Dissertations, Theses, and Capstone Projects

Date of Degree

9-2015

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor

Laura J. Juszczak

Committee Members

Sébastien Poget

Richard Magliozzo

Ruel Desamero

Ryan Murelli

Keywords

conotoxin; fluorescence; terebridae; tryptophan

Abstract

This dissertation focuses on expanding chemical derivatization methodologies of peptides with the ultimate goal of studying proteins that are not amenable to traditional high-resolution structural techniques. The first project, conducted in the laboratory of Dr. Mandë Holford, uses improved synthetic and chemical derivatization methods to access and characterize peptidic natural products from venomous marine snails belonging to the family Terebridae. Closely related to Conus snails, the Terebridae also produce disulfide-rich peptide toxins (teretoxins) that are potent and specific agonists of ion channels and receptors of the central nervous system. Teretoxins are underexplored relative to Conus toxins, and represent a yet untapped pool of tools to investigate neuronal targets that are notoriously hard to characterize, as well as a source of therapeutic candidates for the treatment of neurological conditions. This work demonstrates both the application of specialized and improved solid phase peptide synthesis methods, and a strategy for disulfide mapping of teretoxins through the successful synthesis and structural characterization of the novel toxin Tv1 from Terebra variegata, the first teretoxin to be structurally characterized. The second project, conducted in the laboratory of Dr. Laura Juszczak, focuses on expanding the utility of fluorescence spectroscopy for the study of peptides and proteins by developing a novel, environment-sensitive fluorophore capable of biocompatible incorporation into polypeptides. Using the fluorogenic oxidative coupling reaction of 5-hydroxytryptophan and benzylamine which produces the fluorescent product 2-phenyl-6H-oxazolo[4,5-e]indole (PHOXI), a strategy for site-specific, biocompatible labeling of peptides with this probe is demonstrated. Investigation of PHOXI's photophysics shows that it is a potent environment-sensitive probe, making it a valuable addition to the privileged class of solvatochromic fluorophores capable of probing protein structure, interactions and dynamics.

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