New NMR/Derivatization Methods for Oligosaccharide Structural Elucidation

University Of Colorado At Denver, Aurora CO

Investigators

Abstract

Complex carbohydrates are a diverse group of molecules found in virtually all living organisms, and are involved in a wide variety of crucial biological functions. An understanding of their many roles relies on a detailed knowledge of their structures. Novel NMR experiments are described that take advantage of doubly 13 C-labeled acetyl groups after peracetylation of hydroxyl functions, and are specifically tailored to extract detailed stereochemical and linkage information in unknown oligosaccharides. The procedures should be generally applicable to carbohydrates from virtually any source, without requiring 13 C incorporation into the carbohydrate molecules themselves by isotopic labeling. These experiments are designed to correlate the frequencies of the newly introduced 13 C nuclei to sugar ring protons, using several magnetization transfer/selection methods. These procedures will permit larger oligosaccharides to be elucidated and will be applied to a series of oligosaccharides derived from glycoproteins having from 3-15 sugars. These methods will also be important in the application of NMR spectroscopy to the structural elucidation of many natural products containing hydroxyl and amino functions. These studies will enable the stereochemistry of individual sugars in oligosaccharides to be more effectively determined, permit the assignment of linkages between adjacent sugars to be markedly improved, enable subspectra of larger oligosaccharides to be accumulated, and enable more detailed structural information to be garnered for many natural products. Carbohydrates are a major source of biomaterials used either directly or indirectly in many industries, including the food, chemical and polymer industries. This research will markedly improve their analyses and thereby provide benefits that foster their industrial use. This research project will be combined with teaching and training of students. Students will be encouraged to participate in multidisciplinary research conferences and the results of this research will be incorporated into courses in a local molecular structure program. The work will be broadly disseminated through publication, through participation in national and international meetings, and through the availability of new NMR pulse sequence software to other investigators in academics and industry.