Fragmentation, degradation

The endogenous peptide dynorphin and its C-terminally degraded fragments dynorphin A 3 and dynorphin A2 c, are somewhat K-selective... 

The rate of formation of the degraded fragments, with the symmetry relation (82), is given by ... 

In contrast to the stepwise addition of amino acids to a protein, much of the semisynthesis of proteins has been concerned with the covalent combination of synthetic peptides with natural proteins or their partially degraded fragments. 

In certain examples where the Smith-degradation fragments have been separated more conveniently by paper chromatography, the structure of these fragments has been demonstrated by examining their methylation products by gas-liquid chromatography. This approach has been used in studying the fine structure of lichenan,644 isolichenan,645 and wheat pentosan.848... 

The chemical behavior and reactions of pyrrolizidine derivatives were investigated for the most part during structural analysis of naturally occurring pyrrolizidine alkaloids and in the course of the syntheses of their degradation fragments there are several publications concerned specially with this subject. Pyrrolizidine derivatives are typical tertiary amines, and consequently their chemical behavior is a combination of the properties of tertiary amines and of those of the substituent functions. However, some peculiarities of the class can be explained only in terms of the configuration of the bicyclic system. 

Reaction of human a-L-idosiduronase with glycosides of sulfated-2,5-anhydrohexitols and anhydro-D-mannitol showed that sulfation enhanced catalysis. A model of substrate binding and a relationship to the disease termed mucopolysaccharidosis, which leads to incompletely degraded fragments of heparan and dermatan sulfates, was proposed.2870... 

Much of the early work on the structure of the harmala alkaloids was of necessity directed to the preparation and identification of degradative fragments, many of which were new. The following account will be... 

---