Linkage and sequence analysis of mannose-rich glycoprotein core oligosaccharides by proton nuclear magnetic resonance spectroscopy

The anomeric proton (H-1) chemical shifts of D-mannopyranosides in aqueous solution are affected both by the aglycon and by substitution of the ring [Lee, Y. C., & Ballou, C. E. (1965) Biochemistry 4, 257]. We have examined the 1H NMR spectra for a variety of linear and branched mannooligosaccharides and have assigned the H-1 resonances to the component sugars. The chemical shifts, which range from delta 4.76 to 5.36, provide information regarding the linkages, sequences, and anomeric configurations of mannose residues in an oligomer. Thus, 1H NMR spectroscopy can complement enzymatic hydrolysis, methylation analysis, and acetolysis for the structural characterization of oligosaccharides. Furthermore, small structural differences between otherwise identical oligosaccharides are often accompanied by long-range chemical shift changes for the anomeric protons. Because sugars three or more residues away from the structural alteration can be affected, the changes must reflect conformational differences. We have placed emphasis on the mannose-rich oligosaccharides from glycoproteins, particularly those produced by endo-beta-N-acetylglucosaminidase digestion. Two mannose-rich glycopeptides were isolated from a monoclonal human IgM and their positions of origin on the polypeptide chain were determined. The oligosaccharides were released with endo-beta-N-acetylglucosaminidase and fractionated into several size classes. Our structural studies show that each glycopeptide possessed a unique set of oligosaccharides, in agreement with a recent report [Chapman, A. & Kornfeld, R. (1979) J. Biol. Chem. 254, 816]. The NMR spectra were particularly valuable in detecting and quantitating isomeric fragments not observed previously, and our results suggest a modification of the scheme presented by Chapman and Kornfeld for the processing of mannose-rich IgM oligosaccharides.

Carbohydrate structure of yeast invertase. Demonstration of a form with only core oligosaccharides and a form with completed polysaccharide chains

Invertase, extracted from broken cells of Saccharomyces cerevisiae X-2180 mm2 mannan mutant, was separated into a fraction insoluble in 75% ammonium sulfate (P75 invertase, 36% carbohydrate) and a soluble fraction (S75 invertase, 53% carbohydrate). The latter reacted with antibodies specific for the alpha 1 leads to 6-linked mannose of the mannoprotein outer chain, whereas the P75 invertase failed to react with this antiserum although it did react with serum against terminal alpha 1 leads to 3-linked mannose units that are characteristic of the mannoprotein core. A bacterial endo alpha 1 leads to 6-mannanase removed the outer chains from the S75 invertase and converted it to a form that was similar in electrophoretic and immunochemical properties to the P75 invertase, whereas the endomannanase had little effect on the latter invertase. The results suggest that the P75 invertase is a form of the enzyme to which only the core oligosaccharide units had been added, and the S75 invertase represents an enzyme fraction to which the polysaccharide outer chains were also attached. A strong anomeric PMR signal for unsubstituted alpha 1 leads to 6-linked mannose in the S75 invertase, and a much reduced signal in the P75 invertase and endomannanase-digested S75 invertase, support these conclusions. Endo-N-acetyl-beta-glucosaminidase digestion of the S75 and P75 invertases, as well as of a purified wild type yeast invertase, produced an apparently identical series of 3 to 4 carbohydrate-containing proteins that were separable by polyacrylamide gel electrophoresis in sodium dodecyl sulfate but that migrated as a single band on isoelectric focusing. The bands ranged from about 63,000 to 69,000 daltons and differed by the size of one or more carbohydrate core units each of 15 mannoses and 1 N-acetylglucosamine. The results suggest that the external invertase molecules contain some core units without attached outer chains, and that the cells contain a precursor form of the enzyme to which only the core units have been added. In support of this conclusion, PMR spectra and chromatographic patterns show that the core fragments from the P75, S75, and wild type invertases are essentially identical.

Conformational changes associated with complex formation between a mycobacterial polymethylpolysaccharide and palmitic acid

The anomeric proton magnetic resonances of Mycobacterium smegmatis 3-O-methylmannose polysaccharide have chemical shifts intermediate betwen those of nonaglucoamylose and alpha-cyclodextrin, and on addition of palmitic acid most of these resonances are shifted upfield toward that of the cyclodextrin. This suggests that the methylated polysaccharide could have a conformation with some secondary structure intermediate between those of the two reference compounds, and that it forms a tightened coil upon addition of the lipid which yields an inclusion complex with the polysaccharide. The change in chemical shift is linear with lipid concentration, which indicates that the complex undergoes rapid exchange with free polysaccharide. The changes in proton chemical shifts of the polysaccharide and of the palmitic acid are consistent with the fatty acid being inserted in the coiled polysaccharide with its carboxyl group near the methyl aglycon.

The functions of experimental participatory experiences in the learning-teaching process

The author analyzes the process by which experimental approaches and observations are transformed into usable knowledge. She examines her past work within this framework. Flexibility and open-ended beliefs permit the testing of new, unfamiliar data against known theoretical backgrounds and their subsequent organization and incorporation into further learning experiences. This material, in turn, can be formulated into new content that enhances one's learning and teaching potentials.

Intake procedures at a community mental health clinic

It is suggested that it is necessary to modify classical techniques so that the responsibility for the care of large numbers of people can be discharged. One approach has been practiced for three years at the North Suffolk Mental Health Center in Boston. This method allows for diagnostic procedures to be integrated with administrative follow through enabling a family to be helped rapidly. After three years, this approach has made it possible to see more than 700 families without a waiting list and with a possibility of making diagnoses within the major diagnostic categories of child pathology. This procedure has been an important reason for a positive relationship with the community and has enabled the Center to enter areas of consultation and education more easily.