Chemical Analogous Modifications in Collagen Molecule

The effects encountered in chemical functionalization are the removing of a specific functional group or the creation of a new functional group that can be targeted in a subsequent reaction step. The functionalization reactions also can include solid-phase or solution procedures [36]. 

The chemical modification by N-terminal extensions involves the reaction of the free N-terminus of the completed collagen chain with an alkylating or acylating species. 

Reactions at carboxyl groups are generally carried out using solution procedures. Esterification of carboxyl groups are achieved in order to increase the reactivity or to block some chemical functions. 

Oxidative modification of collagen may be provoked by at least two mechanisms the external impact of different oxidizing substances (hydrogen peroxide or hydroxyl radical) [37] and in-vivo by inflammatory processes [38,39]. The oxidative reaction includes deamination of the amino groups in lysine or hydroxylyline, deguanidation in arginine, etc. The deamination leads to the formation of two aldehydes allysine and hydroxyallysine, which are further processed via two other independent aldehyde-specific pathways [40]. 

The alkaline treatment of collagen causes hydrolysis of carboxyamides of asparagine and glutamine residues from collagen in carboxylic groups [41]. 

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