The Properties of Proteins

The phosphorylation and dephosphorylation of seryl, threonyl, and tyrosyl residues regulate the activity of certain enzymes of lipid and carbohydrate metabolism and the properties of proteins that participate in signal transduction cascades. 

The multilamellar bilayer structures that form spontaneously on adding water to solid- or liquid-phase phospholipids can be dispersed to form vesicular structures called liposomes. These are often employed in studies of bilayer properties and may be combined with membrane proteins to reconstitute functional membrane systems. A valuable technique for studying the properties of proteins inserted into bilayers employs a single bilayer lamella, also termed a black lipid membrane, formed across a small aperture in a thin partition between two aqueous compartments. Because pristine lipid bilayers have very low ion conductivities, the modifications of ion-conducting... 

Polyclonal bovine IgG, recombinant human antibody (type IgG-ic) Separation, comparison of the properties of Protein A, Protein G and Protein L SMC (CIM ) disks Affinity (Protein A, Protein G, Protein L) disks [81]... 

IEF is an electrophoretic method in which proteins are separated on the basis of their pis.1 214-6 10 64-69 p makes use of the property of proteins that their net charges are determined by the pH of their local environments. 

Figure 20.18 The central dogma of molecular biology a summary of processes involved inflow of genetic information from DNA to protein. The diagram is a summary of the biochemical processes involved in the flow of genetic information from DNA to protein via RNA intermediates. This concept had to be revised following the discovery of the enzyme, reverse transcriptase, which catalyses information transfer from RNA to DNA (see Chapter 18). It may have to be modified in the future since changes in the fatty acid composition of phospholipids in membranes can modily the properties of proteins, and possibly their functions, independent of the genetic information within the amino acid sequence of the protein (See Chapters 7, 11 and 14).

Ionic Medium - Since many of the properties of protein products depend on their ionic configuration and amphionic nature, changes in pH will strongly influence the results. Standardized media are to be recommended, or preferably, correlate the results with pH changes in the medium. Similarly, the presence of other ions needs to be either clearly stated or excluded. 

Mutations are only rarely beneficial, but we know that many mutations alter the properties of proteins very little. We can anticipate that most genes may undergo mutations that cause some loss of good health and vitality without being diagnosed as causing disease. 

The properties of protein in aqueous systems depend on179) ... 

Tanaka s discovery of smart gels revolutionized many fields of theoretical and applied science. Their behavior provides an insight on the properties of proteins, and they are expected to have a number of practical applications in... 

It is clear that the main reason for the deviation of the properties of protein-like copolymers from those of random copolymers is the special sequence design scheme [18], not just differences in the degree of blockiness. 

The structure of a real biopolymer landscape is highly complex. Recently, researchers have started to understand some of the properties of proteins that lead to specific landscape structures. To simplify the problem, it is desirable to identify which physical characteristic of proteins give rise to dynamic trends in evolution. In this section, we review the experimentally deduced properties of coupling and additivity, with the intention of demonstrating that these properties are correlated and discussing the landscape features that they produce. 

In summary, enzymatic hydrolysis presents numerous possibilities to modify the properties of proteins. Several food-grade enzymes with different specificities are now available. The selection of an enzyme is mainly dictated by its cost, while the cost of an enzyme accounts for only a small percentage of the protein hydrolysate production cost. 

Al any methods used to study protein interactions and proteolysis in - - complex mixtures are often unsuitable for application to food systems, where severe heat treatments or enzymic modification may change the properties of proteins and their reactivity in an analytical procedure. Chromatographic, electrophoretic, and immunochemical methods are excellent tools for fractionating protein mixtures and measuring the concentrations of the individual components, but heat treatment or enzymic... 

In addition to the use of micelles as models for hydrophobic interactions in protein systems, information concerning the dilferent binding sites of protein molecules can be obtained by studying the elFects of surfactants on the properties of proteins and related compounds. The ensuing discussion is centered on these two applications of amphiphilic systems. 

The properties of protein-polysaccharide complexes formed near the protein lEP are independent of the way in which their have been produced. This indicates an equilibrium nature of complexing under conditions of weak protein-polysaccharide interaction. 

The properties of protein fragments can Ik also used for the fluorometric assay of proteolytic activity. Curoffproposed that the increase in trichloroacetic acid-soluble tyrosine (both free and bound in small peptides) can be fluorometrically assayed after the condensation with nitrosonaphthol. 

Micelles form when a suitable amphiphile [e.g., sodium bis(2-ethyl-hexyl)sulfosuccinate (AOT)], is introduced into a hydrocarbon solvent (e.g isooctane). Reverse micelles containing water form when water is taken up by an isooctane—AOT solution. At water contents exceeding what is needed to saturate the polar head groups forming the micelle wall, the system can properly be termed a water-in-oil microemulsion, in which water droplets stabilized by a monolayer of surfactant are dispersed in an organic solvent. For convenience, the terms reverse micelle and microemulsion are sometimes considered equivalent. There is a considerable literature on the properties of proteins, particularly enzyme activity, in reverse micelles (see Luisi and Steinmann-Hofmann, 1987, and references cited therein). 

---