Macromolecular adsorbents

The forces acting between atomically smooth mica surfaces immersed in both organic and aqueous liquid media have been determined in the range of surface separations 0 - 300 nm, both in the absence and the presence of adsorbed polymer layers. In this way the interactions between the adsorbed macromolecular layers themselves were determined. We present results for the following cases i) Poor solvent, ii) 0 - solvent, iii) good... 

The relationship between the maximum adsorption value and the average molecular weight allows in some cases to estimate the mean statistical thickness of adsorbed polymer layer. If adsorbed macromolecular coils straightened out in the field of adsorption forces, it could be expected that the dependence n° vs is very slight. Such dependence was fo-... 

The consideration made above allows us to predict good chromatographic properties of the bonded phases composed of the adsorbed macromolecules. On the one hand, steric repulsion of the macromolecular solute by the loops and tails of the modifying polymer ensures the suppressed nonspecific adsorptivity of a carrier. On the other hand, the extended structure of the bonded phase may improve the adaptivity of the grafted functions and facilitate thereby the complex formation between the adsorbent and solute. The examples listed below illustrate the applicability of the composite sorbents to the different modes of liquid chromatography of biopolymers. 

Macromolecules bearing reactive groups in the repeat units along their chains are capable of multiple interaction with the matrix. As early as 1973, Wilchek prepared Sepharose-based supports chemically modified by chemisorbed polylysine and polyvinylamine [41]. The leakage of dyes covalently bonded to these supports was reduced remarkably as compared to non-modified Sepharose activated by cyanogen bromide. Thus, stable and high capacity affinity adsorbents could be prepared by the introduction of macromolecular spacers between a matrix and a biospecific ligand. 

Further examination of the infrared spectra reveals a decrease in the C-H vibrations at 3029 and 2946 cm-1, appearing to occur at different rates. A new broad signal that appears at 1879 cm-1 may be due to CO adsorbed on metallic palladium. The position of this stretch is also suggestive of a carbonyl or anhydride group perhaps contained in a macromolecular residue, as discussed below. 

Carbon nanotubes have been also used as a macromolecular scaffold for Gdm complexes. An amphiphilic gadolinium(III) chelate bearing a C16 chain was adsorbed on multiwalled carbon nanotubes (264). The resulting suspensions were stable for several days. Longitudinal water proton relaxivities, r] showed a strong dependence on the GdL concentration, particularly at low field. The relaxivities decreased with increasing field as predicted by the SBM theory. Transverse water proton relaxation times, T2, were practically independent of both the frequency and the GdL concentration. An in vivo feasibility MRI study has been... 

The final proof of the physical reality of our model of macromolecular adsorption was provided by simultaneous independent work, by an entirely different method, at the National Bureau of Standards (27). Stromberg et al., allowed polystyrene fractions, besides other polymers, to become adsorbed on ferrochrome plates and determined the thicknesses of the adsorbed layers... 

The substantial thickness of adsorbed polymer layers has important consequences for many systems that contain macromolecular components. When adsorbed, e.g., on the particles of fluid dis-... 

The UV radiation adsorbed by chromophoric DOM stimulates production of free radical (singlet) O2. This leads to high concentrations of the free radicals within and around the CDOM, creating local conditions of high reactivity. Thus, chromophoric DOM, which tends to be HMW, can be thought of as a photochemical micro reactor in which free radical oxidations are promoted. Given its macromolecular nature, CDOM... 

Motivating the research is the need for systematic, quantitative information about how different surfaces and solvents affect the structure, orientation, and reactivity of adsorbed solutes. In particular, the question of how the anisotropy imposed by surfaces alters solvent-solute interactions from their bulk solution limit will be explored. Answers to this question promise to affect our understanding of broad classes of interfacial phenomena including electron transfer, molecular recognition, and macromolecular self assembly. By combining surface sensitive, nonlinear optical techniques with methods developed for bulk solution studies, experiments will examine how the interfacial environment experienced by a solute changes as a function of solvent properties and surface composition. 

AFFINITY CHROMATOGRAPHY OF MACROMOLECULAR SUBSTANCES ON ADSORBENTS BEARING CARBOHYDRATE LIGANDS... 

Affinity adsorbents having carbohydrate ligands have been used for the isolation and purification of many types of macromolecular substances. To illustrate, several types of antibodies, enzymes, lectins, and myeloma proteins have been obtained in highly purified form. All of the substances that have been purified by this procedure exhibit specificity for a particular carbohydrate moiety. It is the purpose of this article to assemble information on the methods for preparing affinity adsorbents having carbohydrate ligands, and to illustrate the use of these adsorbents for the purification of representative, macromolecular substances. 

On the basis of the separation mechanism, restricted-access media can be classified into physical or chemical diffusion barrier types. The limited accessibility of the former type is due to the pore structure of the support that represents physical diffusion barriers for macromolecular compounds. The restricted access of the latter type is due to covalently or adsorptively bonded synthetic or natural polymers that cover the support surface, preventing macromolecules from being adsorbed on or denatured by the column packing material. 

Evidence for Macromolecular Bridging. Our current concept of the mechanism of RBC aggregation is that it results from macromolecular bridging (2) (see Figure 18). In this model the macromolecules in the suspending medium are adsorbed to the RBC membrane surface. When RBCs are brought into close proximity of each other by thermal motion,... 

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