Investigations on the specificity of DNA aptamers binding to ethanolamine

In our previous work, we selected aptamers binding to ethanolamine, one of the smallest molecular aptamer targets so far (Mann, D., Reinemann, C., Stoltenburg, R. and Strehlitz, B. Biochem. Biophys. Res. Commun. 2005, 338, 1928-1934). Two representatives of these aptamers (EA#14.3 and EA#9.4) were analyzed regarding their specificity. Ethanolamine is a very small organic molecule (M(w) = 61.08) with biological, medical, and industrial relevance. Its small size represented a challenge for aptamer development, as ethanolamine only consists of a short carbon chain (2C) and two functional groups (amino and hydroxyl group). Related organic molecules, ethanolamine derivatives, and some amino acids were tested to act as potential binding partners for these aptamers. In this way we were able to determine the exact binding domain within the target. The results revealed that both aptamers bind to various molecules, which contain a freely accessible ethyl- or methylamine group. In contrast to the amino group (in a primary, secondary, or tertiary amine) the hydroxyl group was not necessary for the aptamer binding. The aptamers were not able to bind to negatively charged organic molecules, despite containing an ethyl- or methylamine group, nor did they bind to molecules with quaternary amines. The selected ethanolamine binding aptamers are useful for the detection of molecules containing accessible ethyl- or methylamine groups; they can be used as linker elements to immobilize a target molecule of interest on a surface or to purify targets from complex samples.