R. Miclette Lamarche * , C. DeWolf
Thiol containing molecules can chemisorb onto gold surfaces to form a monolayer, this is done by immersion in a solution of the thiol compound, creating a SAM (self-assembled monolayer). An alternative would be to deposit the monolayer after it was formed in a different organisation than the one obtained by SAM. We propose to do this by pre-assembling the monolayer at the air-water interface using surfactants that have been ω-functionalized to have a thiol at the end of their carbon chain. To deposit the monolayer, we first need to study the behavior of surfactants that have been modified. Using a Langmuir trough balance with ellipsometric measurement at the air-water interface revealed that the surfactants first stand upright, the headgroup (phenol) in the water and the thiol point upward toward the air but over time the thiol contact the water. Thiol location dictates the deposition process and possible strategy. Learning more about its location and behavior at the air water interface would make it possible to create monolayer with organisation customized for specific task.
C. Liczner * , V. Grenier , C. Wilds
The chemical modification of nucleic acids, achieved through organic synthesis, can enhance the properties of these molecules and expand their range of applications. For example, incorporation of selenium in DNA has been shown to be a powerful approach to aid in the X-ray crystallographic determination of nucleic acid structures by assisting with solving the phase problem. Selenium is a heavy atom of choice due to its efficient anomalous scattering, resemblance to oxygen and the many sites available for modification, including the sugar, phosphate backbone and nucleobase. Our lab was initially interested in expanding the incorporation sites of selenium in an oligonucleotide through the synthesis of a nucleobase modified 2’-deoxyinosine (dI). The novel d6SeI phosphoramidite was synthesized and incorporated into an oligonucleotide by solid-phase synthesis. Unexpectedly, after deprotection, spontaneous diselenide cross-linking between two non-complementary DNA strands was observed. This cross-link, which has not been observed before for other selenium nucleobase modified nucleic acids, is readily formed in aerobic conditions. Moreover, it is quickly and quantitatively removed under mild reducing conditions. This opens up a facile synthetic route to site-specific cross-linking of oligonucleotides (or conjugation to other biomacromolecules) while having the added advantage of facilitating the determination of structures by X-ray crystallography.