Proteins macromolecule interactions

High sorption capacities with respect to protein macromolecules are observed when highly permeable macro- and heteroreticular polyelectrolytes (biosorbents) are used. In buffer solutions a typical picture of interaction between ions with opposite charges fixed on CP and counterions in solution is observed. As shown in Fig. 13, in the acid range proteins are not bonded by carboxylic CP because the ionization of their ionogenic groups is suppressed. The amount of bound protein decreases at high pH values of the solution because dipolar ions proteins are transformed into polyanions and electrostatic repulsion is operative. The sorption maximum is either near the isoelectric point of the protein or depends on the ratio of the pi of the protein to the pKa=0 5 of the carboxylic polyelectrolyte [63]. It should be noted that this picture may be profoundly affected by the mechanism of interaction between CP and dipolar ions similar to that describedby Eq. (3.7). 

In a qualitative way, colloids are stable when they are electrically charged (we will not consider here the stability of hydrophilic colloids - gelatine, starch, proteins, macromolecules, biocolloids - where stability may be enhanced by steric arrangements and the affinity of organic functional groups to water). In a physical model of colloid stability particle repulsion due to electrostatic interaction is counteracted by attraction due to van der Waal interaction. The repulsion energy depends on the surface potential and its decrease in the diffuse part of the double layer the decay of the potential with distance is a function of the ionic strength (Fig. 3.2c and Fig. 

Before we examine some specific solvation effects on cooperativity we must first consider various aspects of the solvation Gibbs energy of a macromolecule a. We present here one possible decomposition of AG which will be useful for our purposes. Consider a globular protein a which, for simplicity, is assumed to be compactly packed so that there are no solvent molecules within some spherical region to which we refer as the hard core of the protein. The interaction energy between a and the fth solvent molecule (the solvent is presmned to be water, w) is written as... 

In Section 15.6, the retention of proteins in ion exchange chromatography is discussed. The ions in the surrounding electrolyte form an electrical double layer around a charged macromolecule, e.g., a protein. The interaction between a protein and an oppositely charged surface can, therefore, be described as taking place between two overlapping double-layer systems. 

Many biological processes depend on a specific interaction between molecules. The interaction often involves a macromolecule (protein or nucleic acid) and a smaller molecule, a ligand. Specific examples include enzyme-substrate interactions and receptor protein-hormone interactions. One of the most... 

A neutron scattering investigation of the polymer solution structure and protein-polymer interactions, Macromolecules 1992b, 25, 3932-3941. N. L. Abbott,... 

Tertiary structures are formed by the twisting of alpha-helices into specific shapes. They are produced and held in place by the interactions of amino side chains on the amino acid residues constituting the protein macromolecules. Tertiary protein structure is very important in the processes by which enzymes identify specific proteins and other molecules upon which they act. It is also involved with the action of antibodies in blood, which recognize foreign proteins by their shape and react to them. This is what happens in the phenomenon of disease immunity, where antibodies in blood recognize specific proteins from viruses or bacteria and reject them. 

Sequence analysis is a core area of bioinformatics research. There are four basic levels of biological structure (Table 1), termed primary, secondary, tertiary, and quaternary structure. Primary structure refers to the representation of a linear, hetero-polymeric macromolecule as a string of monomeric units. For example, the primary structure of DNA is represented as a string of nucleotides (G, C, A, T). Secondary structure refers to the local three-dimensional shape in subsections of macromolecules. For example, the alpha- and beta-sheets in protein structures are examples of secondary structure. Tertiary structure refers to the overall three-dimensional shape of a macromolecule, as in the crystal structure of an entire protein. Finally, quaternary structure represents macromolecule interactions, such as the way different peptide chains dimerize into a single functional protein. 

We have discussed both target receptors and pharmacokinetics in this book. Protein manufacture is under direct genetic control, and two factors are of particular relevance here. First, the precise structure and function of protein macromolecules (receptors) targeted by a specific drug molecule will vary in different individuals. Since the structure and function of the protein are directly related to how the drug molecule will interact with that protein, individuals responses to the drug will vary. Second, there are genetic variations in metabolic enzymes (proteins) and hence metabolism. Both of these processes fall neatly into the domain of pharmacoproteomics (see Section 14.8). 

Most physiological processes are the consequences of an effector interaction with biomacromolecules (Harding and Chowdhry, 2001 Weber, 1992), such as interactions between enzymes and their substrates, between hormones and hormone receptors, between antigens and antibodies, between inducer and DNA, and so on. In addition, there are macromolecule-macromolecule interactions such as between proteins (Kleanthous, 2000), between protein and nucleic acid (Saenger and Heinemann, 1989), and between protein and cell-surface saccharide. The effector of small molecular weight is normally referred to as the ligand, and the macromolecular combinant is known as the receptor. 

It should be noted that this chapter has been limited to physical-chemical interactions between food macromolecules in model systems. The main reason is that in food systems, chemical protein-polysaccharide and protein-polyphenols interactions have not yet been sufficiently studied. A new trend in this area is covalent protein-polysaccharide hybrids (conjugates natural and synthetic) that are of great interest as functional additives and food ingredients... 

Pascal, C., Poncet-Legrand, C., Sami-Manchado, R, Cheynier, V., Vemhet, A. (2006). Effect of ionic strength, tartaric acid and ethanol on the interactions between flavan-3-ols and salivary proline rich proteins. Macromolecules and Secondary metabolites in Grapevine and Wines. Reims. 

Glycan arrays are an equally powerful technology for the evaluation of carbohydrate-macromolecule interactions. Analogous to DNA and protein arrays, glycan arrays contain many different carbohydrates affixed to a solid support. This review will focus on development strategies, challenges, and applications of glycan arrays. Several other reviews have been published over the last few years (1 ). ... 

---