M. Kobayashi et al., 2 CHAINS OF RHAMNOGALACTURONAN-II ARE CROSS-LINKED BY BORATE-DIOL ESTER BONDS IN HIGHER-PLANT CELL-WALLS, Plant physiology, 110(3), 1996, pp. 1017-1020
Polysaccharide moiety of the boron-polysaccharide complex (T. Matoh, K
. Ishigaki, K. Ohno, J. Azuma [1993] Plant Cell Physiol 34: 639-642) i
solated from radish (Raphanos sativus) roots has been shown to be rham
nogalacturonan II by glycosyl-linkage analysis and the presence of dia
gnostic monosaccharides, including apiose, aceric acid, 2-O-methylfuco
se, and 3-deoxy-D-manno-2-octulosonic acid. Removal of boron from the
complex reduced the molecular weight by one-half without causing a sig
nificant increase in the number of reducing end groups, indicating tha
t boron, as boric acid, links two rhamnogalacturonan II chains togethe
r to form the boron-polysaccharide complex.