Proteins, functional properties surface activity

This particularly organized structure determines a well-defined surface of the protein. Recently, special attention has been focused on the surface activity of food proteins as the most important factor related to the functional properties and biological character of the proteins. The hydrophobic regions of the globular proteins are in general in the interior of the molecule, and the hydrophilic regions constitute its surface. Thus the globular proteins are less surface active in their native form. 

The functional properties of proteins depend also on their structure and interactions with the environment. The functional properties of surfactants depend on their hydrophilic-hydrophobic balance, too. Protein chains modified by proteolysis, amino acid incorporation, and transpeptidation may display different functional properties. As milk proteins possess good surface activities [131], the question of the changes in the functional properties of the enzymatically modified protein products is of especial interest. 

The hydrophobias are a case where protein nanofibers can play a dual role in creating a biosensor. They can aid in the immobilization of bioactive components within a biosensor and also add further functionality to the transducing element of a biosensor device. Hydrophobins are self-assembling [3-sheet structures observed on the hyphae of filamentous fungi. They are surface active and aid the adhesion of hyphae to hydrophobic surfaces (Corvis et al., 2005). These properties can be used to create hydrophobia layers on glass electrodes. These layers can then facilitate the adsorption of two model enzymes glucose oxidase (GOX) and hydrogen peroxidase (HRP) to the electrode surface. The hydrophobin layer also enhances the electrochemical properties of the electrodes. 

Lefebvre J, Relkin P. Denaturation of globular proteins in relation to their functional properties. In Magdassi S, ed. Surface Activity of Proteins—Chemical and Physiochemical Modifications. New York Marcel Dekker Inc., 1996 181-236. 

The cytosol-facing domains of CAMs recruit sets of multifunctional adapter proteins (see Figure 6-1). These adapters act as linkers that directly or indirectly connect CAMs to elements of the cytoskeleton (Chapter 5) they can also recruit intracellular molecules that function in signaling pathways to control protein activity and gene expression (Chapters 13 and 14). In some cases, a complex aggregate of CAMs, adapter proteins, and other associated proteins is assembled at the inner surface of the plasma membrane. Because cell-cell adhesions are intrinsically associated with the cytoskeleton and signaling pathways, a cell s surroundings Influence its shape and functional properties ( outslde-ln ... 

Evidently, in many cases the effect of each factor can hardly be evaluated, and the differences in surface activity of proteins are complex functions of their molecular properties. 

Development of methods for control of surface activity by means of chemical and physicochemical modifications of the protein molecules. These modifications may help to elucidate the basis of protein functionality and should enable the design of better protein derivatives with the needed properties. 

In the past ten years, protein modification has been the subject of many excellent publications and reviews [4,5,6,7,59]. Chemical or enzymatic food protein modification is theoretically feasible [8,9,10,175], Modification of proteins may alter their net charge, hy-drophobicity, structure, and furthermore their surface activity and thus the functional properties of the proteins. [11,12],... 

Enzymatic modification of proteins has been elaborated also for desired modifications of functional properties of food proteins. The surface properties of a functional protein can radically change when the protein associates with other types of molecules possessing surfactant properties. The versatility of proteins is mainly due to their complex structure, and the variability of functional properties of proteins can be ascribed to differences in the structure of protein molecules, more exactly to varieties of their building amino acids [11], The most important properties like surface activity and proteolytic degradability are basically influenced by compositional and structural features [129], Enzymatic modification of food proteins may alter their charge... 

Proteins are biopolymers that are encountered in many applications, such as food emulsions, hair conditioners, photographic emulsions, and various medical diagnostic products. Many of these applications are frequently based on the unique surface activity of the proteins, which is reflected in functional properties such as foaming, emulsification, and gelling. The proteins are composed of polymeric chains containing many hydrophobic and hydrophilic domains, often giving the molecules an amphipathic structure somewhat similar to that of polymeric surfactants. 

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