes and polyacrylonitrile because it eliminates adsorption and dissolves the polymers. When aqueous mobile phases are required, highly polar macromolecules such as Carbowax can be used to coat the silica surface and eliminate adsorption. Table 3.5 provides a list of recommended mobile-phase conditions for some common polymers. 

It is evident from these results that the interactive properties of the investigated SEC PS/DVB or DVB gels are very different. Because polar electroneutral macromolecules of PMMA were more retained from a nonpolar solvent (toluene) than from polar ones (THF, chloroform), we conclude that the dipol-dipol interactions were operative. Columns No. 1 and No. 2 were very interactive and can be applied successfully to LC techniques that combine exclusion and interaction (adsorption) mechanisms. These emerging techniques are LC at the critical adsorption point (18), the already mentioned LC under limiting conditions of adsorption (15,18), and LC under limiting conditions of desorption (16). In these cases, the adsorptivity of the SEC columns may even be advantageous. In most conventional SEC applications, however, the interactive properties of columns may cause important problems. In any case, interactive properties of SEC columns should be considered when applying the universal calibration, especially for medium polar and polar polymers. It is therefore advisable to check the elution properties of SEC columns before use with the... 

The adhesive macromolecules are adsorbed on to the surface of the substrate and are held by various forces of attraction. The adsorption is usually physical, i.e., due to van der Waals forces. However, hydrogen bond-... 

We think, therefore, that the conformation, chain and segment mobilities in the attached macromolecules can play a significant role in the shielding behavior of the polymeric stationary phase as well as in the processes of its formation of complexes with solutes. Obviously, the chromatographic studies relevant to composite supports suffer from a lack of information on the structure of the attached polymer. Nevertheless, we will attempt to point out some relevant data from independent studies on polymer adsorption and/or graft polymerization. 

Adsorption of macromolecules has been widely investigated both theoretically [9—12] and experimentally [13 -17]. In this paper our purpose was to analyze the probable structures of polymeric stationary phases, so we shall not go into complicated mathematical models but instead consider the main features of the phenomenon. The current state of the art was comprehensively summarized by Fleer and Lyklema [18]. According to them, the reversible adsorption of macromolecules and the structure of adsorbed layers is governed by a subtle balance between energetic and entropic factors. For neutral polymers, the simplest situation, already four contributor factors must be distinguished ... 

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