Author (Your Name)

Baskut O. Tuncak, Colby College

Date of Award


Document Type

Honors Thesis (Colby Access Only)


Colby College. Chemistry Dept.


Stephen U. Dunham

Second Advisor

Duncan A. Tate

Third Advisor

Bradford P. Mundy


A thioderivative of the nucleic acid base guanine. 6-thioguanine (65G), is a metabolic inhibitor and possesses anti-tumor activity. 65dG can be readily incorporated into nucleic acids, substituting for deoxyguanosine. It has been proposed that biological activity 65G is the result of alterations in the conformation of duplex DNA. We are interested in determining the structure and dynamics of 65dG modified DNA. Automated synthesis has been used to obtain 11-base pair DNA sequences with incorporation of 6sdG and/or convertible nucleosides. Modification of convertible nucleosides with either 4-aminoTEMPO or NH4OH respectively has been used to incorporate specific electron paramagnetic spin resonance (EPR) or nuclear magnetic resonance (NMR) probes. High performance liquid chromatography (HPLC) was used to purify the modified single stranded 11-base pair DNA and subsequent DNA duplexes. NMR and EPR spectroscopy have been used to characterize DNA structure and dynamics upon incorporation of 65dG. 15N-edited H NMR spectroscopy failed to detect a 15N signal for an 11-mer duplex. Resonance was detected in the 11-mer duplex by EPR spectroscopy. Deviations in line shape were not observed between duplexes with and without 65dG. Thus, the rotation of the nitroxide spin-label did not appear to be hindered by the presence of 65dG within the duplex.


Full-text download restricted to Colby College campus only.


Structural Analysis, DNA Duplex, NMR Spectroscopy, EPR Spectroscopy, High performance liquid chromatography (HPLC)