The origin of the periodate-resistant D-glucose residues in starches and glycogens
1974; Elsevier BV; Volume: 32; Issue: 2 Linguagem: Inglês
10.1016/s0008-6215(00)82101-1
ISSN1873-426X
AutoresMona Fahmy Ishak, Terence Painter,
Tópico(s)Phytochemicals and Antioxidant Activities
ResumoAbstract Under ordinary analytical conditions, the proportion of periodate-resistant- D -glucose residues in starches and glycogens was consistently about one-third of the proportion of branching points. The resistant D -glucose residues became freely oxidisable after the limit-oxidised glucans had been reduced with sodium borohydride. The results can be explained by assuming that, when a D -glucose residue carrying a branch at position 6 is oxidised, the resulting two aldehyde groups both form 6-membered hemiacetal rings with the closest hydroxyl groups on neighbouring, unoxidised residues in the same, (1→4)-linked chain, whereas when the other D -glucose residues are oxidised, only one of the aldehyde groups shows a strong tendency to form a hemiacetal of this kind. It is suggested that, in the unbranched units, the other aldehyde group preferentially forms a hemiacetal with the primary hydroxyl group in the same unit.
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