Aggregation stabilization

Non-stoichiometric oxides with high levels of disorder may adopt two modes of stabilization aggregation or elimination of point defects. Point defect aggregates forming clusters are examples of the former and extended defect structures like crystallographic shear-plane structures are examples of the latter. 

Vinblastine (6.73) is an antimitotic drug that prevents polymerization of tubulin (Figure 6.26). When incubated with tubulin, vinblastine complexes in a 1 1 ratio with tubulin proteins. By blocking polymerization, vinblastine prevents microtubule formation and therefore mitosis. In contrast, paclitaxel (Taxol, 6.74) and epothilone B (6.75) stabilize aggregated tubulin. As a result, in the presence of paclitaxel and epothilone B, cells form static bundles of microtubules that are nonfunctional. Vinblastine and paclitaxel are both approved for clinical use against cancer. Ixabepilone (6.76), an analogue of epothilone B (6.75), has been approved by the FDA for treatment of certain forms of breast cancer. The European Medicines Agency (EMEA) did not approve ixabepilone out of concern over severe side effects.27... 

Reversed-phase chromatography (RPC) Separation by hydrophobicity Quantitative, stability (aggregation), ... 

Crops can also play a major role in reducing erosion through the kind and amount of residues that they produce. Dense masses of roots that remain in the soil, as well as the tops that are left on the surface, can be handled so as to be effective in minimizing both raindrop erosion and channelization of the water. If incorporated into the soil the residues are the source of the organic compounds that serve to stabilize aggregates being formed by root action. 

In the foregoing chapters the effects of attached polymer chains on colloid stability have been set forth. We now turn to consider the effects of macromolecules that are not attached to the particles but rather are free in solution. Surprisingly, such free polymer is still able to affect colloid stability, being capable of generating both stability and flocculation. Stability that is imparted by free polymer is termed depletion stabilization. Aggregation that is induced by free polymer is called depletion flocculation. The latter will be discussed in this Chapter, consideration of depletion stabilization being postponed until the next Chapter. 

Phosphogypsum Aggregate base - stabilizer/aggregate replacement... 

PS3io-b-PAA45 served as a surfactant, stabilizing aggregates of the random copolymer and forming large spheres. 

In a cooling process of gellan solutions, in the presence of salt, double-helices and cation mediated aggregates of double-helices are formed, whereas in the absence of (a sufficient amount of) salt only non-stabilized aggregates of doublehelices are formed. 

Liposomes composed of one or more concentric bilayers enclosing an aqueous phase are among the most studied systems for drug delivery appHcations [1, 2, 3]. When made from natural phospholipids, Hposomes are completely biocompatible [4, 5]. They can entrap hydrophilic and hydrophobic compounds and usually release their content in a continuous manner [6, 7, 8]. The considerable shortcoming in the use of conventional liposomes is the relatively low physical stability (aggregation and fusion of vesicles may take place) [9]. The kinetic stability of liposomes will largely depend on the physical characteristics of the vesicles (lipid compositions, type and size of vesicles) and the nature of the encapsulated material and its interaction with the liposome components. In that regard, the formation and stability of proanthocyanidin (PRO)-loaded liposomes was studied. 

Sarah Keller and a team mixed oily oxygen-tagged carbon chains. .. R. A. Black et al. Nucleobases bind to and stabilize aggregates of a prebiotic amphiphUe, providing a viable mechanism for the emergence of protocells. 2013. Proc Natl Acad Sci. 110(33), p. 13272. DOl 10.1073/pnas.l300963110. 

SALS Molecular weight, second virial coefficient Particle shape, size distribution Colloid stability (aggregation) Polymer, proteins, micelles, particles... 

Humic substances influence soil properties to a degree out of proportion to then-small percentage in soil. They strongly bind metals, and serve to hold micronutrient metal ions in soil. Because of their acid-base character, humic substances serve as buffers in soil. The water-holding capacity of soil is significantly increased by humic substances. These materials also stabilize aggregates of soil particles, and increase the sorption of organic compounds by soil. 

Multiple emulsions made of low-molecular-weight emulsifiers (the so-called monomeric emulsifiers) are mostly unstable thermodynamically. This is mainly because in the second stage of the emulsification severe homogenization or shear are not recommended, and as a result large droplets are obtained. During years of research attempts have been made to find proper and more suitable combinations of emulsifiers to reduce droplets sizes and to improve the emulsion stability. Aggregation, flocculation, and coalescence (occurring in the inner phase and between the multiple-emulsion droplets) lead to rupture of droplets and separation of the phases and thus are major factors behind the instability of the emulsions. 

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