Protein physico-chemical properties

New insights into the analysis of hydrophobically post-translational modified proteins could be achieved by the construction of lipidated proteins in a combination of bioorganic synthesis of activated lipopeptides and bacterial expression of the protein backbone (Fig. 19). The physico-chemical properties of such artificial lipoproteins differ substantially from those of the corresponding lipopeptides. The pronounced dominance of the hydrophilic protein moiety (e.g., for the Ras protein 181 amino acids) over a short lipopeptide with one or two hydrophobic modifications provides solubility up to 10 4 mol/1, while the biotinylated or fluorescence labeled lipopeptides exhibit low solubility in aqueous solutions and can be applied in the biophysical experiments only in vesicle integrated form or dissolved in organic solvent. 

The use of models that mimic a protein active site is normally prompted by the desire to eliminate any influence of the polypeptide backbone surrounding the active site in real biological molecules, which may obscure its physico-chemical properties. The first attempts to synthesize metal complexes similar to the active site of haemoproteins, through the use of simple metalloporphyrin derivatives, failed. The failure was due to the fact that these complexes react irreversibly with dioxygen as a consequence of side autooxidative reactions of the type ... 

Takahashi 1, Saitoh Y, Yoshida M, Sano H, Nakano H, Morimoto M, Tamaoki T. (1989) UCN-01 and UCN-02, new selective inhibitors of protein kinase C. 11. Purification, physico-chemical properties, structural determination and biological activities. J Antibiot 42 571-576. 

FIGURE 5.6 Physico-chemical and protein-related functional properties of defatted morama bean flours and their potential applications in food systems (adapted from Maruatona, 2008). 

Rodriguez Patino, J.M., Rodriguez Nino, M.R., Sanchez, C.C. (2007). Physico-chemical properties of surfactant and protein films. Current Opinion in Colloid and Interface Science, 12, 187-195. 

The factors influencing the functional properties of protein products are the innate characteristics (physico-chemical) of proteins, and processing and modification steps that alter them. Physico-chemical properties include ... 

In a previous section some general functional properties that are commonly looked for in protein products were classified according to physico-chemical properties. In this section, the general methodology for the objective evaluation (excluding sensory subjective methods), of these properties will be outlined. 

Milk protein system. The nomenclature and physico-chemical properties of the major milk proteins and their subunits have been provided by Whitney et al. (13) and Brunner (1 ). The conformation and related properties of the individual proteins and their subunits and aggregates have been reviewed by Morr (15) with special reference to their functional properties in food systems, and drawing heavily upon previous considerations by Bloomfield and Mead (16) and Slatterly (17). 

It is essential to consider the physico-chemical properties of each WPC and casein product in order to effectively evaluate their emulsification properties. Otherwise, results merely indicate the previous processing conditions rather than the inherent functional properties for these various products. Those processing treatments that promote protein denaturatlon, protein-protein Interaction via disulfide interchange, enzymatic modification and other basic alterations in the physico-chemical properties of the proteins will often result in protein products with unsatisfactory emulsification properties, since they would lack the ability to unfold at the emulsion interface and thus would be unable to function. It is recommended that those factors normally considered for production of protein products to be used in foam formation and foam stabilization be considered also, since both phenomena possess similar physico-chemical and functionality requirements (30,31). 

Harwalker, V. R. 1979. Comparison of physico-chemical properties of different thermally denatured whey proteins. Milchwissenschaft 34, 419-422,... 

The volume of distribution of a peptide or protein drug is determined largely by its physico-chemical properties (e. g., charge, lipophilicity), protein binding, and dependency on active transport processes. Due to their large size - and therefore limited mobility through biomembranes - most therapeutic proteins have small volumes of distribution, typically limited to the volumes of the extracellular space [26, 51]. 

Larman, V. N., Gabbott, P. A., and East, J., Physico-chemical properties of the settlement factor proteins from the barnacle Balanus balanoides, Comp. Biochem. Physiol. B., 72, 329, 1982. 

Briand L., Nespoulous C., Huet J. C., Takahashi M. and Pernollet J. C. (2001) Ligand binding and physico-chemical properties of ASP2, a recombinant odorant-binding protein from honeybee (Apis mellifera L.). Eur. J. Biochem. 268, 752-760. 

It is now recognised that a substantial number of proteins, especially enzymes, are polymorphic in that they exist in the cell as multiple molecular forms differing in certain of their physico-chemical properties. Each form of a polymorphic enzyme is called an isoenzyme or isozyme. Electrophoretic techniques provide convenient methods whereby this protein heterogeneity can be investigated and the approach has been widely exploited to characterise parasites. In short, aqueous parasite extracts are electro-phoresed, or focused isoelectrically, and separated proteins are stained generally (usually with Coomassie Blue) or more specifically with a histochemical (enzyme) stain (the zymogram technique). Further details of individual procedures and the use of the approach in parasite identification are to be found in a number of recent reviews (104,258,413,536,615,856). 

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