Cationic physicochemical properties

The intent of this chapter is to establish a comprehensive framework in which the physicochemical properties of permeant molecules, hydrodynamic factors, and mass transport barrier properties of the transcellular and paracellular routes comprising the cell monolayer and the microporous filter support are quantitatively and mechanistically interrelated. We specifically define and quantify the biophysical properties of the paracellular route with the aid of selective hydrophilic permeants that vary in molecular size and charge (neutral, cationic, anionic, and zwitterionic). Further, the quantitative interrelationships of pH, pKa, partition... 

Panov, A.G., Larsen, R.G., Totah, N.I., Larsen, S.C. and Grassian, V.H. (2000). Photooxidation of toluene and p-xylene in cation-exchanged zeolites X, Y, ZSM-5, and beta the role of zeolite physicochemical properties in product yield and selectivity. J. Phys. Chem. B 104, 5706-5714... 

During a study of the physicochemical properties of some aminoglycoside antibiotics Kuzyaeval- - determined the static and dynamic exchange capacities of neomycin on the cation exchange resin KB-4P-2(a phenoxyacetic ac. d-f ormaldehyde resin) using the resin in the Na form. 

Formation of a complex between DNA and polycationic compounds appears to be the initial and quite possibly a critical parameter for nonviral gene delivery. Several synthetic vector systems, which are generally cationic in nature, including poly(lysines), cationic liposomes or various types of block copolymers and recently dendrimers, have been shown to self-assemble with plasmid DNA [13-15] [16]. Specific physicochemical properties manifested by these DNA complexes depend on the type of cationic agent used however, interesting patterns for such interactions are beginning to evolve [17, 18]. Under certain conditions, the interaction of DNA with polyvalent cations results in... 

Abstract Layered double hydroxides (LDHs) comprise au extensive class of materials that are very easy to synthesize in the laboratory, albeit not always as pure phases. In this chapter, we review the wide variety of methods that are available for the synthesis of LDHs and focus on the way in which the physicochemical properties of the materials (such as phase piuity, crystallinity and surface area) vary with synthesis method. The flexibility of the different methods is also discussed some methods can be used to synthesize LDHs containing a wide range of constituent cations and anions, whilst others are more limited in scope. In some cases, the potential for scale-up of a method to produce larger quantities of material is also noted. 

The most commonly employed crystalline materials for liquid adsorptive separations are zeolite-based structured materials. Depending on the specific components and their structural framework, crystalline materials can be zeoUtes (silica, alumina), silicalite (silica) or AlPO-based molecular sieves (alumina, phosphoms oxide). Faujasites (X, Y) and other zeolites (A, ZSM-5, beta, mordenite, etc.) are the most popular materials. This is due to their narrow pore size distribution and the ability to tune or adjust their physicochemical properties, particularly their acidic-basic properties, by the ion exchange of cations, changing the Si02/Al203 ratio and varying the water content. These techniques are described and discussed in Chapter 2. By adjusting the properties almost an infinite number of zeolite materials and desorbent combinations can be studied. 

Most local anesthetics exist in part in the cationic amphiphilic form (cf. p. 208). This physicochemical property favors incorporation into membrane interphases, boundary regions between polar and apolar domains. These are found in phospholipid membranes and also in ion-channel proteins. Some evidence suggests that Na+-channel blockade results from binding of local anesthetics to the channel protein. It appears certain that the site of action is reached from the cytosol, implying that the drug must first penetrate the cell membrane (p. 206). 

Oxygenic photosynthetic organisms, [2Fe-2S] ferredoxins, 38 224-233 Oxygenyl ion, preparation of, 9 229 Oxyhalides, of berkelium, 28 49, 51-53 Oxyhalogeno cations, 9 276-279 Oxyhemerythrin, 40 373-374, 45 84 XAS, 36 325 Oxyhemocyanin, 40 363 m-peroxo dinuclear copper complexes as models for, 39 41-52 physicochemical properties, 39 47-48 Oxyhemocyanins, XAS, 36 326-327 Oxyhemoglobin, 21 135 Oxyiodonium cations, 9 277 Oxymanganese phthalocyanine, strucmre of, 7 31-35... 

The physicochemical properties of HTs and the solid solutions produced after their calcination can be easily tuned by changing the nature and amount of metal cations and anions (10). Therefore, to elucidate the role of the chemical composition on the gas phase acetone self-condensation reaction, a series of bimetallic and trimetallic HTs were prepared, characterized and tested. 

Separation selectivify is one of the most important characteristics of any chromatographic sfationary phase. The functionality of the cation and anion and their unique combinations result in ILs with not only tunable physicochemical properties (i.e., viscosity, thermal stability, and surface tension), but also unique separation selectivities. Although the selectivity for different analytes is dominated by the solvation interactions imparted by the cation and anion, all ILs exhibit an apparent and xmique dual-nature selectivity that is uncharacteristic of other popular nonionic stationary phases. Dual-nature selectivity provides the stationary phases the ability to separate nonpolar molecules like a nonpolar stationary phase but yet separate polar molecules like a polar stationary phase [7,8]. Typically, GC stationary phases are classified in terms of their polarity (see Section 4.2.2) and the polarity of the employed stationary phase should closely match that of the analytes being separated. ILs possess a multitude of different but simultaneous solvation interactions that give rise to unique interactions with solute molecules. This is illustrated by Figure 4.2 in which a mixture of polar and nonpolar analytes are subjected to separation on a 1-benzyl-3-methylimidazolium triflate ([BeQlm][TfO] IL 6 in Table 4.1) column [21]. 

Thus far, emphasis in characterizing the role of the IL in separations has been in assessing the role of cation. Examination of the role of the anion on various physicochemical properties (e.g., viscosity and water solubility) [16] of ILs with identical cations suggest that the anions may be important... 

Qynthetic and natural zeolites are becoming increasingly important as catalysts, carriers of catalysts, and adsorbents. Zeolites are especially suited to these purposes because their properties can be modified by cation exchange. The literature describes several studies which show characteristic changes in physicochemical properties resulting from cation exchange— e.g., catalytic activity (1,2), acidic properties (3), adsorption behavior (4), structure of solid (5,6), and thermal stability (7,8). 

Physicochemical properties of polyplexes greatly depend on the ratio of poly cation and DNA units in the mixture Z=[polycation units]/[DNA bases] referred to as composition of the mixture (Kabanov and Kabanov, 1995). In the case of polycations containing amino groups, the composition of the mixture is commonly expressed as N/P ratio, i.e., the ratio of the numbers of amino groups of the poly cation to phosphate groups of the DNA. It should be emphasized that the composition of the complex formed after mixing of the polycation and DNA solutions, [Pg.153]

In this chapter, the synthesis and structure of commonly used cationic lipids for gene delivery and the influence of their physicochemical properties on transfection activity will be described. 

Polymer. The field of nonviral gene delivery using cationic polymers is at its early stage compared to that of cationic lipid. However, this system is also known to have advantages over lipid-based systems in controlling the size, charge, and other physicochemical properties. Polycation-DNA complexes, also called as polyplexes, are formed by a cooperative... 

Synthetic polymer. Among the cationic synthetic polymers used for gene delivery are polyethylenimine (PEI), polyamidoamine dendrimers, and poly(2-dimethylaminoethyl methacrylate).161-164 Depending on the flexibility (or rigidity) of the polymers, they form either a small (<100 nm) DNA polyplex or a large (>1 to 10 pm) DNA polyplex.165 More detailed physicochemical properties and their transfection efficacy are to be discussed. 

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