Aisosa Omere / Chemistry & Biochemistry / Faculty Mentor: Joseph Buonomo
Of the 20 canonical amino acids, only aspartic acid (Asp) and glutamic acid (Glu) bear a carboxyl-terminating sidechain. As a result of the peptide bond, proteins also contain a carboxyl terminus (C-terminus) and an amino (N-terminus). The physical properties of the carboxyl functional groups make them a highly versatile functional group capable of engaging in molecular interactions with a wide variety of complementary functional groups. Because of the electrostatic interactions within their microenvironments, carboxylic acids can display a wide range of pKa values, with their apparent pKa either increasing or decreasing, leading them to either favor remaining protonated in the acid form or being deprotonated to become the negatively charged carboxylate ion. Since the two forms exist in equilibria, the carboxylic acid and its conjugate base display a degree of reactive tunability. That is, in a compound containing multiple carboxylic acid functional groups, one can selectively interact with only one of them by utilizing the known differences in the pKa. In the case of proteinaceous samples, this tunability allows us to distinguish between the sidechain and the C-terminal carboxylic acid. In this poster, we demonstrate the ability to separate sidechain and C-terminal reactivity, harnessing the chemoselectivity of diazo compounds and pH control.
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