Physical Geography and Sciences
Study on The Conformation of Oligo-Arylureido Peptoids


Study on The Conformation of Oligo-Arylureido Peptoids



Gregory O’Brien, Independent Study, Patrick Parnel, Biology, Kanwal Asif, Forensic Science and Victoire Grace-Karambizi, Biology
Faculty Mentor: Professor Sujit Suwal, Chemistry

The arylureido peptoid isobars undergo distinct fragmentations in MALDI-TOF mass spectrometry depending on the relative substituents disposition around the benzene ring. Using two commercially available chlorophenylisocyanate isobars, recently we demonstrated the synthetic compatibility of arylureides on the solid support and proposed SS1 and SS2 fragmentation mechanisms. The compounds isolated from the pool of libraries were successfully identified using mass spectrometry without isotopic labeling or internal molecular encoding. To this point, we extended our study towards the synthesis of olioarylureides using 2-chlorophenylisocyanate submonomer, which results in 1, 2 di-substituted arenes having urea backbone. Due to ortho-substituent disposition in the molecule, we hypothesized the resultant oligomers could potentially adopt secondary structure, similar to polyproline helix. To affirm our hypothesis, we synthesized a series of arylureides--trimer to nonamer, without any synthetic challenges. The purities of the compounds are determined by HPLC and authenticated using LC-MS. Under MS condition, the compounds larger than pentamer showed enough stability without undergoing significant fragmentation. Based on this evidence, we presumed the arylureides that are larger than pentamer possibly exist in unique 3D conformation that prohibits the molecular fragmentations under LC-MS. To confirm the structures of the oligomers, we further carried out molecular modeling of oligomers and corroborate our evidence by NOESY experiment.

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Study on The Conformation of Oligo-Arylureido Peptoids