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Chemical Glycobiology and Bionanotechnology
Summary: Carolyn Bertozzi is interested in developing chemical and nanoscale tools for probing biological processes, particularly those involving glycans. Her research involves the use of bioorthogonal chemistry for imaging glycans in living systems and profiling changes in the glycome associated with diseases such as cancer and bacterial infections.
A major lesson from eukaryotic genome-sequencing projects is that the absolute number of genes an organism's genome encodes is not the best parameter for defining biological complexity. Instead, the complex functions associated with human health and disease are determined by combinatorial expansion of genomic information in the form of post-translational modifications. Of these, the most ubiquitous is glycosylation, highlighting the importance of glycobiology in the postgenomic era. Our research group is pursuing three major areas: (1) development of chemical tools for profiling the glycome using molecular imaging and mass spectrometry techniques; (2) investigation of the roles of microbial glycoconjugates in pathogenesis, with an emphasis on Mycobacterium tuberculosis; and (3) engineering of nanoscale interfaces between cells and synthetic materials.
Chemical Tools for Glycomics Research
Cell surface oligosaccharides are major determinants of cell-cell interactions during development, the immune response, and pathogenic processes such as microbial infection and tumor cell metastasis. The goal of this program is to develop chemical tools for profiling glycans in cells and living organisms and for elucidating their functions with respect to human disease. One such tool is a chemical reporter system for visualizing glycans on cells. We developed two chemical reactions that employ the azide as a bioorthogonal chemical handle. The azide is delivered to specific glycan types via metabolism of synthetic azido sugars. Once incorporated into cellular glycans, the azido sugars can be selectively reacted with probes for detection, enrichment, or visualization. We are applying this technology to proteomic analysis of protein glycosylation, to the identification of glycan tumor and stem cell biomarkers, and to noninvasive imaging of glycosylation changes during development and disease progression. (Grants from the National Institutes of Health and the California Initiative for Regenerative Medicine have also supported this work.)
A second component of this program is the development of tools for probing changes in protein glycosylation that are associated with disease. We have developed a technique for labeling glycoproteins from serum or tissue samples with isotopically unique probes that enable their rapid detection from complex mixtures by mass spectrometry. We are applying this technology to the identification of novel cancer biomarkers. (Grants from the National Institutes of Health have also supported this work.)
Mycobacterial Metabolites Involved in Pathogenesis
Mycobacterium tuberculosis, the causative agent of tuberculosis, is responsible for around 3 million deaths per year. Current treatment protocols are lengthy and complicated, and multidrug-resistant strains have arisen in recent years that remain impossible to treat. Mycobacteria have many unusual features, including a complex cell wall structure comprising sulfated trehalose metabolites that are thought to mediate host-pathogen interactions. We are interested in the biological activities of these metabolites and their biosynthetic origin inside the bacterial cell, with an eye for identifying new avenues for drug development. Toward this end, we are disrupting the genes that encode key biosynthetic enzymes, analyzing their phenotypes in mouse models of tuberculosis, and screening compound libraries for inhibitor leads. We are also pursuing x-ray crystal structures of the most promising enzyme targets. (Grants from the National Institutes of Health and Gilead Sciences also support this work.)
Nanoscience Tools for Biological Imaging
Carbon nanotubes (CNTs) have remarkable electrical, magnetic, optical, and mechanical properties that are potentially useful in biological sensing and imaging applications. CNTs are not, however, compatible with living cells because of their lack of water solubility and their intrinsic toxicity. We are developing synthetic coatings and chemical modification strategies that cloak CNTs in a layer of biomimetic materials. The coated CNTs are rendered nontoxic and are suitable for integration into biosensing and imaging platforms. (Grants from the Department of Energy have also supported this work.)
Last updated: June 16, 2008
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