Macromolecular complex formation

Next, in the system of two proton-accepting polymers, e.g. polyacrylamide) (PAAm), poly(vinyl alcohol) (PVA), PVPo and PEO, and a proton-donating polymer, e.g. PMAA, selective macromolecular complex formation is realized as shown in Table 24. Thus, under these experimental conditions, the complexation abilities of these proton-accepting polymers with respect to PMAA (mainly due to hydrogen bonds) follows the order... 

Macromolecular Complex Formation and Polymer Adsorption on Colloidal Particles in Aqueous Solution... 

The goal of this chapter is to explore the analogy between macromo-lecular complex formation of the labeled probe chain and a polymeric proton donor, such as poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMAA), and the adsorption of the probe chain on colloidal particles such as silica or polystyrene. The basis for a possible analogy between these two situations arises from the nature of the local interactions. Macromolecular complex formation arises from specific interactions such as hydrogen bonding likewise, we expect that similar specific interactions exist between the PEG and the silica or polystyrene substrate. In essence, we consider the macromolecular complex to represent an interaction with a molecular substrate, whereas the colloidal problem involves a solid substrate. 

To explore this analogy, we will review previous work on the influence of stoichiometry as well as present new results on the effect of neutralization on macromolecular complex formation. In addition, we will review very recent results for adsorption on colloidal silica and present preliminary results for the adsorption on colloidal polystyrene. The excimer to monomer emission intensity ratio, the excitation spectra, and the lifetimes of the excimer and monomer are the observable experimental parameters. 

Macromolecular Complex Formation. The ultimate objective of the studies on complex formation between polymers in aqueous solution is to understand how the PEG chains interact with either the PMAA or PAA chains on the molecular level. For example, we would like to know whether... 

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. 

The reaction proceeds at the stage of pseudo-cyclocopolymerization involving complex formation between the growing macroradical and the monomer which is responsible for the alternation of monomer units along the macromolecular chain ... 

Not only do the macromolecular components which are the direct products of the genes participate in the formation of complex pathways and networks, they can also assemble to form macromolecular complexes and micromachines . Some of these micromachines are now well known, such as ATPase, some parts of which turn like a rotor in the mitochondrial membrane to generate the energy of the cell, or the micromachines responsible for transcription or DNA replication. Some others are less known, but play critical roles, such as the complex that forms in the cell membrane and can induce the cell to commit suicide . 

Developments in the Theory of Cationic Polymerisation IX. Some Effects of the Complex Formation between Cations and Monomers. P.H. Plesch, Die Makromolekulare Chemie, Macromolecular Symposia, 1990, 32, 299-306. 

Unmodified poly(ethyleneimine) and poly(vinylpyrrolidinone) have also been used as polymeric ligands for complex formation with Rh(in), Pd(II), Ni(II), Pt(II) etc. aqueous solutions of these complexes catalyzed the hydrogenation of olefins, carbonyls, nitriles, aromatics etc. [94]. The products were separated by ultrafiltration while the water-soluble macromolecular catalysts were retained in the hydrogenation reactor. However, it is very likely, that during the preactivation with H2, nanosize metal particles were formed and the polymer-stabilized metal colloids [64,96] acted as catalysts in the hydrogenation of unsaturated substrates. 

An important function of the PDZ domains hes in the formation of macromolecular associates at the cell membrane (review Pawson and Scott, 1997). PDZ proteins can also provide a framework for clustering of proteins, such as ion channels, at the cell membrane and they may help to recruit proteins into membrane-bound macromolecular complexes. 

Kubinski, H., Kubinski, Z.O., Fiandt, M. Konopa, G. (1981) Formation of macromolecular complexes and other effects of DNA treatment with diethyl and dimethyl sulfate physicochemical and electron microscopic studies. Carcinogenesis, 2, 981-990... 

The plasma lipoproteins are spherical macromolecular complexes of lipids and specific proteins (apolipoproteins or apoproteins). The lipoprotein particles include chylomicrons, very-low-density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). They differ in lipid and protein composition, size, and density (Figure 18.13). Lipoproteins function both to keep their component lipids soluble as they transport them in the plasma, and also to provide an efficient mechanism for transporting their lipid contents to (and from) the tissues. In humans, the transport system is less perfect than in other animals and, as a result, humans experience a yradual deposition of lipid—especially cholesterol—in tissues. This is a potentially life-threat-en ng occurrence when the lipid deposition contributes to plaque formation, causing the narrowing of blood vessels (atherosclerosis). 

It is argued here that the formation of casein micelles is a highly controlled process, producing a macromolecular complex with a specific structure and function. This point needs to be stressed because of a long-standing view of caseins as random coil-type proteins which associate to produce a largely random coil complex having only a nutritional function. 

Such a decrease in the linewidth may result from a decrease in the Gd3+ coordination number upon formation of the macromolecular complex, which could result in greater symmetry and a lower zero-field splitting for the Gd3+ ion. This spectrum is independent of temperature between 4 and 25°C and is independent of the Gd3+/ ATPase ratio up to 2 Gd + ions/ATPase molecule. The peak-to-peak linewidth of 285 G sets a lower limit of 2,3 x 10"10s Qn the electron spin relaxation time of enzyme-bound Gd +t This symmetric, narrow EPR spectrum for the Gd3+-ATPase complex is compared in Figure 13B to that of Gd3+ bound to parvalbumin, a Ca2+-binding protein from carp. In this case, the spectrum is extremely broad and suggests a greatly distorted Gd3+ coordination geometry compared to the Ca2+-ATPase. 

In biological systems, a macromolecular chain effectively selects a complementary one to form an intermacromolecular complex. In this way, very specific functionalities become effective. Synthetic polymers can also form intermacromolecular complexes, but the ability of a synthetic polymer to select only one objective polymer as in biological systems has not yet been realized, except for several specific systems of pairs of polymers which include one of the complementary base pairs of nucleic add individually, e.g. po y(A)-poly(U) and poly(I)-poly(C) (see Sect. 3.3). The intermacromolecular complex formation of synthetic polymers is controlled by many factors such as interaction forces, solvent, ionic strength, temperature, pH, etc. Moreover, the cooperative and concerted interactions of each active site play an important role in complex formation. These phenomena suggest that the selective intermacromolecular complexation can be realized under suitable conditions. 

The second mode of crystal formation that occurs in dentin is via matrix vesicles. These are phospholipid delimited packages of specialized enzymes, macromolecular complexes and ions, that induce the precipitation of amorphous calcium phosphate. At some point the latter crystallizes into carbonated apatite crystals, that have no preferred orientation [62], These appear smaller and denser than the crystals that form in the collagen framework. 

The experimental results may be represented both by the titration curves or property-composition dependences. The extremums or bends on the titration curves indicate the formation of complexes and their composition. Thus, investigating the-possi-bility of complex formation in polyelectrolyte - nonionic polymer systems, one can use the methods of conductometric and potentiometric titration. The formation of interpolymer complexes in these systems, as some authors suggest18,211, is caused by a co-operative formation of hydrogen bonds between carboxy groups of the polyacid and oxygen atoms of nonionic polyvinylpyrrolidone or poly(ethylene glycol) and is therefore accompanied by an increase of pH of the solution. The typical titration curves for the system polyvinylpyrrolidone - copolymer maleic anhydride and acrylic add are shown in Fig. 1. The inflection points of the titration curves indicate the ratio at which the macromolecular components react with each other, i.e. the composition of the formed complexes. 

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