Carrier complexes with cations

The cationic lipopolymer is biodegradable, the polymers may form complexes with biomolecules and thus are useful as carriers for the delivery of biomolecules to cells. Examples of biomolecules that form complexes with cationic Upopolymers include nucleic acids, proteins, peptides, lipids, and carbohydrates. 

In contrast to the above-described carriers, which form positively charged complexes with cations, polyether antibiotics form neutral salts L with monobasic metal ions, because their carboxy group is dissociated at physiological pH [317],... 

A certain crown ether having additional coordination sites for a trasition metal cation (71) changes the transport property for alkali metal cations when it complexes with the transition metal cation 76) (Fig. 13). The fact that a carrier can be developed which has a reversible complexation property for a transition metal cation strongly suggests that this type of ionophore can be applied to the active transport system. 

FIG. 15 Cellular entry and intracellular kinetics of the cationic lipid-DNA complexes. Cationic lipid-DOPE liposomes form electrostatic complexes with DNA, and, in this case, also transferrin (Tf) is incorporated. Cellular uptake by endoc5dosis and endosomal acidification can be blocked with cytochaiasin B and bafilomycin Aj, respectively. DNA is proposed to be released at the level of endosomal wall after fusion of the carrier lipids with endosomal bilayer. This process is facilitated by the formation of inverted hexagonal DOPE phase as illustrated in the lower corner on the right. After its release to the C5doplasm DNA may enter the nucleus. (From Ref. 253. By permission of Nature Publishing Group.)... 

A number of substances have been discovered in the last thirty years with a macrocyclic structure (i.e. with ten or more ring members), polar ring interior and non-polar exterior. These substances form complexes with univalent (sometimes divalent) cations, especially with alkali metal ions, with a stability that is very dependent on the individual ionic sort. They mediate transport of ions through the lipid membranes of cells and cell organelles, whence the origin of the term ion-carrier (ionophore). They ion-specifically uncouple oxidative phosphorylation in mitochondria, which led to their discovery in the 1950s. This property is also connected with their antibiotic action. Furthermore, they produce a membrane potential on both thin lipid and thick membranes. 

Consider now a pseudo-cationic polymerization in which the non-ionic chain-carrier can form a complex with the compound R. The algebra and resulting equations are the same as above, with the one difference that q now signifies the concentration of uncomplexed chain-carriers and w the concentration of those which are complexed with R. 

If the liquid membrane contains carrier molecules that form 1 1 complexes with all cations, and if the concentration of the free ligand within the membrane is assumed to be constant, then Eq. (18) can be formulated as ... 

Self-Test M4.1B Inorganic cations can be separated by liquid chromatography according to their ability to form complexes with chloride ions. For the separation, the stationary phase is saturated with water and the carrier solvent is a solution of HC1 in acetone. The relative solubilities of the following chlorides in concentrated hydrochloric acid are CuCl2 > CoCI2 > NiCl2. Predict the relative values of the capacity factor k for the three salts. 

---