This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A series of oligomeric glycans can be extracted from the cell walls of developing cotton fibers with weak acid. Glycans that produce similar profiles on high pH anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) are also found in a protein complex extracted from developing fibers. The oligomers are most abundant at about 21 days postanthesis when cell wall biosynthesis is shifting from primary to secondary wall synthesis. The oligomers were extracted from a particulate precipitate released from rehydrated fibers or from the fibers with 0.1N HCl at 100 . At the time of collection, incubation of the bolls in water at ambient temperature for one hour prior to freezing appears to decrease the amount of particulate matter, which is later obtained from the extract. This decrease is assumed to be due to depletion of substrate for wall synthesis. The solubility of the oligomers has been investigated to optimize the extraction of the oligomers and to increase our understanding of the conversion of cell wall precursors from the soluble to the insoluble state. Complete extraction is essential to permit investigation of quantitative relationships. Following extraction, the oligomers were chromatographed on molecular sieve columns BioGel P-4 or Sephadex G-25. The oligomers were resolved into fractions that yielded 10-12 peaks on HPAEC-PAD. The UV-MALDI mass spectra were obtained for these fractions where the dominant ion series in each case was that of (hexose)n up to n=32. Treatment of the oligomers with a highly purified endo-beta-1,4-glucanase readily converts the larger ones to the smaller ones and liberates glucose. The oligomers contain glucose, galactose and mannose. With increasing size of the oligomers, the amount of galactose and mannose appears to remain the same with the difference being increasing amounts of glucose. We hypothesize that the oligomers play a role in the biosynthesis of the cell wall of developing cotton fibers.
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