Non-reducing End Groups

The only pentosans which have been studied to any great extent are the xylans. These can be obtained from all lignified cell membranes by extraction with 5% sodium hydroxide solution after lipids, pectic materials etc. have been removed. The conditions necessary to avoid degradation during isolation have been outlined.2 Early structural determinations indicated that arabinose was present as a non-reducing end-group in a branched molecule which had a chain-length of 18-20 D-xylo-furanose residues.27 It has been shown recently, however, that the xylan from esparto holocellulose can be purified free of arabinose after several re-precipitations of the copper-complex.28... 

The possibility of the presence of cross linkages in the molecular structure of cellulose has been indicated by the work of Heuser, in cellulose nitrate by the work of McBain and Scott, and, by inference, in cellulose acetate. It is evident that the conclusions which have been drawn from studies of the reducing and non-reducing end groups in... 

The /8-amylase starts from the non-reducing end group and attacks chains with maltose linkages. Only maltose is liberated. Anomalies in the constitution of the chain molecule, such as isomaltose linkages, stop the enzyme action. The length of the chain plays no significant role. Maltotriose and maltose are not attacked. The enzyme is an exo amylase. ... 

Peat and Whetstone claimed that the use of acetyl bromide in chloroform for very short reaction-times (6 min.) selectively removes the non-reducing end-group from methylated starch, and proposed the method as a possible one for end-group assay. 

Fig. 2. Schematic picture of dextran B 512 molecule showing randomly coiled main chain composed of a 1-6 linked glucose units, and with reducing and non-reducing end groups. The distribution of a 1-3 linked side chains and the approximate size of an antigenic determinant are also indicated. C/rc/ = reducing = non-reducing end group. (Hedin and...

Ketha contains 4-O-methyl-D-glucuronic acid rather than the unsubstituted acid (6). Anti-Pn II seems to react equally well with polysaccharides containing either of these acids as lateral, non-reducing end-groups. 

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