Alkaline degradation structure changes

It is apparent that attempts to correlate the effect of changes in structure with two or more different properties of a compound must take into account the mechanisms by which the different properties are manifested. The mechanisms (and often the products) of alkaline degradation differ from those of acid-catalyzed hydrolysis, and the comparison of reactivities should be made with due recognition of these facts. In this respect, the degradation of picrocrocin has been well investigated.13 Both acid- and... 

Alkaline Degradations - Change in Physical Structure. The hydroxyl accessibility of the fibrous hydrocellulose was initially 51.4 0.8%. In contrast, the amorphous substrate had an accessibility of 99.2 1.0%. Exposure of the fibrous hydrocellulose to the alkaline media caused the accessibility to decrease slightly to 50.7 1.0% and 49.1 1.2% at 60 and 80°C, respectively, but accessibility did not change significantly during the reaction periods (0-168 hr). 

Other chemical degradation pathways include -elimination, which can lead to racemization and disulphide exchange reactions. The amino acids that may undergo P-elimination include Cys, Ser, Thr, Phe, and Lys (40) and occur especially at alkaline pH (64). The reduction and oxidation of the disulphide bonds are often accompanied by a considerable change in the protein conformation (23,33). An example is the secondary structure of insulin that is disrupted or completely lost when the disulphide bonds are broken (23). The disulphide bond disruption or interchange can also result in an altered three-dimensional structure and therefore a possible loss of activity (40) or aggregation (29). For further details, the reader is directed to the following reviews and book chapters (30,40,62,65). 

Thus, observed reduction of organic matter content (fats, non-collagen proteins) is obviously associated with the change of leather tissue structure. The destmctive effect on the structure of studied materials may also cause alkalinity of the medium, which, as known, increases at natural proteins degradation [32]. Table 3 shows data of pH change of water extract of initial and test samples. In all cases, system alkalinity increase was observed. 

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