Physical Chemistry of Foods
7 Proteins Proteins are polymers, more specifically polyelectrolytes, which are discussed in Chapter 6. However, proteins were h ...
The formation of more or less ordered macroscopic structures, especially gels. This is governed by the tendency of many protein ...
TABLE7.1 Properties of Amino Acid Residues Name of acid Symbolsa Side chain Reactive group pKb Fc Fd Glycine Gly G 22 H Alanine ...
TABLE7.1 Continued Name of acid Symbolsa Side chain Reactive group pKb Fc Fd Tryptophan Trp W Indole 14.2 5.8 Histidine His H Im ...
Other side groups occur when the protein isconjugated, implying that other groups become covalently bonded to some amino acid re ...
(Section 7.3). It is to be expected that the charged groups can be strongly hydrated (Section 3.2) and that the aliphatic groups ...
theless, it is mostly not possible to predict the higher structures from the primary structure. One reason is that the number of ...
FIGURE7.1 Illustration of some aspects of the primary structure of two proteins,b-lactoglobulin (genetic variant B) andb-casein ...
Despite the flexibility of the peptide chain, most proteins do not assume random conformations in solution. Contrariwise, the co ...
stabilize it. This is comparable to the formation of a molecular crystal from a solution, where bond energies often are 1 or 2kB ...
method of excluding hydrophilic residues from the core, if they make up a high proportion of the residues, is the formation of a ...
conformation, unless it is very hydrophobic. Often, such large molecules contain a number of separate, globulardomainsof 100 or ...
7.1.5 Other Aspects Some proteins do not fit in the scheme of globular versus fibrous, and they may be calleddisordered. Such pr ...
(b) Post-translational modificationsoccur in the cell producing the protein. Of these, proteolytic removal of nonfunctional part ...
because of their dipole. A large proportion of the polar noncharged surface in the interior did indeed comprise peptide bonds. ( ...
7.2.1 Thermodynamic Considerations We will first consider fairly ideal cases, implying globular protein molecules containing one ...
FIGURE7.5 Approximate example of the stability of a fairly small globular protein as a function of temperature. Change from the ...
conformational stability, and it is seen to be fairly small, in this case about 25 kJ?mol^1 at its maximum. Equation (7.3) then ...
abruptness directly follows from the strong temperature dependence ofDG, which is largely due toDHbeing very large (see Figure 7 ...
Salt bridges. This concerns only a few bonds; they may on average contribute by an amount of about20 kJ?mol^1 toDH. Some othe ...
«
7
8
9
10
11
12
13
14
15
16
»
Free download pdf
