Average hydrophobicity

There are two definitions of protein hydrophobicity average hydrophobicity and surface hydrophobicity. The average hydrophobicity was defined by Bigelow (1967) as the total hydrophobicity of all amino acid residues comprising a protein divided by the number of amino acids in the protein. There is no standard definition of surface (or effective) hydrophobicity except the concept that there must be hydrophobic regions on the molecular surface that play an effective role in protein function. Readers who are interested in a more detailed discussion are referred to Nakai and Li-Chan (1988). 

Figure 3.11. Top. Single-residue hydrophobicity average) for proinsulin. The T,-based hydrophobicity plot of porcine proinsulin. At each residue position scale is derived in Chapter 5 and utilized in Chapters the hydrophobicity of the residue is given as derived 7 and 8 to understand the hydrophobic associations from the T,-based hydrophobicity scale. Bottom, attending function for selected protein systems. Mean residue hydrophobicity plot (11-residue...

The hydrophobic character of proteins and peptides depends primarily on their amino acid composition, i.e., the relative amount and lipophilicity of nonpolar residues in the molecule. A measurement of protein hydrophobicity (average hydrophobicity HOave) can be derived theoretically as the average of the individual A/t values based on the molar amino acid composition, where A/, is the change in free energy for the transfer of one mole of amino acid from ethanol to water (63-65). The average hydrophobicity values of the principal source proteins of cosmetic interest are listed in Table 3. A different way to express protein hydrophobicity is the so-called surface hydrophobicity, an entity measured experimentally on proteins by the adsorption of a chemical compound (cis-... 

Figure C2.5.2. Scaling of the number of MBS C(MES) (squares) is shown for the hydrophobic parameter = -0.1 and A = 0.6. Data were obtained for the cubic lattice. The pairs of squares for each represent the quenched averages for different samples of 30 sequences. The number of compact stmctures C(CS) and self-avoiding confonnations C(SAW) are also displayed to underscore the dramatic difference of scaling behaviour of C(MES) and C(CS) (or C(SAW)). It is clear that C(MES) remains practically flat, i.e. it grows no faster than In N.

Thiourea will react with neutralised formalin at 20-30°C to form methylol derivatives which are slowly deposited from solution. Heating of methylol thiourea aqueous solutions at about 60°C will cause the formation of resins, the reaction being accelerated by acidic conditions. As the resin average molecular weight increases with further reaction the resin becomes hydrophobic and separates from the aqueous phase on cooling. Further reaction leads to separation at reaction temperatures, in contrast to urea-formaldehyde resins, which can form homogeneous transparent gels in aqueous dispersion. 

Radicals typically are generated in the aqueous phase and it is now generally believed that formation of an oligomer of average chain length z (z-mer P/) occurs in the aqueous phase prior to particle entry.44 The steps involved in forming a radical in the particle phase from an aqueous phase initiator are summarized in Scheme 3.17. The length of the z-mcr depends on the particular monomer and is shorter for more hydrophobic monomers. 

FIG. 9 CMC vs. the average number of carbon atoms (n) in the hydrophobic chain for mixtures of two sodium alkyl sulfates [123]. 

Dioxins have effects similar to and potentially even more far-reaching than those of DDT, because they apparently affect a wide variety of species. Predatory birds are especially susceptible, and there is growing evidence that humans may be at risk. Tests have shown that when the concentration of dioxins in the blood of laboratory animals reaches a critical level, reproductive and immune-system defects result. Moreover, recent data indicate that the concentration of dioxins in the blood of the average U.S. resident has nearly reached that level. A major reason is that dioxins are hydrophobic, so they accumulate in fatty tissue rather than being readily processed and excreted from the body. 

Stable dispersion of water-insoluble and/or hydrophobic natural pigment such as carotenoid, curcumin, porphyrin pigment, or vegetable carbon black in form of bodies of average size of 10 ram Addition of 0.5 ppm P-carotene to yogurt containing 200 ppm riboflavin color did not change after 40 days at 6°C compared with control (decoloration at 1 day)... 

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