Detection of hydrogen-bonded adenine-thymine base-pair complexes by electrospray mass spectrometry

Bibracchial lariat ether compounds having three-carbon sidearms terminated in either adenine or thymine have the potential to form a molecular box in which the ''ends'' are crown ethers and the ''sides'' are hydrogen-bonded base pairs. Previous solution studies relying upon NMR and vapor pressure osmometry confirmed the formation of complexes. In the present study, four diaza-18-crown-6 derivatives having either one or two sidearms each terminated in either adenine or thymine have been studied in a mixture of CHCl3 and CH3OH. Either acetic acid or sodium chloride was added to the solutions. For the two-armed systems, the preferred complex was the dimer involving adenines on one monomer and thymines on the other. Homodimers and other complexes sere detected as well, The preferred single-armed complex was that occurring between the monomer whose sidearm was terminated in thymine and either H+ or Na+.