11B solid-state NMR investigation of the rhamnogalacturonan II-borate complex in plant cell walls.
The boron in plant cell walls, which is water-insoluble and in the solid state, is solubilized by pectinase digestion to give a dimeric rhamnogalacturonan II-borate (dRG-II-B) complex. To clarify the nondestructive structure of boron present in plant cell walls (as represented by sugar beet fiber), we performed 192- and 96-MHz 11B solid state NMR measurements. The use of a high field magnet frequency of 192-MHz enabled us to observe 11B isotropic chemical shifts at -9.7 and -9.6 ppm for dRG-II-B and sugar beet fiber in the solid state, respectively, demonstrating that the boron in isolated dRG-II-B and in plant cell walls is present as a borate-diol ester (1:2). The observation of the magnetic field dependence of the chemical shift and lineshape for the borate-diol ester (1:2) by quadrupolar interaction suggested that the borate complex had a distorted tetrahedral boron structure.
Kameda
Tsunenori
T
National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan.
Ishii
Tadashi
T
Matsunaga
Toshiro
T
Ashida
Jun
J
D027461:Beta vulgaris; D001881:Borates / Q000737:chemistry*; D001895:Boron / Q000737:chemistry; D002473:Cell Wall / Q000378:metabolism*; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D010368:Pectins / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry; D010944:Plants / Q000378:metabolism
D001881:Borates; D010940:Plant Proteins; C042492:rhamnogalacturonan II; D010368:Pectins; D001895:Boron