2.1.8.2. Absorbency Under Load (AUL) - BADA

All the nucleophilic groups in proteins are sensitive to acylating. Tyrosine phenolic groups against
nucleophilic reactions are usually less reactive than linear amino groups partly because of their
higher pKa and partly because they are normally shielded in proteins structure. Another important
difference is instability of acylated tyrosine due to acylation of tyrosine residues may easily
reversible.
Comparable case of reversibility of acylated products of other nucleophiles, such as imidazolyl,
carboxyl and sulfhydryl are more selective than amino groups, hence EDTAD or succinic
anhydride has been utilized to convert amino groups to carboxylic acid [22] (Fig. 7).
1.7. Crosslinking
Figure 7. Conversion of an amine to carboxylic acid with succinic anhydride
The most common method for decreasing molecular freedom is crosslinking which joins the
polymer chains together through covalent or ionic bonds to form a network (Fig.8). Frequently the
term curing is used to indicate crosslinking.
The crosslinking may possibly contain the same structural features as the main chains, or they may
have a completely different structure. In the presence of solvent, a crosslinked polymer swells for
the reason that solvent molecules penetrate into the network. The degree of swelling depends on
the affinity of solvent and polymer for one another, as well as the level of crosslinking, protein
concentration during the crosslinking step, gel particle size, and environmental condition, such as
temperature, pH, and ionic strength [17] .
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