Macromolecular association

In this section, we study the non-covalent association of macromolecules, say of proteins A and B to form a complex AB  

Such associations are fundamental in protein-protein interaction networks in cell signaling. 

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The effect of media viscosity on polymerization rates and polymer properties is well known. Analysis of kinetic rate data generally is constrained to propagation rate constant invarient of media viscosity. The current research developes an experimental design that allows for the evaluation of viscosity dependence on uncoupled rate constants including initiation, propagation and macromolecular association. The system styrene, toluene n-butyllithium is utilized. 

The initiator association number y depends upon temperature, solvent and concentration of the system and is reported to be between two and seven (2) The association of polystyryl anions results in species A. Ak which do not react with styrene monomer. The macromolecular association is analogous to a reversible termination by combination. 

C. Nabuurs, B. Huijbregts, B. Wieringa, C. W. Hibers and A. Heerschap, P saturation transfer spectroscopy predicts differential intracellular macromolecular association of ATP and ADP in skeletal muscle. /. Biol. Chem., 2010, 285,39588-39596. 

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. 

Some enzymes are parts of multienzyme complexes in which reactants are channeled from one enzyme to another without ever entering the bulk solvent. Diffusion is hindered in the gel-like cytosol, and the cytosolic composition varies in different regions of the cell. In short, a given molecule may function quite differently in the cell than in vitro. A central challenge of biochemistry is to understand the influences of cellular organization and macromolecular associations on the function of individual enzymes and other biomolecules—to understand function in vivo as well as in vitro. 

A relatively common feature of many problems involving molecular weight determination of biopolymers is that of association-dissociation equilibrium. Subunit structure of enzyme proteins is well recognized (1), and methods of dissociation of subunits to obtain monomer molecular weight are widely utilized (2). A previous paper described the application of an equilibrium gel partition method to the analysis of macromolecular association in a monomer-dimer case (3). The experimental parameters in a system utilizing the Sephadex series of gel filtra-... 

Nguyen, R., and Harvey, R. (2003). Preservation via macromolecular associations during Botryococcus braunii decay proteins in the Pula Kerogen. Org. Geochem. 34, 1391-1403. 

The analogous considerations are valid for polymer systems as well. Indeed, amphiphilic monomer units also tend to occupy interfacial areas of macromolecular associates as it is normal for low molecular weight surfactants to adsorb at polymer-poor solvent boundaries. And, if such interfacial groups of the polymer associate catalyze chemical transformation of a compound which tends to adsorb at the associate interfaces, this can result in unusual kinetics effects. Okhapkin et al. [18] studied the influence of temperature-induced aggregation on the catalytic activity of thermosensitive... 

The events leading to the macromolecular associations observed with (3-lactoglobulin appear to be mediated by disulfide interactions. The initial solution proposed to reduce thermoinduced aggregation was to remove the Cys 121 and replace it with alanine (Cho et al., 1994). Unfortunately, recombinant protein could not be purified from inclusion bodies. The alternative... 

Even relatively weak van der Waals and dipole-dipole interactions very often prove sufficient for maintaining the stabilization of some macromolecular associates in solution4965. This may be exemplified by the stereocomplexes or the associates of the right- or left-handed helices of poly (y-methyl-L(or -d)-glutamate) in organic solvents4975. 

The probabilistic model of macromolecular association introduced in the previous section, for the case of large a and n B, may be recast into the formal language in terms of statistical thermodynamics. Recall from Chapter 1 that the chemical potential of a species has two terms, a structural energy (enthalpy) term and a concentration/entropy term ... 

Chapiro and Dulieu have established the dominant role of macromolecular associations from the reasons for the effects described [63]. Acrylic acid associates by hydrogen bonds, yielding a cyclic dimer or an oligomer... 

Continuum Models of Macromolecular Association in Aqueous Solution (M. A. 

The hydration forces can stabilize macromolecular association or prevent macromolecular interactions with a strength that depends on the surface characteristic of the molecules and the ionic composition of the medium. 

Absence of association in the oligomer is indicated by the fact that the values of the parachor (calculated from the experimental data and from the summation of atoms, bonds, and groups in a molecule according to the additive rule) coincide and hardly depend on the temperature. A similar picture was observed for the siuface molar entropy. This indicates that the extent of macromolecular association does not change within the studied range of temperatures. The entropy of formation of the surface per cm ... 

Fluorescence anisotropy or polarization is a technique generally employed in biophysical and bioanalytical applications. Such measurements provide information related to the size and shape of macromolecular structures, including proteins or membranes, as well as the rigidity of various molecular microenvironments. Information can also be gathered on protein-protein (macromolecular) associations and the... 

Y. Li, and PI. Lee, A new bioerodible system for sustained local drug delivery based on hydrolytically activated in situ macromolecular association, Int. J. Pharm., 383, 45-52, 2010. 

Hydrophobic associations in random copolymers of sodium 2-(acrylamido)-2-methylpropanesulfonate and some methacrylamides and methacrylates substituted with bulky hydrophobes are described with a focus on preferential intrapolymer self-association which leads to the formation of single-macromolecular assemblies (i.e., unimolecular micelles). Structural parameters that critically determine the type of the macromolecular association (i.e., intra- vs. interpolymer associations) are discussed, which include the type of hydrophobes, their content in a polymer, sequence distribution of electrolyte and hydrophobic monomer units, and the type of spacer bonding. Functionalization of single-macromolecular assemblies with some photoactive chromophores is also presented. 

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