Doctoral Dissertations

Date of Award

5-1999

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

David C. Baker, James Q. Chambers

Committee Members

Spiro D. Alexandratos, Donald K. Dougall, Engin H. Serpersu

Abstract

Anthocyanins, which are the highly colored compounds responsible for most of the non-green colors in plants, are glycosides of benzopyrilium (flavylium) salts that are subject to hydration by water at the flavylium C-2 position, with loss of coloration at near-neutral pH. Biosynthetic acylation with supplied cinnamic or benzoic acids at the O-6 Glc terminus of a set of anthocyanins produces compounds with enhanced color stability that are of the structure, 6-O-acyl-β-D-Glcp-(1-6)-β-D-Galp-(1-O3)-cyanidin, with and without a β-D-Xylp branch at the 2-O-Gal position. In order to investigate the conformational behavior of these compounds with the aim of probing the mechanism for their color stabilization, five compounds, four with the 2-O-β-Xyl branch, including the non-acylated compound and three compounds where acyl = 3,4,5-trimethoxybenzoyl, 4- fluorocinnamoyl, 3,4,5-trirnethoxycinnamoyl, plus the latter compound lacking the 2-O-β-Xyl group, were subjected to quenched molecular dynamics (QMD) using a dielectric continuum of methanol, and the results of these calculations were correlated with NMR data to yield families of conformers. The result was the finding that these molecules were quite flexible, with discrete families of conformers that afforded differing degrees of protection from attack at C-2 by solvent. MOLCAD was further used to visualize these characteristics. Two mono-cinnamoylated anthocyanins have been subjected to similar QMD studies in a continuum of water, with the aim of correlating conformational preferences with color stability in an aqueous environment. Structure-activity relationships that emerged are being used to design highly color-stabilized anthocyanins that have potential as food colorants.

The design and programmable synthesis of electroactive oligodeoxynucleotides (ODNs) that bear a covalently attached 9, 10- anthraquinone (AQ) moiety via a hexylamino linker arm was achieved using a phosphoramidite derivative of a 2'-O-modified uridine. Prior to the successful synthesis of these ODNs, attempts were made to synthesize C-8-modified 2'deoxyadenosine derivatives that could be similarly used in an automated ODN synthesizer; however, these were difficult to prepare and do not readily form duplexes. Electrochemical studies of the 2'-O-modified AQ--ODNs on a hanging drop mercury electrode (HMDE) suggest that these ODNs may be useful as probes for hybridization, but that the HMDE is an unsuitable electrode to study these processes.

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