Macromolecular medium

The fact that the effective viscosity is intermediate between that of solvent and polymer solution can be rationalized as follows. Within the depletion layer, the viscosity is expected to follow the polymer density distribution [289] and it gradually increases from the solvent viscosity at the solid surface to the bulk viscosity far from the particle. Therefore, as a particle difliises, the hydrodynamic resistance force is also in between the two limits. Fan et al. [294, 295] derived analytical expressions for the friction felt by a sphere when it moves through a macromolecular medium, and showed that the friction is strongly reduced compared to Stokes law. This means that depletion-induced slip effects facilitate protein transport through crowded media. 

Through this study, we have shown that the excimer fluorescence technique of a probe simply dispersed in a macromolecular medium provides detailed information about the molecular motions of the polymer. Although the intramolecular rotational process reflects the glass transition of the host medium, within the same matrix, the absolute values of the experimental correlation times, differ for each probe. In Table 3... 

The structure of these gel-like systems of micelles is very different from that of conventional electrophoresis media made from chemically and physically cross-linked polymers of polyacrylamide and agarose [75], The absence of chemical or physical cross-links in the Pluronic gel-like phases may allow a larger degree of freedom for macromolecular transport around the obstacles that make up the medium than occurs in conventional electrophoresis media. 

Natural macromolecular materials, which form multimolecular films around the disperse droplets of O/W emulsions. They are frequently called auxiliary emulsifying agents and have the desirable effect of increasing the viscosity of the dispersion medium. However, they often suffer from the disadvantages of being subject to hydrolysis and sensitive to variations in pH. 

K Morimoto, T Nakamura, K Morisaka. (1989). Effect of medium-chain fatty acid salts on penetration of a hydrophilic compound and a macromolecular compound across rabbit corneas. Arch Int Pharmacodyn 302 18-26. 

These traps, (Fig. 6) and similar effects in the motion of holes and other charges through polymers, would eventually be correlated also with such structural probes as positron lifetimes in macromolecular solids. Extensive recent studies of positron lifetime are based on positronium decay. In this, the lifetime of o-positronium (bound positron-electron pair with total spin one) is reduced from about 140 nanoseconds to a few nanoseconds by "pick-off annihilation" in which some unpaired electron spins in the medium cause conversion quenching of orthopositronium to para-positronium. The speed of the t2 effect is supposed, among other things, to represent by pick-off annihilation the presence of defects in the crystalline lattice. In any case, what amounts to empty space between molecules can then be occupied by orthopositronium.(14,15,16) It is now found in linear polyethylene, by T. T. Wang and his co-workers of Bell Laboratories(17) that there is marked shift in positron lifetimes over the temperature range of 80°K to 300°K. For... 

Particulate sorbents are available almost exclusively in the shape of micrometersized beads. These beads are packed in columns and represent currently the most common stationary phases for high-performance liquid chromatography (HPLC). Despite their immense popularity, slow diffusional mass transfer of macromolecular solutes into the stagnant pool of the mobile phase present in the pores of the separation medium and the large void volume between the packed particles are considered to be major problems in the HPLC of macromolecules, frequently impairing their rapid and efficient separation [1]. 

On the other hand, two important factors of macromolecular chain reactivity in solution deserve more attention,namely the nature of the reaction medium and the polymer concentration. 

Rate equation analyses for classical size exclusion chromatography have been based on treating the porous matrix as a homogeneous, spherical medium within which radial diffusion of the macromolecular solute takes place (e.g. (28,30,31)) or If mobile phase lateral dispersion Is considered Important, a two dimensional channel has been used as a model for the bed (32). In either case, however, no treatment of the effects to be expected with charged Brownian solute particles has been presented. As a... 

Cultures consisting of cell suspensions may be used directly to determine the efficacy of macromolecular antitumor agents. For example, suspensions of L12 10 leukemia cells were used to show the activity of HPMA copolymer anticancer drug conjugates [39], The cells, while in exponential growth, were diluted in culture medium to produce a cell density of approximately... 

---