Bioorganic and Macromolecular

mcloningerchemistry.montana.edu

My research program is based on key questions in chemical biology. How do cells 'talk' to one another? What are the signaling mechanisms that are used to control cell functions? What processes mediate the adhesions and metastatic migrations of cancer cells?
One way to study these complex natural processes is to build and evaluate simpler model systems. Our approach is to synthesize synthetic multivalent frameworks for the study cellular recognition events.

Keywords:
Bioinorganic, Chemical Biology, Organic, Spectroscopy, Synthesis

Many reports suggest that cell surface carbohydrates serve a critical function in malignant transformation and metastasis. We are developing artificial carbohydrate arrays to mimic and interfere with metastasis. Our goal is to advance fundamental knowledge regarding the role of protein-carbohydrate and carbohydrate-carbohydrate interactions in the metastatic spread of cancer. Concurrently, new therapeutic agents to arrest cancer metastasis may also emerge.

Keywords:
Biochemistry, Bioinorganic, Chemical Biology, Organic

The evaluation of dendrimer properties is another area of macromolecular chemistry that is of interest to us. To study the relative locations and the dynamic nature of dendrimer endgroups, we have functionalized dendrimers with varying amounts of spin-labels. EPR spectra of TEMPO-labeled G(4)-PAMAM dendrimers (Figure 4) suggest that termini are randomly distributed on heterogeneously-functionalized dendrimers. Additional EPR studies with other generations of dendrimers and with non-random surface spin-labeling distributions are underway.

Selected Publications

Morgan JR, Cloninger MJ :
Synthesis of Carbohydrate-linked Poly(polyoxometalate) PAMAM Dendrimers
J. Polym. Sci. A., Polym. Chem. 43 3059-3066 (2005)

Walter ED, Sebby KB, Usselman RJ, Singel DJ, Cloninger MJ :
Characterization of Heterogeneously Functionalized Dendrimers by Mass Spectrometry and EPR Spectroscopy
J. Phys. Chem. B. 109 21532-21538 (2005)

Morgan JR, Cloninger MJ :
Heterogeneously Functionalized Dendrimers
Curr. Op. Drug Disc. Dev. 5 966–973 (2002)

Keywords:
Chemical Biology, Organic, Spectroscopy, Structure, Synthesis

We are using dendrimers (macromolecules consisting of a series of branches around an inner core) to study the interaction of carbohydrates with receptor proteins called lectins. Although a wide variety of biological processes including fertilization, development, and the mounting of an immune response rely on protein-carbohydrate interactions for cellular recognition and adhesion (Figure 1), these interactions are not well understood. Because the affinity of lectins for individual saccharide units is relatively weak, the adhesion of lectins to saccharides on the surface of a cell involves multipoint attachment (multivalency).

We are using saccharide-functionalized poly(amidoamine) (PAMAM) dendrimers (Figure 2) to learn more about multivalency in protein carbohydrate interactions. Dendrimers are ideal frameworks for the study of how systematic structural changes alter the way that a glycopolymer interacts with a protein. In addition to changing the dendrimer generation, the degree of carbohydrate loading on a dendrimer can also be readily changed by controlling the number of equivalents of sugar residues that are added to the dendrimer (Figure 3). We can systematically and predictably attenuate the relative affinities of the dendrimers for the lectins by incorporating low and high affinity ligands into the dendrimer. We can also influence how many proteins bind to each dendrimer. We're evaluating the comparative activity of these dendrimers for lectins such as Concanavalin A, Pisum Sativum, and Cyanovirin N using a variety of assays. In this way, we are learning about the factors that control physiologically relevant multivalent protein-carbohydrate interactions. Because of their ready tunability, the carbohydrate functionalized dendrimers described here should provide guidelines for the development of synthetic multivalent frameworks for many applications in chemical biology.

Selected Publications

Samuelson, L. E., Sebby, K. B., Walter, E. D., et al.:
EPR and affinity studies of mannose-TEMPO functionalized PAMAM dendrimers
Organic and Biomolecular Chemistry 2 (21) 3075, 2004.

Woller EK, Cloninger MJ :
The Lectin-binding Properties of Six Generations of Mannose-functionalized Dendrimerss
Org. Lett. 4 7-10 (2002)

Woller EK, Cloninger MJ :
Mannose Functionalization of a Sixth Generation Dendrimer
Biomacromolecules 2 1052-1054 (2001)

Mangold, S. L.; Cloninger, M. J. :
Binding of monomeric and dimeric Concanavalin A to mannose functionalized dendrimers
Org. Biomol. Chem. 2006, 4, 2458-2465.

Wolfenden, M. L.; Cloninger, M. J. :
Mannose/glucose-functionalized dendrimers to investigate the predictable tunability of multivalent interactions.
J. Am. Chem. Soc., 2005, 127, 12168-12169

Schlick, K. H.; Udelhoven, R. A.; Strohmeyer, G. C.; Cloninger, M. J. :
Binding of Mannose-Functionalized Dendrimers with Pea (Pisum Sativum) Lectin
Mol. Pharm. 2005, 2, 295-301

Mangold, S. L.; Morgan, J. R.; Strohmeyer, G. C.; Gronenborn, A. M.; Cloninger, M. J.:
Cyanovirin-N binding to Mana1-2Man functionalized dendrimers
Org. Biomol. Chem., 2005, 3, 2354-2358

Woller EK, Walter ED, Morgan JR, Singel DJ, Cloninger MJ :
Altering the Strength of Lectin Binding Interactions and Controlling the Amount of Lectin Clustering Using Mannose/hydroxyl Functionalized Dendrimers
J. Am. Chem. Soc. 125 8820–8826 (2003)

Keywords:
Biochemistry, Chemical Biology, Organic