Biopolymer interactions

The assembly of biopolymers with inorganic layered solids can lead to bionanocomposites in which the biopolymer becomes intercalated between the layers of the inorganic hosts [3]. The intercalation is a complex process that may simultaneously involve several mechanisms. Thus, in addition to hydrogen bonding, it has been invoked that certain biopolymers interact with the inorganic layers through... 

In liquid chromatography, affinity purification protocols (4-8) have been known for a long time. Naturally, electrophoresis can be used just as well to observe molecular or noncovalent interactions of DNA oligomers, provided the complex has distinct electrophoretic properties different from those of the free molecules. Therefore, affinity capillary electrophoresis (ACE) can be a powerful tool for studying DNA-drug or DNA-biopolymer interactions. Several reviews discussing these aspects of ACE have been published in recent years (9-19). The crucial aspects of DNA in this field are covered comprehensively in a recent overview article (20). 

An interesting extension of enantioselective chromatography on protein based CSPs in LC has been made15-17 using proteins to show qualitative and quantitative aspects of ligand-biopolymer interactions this includes chiral aspects. 

SIGNIFICANCE OF BIOPOLYMER INTERACTIONS IN CONTEXT OF NANOSCIENCE AND NANOTECHNOLOGY... 

We begin by attempting to put the subject of biopolymer interactions into some kind of technological and sociological context. Our observations of the current commercial scene would suggest that the main areas of focus of ongoing research and development in the food industry are ... 

Table 1.3 Potential impact of different kinds of biopolymer interactions affecting phenomena relevant to the nanostructuring of food colloids.

At its best, the thermodynamic approach can reveal both the role and the significance of the biopolymer interactions involved in these phenomena and processes, as well as allowing prediction or manipulation of the equilibrium under specific experimental conditions. 

Table 3.1 The influence of the character of the biopolymer-biopolymer interactions on the protein loading on emulsion oil droplets.

In this chapter we have outlined how the use of a universal thermodynamic approach can provide valuable insight into the consequences of specific kinds of biopolymer-biopolymer interactions. The advantage of the approach is that it leads to clear quantitative analysis and predictions. It allows connections to be made between the molecular scale and the macroscopic scale, explaining the contributions of the biopolymer interactions to the mechanisms of microstructure formation, as well as to the appearance of novel functionality arising from the manipulation of food colloid formulations. Of course, we must remind ourselves that, taken by itself, the thermodynamic approach cannot specify the molecular or colloidal structures in any detail, nor can it give us information about the rates of the underlying kinetic processes. 

Appelqvist, I., Debet, M. (1997). Starch-biopolymer interactions. Food Reviews International, 13,163-224. 

Semenova, M.G. (1996). Factors determining the character of biopolymer-biopolymer interactions in multicomponent aqueous solutions modelling food systems. In Parris, N., Kato, A., Creamer, L.K., Pearce, J. (Eds). Macromolecular Interactions in Food Technology, ACS Symposium Series No. 650, Washington, D.C. American Chemical Society, pp. 37 19. 

ENERGY AND CHARACTER OF MAIN TYPES OF BIOPOLYMER INTERACTIONS... 

Van der Waals forces act between all groups to some extent, but they rarely have a crucial or predominant influence on the net biopolymer-biopolymer interactions. 

The relationship between the statistical expression (equation (5.6)) and the classical expression (equation (5.8)) for determination of the entropy can be explained by the statement that, due to the additional heat taken up, the system acquires more available microstates (Edsall and Gutfreund, 1983). Equation (5.8) introduces a procedure for the direct calorimetric measurement of the entropy change for a specific process such as the reversible formation of a new set of biopolymer interactions. 

Experimental Techniques for Determining Thermodynamic Quantities of Biopolymer Interactions in Solution... 

For the case of flexible non-rigid particles, a penetration parameter can be used to take into account the softness of the biopolymer interactions. This parameter is defined as the ratio of the equivalent hard sphere radius to the corresponding radius of gyration (Tanford, 1961) ... 

In principle, the nature of biopolymer interactions in solution can also be determined from sedimentation equilibrium of a single biopolymer component at constant temperature T and angular velocity co. The thermodynamic activity on a weight-concentration basis, z, = yiC/M at radial distance r is related to that at a selected reference radial position (r ) by the following formal expression (Deszczynski et al., 2006) ... 

BIOPOLYMER INTERACTIONS IN THE BULK AQUEOUS MEDIUM OF FOOD COLLOIDS... 

Self-Assembly due to Specific Kinds of Biopolymer Interactions... 

The situation is complicated by the fact that the cmc value determined in the pure surfactant solution generally differs from that fomid in the presence of biopolymer. This is mainly because the surfactant-biopolymer interactions can shift the equilibrium between free surfactant molecules and their micelles, leading to a change in the effective cmc of surfactant molecules in the biopolymer system (Kelley and McClements, 2003 McClements, 2000 Thongngam and McClements, 2005). 

Nowadays it is well established that the interactions between different macromolecular ingredients (i.e., protein + protein, polysaccharide + polysaccharide, and protein + polysaccharide) are of great importance in determining the texture and shelf-life of multicomponent food colloids. These interactions affect the structure-forming properties of biopolymers in the bulk and at interfaces thermodynamic activity, self-assembly, sin-face loading, thermodynamic compatibility/incompatibility, phase separation, complexation and rheological behaviour. Therefore, one may infer that a knowledge of the key physico-chemical features of such biopolymer-biopolymer interactions, and their impact on stability properties of food colloids, is essential in order to be able to understand and predict the functional properties of mixed biopolymers in product formulations. 

Biopolymers are, of course, poly electrolytes. This means that electrostatic repulsion between them, as well as the contribution of counterions to the total free energy of the system, are to be included amongst the key factors affecting the character of the biopolymer interactions, and hence the stability of mixed biopolymer solutions with respect to phase separation (Antipova and Semenova, 1997 Grinberg and Tolstoguzov, 1997 Polyakov et al., 1997 Semenova, 1996 Wassennan et al., 1997). For... 

The term food colloids can be applied to all edible multi-phase systems such as foams, gels, dispersions and emulsions. Therefore, most manufactured foodstuffs can be classified as food colloids, and some natural ones also (notably milk). One of the key features of such systems is that they require the addition of a combination of surface-active molecules and thickeners for control of their texture and shelf-life. To achieve the requirements of consumers and food technologists, various combinations of proteins and polysaccharides are routinely used. The structures formed by these biopolymers in the bulk aqueous phase and at the surface of droplets and bubbles determine the long-term stability and rheological properties of food colloids. These structures are determined by the nature of the various kinds of biopolymer-biopolymer interactions, as well as by the interactions of the biopolymers with other food ingredients such as low-molecular-weight surfactants (emulsifiers). 

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